For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptor

DTC B1009: EEPROM Checksum Mismatch/Error

### Circuit/System Description

The electrically erasable programmable read-only memory (EEPROM) check sum error detection is handled inside the control module.

### Conditions for Running the DTC

The control module runs the program to detect an EEPROM checksum error after each wake-up. The only requirements are battery positive voltage and ground.

### Conditions for Setting the DTC

The control module retains an inverse copy of the digital value stored in certain blocks of memory in the EEPROM. The control module then reads the information from those certain blocks and adds the stored inverse value to the current value. If they do not equal 0, the module sets the DTC.

### Action Taken When the DTC Sets

The control module reverts to base operation values programmed for those blocks of data that have failed the check sum test.

### Conditions for Clearing the DTC

• | A current DTC clears when the malfunction is no longer present.

• | A history DTC clears when the control module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

### Reference Information

#### Schematic Reference

Data Communication Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Data Link Communications Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool References

Control Module References for scan tool information

### Circuit/System Verification

1. With a scan tool, clear the DTC.

⇒ | If the DTC will not clear, replace the module that set the DTC.

2. Ignition OFF, remove the scan tool, open and close the drivers door.
3. Wait 60 seconds, verify DTC B1009 is not set.

⇒ | If the DTC is set, replace the module.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for control module replacement, setup, and programming