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If you own a C5, your ‘legend' has it's own powerful diagnostic capabilities built into the car, accessed through DIC. The C5 has 11 microprocessors that report to the PCM. If any of the fault codes are current faults i.e., have a ‘C' behind them, the troubleshooting procedure is found in the GM service manual. Fault codes for these microprocessors can be accessed by performing the following function:

Turn the key to the ON position, but don't start the engine. Clear any present messages by pressing the RESET button. Hold the OPTIONS button down, and press the FUEL button 4 times. This will get you into the CODES section of the DIC. The computer will automatically display all the codes your car has created. It will cycle through each code every 3 seconds. Any code that ends in H is a history code (something that has occurred in the past) but is fine now. Once the computer has finished going through all of it's codes, press RESET to enter Manual Configuration mode. It should start with a module and show "NO CODES" or "# CODES".

To optionally reset the codes once in manual mode, press and hold RESET until it displays "NO CODES". Press OPTIONS to go to the next module. Repeat the steps in this paragraph until you have reset the codes in all the computer modules.

NOTE !! Only reset the codes IF you want to - it is NOT necessary to do this.

For the full list of codes, go to http://www.stengel.net/diccodes.htm