Circuit Description
The powertrain control module (PCM) converts the data from the vehicle speed sensor to a 128k pulses/mile signal. The electronic brake control module (EBCM) uses the vehicle speed signal from the PCM in order to calculate the rear wheel speed.
Conditions for Running the DTC
C0235
The ignition is ON.
C0236 and C0237
| • | The ignition is ON. |
| • | The vehicle speed is greater than 32 km/h (20 mph) when the brake is applied or 19 km/h (12 mph) when the brake is released. |
P1504
| • | The ignition is ON. |
| • | The vehicle is not moving. |
Conditions for Setting the DTC
C0235
The EBCM detects low voltage on the vehicle speed signal circuit for 500 milliseconds.
C0236
The rear wheel speed signal is less than 6 km/h (4 mph) for 5 seconds, or 120 seconds in order to set multiple missing sensor signal DTCs.
C0237
The EBCM detects an erratic rear wheel speed signal for 105 milliseconds.
P1504
The PCM detects low voltage on the vehicle speed signal circuit for 45 seconds.
Action Taken When the DTC Sets
If equipped, the following actions occur:
| • | The EBCM disables the ABS/TCS/DRP. |
| • | The ABS indicator turns ON. |
| • | The TRACTION OFF indicator turns ON. |
| • | The red brake warning indicator turns ON. |
Conditions for Clearing the DTC
| • | Repair the condition responsible for setting the DTC. |
| • | Use a scan tool in order to clear the DTC. |
| • | After the DTC is cleared and the ignition is ON, the ABS indicator may remain ON until the EBCM completes a power-up self-test. This test concludes when the vehicle reaches a speed greater than 13 km/h (8 mph) and the wheel speeds are verified by the EBCM. |
Diagnostic Aids
Thoroughly inspect connections or circuitry that may cause an intermittent malfunction. Refer to the following:
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests for a voltage signal from the PCM.
-
This step tests for a missing or erratic vehicle speed signal from the PCM. An assistant may be required to perform this test.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Antilock Brake System Schematics Connector End View Reference: Antilock Brake System Connector End Views Connector End View Reference: Powertrain Control Module Connector End Views in Engine Controls--4.3L Connector End View Reference: Engine Controls Connector End Views in Engine Controls--4.3L | ||||
1 | Did you perform the ABS Diagnostic System Check? | -- | Go to Step 2 | |
2 |
Does the DTC set? | -- | Go to Step 3 | Go to Diagnostic Aids |
Does the voltage measure greater than the specified value? | 10 volts | Go to Step 4 | Go to Step 7 | |
Does the voltage measure within the specified range the entire time the driveshaft is rotating? | 5-7 volts | Go to Step 5 | Go to Step 7 | |
5 | Inspect for poor connections at the harness connector of the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 6 |
6 |
Important: Following EBCM replacement, use the scan tool to perform the Tire Size Calibration procedure. Replace the EBCM. Refer to Electronic Brake Control Module Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- |
7 | Test the vehicle speed signal circuit for an open, a short to ground or a short to voltage. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 8 |
8 | Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9 |
9 |
Important: Perform the setup procedure for the PCM. Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls - 4.3L. Did you complete the replacement? | -- | Go to Step 10 | -- |
10 |
Does the DTC reset? | -- | Go to Step 3 | System OK |
