[fdickinson]

Okay, so I just finished the head gaskets in my 2000 disco 2 after misfire codes prevented it from passing emissions. No misfires and the truck runs great! But, once reassembled I instantly got Fuel Pressure Switch Error and purge cannister vent valve/DMTL power stage fault. The OBDII codes are P0453 & P0457. I'm not really a rookie at this. First, tested the purge valve and have just over 5V difference between the two leads. I know that is high, but I have replaced the Purge Valve, Vent Solenoid, Canister and even swapped ECM/BCM and the code is still there. I also test the FTP and in is operating perfectly with 5v in and fluctuating from 2.3 - 4.6v out as pressure fluctuates. Smoke test - no leaks.

The codes are not intermittent at all and there is no delay in the error registering... it instantly shows on the code reader every time.

During the process, I did swap the engine wiring harness because the front passenger O2 sensor melted against the exhaust manifold, but check the continuity of every wire and there is no shorts and no resistance. honestly, it seems like I might have forgotten a plug or ground somewhere, but I can't see where and everything has voltage. I do have one plug loose that I believe would hook to a temp sensor under the radiator, but my original harness didn't have this wire. I was told that I could just let it hang loose because the ECM is not going to look for it. Is there a difference in the wiring harnesses from 2000 to 2002 w/ secondary air? Thought I would post before I give up and take it to a shop to trouble-shoot.

I'm stumped

Fred

 

[fdickinson]

Okay, so I fixed this.

First, the ECM I replaced was not matching... but works with some rewiring.

Second, there is a difference between the 2000 and 2002 wiring harness I swapped, also worked with some rewiring.

Using the old harness, I mapped the pins on the old ECM... then mapped the harness on the truck I pulled the ECM from and made the pin sequence match. Finally, I had to add a wire that was missing and run it to pin 6 on Bank C0636 of the ECM.

It actually only took about an hour once I figured out what the issue was. Runs great and passed emissions earlier this week.