Circuit Description
The PCM or vehicle speed sensor buffer (diesel) converts the data from the vehicle speed sensor to a 128k pulses/mile signal. The EBCM uses the vehicle speed signal from the PCM or VSSB 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
| • | The EBCM disables the ABS. |
| • | The ABS indicator turns ON. |
Conditions for Clearing the DTC
The conditions for setting the DTC are no longer present and you use the scan tool Clear DTCs function.
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 or the VSS buffer.
-
This step tests for a missing or erratic vehicle speed signal from the PCM or VSS buffer. An assistant may be required in order to perform this test.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Antilock Brake System Schematics | ||||
1 | Did you perform the ABS Diagnostic System Check? | -- | Go to Step 2 | |
2 |
Does the DTC set? | 19 km/h (12 mph) | Go to Step 3 | Go to Diagnostic Aids |
Does the voltage measure greater than the specified value? | 10 V | 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 V | 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 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 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 or vehicle speed sensor (VSS) buffer. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9 |
9 |
Important: For vehicles equipped with gasoline engines, perform the setup procedure for the PCM. Replace the PCM or VSS buffer. Refer to Powertrain Control Module Replacement in Engine Controls - 4.3L, Powertrain Control Module Replacement in Engine Controls - 5.0L and 5.7L, Vehicle Speed Sensor Module Replacement in Instrument Panel, Gages, and Console or Powertrain Control Module Replacement in Engine Controls - 8.1L. Did you complete the replacement? | -- | Go to Step 10 | -- |
10 |
Does the DTC reset? | -- | Go to Step 3 | System OK |
