Thoroughly inspect connections or circuitry that may cause an intermittent malfunction. Refer to Testing for Electrical Intermittents, Testing for Intermittent and Poor Connections, Connector Repairs and Wiring Repairs in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
- 4: This step tests for voltage supplied to the EBCM from the PCM.
- 5: This step tests for a shorted resistor in the PCM or a short to voltage within the requested torque circuit by verifying that a large voltage drop occurs when a test lamp is connected in parallel with the DMM.
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| Schematic Reference: ABS Schematics Connector End-View Reference: ABS Connector End Views | ||||
| 1 | Did you perform the ABS Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - ABS | |
| 2 | Is DTC P0856 set? | Go to Step 3 | Go to Diagnostic Aids | |
| 3 | Use a scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text. Does DTC P0856 set? | Go to Step 4 | Go to Diagnostic Aids | |
| 4 | Turn OFF the ignition. Disconnect from the electronic brake control module (EBCM), the harness connector containing the requested torque signal circuit. Turn ON the ignition. Use a DMM in order to measure the voltage between the requested torque signal circuit and a good ground. Does the voltage measure greater than the specified value? | 4.75 V | Go to Step 5 | Go to Step 8 |
| 5 | With the DMM still connected to monitor the requested torque signal circuit, connect one end of a test lamp to a good ground. Connect the other end of the test lamp to the positive lead of the DMM. Does the voltage measure less than the specified value? | 0.15 V | Go to Step 6 | Go to Step 9 |
| 6 | Turn OFF the ignition. Install a J 39700 universal breakout box and a J 39700-325 adapter cable. See Special Tools . Install the equipment between the EBCM and the EBCM harness connector. Start the engine. Use the DMM in order to measure the Hz frequency of the requested torque signal. Does the Hz frequency of the requested torque signal measure within the specified range? | 121-134 Hz | Go to Step 7 | Go to Step 11 |
| 7 | Use the DMM in order to measure the duty cycle of the requested torque signal circuit. Does the duty cycle of the requested torque signal measure within the specified range? | 40-95% | Go to Step 12 | Go to Step 13 |
| 8 | Test the requested torque signal circuit for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 10 | |
| 9 | Test the requested torque signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 12 | |
| 10 | Inspect for poor connections at the harness connector of the 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 14 | Go to Step 12 | |
| 11 | 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 14 | Go to Step 13 | |
| 12 | IMPORTANT: Perform the set up procedure for the PCM. Replace the powertrain control module (PCM). Refer to Powertrain Control Module (PCM) Replacement in Engine Controls - 4.8L, 5.3L and 6.0L.Did you complete the replacement? | Go to Step 14 | ||
| 13 | IMPORTANT: Following EBCM replacement, use the scan tool to perform Tire Size Calibration procedure. Replace the EBCM. Refer to Electronic Brake Control Module Replacement .Did you complete the replacement? | Go to Step 14 | ||
| 14 | Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text. Does DTC P0856 reset? | Go to Step 4 | System OK | |
| IMPORTANT |
|---|
| Perform the set up procedure for the PCM. |
| IMPORTANT |
|---|
| Following EBCM replacement, use the scan tool to perform Tire Size Calibration procedure. |
DTC C0298 or P0856
Circuit Description
The EBCM performs several self-tests for any internal problems which may affect proper operation.
Conditions for Running the DTC
- The ignition is ON.
- The engine is running at a rate greater than 450 RPM.
Conditions for Setting the DTC
The EBCM detects an internal malfunction.
Action Taken When the DTC Sets
The following actions may occur.
- The EBCM disables the ABS/DRP.
- The ABS indicator turns ON.
- The brake warning indicator turns ON.
Conditions for Clearing the DTC
Certain failures that may cause this DTC to set cannot be cleared. Other failures that may cause this DTC to set may be cleared, at least temporarily, by using the scan tool Clear DTCs function.
Diagnostic Aids
Replace the EBCM if this DTC continues to set intermittently.
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Did you perform the ABS Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - ABS |
| 2 | Use a scan tool in order to clear the DTCs. Can the DTC be cleared? | Go to Step 3 | Go to Step 4 |
| 3 | Start the engine and allow the engine to idle. Does the DTC reset? | Go to Step 4 | Go to Diagnostic Aids |
| 4 | 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 5 | |
| 5 | Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text. Does the DTC reset? | Go to Step 3 | System OK |
| IMPORTANT |
|---|
| Following EBCM replacement, use the scan tool to perform the Tire Size Calibration procedure. |
DTC C0550
Symptoms - Antilock Brake System
| IMPORTANT | The following steps must be completed before using the symptom tables. Perform the ABS Diagnostic System Check before using the symptom tables in order to verify that all of the following are true: There are no DTCs set. The control modules can communicate via the serial data link. Review the system description and operation in order to familiarize yourself with the system functions. Refer to ABS Description and Operation (8600 GVW or less except PHT) or ABS Description and Operation (Over 8600 GVW or PHT) . |