Check engine light but no fixes....

[Nightkid]

I have a 5.4L 1997 Ford expedition XLT. A Few months ago i got a check engine light p0340 which seems to be a loss of signal from the cam position sensor. I changed the sensor same time from pepboys and within a week issue came back with rough idling. Planned to do full tune up for the summer so my mechanic, also my best friend, changed IAC valve, EGR Valve & Sensor, 8 spark plugs and boots, Throttle position sensor, removed and cleaned throttle body, and Downstream Oxygen sensors since they had also started to fail.

After doing all this CEL was cleared with his snap-on scanner and all was well. About 2 weeks ago the light reappeared with the following codes:

p0113, p0118, p0123, p0340, p0453

I'v cleaned the MAF as per a post i've seen on the forum, IAC is new, and the cam position sensor has been changed 2x in the past 2 weeks. Fuses were checked with test light and visually (which is quite time consuming). Ecu & PCM are also working properly along with PCM relay, Diode, and Fuse. Please help if anyone has an idea how to fix before i am forced to get rid of it.

 

[stamp11127]

I looked at 3 of your codes - all were high voltage input. I would check the electrical system to see if you really have a high value in the system and troubleshoot from there. You'll need a DMM to check system voltage with the engine running. Anything past 15.0 volts can be a problem.
Also since your in "The City" you have salted roads to contend with. Corrosion raises hell on electrical systems.

How did you check all the components you listed as working properly?

 

[Nightkid]

With the exception of the fuses and the PCM Components everything else has been replaced with new parts. Pcm fuse and relay i removed and checked. Fuses from all fuse boxes were removed and visually inspected along with using test light while in fuse box.

 

[stamp11127]

Start with the basics. Check the battery voltage at the battery posts with the engine at 2000+ rpms. Use a voltmeter for this.

 

[98EXPnSRQ]

I know this sounds silly, but did you disconnect the battery for a while after replacing all of the sensors? The computer needs to reset and relearn the sensors, or at least that's what I've read. When you start it back up, let it idle for a few minutes before touching the throttle.

 

[Nightkid]

ok will do that in the morning.

 

[Nightkid]

The more I try the worst it seems to get. Had an accident a while back and it seems to have caused more issues below the surface. something causing those electrical problems along with what I believe to be slipping of the transmission. while driving it will just start reving before catching and returning to normal. intermittent but annoying when it happens on highway

 

[Nightkid]

Problem has been found

So here is the a recap of what I had to do since then.

1. Sensor replaced 3 times with no change in CEL code
2. Checked harness plug and wires from sensor to pcm. (all fine)
3. Body grounds in engine bay were cleaned and checked.
4. Battery Terminal connectors both + and - were replaced.

#4 turned out to be the cause of the CEL. The negative had been corroded so much that when it was tightened around the battery terminal it would shake while driving and causing the pcm & harness to lose ground or short out. So to all having this issue check the grounding areas and battery terminals.

2 years of headaches turns out to be the negative battery terminal