A rat or something ate through most of the ecm wires under the hood right before it goes through the firewall, twice.... I am keeping it in the shop now.

Since then, probably unrelated, but my oil idiot light comes on when idling or between shifts.
I changed the oil and filter- went to straight 30 weight oil, had been running 10-30.

I bought a new sending unit and it does the same thing. The strange thing is it still does it even unconnected. I can leave the sending unit wire unplugged and it goes out when the engine is revved up and comes on when it idles down.
It does not matter if it is hooked up or not. How can rpms affect the light?

I thought if it was unconnected it would stay off.
Thanks

 

Probably not unrelated actually. You could ohm that wire out from the ecu plug to the sending unit and see what you come up with. Maybe it's picking up some voltage from induction or bare wires somewhere. If it's unplugged it should definitely stay on.

 

http://personal.utulsa.edu/~nathan-b.../6combinat.pdf says that when unconnected, the oil pressure warning light is OFF.

But the rest of what vasinvictor says is probably correct. While I doubt it's inductance, there is almost certainly some "cross-talk" between wires. I even suspect it will change with humidity.

Start with an ohmmeter.

 

I stand corrected, thanks. Although that doesn't make sense

 

I just realized I didn't post what vehicle I have. I appreciate none of you slapping me around....
It is a 91 4x4 with a 22re.


A guy I work with suggested that it is possible that I have a bare wire and the engine being revved up is moving it and it is not grounded again until I let off the gas.


The light even comes on when I have high rpms going downgrade coasting in gear. only pushing the accelerator pedal will make it go out.


I am going to put a actual gauge on it tonight. If I can find a good place to mount it in the cab. I could just zip tie it to the turn signal, you know be classy.....

 

Because you'd like the light to go ON if the wire breaks? I suppose that's part of the reason the light comes on with key-on, engine-off. To verify that the "system" is working.

 

Most pressure switches and temp switches ground out when pressure drops or temp gets too hot etc. Although if it become disconnected you have no way of knowing, unless the connector grounds out on something. Kind of a catch 22.

 

I put a cheap equus gauge on it last night, plastic tube was too short so zip tied it to a heater hose.

Now it shows 75 pounds at idle. I shut it off and went to bed....

 

now get that gauge working. Or not.