Chart A6 - Won't Flash Code 12
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- 1) This step checks for short to battery voltage in wire to terminal "C" or faulty light driver. Normal reading is 9-11 volts.
- 2) This step checks to see if problem is related to the ECM or light driver. Grounding terminal "C" should turn light off.
- 3) Grounding terminal "G" at ECM and finding light on indicates an open in circuit No. 487 to terminal "C" of light driver. Grounding terminal "G" should turn light off.
- 4) This step checks for open in circuit No. 451 from ECM to test terminal in ALDL connector. The light should flash Code 12 when terminal No. 5 is grounded.
- 5) This checks for proper voltage supply to ECM. Both should read greater than 9 volts. Terminal "C" is ignition and terminal "R" is constant battery voltage for long term memory.
- 6) This test checks for bad ground in ECM. Terminals "A" and "U" are connected together inside ECM.
- 7) This step distinguishes between a faulty ECM and PROM. Normal response is for Code 51 to flash even though PROM is not installed in ECM. If there is no Code 51, ECM is faulty.
NOTE:
Check fuses that supply power to ECM. Repeat Diagnostic Circuit Check after any repair.