Pinpoint Test H: DTC C1288
Anti-Lock Control
Pinpoint Tests
Pinpoint Test H: DTC C1288
Normal Operation
The brake pedal 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 must be installed.
- DTC C1288 (Pressure Transducer Main/Primary Input Circuit Failure) - The pressure transducer signal sent to the ABS module is checked against other ABS module brake pedal inputs and if it does not agree with those inputs, DTC C1288 is set. Also, if the transducer is open, shorted to ground or shorted to voltage, DTC C1288 will be set.
This pinpoint test is intended to diagnose the following:
- HCU
- ABS module
PINPOINT TEST H: DTC C1288
NOTICE: Use the Flex Probe Kit for all test connections to prevent damage to the wiring terminals. Do not use standard multi-meter probes.
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H1 MONITOR THE PCM BRAKE ON/OFF (BOO) PID
- Connect the scan tool.
- Ignition ON.
- 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
GO to H2.
No
RETRIEVE any PCM DTCs. REFER to Computers and Control Systems Information for non-communication DTCs and REFER to Information Bus for any communication DTCs.
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H2 MONITOR THE ABS MODULE MASTER CYLINDER PRESSURE (MC_PRES) PID
NOTE: To obtain the most accurate reading, it is recommended to use a graph display for this PID.
NOTE: Residual pressure may be present in the brake lines, contributing to a possible data spike within the first second of brake pedal application. This is a normal condition.
- Enter the following diagnostic mode on the scan tool: DataLogger - ABS Module.
- Steadily press and release the brake pedal while monitoring the MC_PRES PID.
- Does the PID smoothly increase with firm pressure on the brake pedal and then smoothly decrease with the brake pedal released, without any spikes in the data?
Yes
GO to H3.
No
GO to H4.
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H3 ROAD TEST THE VEHICLE AND MONITOR THE ABS MODULE MC_PRES PID WHILE DRIVING THE VEHICLE
NOTE: To obtain the most accurate reading, it is recommended to use a graph display for this PID.
- Enter the following diagnostic mode on the scan tool: DataLogger - ABS Module.
- Road test the vehicle and have an assistant monitor the MC_PRES PID.
- Does the PID smoothly increase with firm pressure on the brake pedal and then smoothly decrease with the brake pedal released, without any spikes in the data?
Yes
The system is operating correctly at this time. CLEAR the DTCs. REPEAT the self-test.
No
GO to H4.
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H4 ISOLATE THE HCU
NOTE: To obtain the most accurate reading, it is recommended to use a graph display for this PID.
- Install a new HCU. Refer to Hydraulic Control Unit (HCU) Service and Repair. Calibrate the ABS module. Follow the scan tool directions for the calibration procedure.
- Enter the following diagnostic mode on the scan tool: DataLogger - ABS Module.
- Steadily press and release the brake pedal while monitoring the MC_PRES PID.
- Does the PID smoothly increase with firm pressure on the brake pedal and then smoothly decrease with the brake pedal released, without any spikes in the data?
Yes
The concern has been corrected. RETURN the vehicle to the customer.
No
INSTALL a new ABS module, REFER to Anti-Lock Brake System (ABS) Module Service and Repair. CLEAR the DTCs. REPEAT the self-test with the brake pedal not applied.
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