How To Install A New Ecm

X-man · March 10, 2008

2001 S10 4.3L Pickup.

The truck has had a continuing problem with the fuel pump failing to run.

First the pump and connector were replaced after the pump failed. At that time the relay was working.

A month or so later, the pump would not prime again. This time the relay was not activating. A different relay appeared to fix the problem... for a while. Then it started acting up again. This time I installed a bypass wire to the relay from a 12V ignition key-on source. All went well for several months then the pump started playing up again. This time the new connector was the culprit, jiggling the wire harness would cause the pump to start and stop. The connector had no obvious damage. I replaced it and all is now working again without the bypass wire ( I was concerned about safety by having the pump run all the time when the key is on). But it will obviously fail again as I have not fixed the intermittent relay problem.

The ECM has two codes set, both for low voltage to the TPS and another sensor I forget.

I am thinking that the ECM may be bad and not sending a consistent 12V to the relay. One time I checked it the reading was only 8V.

Does this seem like an ECM problem or could it be a wiring issue?

If I replace the ECM, does this mean a trip to the dealer to reflash the new unit?

Also can I use a OBD scan tool to do the the crank variation learn procedure with the new ECM or does this require a more sophisticated tool?

Thanks.

neonhomer · March 14, 2008

I'm not a GM tech, but I can put in my $.02 worth...

If you are using a brand new ECM from GM, you will most likely have to get it flashed for your particular vehicle. If you are using a used ECM from the SAME vehicle (same engine, tranny, options, etc) then it should work, but then you might have other problems with other modules because of the VIN mismatch.

If you are only getting 8v to the fuel pump relay, and it is supposed to get battery voltage, then I would suspect a bad wire. Do a resistance test on the wire to see if there is a problem with it.

Harness connectors can go bad or be poorly made. I bought a brake controller harness for my brother-in-law's 02 Silverado 2500HD, and when I plugged it in, it worked intermittently. I ordered another harness from the brake controller manufacturer, and it worked fine. (the first harness was from GM and was the universal one that normally comes with the vehicle.)

As for the relearn, I am not sure. I would assume you would need a Tech-II to do it.