The anti-lock brake control module simultaneously manages the anti-lock braking and traction control in conjunction with the engine control systems to maintain vehicle control during deceleration and acceleration.
When the ignition switch is put in the RUN position, the module does a preliminary electrical check and, at approximately 12 mph (20 km/h), the hydraulic pump motor is turned on for approximately 1 half-second. Any malfunction of the anti-lock brake system disables the ABS and the traction control. The anti-lock brake warning indicator illuminates. However, the power-assist braking system functions normally.
Electronic Brake Distribution
The electronic brake distribution (EBD) controls rear brake pressure and acts as an electronic proportioning valve. It is controlled by the ABS module. When EBD is disabled, the amber ABS warning indicator and the red brake warning indicator illuminate.
Inspection And Verification
- Verify the a malfunction by operating the vehicle to duplicate the condition.
- Verify the stoplamps operate correctly by applying and releasing the brake pedal with the ignition switch in the OFF position. If the stoplamps operate correctly, proceed to the next step.
- Verify that the PRNDL operates correctly on the instrument cluster. If the PRNDL operates correctly, proceed to the next step.
- Inspect to determine if one of the following mechanical or electrical concerns apply.
If the concern remains after the inspection, connect the scan tool to the data link connector (DLC) located beneath the instrument panel and select the vehicle to be tested from the scan tool menu. If the scan tool does not communicate with the vehicle:
- check that the program card is correctly installed.
- check the connection of the Data Link Connector (DLC) to the vehicle.
- check that the ignition switch is in the RUN position.
- If the scan tool still does not communicate with the vehicle, refer to the scan tool manual.
Carry out the scan tool data link test. If scan tool responds with:
- System passed, retrieve and record the continuous diagnostic trouble codes (DTCs), erase the continuous DTCs and carry out the ABS module self-test.
If the DTCs retrieved are related to the concern, go to Anti-lock Brake System (ABS) Module Diagnostic Trouble Code (DTC) Index to continue diagnosis.
NOTEAlways retrieve the continuous DTCs after running the self-test.
NOTEIf DTC B1342 as well as other DTCs are present, REPAIR the others first before replacing the control module. Next CLEAR the DTCs and then RETRIEVE the DTCs. If DTC B1342 is still retrieved, INSTALL a new module and REPEAT the self-test.
B1342 ECU Is Defective
B1485 Brake Pedal Position (BPP) switch
B1676 Battery Pack Voltage Out of Range
B2477 Module Configuration Failure
B2900 VIN Mismatched
C1095 ABS Hydraulic Pump Motor Circuit Failure
C1145 Wheel Speed Sensor RF Input Circuit Failure
C1155 Wheel Speed Sensor LF Input Circuit Failure
C1165 Wheel Speed Sensor RR Input Circuit Failure
C1175 Wheel Speed Sensor LR Input Circuit Failure
C1233 Wheel Speed LF Input Signal Missing
C1234 Wheel Speed RF Input Signal Missing
C1235 Wheel Speed RR Input Signal Missing
C1236 Wheel Speed LR Input Signal Missing
C1805 Mismatched PCM and/or ABS Module
U1009 SCP (J1850) Invalid or Missing Data for Engine Torque
U1027 SCP (J1850) Invalid or Missing Data for Engine Torque
U1262 SCP (J1850) Invalid or Missing Data for Engine Torque
Panic Assist Braking (ABS) With Traction Control)
Panic assist braking functions by fully applying the brakes during a panic stop, using a specially developed pressure/pedal movement mechanism. Depending on vehicle speed, if brake pedal stroke is more rapid than normal, the brake booster automatically applies full brake boost. Panic assist is disabled when the driver releases the brake pedal.
The ABS module communicates with the Powertrain Control Module (PCM) to assist with traction control. At speeds under 62 mph (100 km/h), when the drive wheels lose traction and begin to spin, the stability assist module requests the PCM to reduce engine torque while simultaneously applying and releasing the appropriate brake caliper(s) to maintain traction. The PCM accomplishes this by minor incremental timing changes and fewer fuel injector pulses until the stability assist module ends the request. The request ends when the driven wheel speed returns to the desired speed. After the vehicle speed exceeds 62 mph (100 km/h), the traction control is accomplished only through the PCM torque control.
The stability assist control switch allows the driver to control the use of the stability assist system. This is independent of the ABS function, which cannot be switched off by the driver. The stability assist system status is indicated by a stability assist warning lamp in the stability assist/traction control switch. An illuminated stability assist/traction control switch indicates that the stability assist system is switched off. In vehicles with a message center, the message AdvTrac Off, T/C ON is displayed. The anti-lock brake function continues to work as designed unless the yellow anti-lock brake warning indicator is also illuminated. Normal braking function always occurs, unless the red brake warning indicator is illuminated.
When stability assist activates, any of the following can occur:
- Some drivers may notice a slight movement of the brake pedal when the system checks itself. The brake pedal moves when an active test of the brake booster is run. During this test a small amount of pressure is generated at the master cylinder, but no pressure is generated in the brake calipers.