Acert SDP ECM doesn't read oil pressure

The gauge..?

 

The ECM must be seeing oil pressure or you'd have an engine shutdown light and it would shut down. There is something wrong on the OEM side related to the gauge.

First things first, do you know what make and model the truck is? When the mechanic had his laptop on it, did he use Cat ET to monitor oil pressure?

 

When I key on my oil pressure gauge doesn't move until the truck starts......

 

Was this truck tuned and/or had emissions deleted? I assume that when you swapped ECM's, you did the normal procedure of copying the parameters from your ECM to the test ECM? What you're describing is possible if the engine monitoring parameter has been changed to not not allow a fault or shutdown. Why someone would do that is beyond me, but I have seen some pretty crappy deletes that disable many fault codes.

You're problem is confusing. The oil pressure problem is not a hard diagnosis, verify with a manual gauge. If it has good oil pressure ohm all all the wires from the sensor to the ECM plug. The confusing part is why it is not setting a low oil pressure fault.

 

Omg.
Put a gauge in the oil galley and test the oil pressure!!

You could have 2 psi and oil will come out. Quit assuming .

Cracking the sending unit to see if oil comes out tells you nothing.

 

Unfortunately, we can't discuss emission modifications here, so I don't think you're going to get much more help. Like swaan said, use a gauge and verify whether or not the oil pressure is in spec. If it is, you most likely have a wiring issue between the sending unit and ECM, so ohm it out. Shouldn't be hard to find, it's a pretty short harness section from the sending unit to the ECM plug.

This may sound dumb, but make sure they changed the correct sensor. The oil pressure sensor is right next to the atmospheric pressure sensor, I've caught people messing with the wrong one before.