Chart A-6, "SES" Light On, Won't Flash Code 12
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- This step checks for short to battery voltage in wire to terminal "C" or faulty light driver. Normal reading is 9-11 volts.
- This step checks to see if problem is related to the ECM or light driver. Grounding terminal "C" should turn light off. If it does, problem is related to ECM and its wiring. If it does not, fault is related to light driver and its wiring. Light driver is located in wiring harness near ECM.
- 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.
- 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.
- 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.
- This test checks for bad ground in ECM. Terminals "A" and "U" are connected together inside ECM.
- 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.