Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCADILLAC1991SEVILLE STSREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROLS - TESTS W/CODESDISPLAYING TROUBLE CODES
1991 Cadillac Seville STS
Displaying Trouble Codes
1991 Cadillac Seville STSSECTION Displaying Trouble Codes
- Powertrain Control Module (PCM), Body Control Module (BCM) and Supplemental Inflatable Restraint (SIR) trouble codes automatically display after system enters self-diagnostics.
- PCM trouble codes are displayed first. They appear in ascending (3-digit) numerical order and are prefixed with the letter "E". For complete list of available PCM trouble codes, see PCM TROUBLE CODES table. If no PCM trouble codes are stored, a NO PCM CODES message will be displayed.
- BCM trouble codes are displayed immediately following the PCM trouble code display. BCM trouble codes appear in ascending (3-digit) numerical order and are prefixed with the letter "B". For complete list of available BCM trouble codes, see BCM TROUBLE CODES table. If no BCM trouble codes are stored in memory, a NO BCM CODES message is displayed.
- SIR system trouble codes are displayed last. These codes are displayed in ascending (3-digit) numerical order and are prefixed with the letter "R". The SIR system is not covered in this article, see the AIR BAG RESTRAINT SYSTEM
article in the ACCESSORIES/SAFETY EQUIP section.NOTE: If no codes are present or the communication link between a component and the BCM is not operating, a NO X DATA message will be displayed, indicating the BCM could not communicate with the particular component (X = the particular component).
- During the actual trouble codes display cycle, all BCM and PCM trouble codes are followed by the letter "C" or "H". The letter "C" stands for current and indicates a trouble code related fault presently exists. The letter "H" stands for history and indicates the system failure was not present during the last key cycle but was present during one of the previous 50 key cycles. For example: Code B410H is BCM code number 410, set in response to a malfunction that occurred in the past (history).
- At any time during the display of trouble codes, if the RESET/RECALL button on the DIC is depressed, the system will exit service mode and go back to normal vehicle operation.
NOTE:
After all trouble codes have been displayed, depressing the OFF button on the ECC will activate a repeat of the trouble code display.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.