Diagnostic Aids

When DTC C1604 is displayed on the scan tool, it should be followed by 2 additional numbers, which should be documented along with any other DTCs that may be displayed.
Repair the low voltage, driveability, or other electrical complaints first, prior to performing DTC C1604.
Ensure the integrity of the connection between the EBCM and the brake pressure modulator valve (BPMV) is secure, tight, and free of corrosion, leaks, and/or damage.

DTC C1604

Step	Action	Yes	No
1	Did you perform the Diagnostic System Check - Vehicle?	Go to Step 2	Go to Diagnostic System Check - Vehicle
2	Install the scan tool. Turn ON the ignition, with the engine OFF. Using the scan tool, observe the DTC information. Does the scan tool display any DTCs set in current or history data other than DTC C1604?	Go to Diagnostic Trouble Code (DTC) List - Vehicle	Go to Step 3
3	Turn the ignition switch OFF. Disconnect the harness from the electronic brake control module (EBCM). Check the connectors for damage, corrosion, and terminal contact. Were any problems found?	Go to Step 4	Go to Step 5
4	Repair as needed. Did you find and correct the condition?	Go to Step 6	-
5	Replace the EBCM. Refer to Brake Modulator Assembly Replacement . Did you complete the replacement?	Go to Step 6	-
6	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 2	System OK