ECM Check Service Engine Soon Light "on" or Won't Flash Code 12

Circuit Description:
The ECM check is made to determine why the "Service Engine Soon" light remains "ON" or does not flash Code 12. Normally, the ECM will not recognize a fault for at least 10 seconds after start-up. If the "Service Engine Soon" remains "ON," the ECM has lost power, ground, or the signal that turns the "Service Engine Soon" "OFF" has been lost.
When the engine is started, the ECM grounds terminal "A10" to turn "OFF" the "Service Engine Soon" light. It, alternately, grounds and opens it to flash a code.

Test Description:
Numbers below refer to the circled numbers on the diagnostic chart.
1. This step checks for short to battery voltage in wire to terminal "C" or faulty lamp driver. Normal voltage reading is 9-11 volts.
2. This step checks to see if problem is related to the ECM or the lamp driver. Normally, grounding terminal "C" should turn lamp "OFF." If it does, the problem is related to the ECM and its wiring. If not, it is related to the lamp driver and its wiring.
3. Grounding terminal "A10" at ECM and finding light "ON," indicates an open in CKT 487 to terminal "C" of lamp driver. Normally, grounding terminal "A10" should turn lamp "OFF."
4. This step checks for open CKT 451 from ECM to diagnostic terminal in ALDL connector. The lamp should flash Code 12, when terminal "A6" is grounded.
5. Checks for proper voltage supply to ECM. Both should read over 9 volts. Terminal "C14" is ignition, and terminal "C16" is constant battery for long term memory.
6. Checks for a bad ground to ECM; terminal "C2" is connected in the ECM.
7. 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 it doesn't, it means that the ECM is faulty.