I have an ECU that was removed from a 2002 truck. Truck was wrecked, but, it ran fine and held good oil pressure.
Sold the ECU and the customer says his truck now runs great, but, he has no oil pressure showing on the gauge.
I'm simply curious as to "why"?

Best I can remember, all, or some, 02 model trucks use an oil pressure sending unit that is "different".
It's much like a dummy light switch and won't work a gauge. (yea? nay?)

Where-as a sending unit off of an 01 will control a gauge. (yea? nay?)

Does any of this make sense?
What am I running into here?
Just a bad ECU, or, A good ECU being installed in the wrong environment?

 

Depends on what what in the truck that the ECU came from.

If the engine had the pressure switch, then the ECU was programmed for that. However, if the engine had the pressure sensor (like my 2001.5 has), then the ECU will be looking for a sensor.

The pressure sensor has three wires and costs about $90 at a Cummins shop. The pressure switch has either one or two wires (don't remember which), and is a lot cheaper.

Hope this helps.

 

Thanks!
That is "sort of" what I was thinking, but....
I was wondering if an ecu off of a "sensor" truck had nothing to do with the gauge.
And an ecu off of a "switch" truck had everything to do with the gauge.
??

 

Hey redlinear have another ECU?

 

My mistake.

It is not the ECM that monitors oil pressure (at least not for the guage). It is the PCM.

From the service manual:
The service manual indicates that this is the same for gas and diesel Rams.