Chart A6: Won't Flash Code 12 Test
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NOTE:
The following step numbers refer to the numbers in the accompanying flow chart(s).
- This step checks for short to battery voltage in wire to term. "C" or faulty lamp driver. Normal reading is 9 to 11 volts.
- This step checks to see if problem is related to the ECM or lamp driver. Grounding term. "C" should turn lamp "OFF".
- Grounding term. "G" at ECM and finding light "ON" indicates an open in the wire to term."C" of lamp driver. Grounding term. "G" should turn lamp "OFF".
- This step checks for open in wire from ECM to test terminal in ALDL connector. The lamp should flash Code 12 when term. 5" is grounded.
- This checks for proper voltage supply to ECM, both should read over 9 volts. Term. "C" is ignition and term. "R" is constant battery for long term memory.
- This test checks for bad ground in ECM. Terms. "A" and U" are connected together in the ECM.
- This step distinguishes between a faulty ECM and PROM. Normal response is for Code 51 to flash even though the PROM is not installed in the ECM. If no Code 51, ECM is faulty.