Anti-Lock Brake Systems (ABS)

338

TM 9-2320-312-24-2

Troubleshooting Section

"Fan Override Switch"

transmission shift points

"Exhaust Brake Switch"

engine rpm

"Diagnostic Enable Switch"

load

"A/C High Pressure Switch"

The sensors for power train control provide signals

to the vehicle control module of the "Powertrain Data

"A/C Fan Request Switch"

Link". The vehicle control module of the "Powertrain

Data Link" then communicates with the engine

ECM. The engine ECM receives a request from the

Any combination of the following systems may be

"Powertrain Data Link". The engine ECM responds

installed together on a vehicle:

by momentarily limiting the following characteristics:

Traction Control

engine rpm

Transmission Control

torque

ABS

both engine rpm and torque

Switch Information

The presence of an active J1939 data link circuit

can be determined by observing the "Powertrain

The required components are installed at the OEM

Status" parameter on ET. The ET status screen

when the vehicle is built.

will display "INSTALLED" if the proper Personality

Module is installed on the ECM, and there is no

Powertrain data link sensors, off-engine control

action that is being requested at that time by any of

modules, and wiring are installed by the vehicle

the control modules on the data link.

OEM. Questions that relate to the hardware

configuration, software, and installation should be

If an action is being requested by one of the

referred to the vehicle OEM.

vehicle control modules, the display will indicate the

control that is making the request (traction control

The J1939 refers to the standard for data link

or transmission control) or a combination of the two

communications of the Society of Automotive

(traction control and transmission control). Power

Engineers Inc.. The ECM has a customer

train control is also displayed in the upper right

programmable parameter that is called "Powertrain

hand corner of the display status screen.

Data Link" which can be programmed to either of

the following options:

J1939 Data Link

J1939

SAE J1939 is standard on the Full Feature ECM.

NONE

The SAE J1939 is not available on the Basic ECM.

All 3126B truck engines ((S/N: 8YL)) have the SAE

J1939 Data Link.

Anti-Lock Brake Systems (ABS)

If the "Truck Manufacturer" parameter is

The J1939 data link may be used by an anti-lock

programmed to "GM", then the "Powertrain Data

brake system (ABS) in order to disable the exhaust

Link" parameter defaults to "J1939". If the truck

brake when the anti-lock brake control determines

manufacturer is programmed to "OTHER", then

that the exhaust brake should be disabled. This is

the default is "NONE". If the data link is required,

usually achieved when the ABS system is active.

then the "Powertrain Data Link" parameter must be

programmed to "J1939".

Traction Control Systems

If the "Truck Manufacturer" parameter is

Loss of traction is determined by sensors on the

programmed to "GM" then the "J1939" Data Link is

vehicle that are mounted near the wheels. These

self-adjusting.

sensors are also used by the ABS system. Typically,

a system with traction control includes anti-lock

Note: The "Service Engine Soon lamp" will not be

brakes.

illuminated if a message is not broadcast over the

data link for a period of 5 hours.

Transmission Control

The following characteristics are determined by a

vehicle speed sensor in the transmission: