The PCM (computer) diagnostic port is located below the steering column.
Do NOT disconnect the battery, or the stored codes will be erased.
Have a pen and paper ready to record the resulting code(s).
1. Key off, short pins A & B together using a bent, bare metal paper clip (plugged into the pins).
2. Turn the KEY ON, but do NOT start.
3. Observe the Service Engine light, it will start flashing.
4. First it will flash once ("1"), followed by two flashes ("2"), which represents a "12" and indicates the diagnostics are working.
5. After flashing "12" (1 – 2) three times, stored codes begin being displayed. Start counting & recording.
6. The first digit will flash (count) then the 2nd digit. It will do this 3 times before going to the next code.
7. When it has displayed all codes stored, it repeats the cycle, beginning with the "12" again.
8. You can now power off and remove the clip.
9. Articles that translate the codes are listed below:
88-91 VIN C http://www.pontiacbonnevilleclub.com/fo ... =51&t=1624
1992 VIN L http://www.pontiacbonnevilleclub.com/fo ... =51&t=1625
92-93 VIN 1 http://www.pontiacbonnevilleclub.com/fo ... =51&t=1626
NOTE: This procedure will display any codes stored since last cleared. So you may see some “old” codes the first time. Record them all, etc. This allows you to disconnect the battery to clear any codes stored in the PCM. If/when the Service Engine/Check Engine light illuminates again you may repeat this procedure and obtain the most current codes.
