Circuit Description
The brake pedal position (BPP) sensor provides an analog pedal position signal. Its output is hardwired to the electro-hydraulic power steering (EHPS) connector. The signal must be digitized and differentiated within the EHPS module to provide the necessary pedal rate signal.
The BPP sensor is a resistive sensor with a total resistance between 3-5 k ohms with a maximum current draw of less than 16 ma. The BPP sensor will output an analog signal that is referenced to 5 volt which may increase or decrease monotonically with brake pedal depression. The sensor analog output shall have a specified electrical output over a mechanical range of 32 degrees rotation of the brake pedal pivot. Out-of-range values will be provided outside of the 32 degrees range.
The powertrain control module (PCM) reads the zero adjust brake switch (ZABS) state as depressed or not depressed and reports this information to the EHPS on the GMLAN bus. When the BPP sensor signal voltage is equal to a value that represents the brake pedal is at rest, the PCM should provide a serial data message reporting that the ZABS is not depressed. When the BPP sensor signal voltage is equal to a value that represents the brake pedal has been depressed, the PCM should provide a serial data message reporting that the ZABS is depressed. When the control module detects that the BPP sensor signal does not correlate with the ZABS information, DTC C0294 is set.
DTC Descriptor
This diagnostic supports the following DTC:
DTC C0294 Brake Switch and Brake Pedal Position Sensor Correlation
Conditions for Running the DTC
| • | EHPS module in RUN mode. |
| • | Ignition switch in ACC or ON position. |
| • | Battery voltage between 12-58 volts. |
Conditions for Setting the DTC
The brake pedal position does not correlate to the ZABS switch. The ZABS switch is represented by serial data message Brake Pedal Depressed and is valid as follows:
| • | Brake Pedal Position = 0-0.98 mm (0 .038 in)/Brake Pedal Depressed = False |
| • | Brake Pedal Position = 0.98 mm (0 .038 in) -28.98 mm (1.14 in)/Brake Pedal Depressed = TRUE or FALSE |
| • | Brake Pedal Position = 28.98 mm (1.14 in) -180 mm (7 .08 in)/Brake Pedal Depressed = TRUE |
| • | Manually actuating an aftermarket installed trailer brake control module for more than 14 seconds will set DTC C0294. |
Action Taken When the DTC Sets
| • | System operation is reduced. |
| • | The SERVICE BRAKE SYSTEM message will be displayed. |
| • | Ramp the motor speed input to the commanded flow resolved from a default brake pedal position. |
| • | Stores DTC C0294 in the PCM. |
| • | History DTC C0294 will be set in PCM. |
Conditions for Clearing the DTC
| • | Brake pedal position correlation re-enters a valid state. |
| • | Using the scan tool. |
| • | A history DTC will clear after 255 consecutive ignition cycles if the condition for the malfunction is no longer present. |
Diagnostic Aids
It may be necessary to check Testing for Intermittent Conditions and Poor Connections .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step checks to see if both values are changing.
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This step checks to see which parameter was not changing.
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This step checks for proper connection of BPP sensor harness connector.
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This step checks for proper connection of stop lamp switch harness connector.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Power Steering Schematics Connector End Views Reference: Power Steering Connector End Views | |||
1 | Did you perform the Vehicle Diagnostic System Check? | Go to Step 2 | |
Do the observed readings change accordingly when the brake pedal is depressed? | Go to Diagnostic Aids | Go to Step 3 | |
Is the BPP sensor Output Volts parameter not changing along with the Brake Pedal Travel parameter? | Go to Step 4 | Go to Step 6 | |
Inspect for poor connections at the harness connector of the BPP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 7 | Go to Step 5 | |
5 |
Important: Always perform the calibration procedure for the BPP sensor. Refer to Brake Pedal Position Sensor Calibration Description and Operation . Replace the BPP sensor. Refer to Brake Pedal Position Sensor Replacement . Did you complete the replacement? | Go to Step 8 | -- |
Inspect for poor connections at the harness connector of the stop lamp switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 8 | Go to Step 7 | |
7 | Replace the stop lamp switch. Refer to Stop Lamp Switch Replacement . Did you complete the replacement? | Go to Step 8 | -- |
8 |
Does DTC C0294 reset? | Go to Step 2 | System OK |
