Fuel pump issue

Good morning.

Code 12 is normal if they are checking the codes with key on engine off.

If the code is with the engine running then it has no distributor reference voltage to the ECM.

Which way did they test for code? Is the check engine light on?

As far as the priming, that is all the ECM. That was a very common failure for this issue back in the day.

Roy

Information on the code 12.

Roy

Circuit Description:
There should always be a steady "Service Engine Soon" light when the ignition is "ON" and engine stopped. Battery voltage is supplied to the light bulb. The control module will turn the light "ON" by grounding CKT 419 at the control module.

With the diagnostic terminal grounded, the light should flash a Code 12, followed by any trouble codes stored in memory.

A steady light suggests a short to ground in the light control CKT 419, or an open in diagnostic CKT 451.

Test Description:
Numbers below refer to circled numbers on the diagnostic chart.

1. If there is a problem with the control module that causes a Tech 1 "Scan" tool to not read serial data then the control module should not flash a code 12. If Code 12 does flash, be sure that the "Scan" tool is working properly on another vehicle. If the "Scan" is functioning properly and CKT 461 is OK, the PROM/MEM-CAL or control module may be at fault for the no ALDL symptom.

2. If the light goes "OFF" when the control module connector is disconnected, then CKT 419 is not shorted to ground.

3. This step will check for an open diagnostic CKT 451.

4. At this point the "Service Engine Soon" light wiring is OK. The problem is a faulty control module or PROM/MEM-CAL. If Code 12 does not flash, the control module should be replaced using the original PROM/MEM-CAL. Replace the PROM/MEM-CAL only after trying an control module, as a defective PROM/MEM-CAL is an unlikely cause of the problem.