Circuit Description
The powertrain control module (PCM) converts the signal from the vehicle speed sensor (VSS) to a 128k pulses/mile signal. The electronic brake control module (EBCM) uses the vehicle speed signal from the PCM to calculate the rear wheel speed.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The vehicle speed is greater than 13 km/h (8 mph). |
Conditions for Setting the DTC
| • | The EBCM detects an open or shorted vehicle speed signal circuit for 500 milliseconds. |
| • | The EBCM detects the absence of the vehicle speed signal for 5 seconds. If more than one absent wheel speed sensor signal is detected, the condition must be present for 120 seconds to set DTCs. |
| • | The EBCM detects an erratic vehicle speed signal for 200 milliseconds. |
Action Taken When the DTC Sets
| • | The EBCM disables the ABS/DRP. |
| • | The ABS indicator turns ON. |
| • | The brake warning indicator turns ON. |
The actions above are maintained during subsequent ignition cycles until the EBCM completes a power up self-test. This test concludes when the vehicle achieves a speed greater than 13 km/h (8 mph) and the wheel speeds are verified by the EBCM.
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 Testing for Intermittent Conditions and Poor Connections , Connector Repairs , Testing for Electrical Intermittents and to Wiring Repairs in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests for a voltage signal from the PCM.
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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 | ||||
1 | Did you perform the ABS Diagnostic System Check? | -- | Go to Step 2 | |
2 |
Does the DTC set? | 13 km/h (8 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 for the entire time that 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 powertrain control module (PCM). 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: Perform the setup procedure for the PCM. Replace the powertrain control module (PCM). Refer to Powertrain Control Module Replacement in Engine Controls - 4.2L or Powertrain Control Module Replacement in Engine Controls - 4.8L, 5.3L, and 6.0L. Did you complete the replacement? | -- | Go to Step 10 | -- |
10 |
Does the DTC reset? | -- | Go to Step 3 | System OK |
