Test Description

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

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.

DTC C0298 or P0856

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 toTesting for Intermittent Conditions and Poor Connections andConnector 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