For 1990-2009 cars

### Circuit Description

This DTC identifies a possible malfunction within the electronic brake control module (EBCM).

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C1604 ECU Malfunction

### Conditions for Running the DTC

Ignition is in the ON position.

### Conditions for Setting the DTC

DTC C1604 will set when a possible internal component/microprocessor problem may exist.

### Action Taken When the DTC Sets

• | DTC C1604 is stored.

• | The ABS and DDRP are disabled

• | The ABS warning lamp and brake warning lamp are turned ON.

• | The solenoid relay opens, removing power from the pump motor and solenoids.

### Conditions for Clearing the DTC

• | If the conditions that set DTC C1604 are no longer present, the DTC may be cleared by using the proper scan tool.

• | The DTC that has not occurred in 100 drive cycles will be cleared from the history data.

### 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.

Step | Action | Yes | No
--- | --- | --- | ---
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Install the scan tool.
2. Turn ON the ignition, with the engine OFF.
3. 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 |

1. Turn the ignition switch OFF.
2. Disconnect the harness from the electronic brake control module (EBCM).
3. 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 Pressure Modulator Valve Assembly Replacement . Did you complete the replacement? | Go to Step 6 | --
6 |

1. Use the scan tool in order to clear the DTCs.
2. 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