400 Commonwealth Drive, Warrendale, PA 15096-0001
`
`SURFACE
`VEHICLE
`RECOMMENDED
`PRACTICE
`
`Submitted for recognition as an American National Standard
`
`J1922
`
`REAF.
`SEP2000
`
`Issued
`Reaffirmed
`
`1989-12
`2000-09
`
`Superseding J1922 JAN1995
`
`Powertrain Control Interface for Electronic Controls Used in Medium-
`and Heavy-Duty Diesel On-Highway Vehicle Applications
`
`Foreword—Electronic controls for engines, transmissions, braking systems, and retarders need to share common
`measured parameters and have a method for interaction. To eliminate the need for redundant sensors and
`possible conflicting data, a method of communicating information between electronic controls is required. By
`sharing information, the vehicle installation costs can be reduced and performance enhanced with interactive
`control features.
`
`A method of communicating control parameters between engine, transmission, antilock braking system (ABS)/
`traction control, and retarder systems is required. A long- and short-term approach has been taken to resolve the
`problem. This document addresses the short-term need. The SAE Truck and Bus Control and Communications
`Network Subcommittee is developing a controls communication network document (draft SAE J1939) that will use
`a high-speed data link, which will address the long-term need.
`
`TABLE OF CONTENTS
`
`Foreword .................................................................................................................................................. 1
`
`Scope ....................................................................................................................................................... 2
`
`References ............................................................................................................................................... 2
`Applicable Publications ............................................................................................................................ 2
`SAE Publications ...................................................................................................................................... 2
`
`Definitions................................................................................................................................................. 2
`Percent Torque Value .............................................................................................................................. 2
`Percent Accelerator Pedal (AP) Position.................................................................................................. 3
`Engine Parameter Change ....................................................................................................................... 3
`Engine’s Desired RPM ............................................................................................................................. 3
`Engine’s Desired RPM Asymmetry Adjustment ....................................................................................... 3
`Desired Engine Speed Value ................................................................................................................... 3
`Maximum Engine Override RPM .............................................................................................................. 3
`Current Engaged Gear Number ............................................................................................................... 4
`AP Kickdown Position .............................................................................................................................. 4
`AP Low Idle Position ................................................................................................................................ 4
`
`Powertrain Interface ................................................................................................................................. 4
`
`1.
`
`2.
`2.1
`2.1.1
`
`3.
`3.1
`3.2
`3.3
`3.4
`3.5
`3.6
`3.7
`3.8
`3.9
`3.10
`
`4.
`
`SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely
`voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole responsibility of the user.”
`
`SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions.
`
`TO PLACE A DOCUMENT ORDER: (724) 776-4970 FAX: (724) 776-0790
`SAE WEB ADDRESS http://www.sae.org
`
`Copyright 2000 Society of Automotive Engineers, Inc.
`All rights reserved.
`
`Printed in U.S.A.
`
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`SAE J1922 Reaffirmed SEP2000
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`5.
`5.1
`5.2
`5.2.1
`5.3
`5.3.1
`5.4
`5.5
`5.6
`5.7
`5.7.1
`5.7.2
`5.7.3
`5.7.4
`5.7.5
`5.7.6
`5.7.7
`5.7.8
`
`Message Formats ..................................................................................................................................... 4
`Engine to Powertrain Message................................................................................................................. 6
`Transmission to Powertrain Message....................................................................................................... 7
`Override Control Modes............................................................................................................................ 8
`ABS/Traction Control to Powertrain Message ........................................................................................10
`ABS/Traction Control Modes ..................................................................................................................10
`Retarder to Powertrain Message ............................................................................................................11
`Transmission to Powertrain Current Gear Number Message ................................................................. 11
`Engine to Transmission Current Gear Request Message ...................................................................... 12
`Initialization Messages............................................................................................................................ 12
`Engine to Powertrain Initialization Message ........................................................................................... 12
`Transmission to Powertrain Initialization Message................................................................................. 13
`ABS/Traction Control to Powertrain Initialization Message.....................................................................13
`Retarder to Powertrain Initialization Message ........................................................................................14
`Engine to Powertrain Initialization Request Message............................................................................. 14
`Transmission to Powertrain Initialization Request Message................................................................... 15
`ABS/Traction Control to Powertrain Initialization Request Message ...................................................... 15
`Retarder to Powertrain Initialization Request Message .......................................................................... 16
`
`Appendix A Engine’s Desired RPM Asymmetry Adjustment...................................................................................... 17
`
`1.
`
`Scope—This SAE Recommended Practice provides a development or possibly interim production
`communication protocol between engine, transmission, ABS/traction control, and retarder systems until higher
`speed communication links are established.
`
`2.
`
`References
`
`2.1 Applicable Publications—The following publications form a part of the specification to the extent specified
`herein. Unless otherwise indicated, the latest revision of SAE publications shall apply.
`
`2.1.1
`
`SAE PUBLICATIONS—Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.
`
`SAEJ1708 NOV89—Serial Data Communications Between Microcomputer Systems in Heavy-Duty
`Vehicle Applications
`SAEJ1587 NOV89—Joint SAE/TMC Electronic Data Interchange Between Microcomputer Systems in
`Heavy-Duty Vehicle Applications
`SAEJ1843 JUN89—Accelerator Pedal Position Sensor for Use With Electronic Controls in Medium- and
`Heavy-Duty Diesel On-Highway Vehicle Applications
`
`3.
`
`Definitions—Parameter Definitions
`
`3.1 Percent Torque Value—A percent value for torque which is a percent of the peak engine torque as indicated
`by byte 18 of the engine to powertrain initialization message (see 5.7.1). Percent torque value is broadcast as
`a signed short integer (two’s complement).
`
`Resolution:
`Range:
`
`1%/bit
`+127% peak engine torque
`–128% peak engine torque
`
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`SAE J1922 Reaffirmed SEP2000
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`3.2 Percent Accelerator Pedal (AP) Position—This signal always reflects the percent AP position as interpreted
`by the engine. This value shall never reflect override states, the equivalent cruise control value, nor the road
`speed limiting value. The value is a scaled value such that 0% AP position is represented by 0, and 100% AP
`position is represented by 255. Additionally, the value of AP position shall be 0% during a fault condition of the
`AP.
`
`Resolution:
`Range:
`
`0.392%/bit
`0 to 100%
`
`3.3 Engine Parameter Change—This bit indicates that one of the parameters sent to the transmission in the last
`initialization message has changed (i.e., idle speed has changed, available torque has changed, etc.). This bit
`shall remain set until the powertrain has requested a new initialization message, and it has been sent by the
`engine.
`
`Resolution:
`Range:
`Binary bit mapped:
`
`Not applicable
`Not applicable
`1 = A parameter has changed since last initialization message was sent
`0 = No change since last transmission of the initialization message
`
`3.4 Engine’s Desired RPM—An indication by the engine to the transmission of the optimal operating speed of the
`engine for the currently existing conditions. These conditions may include torques generated to accommodate
`powertrain demand, such as cruise control or vehicle speed governors. Dynamic commands from functions
`such as smoke control or shift control are excluded from this calculation.
`
`Resolution:
`Range:
`
`16 RPM/bit
`0 to 4080 RPM
`
`3.5 Engine’s Desired RPM Asymmetry Adjustment—This byte is utilized in transmission gear selection routines
`and indicates the engine’s preference of lower versus higher engine speeds should its desired RPM not be
`achievable. This is a scaled ratio such that 128 represents an equal preference for a RPM lower or higher than
`the engine’s indicated desired RPM. The higher the asymmetry adjustment value is above 128, the more the
`engine prefers to be operated at or above its indicated desired RPM. Conversely, the lower the asymmetry
`adjustment value is below 128, the more the engine prefers to operate at or below its indicated desired RPM.
`Typically, the engine’s asymmetry adjustment will be predicated on fuel consumption considerations, and
`under these situations, the method for computing the asymmetry adjustment is indicated in Appendix A. It
`should be noted there may be times the engine will deviate from an asymmetry adjustment computation based
`solely on fuel consumption considerations as done in Appendix A. The engine may include other factors into
`its asymmetry adjustment calculation such as temperatures, pressures, and other operating parameters.
`
`Resolution:
`Range:
`
`Not applicable
`Not applicable
`
`Ratio calculated and scaled per the previous discussion and in Appendix A.
`
`3.6 Desired Engine Speed Value—An actual engine speed requested by the transmission for shift control or the
`ABS/traction controls.
`
`Resolution:
`Range:
`
`0.0625 RPM/bit
`0 to 4096 RPM
`
`-3-
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`SAE J1922 Reaffirmed SEP2000
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`3.7 Maximum Engine Override Speed—The maximum engine RPM above high idle allowed by the engine
`control during a momentary high idle override.
`
`Resolution:
`Range:
`
`16 RPM/bit
`0 to 4080 RPM
`
`3.8 Current Engaged Gear Number—The number assigned to the transmission gear ratios in the transmission to
`powertrain initialization message by the order of the data. Reverse gear numbers are denoted by negative
`numbers with the more negative number representing the gear that permits the highest vehicle speed in
`reverse. The current engaged gear number is broadcast as a signed short integer (two’s complement). The
`current engaged gear number has a value of zero when the transmission is in neutral.
`
`Resolution:
`Range:
`
`1 gear/bit
`+127 forward gears
`– 128 reverse gears
`
`3.9 AP Kickdown Position—Same as kickdown state in SAE J1843.
`
`Not applicable
`Resolution:
`Not applicable
`Range:
`Binary bit mapped: 1 = In kickdown position
`0 = Not in kickdown position
`
`3.10 AP Low Idle Position—Same as low idle state in SAE J1843.
`
`Not applicable
`Resolution:
`Not applicable
`Range:
`Binary bit mapped: 1 = In low idle position
`0 = Not in low idle position
`
`4.
`
`5.
`
`Powertrain Interface—A dedicated SAE J1708 data link shall be used to communicate the following
`parameters between engine, transmission, ABS/traction control, and retarder systems. The protocol to
`transfer information is similar to SAE J1587. Variable length message formats shall be used to communicate
`data between the control devices. The data will be formatted order specific to minimize the data link utilization.
`In order to have synchronization of broadcast data, it is recommended that the update timer in each device be
`re-initialized to a fixed time interval (based on the fastest update rate of the data in the message) every time
`the device gains access to the data link. This method of broadcasting is an attempt to minimize the number of
`possible collisions.
`
`Message Formats—Table 1, Message Identification (MID), was reserved in SAE J1708 MID assignment list in
`January of 1989. The use of these MIDs will be discussed in detail throughout the rest of Section 5. Message
`formats adhere to SAE J1708 requirements.
`
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`SAE J1922 Reaffirmed SEP2000
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`TABLE 1—MESSAGE IDENTIFICATION (MID) TABLE
`
`MID
`
`Description
`
`69 Engine to Powertrain Message
`70 Engine to Powertrain Initialization Message
`71 Engine to Powertrain Initialization Request Message
`72 Engine to Transmission Current Gear Request Message
`73 Engine, Reserved
`74 Transmission to Powertrain Message
`75 Transmission to Powertrain Initialization Message
`76 Transmission to Powertrain Initialization Request Message
`77 Transmission to Powertrain Current Gear Number Message
`78 Transmission, Reserved
`79 ABS/Traction Control to Powertrain Message
`80 ABS/Traction Control to Powertrain Initialization Message
`81 ABS/Traction Control to Powertrain Initialization Request Message
`82 ABS/Traction Control, Reserved
`83 Retarder to Powertrain Message
`84 Retarder to Powertrain Initialization Message
`85 Retarder to Powertrain Initialization Request Message
`86 Retarder, Reserved
`
`-5-
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`SAE J1922 Reaffirmed SEP2000
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`5.1 Engine to Powertrain Message
`
`FORMAT = (MID, BYTE1, BYTE2, BYTE3, BYTE4, BYTE5, CHECKSUM)
`PRIORITY 3
`Engine MID = 69
`Update Period = 0.050 s
`
`MESSAGE CONTENTS
`UPDATE
`PERIOD
`0.050
`0.050
`0.050
`0.050
`
`BYTE
` 0
` 1
` 2
` 3
`
` 4
` 5
` 6
`
`
`0.050
`0.050
`0.050
`
` 1
`
` 2
`
` 3
`
`DESCRIPTION
`MID = 69
`Percent Torque Value (calculated torque) (Resolution 1%/bit)
`% AP Position (Resolution ~0.4%) (0% during fault condition)
`Control/Status Byte
`BIT
`DESCRIPTION
` 0
`Cruise Control Status
`1 = Cruise Control Active
`0 = Cruise Control Inactive
`PTO Control Status
`1 = PTO Control Active
`0 = PTO Control Inactive
`Road Speed Limiting Status
`1 = Road Speed Limit Active
`0 = Road Speed Limit Inactive
`Retarder Control Status
`1 = Engine Retarder Enabled
`0 = Engine Retarder Not Enabled
`Alternatively: Retarder Enable Command
`(for a retarder controlled via data link)
`1 = Retarder Enabled
`0 = Retarder Disabled
`AP Kickdown Switch
`1 = In Kickdown Position
`0 = Not in Kickdown Position
`AP Low Idle Switch
`1 = In Low Idle Position
`0 = Not in Low Idle Position
`Engine Parameter Change
`1 = Parameters have changed
`0 = Current Parameters valid
`For Future Use
` 7
`Engine’s Desired RPM (Resolution 16 RPM/bit)
`Desired RPM Asymmetry Adjustment (Scaled Ratio)
`Checksum
`
` 4
`
` 5
`
` 6
`
`-6-
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`SAE J1922 Reaffirmed SEP2000
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`5.2
`
`Transmission to Powertrain Message
`
`FORMAT = (MID, BYTE1, BYTE2, BYTE3, BYTE4, CHECKSUM)
`PRIORITY 2
`Transmission MID = 74
`Update Period = 0.025 s
`
`MESSAGE CONTENTS
`UPDATE
`PERIOD
`0.025
`0.025
`BIT
`0,1
`
`BYTE
` 0
` 1
`
` 2
`
` 3
`
` 4
`
` 5
`
` 2
`
`6,7
`0.025
`
` 3
`
`0.025
`
` 4
` 5
`
`0.025
`0.025
`
`DESCRIPTION
`MID = 74
`Control/Status Byte
`DESCRIPTION
`Override Control Mode
`Mode = 00 Override Disabled
`Mode = 01 Engine Speed Value Control
`Mode = 10 Engine Torque Control Mode
`Mode = 11 Engine Speed/Torque Limit Control
`Retarder Enable
`1 = Enable Retarder
`0 = Disable Retarder
`Momentary High Idle Override
`1 = Override Enabled
`0 = Override Disabled
`Driveline Engaged
`1 = Driveline Engaged
`0 = Driveline Disengaged
`Transmission Retarder Control Status
`1 = Transmission Retarder Active
`0 = Transmission Retarder Inactive
`For Future Use
`For:
`MODE = 00 Not Broadcast
`MODE = 01 Desired Engine Speed Value (LSB)
`(Resolution 0.0625 RPM/bit)
`MODE = 10 Not Broadcast
`MODE = 11 Engine Speed Upper Limit
`(Resolution 16 RPM/bit)
`MODE = 00 Not Broadcast
`MODE = 01 Desired Engine Speed Value (MSB)
`(Resolution 16 RPM/bit)
`MODE = 10 Desired Percent Torque Value
`(Resolution 1%/bit)
` MODE = 11 Percent Torque Value Limit
`(Resolution 1%/bit)
`Output Shaft Speed (Resolution 16 RPM/bit)
`Checksum
`
`For:
`
`-7-
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`SAE J1922 Reaffirmed SEP2000
`
`5.2.1 OVERRIDE CONTROL MODES—The transmission to powertrain message is a variable length message that
`shall have four control modes and they are as defined as follows. The engine shall always honor an override
`request by the transmission (i.e., transmission takes precedence over road speed limiting and cruise
`control). In the absence of continued broadcasts from the transmission, the engine shall default to Mode 00
`after a predetermined length of time.
`
`a. Mode 00—When operating in this mode, the transmission is not required to provide an override
`command to the engine; override is disabled. The sending of bytes 2 and 3 shall be omitted.
`b. Mode 01—When operating in this mode, the engine shall function as a speed regulator with the
`transmission providing the speed command in bytes 2 and 3 of the message.
`c. Mode 10—When operating in this mode, the engine shall function as a torque regulator with the
`transmission providing the torque command in byte 3 of the message with byte 2 being omitted.
`d. Mode 11—When operating in this mode, the transmission shall command an engine speed upper limit
`and an engine torque limit designated in bytes 2 and 3, respectively, of the message. Byte 2 of this
`message is a transmission command to the engine that limits the maximum speed of the engine. Byte
`3 contains a value that commands the engine to limit its available torque for the current engine speed.
`The transmission control shall be able to request an override of the governed engine high idle RPM up
`to the maximum engine override speed as defined in the engine to powertrain initialization message.
`
`5.2.1.1
`
`For Override Control Mode = 00 (Override Disabled)
`
`Byte No.
` 0
` 1
`
` 2
` 3
`
` Bit No.
` Data
`0,1 = 00
` 2 =
` 3 = —
` 4 = —
` 5 = —
`—
`
`6,7 = 00
` Data
` Data
`
`Description
`MID = 74
`Override Disable
`Engine Retarder Enable
`Momentary High Idle Override
`Driveline Engaged
`Transmission Retarder Control Status
`
`For Future Use
`Output Shaft Speed
`Checksum
`
`5.2.1.2
`
`For Override Control Mode = 01 (Desired Engine Speed)
`
`Byte No.
` 0
` 1
`
`Description
` Bit No.
`MID = 74
` Data
`Desired Engine Speed
`0,1 = 01
`Engine Retarder Enable
` 2 =
` 3 = — Momentary High Idle Override
` 4 = — Driveline Engaged
` 5 = — Transmission Retarder Control Status
`—
`
` 2
` 3
` 4
` 5
`
`6,7 = 00
` Data
` Data
` Data
` Data
`
`For Future Use
`Desired Engine Speed Value - LSB
`Desired Engine Speed Value - MSB
`Output Shaft Speed
`Checksum
`
`-8-
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`

`5.2.1.3
`
`For Override Control Mode = 10 (Desired Engine Torque Control)
`
`SAE J1922 Reaffirmed SEP2000
`
`Byte No.
` 0
` 1
`
` 2
` 3
` 4
`
`Description
` Bit No.
`MID = 74
` Data
`Desired Engine Torque Control
`0,1 = 10
` 2 = — Engine Retarder Enable
` 3 = 0
`Momentary High Idle Override
` 4 =
`Driveline Engaged
` 5 = — Transmission Retarder Control Status
`—
`6,7 = 00
` Data
` Data
` Data
`
`For Future Use
`Desired Percent Engine Torque Value
`Output Shaft Speed
`Checksum
`
`5.2.1.4
`
`For Override Control Mode = 11 (Engine Speed and Torque Limiting)
`
`Byte No.
` 0
` 1
`
` 2
` 3
` 4
` 5
`
`Description
` Bit No.
`MID = 74
` Data
`Engine Speed/Torque Limiting
`0,1 = 11
` 2 = — Engine Retarder Enable
` 3 = 0
`Momentary High Idle Override
` 4 =
`Driveline Engaged
` 5 = — Transmission Retarder Control Status
`—
`6,7 = 00
` Data
` Data
` Data
` Data
`
`For Future Use
`Engine Speed Upper Limit - (16 RPM/bit)
`Percent Torque Value Upper Limit - (1%/bit)
`Output Shaft Speed
`Checksum
`
`-9-
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`5.3 ABS/Traction Control to Powertrain Message
`
`SAE J1922 Reaffirmed SEP2000
`
`FORMAT = (MID, BYTE1, BYTE2, CHECKSUM)
`PRIORITY 1
`ABS/Traction Control MID = 79
`Update Period = Maximum rate to be broadcast only while ABS/traction control function is in operation
`with at least one additional transmission after ABS/traction control function has ceased in
`order to communicate a resumption to normal engine and transmission operation.
`
`MESSAGE CONTENTS
`UPDATE
`PERIOD
`0.050
`0.050
`
`BYTE
` 0
` 1
`
` 2
`
`0.050
`
` 2
`
` 3
`
` 4
`
`DESCRIPTION
`MID = 79
`Control/Status Byte
`BIT
`DESCRIPTION
`0,1
`Override Control Mode
`00 = Override Disabled
`01 = Speed Control Mode
`10 = Retarder or Engine Torque Control Mode
`11 = Retarder or Engine Torque Limit Mode
`Retarder or Engine Control Select. Select for modes to control engine
`driving torque or retarder braking torque.
`1 = Retarder Control
`0 = Engine Fueling Control
`Gear Shift Disable
`1 = Inhibit Gear Shifts
`0 = Allow Shifts as Normal
`Retarder Disable
`1 = Disable Driveline Retarders
`0 = Allow Normal Retarder Use
`Torque Converter Lock Up Disable
`1 = Disable Torque Converter Lock Up Clutch
`0 = Enable Lock Up as Normal
`Request to Neutral
`1 = Request Transmission De-clutch to Neutral
`0 = Allow Normal Operation
`For Future Use
` 7
`Data Byte
`FOR MODE = 00Not Broadcast
`FOR MODE = 01 RPM Speed Value Command
`(Resolution 16 RPM/bit)
`FOR MODE = 10Desired Retarder or Engine Percent Peak
`Torque Value Command (Resolution 1%/bit)
`FOR MODE = 11Retarder or Engine Percent Torque Limit Command
`(Resolution 1%/bit)
`
` 5
`
` 6
`
` 3
`
`0.050
`
`Checksum
`
`-10-
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`SAE J1922 Reaffirmed SEP2000
`
`5.3.1
`
`ABS/TRACTION CONTROL MODES—In the event of conflicting torque requests, limiting requests, and speed
`requests from both the transmission and the ABS/traction control, the engine shall honor the transmission
`request.
`
`Note this is a variable length message with byte 2 being omitted if the override control mode is disabled as
`indicated by bits 0 and 1 of the control/status byte. Cruise control functions in either the engine or
`transmission controls must allow for the traction control torque limiting requests to override and/or limit the
`engine output torque. In the absence of continued broadcasts from the ABS/traction controls, the engine
`shall default to Mode 00 after a predetermined length of time.
`
`5.4 Retarder to Powertrain Message
`
`FORMAT = (MID, BYTE1, CHECKSUM)
`PRIORITY 4
`Retarder MID = 83
`Update Period = 0.100 s
`
`MESSAGE CONTENTS
`UPDATE
`PERIOD
`0.100
`0.100
`
`BYTE
` 0
` 1
`
` 2
`
`0.100
`
` 1
`
`DESCRIPTION
`MID = 83
`Retarder Status BYTE
`BIT
`DESCRIPTION
` 0
`Retarder Active/Inactive
`1 = Active
`0 = Inactive
`Retarder Operational Status
`1 = Retarder Selected
`0 = Not Selected
`For Future Use
`2,3
`4,5,6,7 Retarding Level Status
`0000 = Off
`1111 = 100% On
`Resolution: 6.67%/bit
`Range:
`0 to 100%
`Checksum
`
`5.5
`
`Transmission to Powertrain Current Gear Number Message
`
`FORMAT = (MID, BYTE1, CHECKSUM)
`PRIORITY 6
`Current Gear MID = 77
`Update Period = Sent by transmission to powertrain when engine control requires transmission current
`gear number.
`
`MESSAGE CONTENTS
`BYTE
` 0
` 1
` 2
`
`DESCRIPTION
`MID = 77
`Current Engaged Gear Number
`Checksum
`
`-11-
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`5.6 Engine to Transmission Current Gear Request Message
`
`SAE J1922 Reaffirmed SEP2000
`
`FORMAT = (MID, CHECKSUM)
`PRIORITY 5
`Current Gear Request MID = 72
`Update Period = Sent by engine to transmission when engine control requires transmission current gear
`number.
`
`MESSAGE CONTENTS
`BYTE
` 0
` 1
`
`DESCRIPTION
`MID = 72
`Checksum
`
`5.7
`
`Initialization Messages—Initialization messages are used to communicate some of the operating parameters
`of the various powertrain systems that are of importance to the other controls. This is done to reduce the
`amount of calibration data required by each control system and to avoid necessary recalibration of the other
`systems should one device be reconfigured or its operating parameters changed.
`
`Initialization messages are only sent on request by an initialization request message. Typically these requests
`will be broadcast on power up of the systems, after any system resets, and when any of the initialization
`parameters have changed during the current period of operation and are so indicated by a bit in a status byte
`broadcast on a regular basis.
`
`5.7.1
`
`ENGINE TO POWERTRAIN INITIALIZATION MESSAGE
`
`FORMAT = (MID, BYTE1, BYTE2, BYTE3, ... , BYTE21, CHECKSUM)
`PRIORITY 8
`Engine Initialization MID = 70
`Update Period = On request by powertrain.
`The least significant byte of all engine speeds is transmitted first.
`
`MESSAGE CONTENTS
`BYTE
`DESCRIPTION
` 0
`MID = 70
` 1,2
`Engine Speed at Idle
` 3
`% of Peak Torque at Idle
` 4,5
`Rated Engine Speed
` 6
`% of Peak Torque at Rated Engine Speed
` 7,8
`Engine Speed Point 3
` 9
`% of Peak Torque at Point 3
`10,11
`Engine Speed Point 4
` 12
`% of Peak Torque at Point 4
`13,14
`Engine Speed Point 5
` 15
`% of Peak Torque at Point 5
`16,17
`Engine Speed at Peak Torque
` 18
`Peak Torque of Engine
`19,20
`Engine Speed at High Idle
` 21
`Maximum Engine Override Speed
` 22
`Checksum
`
`(Resolution 0.0625 RPM/bit)
`(Resolution 1%/bit)
`(Resolution 0.0625 RPM/bit)
`(Resolution 1%/bit)
`(Resolution 0.0625 RPM/bit)
`(Resolution 1%/bit)
`(Resolution 0.0625 RPM/bit)
`(Resolution 1%/bit)
`(Resolution 0.0625 RPM/bit)
`(Resolution 1%/bit)
`(Resolution 0.0625 RPM/bit)
`(Resolution 10 lb-ft/bit)
`(Resolution 0.0625 RPM/bit)
`(Resolution 16 RPM/bit)
`
`-12-
`
`Page 12 of 18
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`FORD 1240
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`

`

`SAE J1922 Reaffirmed SEP2000
`
`5.7.2
`
`TRANSMISSION TO POWERTRAIN INITIALIZATION MESSAGE
`
`FORMAT = (MID, BYTE1, BYTE2, BYTE3, ... , BYTEn, CHECKSUM)
`PRIORITY 8
`Transmission Initialization MID = 75
`Update Period = On request by the engine
`
`MESSAGE CONTENTS
`BYTE
`DESCRIPTION
` 0
`MID = 75
` 1
`Number of reverse gear ratios
` 2
`Number of forward gear ratios
` 3,4
`Highest Vehicle Speed Reverse Gear Ratio (1/16 Input RPM/Output RPM)
`
`
`
` * , *
` * , *
`
`
`
` * , *
` *
`
`Lowest Vehicle Speed Reverse Gear Ratio (1/16 Input RPM/Output RPM)
`Lowest Vehicle Speed Forward Gear Ratio (1/16 Input RPM/Output RPM)
`
`Highest Vehicle Speed Forward Gear Ratio (1/16 Input RPM/Output RPM)
`Checksum
`
`5.7.3
`
`ABS/TRACTION CONTROL TO POWERTRAIN INITIALIZATION MESSAGE
`
`FORMAT = (MID, BYTE1, CHECKSUM)
`PRIORITY 8
`ABS/Traction Control Initialization MID = 80
`Update Period = On request
`
`MESSAGE CONTENTS
`BYTE
`DESCRIPTION
` 0
`MID = 80
` 1
`Status Byte
`Bit
`1 = ABS installed
` 0
`1 = ASR installed
` 1
`Not used
` 2
`Not used
` 3
`Not used
` 4
`Not used
` 5
`Not used
` 6
`Not used
` 7
`Checksum
`
` 2
`
`-13-
`
`Page 13 of 18
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`FORD 1240
`
`

`

`SAE J1922 Reaffirmed SEP2000
`
`5.7.4 RETARDER TO POWERTRAIN INITIALIZATION MESSAGE
`
`FORMAT = (MID, BYTE1, BYTE2, CHECKSUM)
`PRIORITY 8
`Retarder Initialization MID = 84
`Update Period = On request by powertrain
`
` 1
`
`MESSAGE CONTENTS
`BYTE
`DESCRIPTION
` 0
`MID = 84
`Byte
`Status
`Type of Retarder
`BIT
`DESCRIPTION
` 0
`Not used
` 1
`1 = Engine Compression Release
` 2
`1 = Exhaust
` 3
`1 = Transmission Input
` 4
`1 = Transmission Output
` 5
`1 = Driveline Retarder (Electric, Hydraulic, Wet Friction)
` 6
`1 = Trailer Retarder
` 7
`Not used
`Peak Torque of Retarder (10 lb-ft/bit)
`Checksum
`
` 2
` 3
`
`5.7.5
`
`ENGINE TO POWERTRAIN INITIALIZATION REQUEST MESSAGE
`
`FORMAT = (MID, BYTE1, CHECKSUM)
`PRIORITY 7
`Initialization Request MID = 71
`Update Period = Sent by engine when any initialization message is required (i.e., power up, reset within
`ECU, etc.).
`
`MESSAGE
`BYTE
` 0
` 1
`
` 2
`
`CONTENTS
`DESCRIPTION
`MID = 71
`Status/Enable Byte
`BITS DESCRIPTION
` 0
`1 = Request Engine Initialization Message
` 1
`1 = Request Transmission Initialization Message
` 2
`1 = Request ABS/Traction Control Initialization Message
` 3
`1 = Request Retarder Initialization Message
`4-7
`For Future Use
`Checksum
`
`-14-
`
`Page 14 of 18
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`FORD 1240
`
`

`

`5.7.6
`
`TRANSMISSION TO POWERTRAIN INITIALIZATION REQUEST MESSAGE
`
`SAE J1922 Reaffirmed SEP2000
`
`FORMAT = (MID, BYTE1, CHECKSUM)
`PRIORITY 7
`Initialization Request MID = 76
`Update Period = Sent by transmission when any initialization message is required (i.e., power up, reset
`within transmission ECU, engine parameter change bit set in engine to powertrain
`message, etc.).
`
`MESSAGE CONTENTS
`BYTE
`DESCRIPTION
` 0
`MID = 76
` 1
`Status / Enable Byte
`BITS
`DESCRIPTION
` 0
`1 = Request Engine Initialization Message
` 1
`1 = Request Transmission Initialization Message
` 2
`1 = Request ABS/Traction Control Initialization Message
` 3
`1 = Request Retarder Initialization Message
`4-6
`For Future Use
` 7
`1 = Progressive Shift Disable
`Checksum
`
` 2
`
`5.7.7
`
`ABS/TRACTION CONTROL TO POWERTRAIN INITIALIZATION REQUEST MESSAGE
`
`FORMAT = (MID, BYTE1, CHECKSUM)
`PRIORITY 7
`Initialization Request MID = 81
`Update Period = Sent by ABS/traction control when any initialization message is required (i.e., power up,
`reset within control unit, engine parameter change bit set in engine to powertrain
`message, etc.).
`
`MESSAGE CONTENTS
`BYTE
`DESCRIPTION
` 0
`MID = 81
` 1
`Status/Enable Byte
`BITS
`DESCRIPTION
` 0
`1 = Request Engine Initialization Message
` 1
`1 = Request Transmission Initialization Message
` 2
`1 = Request ABS/Traction Control Initialization Message
` 3
`1 = Request Retarder Initialization Message
`4-7
`For Future Use
`Checksum
`
` 2
`
`-15-
`
`Page 15 of 18
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`FORD 1240
`
`

`

`5.7.8 RETARDER TO POWERTRAIN INITIALIZATION REQUEST MESSAGE
`
`SAE J1922 Reaffirmed SEP2000
`
`FORMAT = (MID, BYTE1, CHECKSUM)
`PRIORITY 7
`Initialization Request MID = 85
`Update Period = Sent by retarder when any initialization message is required (i.e., power up, reset within
`control unit, engine parameter change bit set in engine to powertrain message, etc.).
`
`MESSAGE CONTENTS
`BYTE
`DESCRIPTION
` 0
`MID = 85
` 1
`Status/Enable Byte
`BITS
`DESCRIPTION
` 0
`1 = Request Engine Initialization Message
` 1
`1 = Request Transmission Initialization Message
` 2
`1 = Request ABS/Traction Control Initialization Message
` 3
`1 = Request Retarder Initialization Message
`4-7
`For Future Use
`Checksum
`
` 2
`
`PREPARED BY THE SAE TRUCK AND BUS DIESEL ENGINE ELECTRONIC CONTROLS SUBCOMMITTEE
`OF THE SAE TRUCK AND BUS ELECTRICAL AND ELECTRONIC CONTROLS COMMITEE
`
`-16-
`
`Page 16 of 18
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`FORD 1240
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`

`

`SAE J1922 Reaffirmed SEP2000
`
`APPENDIX A
`
`ENGINE’S DESIRED RPM ASYMMETRY ADJUSTMENT
`
`FIGURE A1—
`
`-17-
`
`Page 17 of 18
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`FORD 1240
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`

`

`SAE J1922 Reaffirmed SEP2000
`
`Rationale—Not applicable.
`
`Relationship of SAE Standard to ISO Standard—Not applicable.
`
`Application—This document provides a development or possibly interim production communication protocol
`between engine, transmission, ABS/traction control, and retarder systems until higher speed
`communication links are established.
`
`Reference Section
`
`SAEJ1708—Serial Data Communications Between Microcomputer Systems in Heavy-Duty Vehicle
`Applications
`
`SAEJ1587—Joint SAE/TMC Electronic Data Interchange Between Microcomputer Systems in Heavy-
`Duty Vehicle Applications
`
`SAEJ1843—Accelerator Pedal Position Sensor for Use With Electronic Controls in Medium-and Heavy-
`Duty Diesel On-Highway Vehicle Applications
`
`Developed by the SAE Truck and Bus Diesel Engine Electronic Controls Subcommittee
`
`Sponsored by the SAE Truck and Bus Electrical and Electronic Controls Committee
`
`Page 18 of 18
`
`FORD 1240
`
`