For 1990-2009 cars

### Circuit Description

The electrically erasable programmable read-only memory (EEPROM) check sum error detection is handled inside the control module. No external circuits are involved.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B1009 EEPROM Checksum Mismatch

### Conditions for Running the DTC

The module runs the program to detect an EEPROM checksum error after each wake-up. The only requirements are battery positive voltage and ground. This program runs even if the voltage is out of the valid operating range.

### Conditions for Setting the DTC

The module retains an inverse copy of the digital value stored in certain blocks of memory in the EEPROM. The 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 module reverts to base operation values programed for those blocks of data that have failed the check sum test. The blocks of data that have not failed the check sum test are not affected.

### Conditions for Clearing the DTC

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

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

### Diagnostic Aids

• | This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.

• | If this DTC is retrieved as both a current and history DTC, replace the module.

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 a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. Retrieve DTCs.

Is DTC retrieved as a current DTC?

Go to Step 3

Go to Diagnostic Aids

3 | Replace the module setting the DTC as current. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 4 | --
4 |

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