C1288

Anti-Lock Control

Pinpoint Test J: DTCs C1288, C1440 and C1446

Refer to Wiring Diagram Set 42, Vehicle Dynamic Systems for schematic and connector information. Diagrams By Number

Normal Operation

The brake pressure transducer is integral to the Hydraulic Control Unit (HCU). The transducer sends a signal to the ABS module that varies in relation to the amount of pressure applied to the brake pedal. The more pressure that is applied, the greater the signal sent to the ABS module. If a new transducer needs to be installed, then a new HCU (Hydraulic Control Unit) must be installed.

- DTC C1288 (Pressure Transducer Main/Primary Input Circuit Failure)- If the transducer is open, shorted to ground or shorted to voltage, DTC C1288 will be set.

- DTC C1440 (Pressure Transducer Main/Primary Signal Faulted)- The signal that the brake pressure transducer sends to the ABS module is checked against other inputs to the module and if it does not agree with those inputs, DTC C1440 is set.

- DTC C1446 (BOO (Brake ON/OFF) Plausibility Fault(s))- During normal operation, the ABS module compares the brake ON/OFF High Speed Controller Area Network (HS-CAN) message to the HCU (Hydraulic Control Unit) internal pressure transducer. If the brake ON/OFF message does not match the HCU (Hydraulic Control Unit) transducer, DTC C1446 will be set.

This pinpoint test is intended to diagnose the following:

- HCU (Hydraulic Control Unit)

- ABS module

PINPOINT TEST J : DTCs C1288, C1440 AND C1446

J1 MONITOR THE ABS MODULE BRAKE ON/OFF (BOO_ABS) PID

- Connect the scan tool.

- Ignition ON.

- Enter the following diagnostic mode on the scan tool: DataLogger- ABS.

- Press and release the brake pedal while monitoring the BOO_ABS PID.

Does the PID switch to ON with the brake pedal pressed and then to OFF with the brake pedal released?

Yes
GO to J3.

No
GO to J2.

J2 MONITOR THE PCM BRAKE ON/OFF (BOO) PID

- Enter the following diagnostic mode on the scan tool: DataLogger- PCM.

- Press and release the brake pedal while monitoring the BOO PID.

Does the PID switch to ON with the brake pedal pressed and then to OFF with the brake pedal released?

Yes
REFER to Information Bus to continue diagnosis of the HS-CAN (High Speed Controller Area Network).

No
REFER to Lighting and Horns to continue diagnosis of the stoplamp switch and stoplamps.

J3 MONITOR THE ABS MODULE BRAKE PRESSURE (BRAKPRESS) PID

- Enter the following diagnostic mode on the scan tool: DataLogger- ABS.

NOTE: It is normal for the brake pressure (BRAKPRES) PID to occasionally spike high due to the test pulse sent to the pressure sensor by the ABS module.

NOTE: Negative brake pressure is considered normal due to the signal is not calibrated.

- With the brake pedal not applied, record the pressure displayed by the BRAKPRES PID.

Is the initial brake pressure greater than -1551 kPa (-225 psi) with the brake pedal not applied?

Yes
The condition is not present at this time. CLEAR the DTCs. CYCLE the ignition key. REPEAT the self-test.

No
INSTALL a new HCU (Hydraulic Control Unit). REFER to Hydraulic Control Unit (HCU) . REPEAT the self-test.