odd change oil light

I went to fuel my Caprice up today, and when I got back in the car, the Change Oil light was on. So I thought, ok, I'll need to reset it, cause I changed the oil obviously when I had the motor swap.

When leaving my friends house, I noticed that when I put the key in on the ON position, I could hear a fan under the hood running (the same fan that if the car was in Field Service Mode), and when I started the car, the check engine light flashed ultra quick, like a dance party strobe light.. then went to ultra slow, then started flashing every 1 second, which did that for the rest of the ride home.

What could have caused such a behavior? When I reset the oil light, while in ON, but engine off, here's the interesting part..

When the OIL light flashed, so did the fan sound (almost as if the fan was connected to the lights power), then as the light finally went off, the fan sound disappeared.. started the engine, and no more flashing check engine light...

so, normal, or computer issues?

Sounds almost like the computer might need to be replaced. I had similar symptoms back with my Grand Prix, it threw me some codes too such as the idle air solenoid. After replacing some sensors and solenoids, nothign changed. Brought it to a shop, they said the computer was shot. Replaced that with a junkyard one, just swapped the prom. That was about 3 years ago and the thing's still going strong.

I went to fuel my Caprice up today, and when I got back in the car, the Change Oil light was on. So I thought, ok, I'll need to reset it, cause I changed the oil obviously when I had the motor swap.

When leaving my friends house, I noticed that when I put the key in on the ON position, I could hear a fan under the hood running (the same fan that if the car was in Field Service Mode), and when I started the car, the check engine light flashed ultra quick, like a dance party strobe light.. then went to ultra slow, then started flashing every 1 second, which did that for the rest of the ride home.

What could have caused such a behavior? When I reset the oil light, while in ON, but engine off, here's the interesting part..

When the OIL light flashed, so did the fan sound (almost as if the fan was connected to the lights power), then as the light finally went off, the fan sound disappeared.. started the engine, and no more flashing check engine light...

so, normal, or computer issues?


the fan should not be on when engine off and ignition on check wires/connectors at pcm/computer....

May be different than with your model, but I do remember when jumping the A & B terminals to put an OBD-I ECM into diagnostic mode, one of the two fans did come on and stay on for the whole time the key was turned to "ON" or until the jumper was removed.

May be different than with your model, but I do remember when jumping the A & B terminals to put an OBD-I ECM into diagnostic mode, one of the two fans did come on and stay on for the whole time the key was turned to "ON" or until the jumper was removed.
Yea, that's field service mode.. mine does that too, but nothing was in the OBD port, and this was directly related to the Change Oil light.. unless perhaps my Change Oil light has a short?

I was hoping the PCM wasn't the issue, because since the motor swap, I've actually survived without that false check engine light, as the flash chip had a bad checksum...

(my PCM has an intel flash chip soldered in place.. can it actually fail regularly?)