Odd electrical PATS problem, or something else?

[Givenator]

My 2001 Lincoln 4x4 Navigator is experiencing PATS problems...I think! My truck starts, idles, runs/drives OK at low speed. Under a load (going uphill or at highway speed) the truck bogs intermittantly like it is starving for gas.
There is no CEL, or codes being thrown to the OBDII port! The THEFT light flashes randomly/constantly at almost 1/sec when the engine is running. Often it will flicker twice, or 3 times fast. The THEFT light is faint, varies in intensity, and can barely be seen in the daylight. The bogging does seem to be tied to the flashing THEFT light somehow, but not perfectly.

First, Before we noticed the THEFT light I replaced the fuel filter (thinking it was clogged,) but it wasn't the problem. Second, thinking this may be the classic electrical corrosion problem, I replaced the GEM and studied the kick-panel/under-dash area for damaged connectors & wires...no luck, no corrosion damage on either side. This isn't a leak problem at the fusebox. Third, I pulled the Instrument Cluster looking for any bad connectors or wires, knowintg the PATS control functions come from there in a Type C Security System like mine. No luck, of course!
Background: I recently did a suspension conversion (to passive springs.) The Suspension Control Module had to be deactivated due to a short in the Compressor Relay. Everything electrical (besides the relay) was left hooked up. I strongly believe this PATS flicker has nothing to do with the suspension conversion: It started after the mechanical work was done, but before the CK SUS light was extingushed by stopping the power to the SCM. After the SCM was turned off, nothing changed. Then I swapped out the GEM for a new one...again, no change.
What do I do next? Where could a short be that could do this? I'm wondering if there are codes somewhere my OBDII scanner can't see...HELP!!!

 

[robbieg]

Have you tried another key? Also by chance do you have a chip installed?

 

[Givenator]

The keys work perectly.

Thanks for the response. I have 2 factory keys, both operate the truck with the same results. There is no failure during the "Prove Out." She starts right up everytime! That's why I say it might be a PATS problem.

No chips installed...bone stock except for the recent suspension conversion.

 

[Shadowless127]

Thanks for the response. I have 2 factory keys, both operate the truck with the same results. There is no failure during the "Prove Out." She starts right up everytime! That's why I say it might be a PATS problem.

No chips installed...bone stock except for the recent suspension conversion.

Do you have any type of aftermarket alarm/PATS bypass units installed?
You may have to have your PATS system reflashed by the dealer.

 

[Thermo]

Sounding like to me that you have a high resistance is the power wire feeding the PATS system. As the voltage starts to drop, it will affect the signal coming out of the PATS system. Also, as I recall, your truck has the CAN bus setup. If your PATS system is starting to fail, it can bog down the CAN bus and lead to lack of information to the ECU, leading to your problem. Unfortunately, unless you are good with electricity and/or electronics, this can prove to be difficult to do and interpret the results.

 

[toms89]

Just some info..

I lost my pats code in the ecu when my sct locked up while flashing tune.

PATS at least on my 2000 expedition cuts ignition and/or the injectors but still have fuel. Mine would actually crank fine and had normal fuel pressure with the theft light flashing but would not start.

Not sure how yours would start at all if pats related unless it was turned off in the tune. Once I turned it off in the tune it would start and run no problem but theft light still flashes and it also set cel. The cel was related to bypassing the pats and I just turned off that particular cel trigger.

 

[Givenator]

Good information!!!

Hey guys,
First, thanks for the advice! Know that I am a 25-year interconnection engineer, so am at home solving problems with the wiring harnesses, connectors, and system integration issues. HOWEVER, this one is not playing nicely. I really have no clues to where the problem is originating, so handing the dealer a blank check to try replacing major components doesn't sit well with me.
There are no aftermarket electronics in truck.
The connectors and wiring all looks perfect, which is amazing!
The PATS functions reside in what Ford calls the HEC (Hybrid Electronic Cluster,) which I believe is the Instrument Cluster. I have pulled it twice, checked all the wires, looked for bad solder joints, etc. There's nothing phsically wrong to my eye, and there was no change. It makes sense that PATS may run off a CAN-bus, but that brings even more variables into the mix. What I think was proposed, was that the PATS controller chip may be going down (or the power to it,) and in turn it's fouling up the bus (which is causing the engine trouble.) Assuming the wiring is good, that means I need a replacement Intstrument Cluster, which requires a dealer to program the PATS data.
I have NOT taken the car to a dealer yet...That's my last-ditch option!

 

[robbieg]

You probably did this when you replaced the GEM but just in case you didn't have you tried disconnecting the battery?

 

[Shadowless127]

You probably did this when you replaced the GEM but just in case you didn't have you tried disconnecting the battery?

If it was a GEM issue the vehicle would never start. I'm wondering if it's the transmitter in the ignition cylinder.

 

[toms89]

What I do not understand is how pats can cause it to run poorly.

Pats sends signal to ECU which in turns cuts injectors and or ignition. (Guessing because mine still would crank and had fuel pressure but would not fire) It should be On/Off type situations in my thinking. So motor should either run or not.

I do understand you have the theft light blinking which is obviously pats.. but if it is blinking from the beginning it should not allow it to start at all !?

Makes me believe somehow the tune in the ecu got corrupted. Just speculating of course.

It will be interesting finding out what the issue and or solution is?