GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2002 🢒 DeVille 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 DTC B1009

Circuit Description

The EEPROM check sum error detection is handled inside the auxiliary HVAC control module.

Conditions for Running the DTC

The microprocessor runs the program to detect a check sum error after each "power up". 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 microprocessor retains an inverse copy of the digital value stored in certain blocks of memory in the EEPROM. The microprocessor 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 microprocessor sets this DTC.

Action Taken When the DTC Sets

The microprocessor 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 MIL/DTC

The DTC clears when the microprocessor runs a successful check sum test of the EEPROM.

Diagnostic Aids
    • Disconnecting and reconnecting the auxiliary HVAC control module connector with the ignition ON will set this DTC.
    • An intermittent loss of battery positive voltage or ground may set this DTC. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Step

Action

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

1

Did you perform the HVAC Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Automatic

2
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition.
  3. Remove the battery positive voltage (Hot at All Times) fuse to the auxiliary HVAC control module.
  4. Install the battery positive voltage (Hot at All Times) fuse to the auxiliary HVAC control module.
  5. Turn ON the ignition, with the engine OFF.

Does the DTC reset?

Go to Step 3

Go to Diagnostic Aids

3

Inspect for poor connections at the harness connector of the auxiliary HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 5

Go to Step 4

4

Replace the auxiliary HVAC control module. Refer to Auxiliary Heater and Air Conditioning Control Module Replacement .

Did you complete the replacement?

Go to Step 5

--

5
  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