Computer problems

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MEMBER
GMC

I have a 1991 chevy cavalier Z24 3.1 L V6 with about 154414km on it. I was driving and
found that my cooling fan was not working and the engine light came on along with that
the motor idles at around 1400rpm and when it gets warm it stars to run weard. So I had
scanned it and the codes were 13 and 14. So I replaced both coolant and oxygen sensor
and the codes still came up and the fan still does not work.I took it to a shop and they said
I needed to replace the fan relay and the oil was full of gas and that the O2 was going
rich, but I had a brand new oxygen sensor in it. So I replaced the fan relay and the problem
with the fan was still there. I don’t know what to do! Could it be the ECM that is causing
the problems and if so do I need s specific GM ECM for my car.

1 Reply

LOSONE

MECHANIC
1,616 POSTS

I hope you have checked to insure all fuses are good

The oil in the gas is caused by a rich condition. It could either be the map sensor or the TPS.

The coolant fan relay is controlled by the ECM which turns on the relay and then the fan. It really isn't the ECM but the problem is the PROM (programable read only memory) that plugs into the computer. It is accessable in the ECM via a small inspection plate that is on the side of the computer.

Take the number and go to a GM dealer and order a new one. They will have the latest upgrade for the PROM. I have seen this a number of times.

I hope you don't have the computer that can only be serviced by a dealer. It would be located in the engine compartment. If that is true then you can have the computer re-programed by the dealer.

If the computer is insidethe car and is a silver box under the right side kick panel then you can replace the prom.

Your rich condition could also be caused by the ECM. CHANGE the oil to get the gas away from the inside of the engine.

Let me know