Hi Everyone,

I am working on my sons 1999 expedition. He was driving back to college when truck suddenly quit on him. After that it was tough starting and ran rough at times and ok at others, at least it would drive ok. However, it kept turning on check engine and the oil pressure gauge would go from showing normal oil pressure to just dropping as if motor had been shut off. No noise from motor however at all that was remotely unusual. Checked for codes and only code showing was PO340 for the cam sensor. Purchased a new one and replaced. Code is still being thrown so also replaced crank sensor, still same issue. Had a mechanic buddy of mine check the sensor and it checks out, so traced the two wires for the cam sensor. One of course when connected to pcm shows routed to ground, I also traced it to the first connector and found 2 pins that showed continuity, traced the second wire and found its pin and also checked for shorting to ground and was fine. Then disconnected from pcm and traced through to that connector found for the grounding wire continuity to 3 pins and again only one for the other wire. I do not have a wiring diagram so am assuming the grounded wire must be reading through other sensors????? Does it make sense that the PCM would be the cause of this issue for both sensors? Oil Pressure and cam sensor. My mechanic buddy reved the motor up and it seemed to run ok when got it to rev, but at idle it struggles to stay running so don't think timing has slipped any. Does anyone have a wiring diagram of the engine wiring and PCM connector diagrams so know what pin is what and where? HELP

 

Here is the cam sensor wiring.

 

ok so the diagram is a bit difficult to read but if I am reading it right, my readings for the ground wire coming from the cam sensor are correct. I should be able to read continuity on 2 pins at the one connector and 3 at the pcm connector, correct?

 

Maybe if you would refer to wire colors folks could better follow your diagnostic procedure.

With the CMP sensor and the PCM disconnected, you should have continuity on the DG (Dark Green) wire running from the CMP sensor harness side to the PCM connector pin 85. (Thanking alloro for the wiring diagram).


And you should have continuity on the LB (Light Blue) wire running from the CMP sensor harness side to the GR/RD (Grey with red stripe) wire at the PCM connector pin 91.


You should also test each one of these two wires while they are disconnected with your DMM to be sure they are not shorted to power someplace within their wiring harness. Place your DMM in DC volts scale, connect the black lead to the battery ground and the red lead to each of the wires. Should not see any voltage. If you do, that wire is shorted to vehicle power.


The CMP sensor is a variable reluctor type sensor and only uses two wires to complete its function. Not sure what you are referring to when you mentioned something about 3 pins. Perhaps you are referring to the shielding wire that protects the CMP sensor wires from EMI that can distort the CMP sensor signal as seen by the PCM.

 

Having trouble editing this ......................

 

Oops, it might help if you also had the pin number layout for the ECM connector...attached.