My ECM may be bad, going to do some tests today, regarding Code 42 and Code 54. Now IF my ECM would be bad, due to fried fuel pump driver and something else, my question is:


Can I replace it with ANY used ECM from the 3rdGen Camaro's ? Would an ECM from a V6 or carbed V8 work ? Does the ECM have to be from the same year ?

Mine's a 91, and I don't see too many 91-92 RS with the L03 engine at the junkyards, mainly V6's and a few carbed V8's

 

You need a TBI car ECM. Either a camaro or B-body varient. If you happen to find say a caprice with a 350, grab the ECM, then put your current prom chip in it. Save the 350 chip though, makes a good starting point, should you upgrade to a 350 TBI down the road.

 

OK, thanks. It has to do with the VATs thingy as well huh ?

One mroe question ... any way to check if the fuel pump driver may be fried on the ECM ?

 

The direct replacement ECM is the 1228746. This can be seen as the service number on the label. As for needing this one it has mostly to do with the type of EFI system.

The fuel pump (FP) driver is a common problem, and easy to fix. It is a transistor on the main board. I use a 2N2907 to replace it.

To test it: at key on the FP driver supplies +12 v (battery voltage) to the fuel pump relay for 2 seconds. A DVM can be used to measure that voltage. Make sure to either leave the relay in place or provide a 100 ohm load. Otherwise the voltage measured will not be correct.

The relay coil should measure around 60 ohms. Anything less then 40 ohms and the relay is bad.

RBob.

 

Oh ok. Well I got this far
https://www.thirdgen.org/techbb2/sho...hreadid=336997
with my tests, so it's not the relay, according to the tests, even though I wish it would just be the relay heh ... a 10 bucks fix.


Can I drive the car, gently, if I have a Code 42 ?

 

Yea, if you grounded the FP relay drive, the transistor is toast.

As for code 42, is the SES on solid? If not then the code 42 was an intermittent. Code 42 will also set if the engine is started with the bypass open (such as when timing it).

Can clear the codes with the battery dance and see if it comes back.

RBob.

 

The Code 42 seems to be constant. I had huge problems starting the car, had to apply throttle or it would die out.

Reason I'm asking is, need a ride to the junkyards

 

The EST connector must have been not fully seated, or something anyway, no code 42. Of course fuel pump circuit problem is still there, but I bypass that one, and no Code 42.


So in order to fix the fuel pump drive, buy the transistor, which they should have at radioshack, take out the ECM, open it up, and solder the replacement transistor in ?


It MAY be the "easier" option, compared to getting another ECM at the junkyards, because, no offense to Hispanic people, but all the Mexicans at the junkyards take out all the good stuff from the cars.


I STILL haven't been able to find an adapter for the wheel locks on the 91 RS wheels, i.e. the Z28 style wheels.

 

Well great, Radioshack don't carry the 2N2907 transistors, so where would I get one ?

 

This picture shows a 2N2907 in place of the original transistor. The harness connector is to the left. While the transistor is opposite of the heat sink.

RBob.

 

Just to the right of the resistor ?

Right on.


(gotta relearn the color coding for the resistors again)

 

Geeze, yanking the ECM out was harder than I had imagined, the assembly had some damn wiring wrapped around it, on top, had to remove front speaker (luckily I had the dash off already) to see what was going on.

OK, now I just have to take the circuitboard out of the box so I can flip it over, remove the transistor and solder in the replacement one.

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Right on. Babe's running now without hotwiring the pump.

 

Where can I find the transistor that I need? I can't seem to find it at radio shack