For 1990-2009 cars

### Circuit Description

The internal fault detection is handled inside the control module. No external circuits are involved.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C1604 ECU EEPROM

### Conditions for Running the DTC

The microprocessor runs the program to detect an internal fault when power up is commanded. The only requirements are voltage and ground. This program runs even if the voltage is out of the valid operating range.

### Conditions for Setting the DTC

• | The control module detects an internal write malfunction.

• | The control module detects an internal checksum malfunction

### Action Taken When the DTC Sets

• | The SSPS warning light will illuminate.

• | Power steering assist will default to partial steering assist.

• | The microprocessor refuses all additional inputs.

### Conditions for Clearing the DTC

• | The SSPS warning lamp will turn OFF when conditions for the fault are no longer present.

• | Use a scan tool in order to clear the DTC.

### Diagnostic Aids

Check for the following conditions if a history or intermittent DTC is indicated.

• | A poor connection at the speed sensitive power steering (SSPS) control module. Inspect the harness connectors for backed out terminals, improper mating, improperly formed or damaged terminals, and poor terminal to wire connections.

• | A damaged wiring harness. Inspect the wiring harness for damages. If the wiring harness appears to be in good condition, observe the display on the DMM while moving the connectors and wiring harnesses related to the circuits. A change in the DMM display during the test will indicate the location of the fault.

• | For additional information, refer to Testing for Intermittent Conditions and Poor Connections .

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Steering Assist Schematics Connector End View Reference: Steering Assist Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. Use a scan tool in order to clear the DTCs.
4. Operate the vehicle within Conditions for Running the DTC.

Did the DTC fail this ignition?

Go to Step 3

Go to Step 4

3 | Replace the speed sensitive power steering (SSPS) control module. Refer to Power Steering Control Module Replacement . Did you complete the replacement? | Go to Step 4 | --
4 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2