2000 F150, 5.4, 4x4. Had my camper hooked up to it in the yard for about a week (pulled it away from the trees dues to the hurricane here in NC last week) and decided to park it back in it's usual place. Started the truck up, parked and unhooked camper, all with the truck running. When I hopped in to pull the truck away, I noticed my tach was sitting at about 4 grand (truck was idling) and my speedometer showed about 75mph. I decided to turn the truck off to see if they would reset themselves and when I tried to start it back, it would turn over but not run. After turning the key on/off several times I realized my fuel pump was not turning on, hence the no start. After checking all fuses, wiring, etc. I noticed that my "THEFT" light was on. It is on solid. No flashing and the only time it goes off is if I disconnect the battery. Also none of the gauges are working. I tried unplugging the ECM for a while and same results. Tried unhooking the battery for a while, same results.

I guess I've narrowed it down to either a bad chip in my key (only have one of these, lawnmower ate my spare about 3 years ago so I can't try that) or a bad PATS transceiver. Verified power to the transceiver but when I try to start the truck, I don't see power in any of the other 3 wires. Is there a way to verify the transceiver is good with a multimeter? I'm honestly looking for the cheapest way to repair this without having to purchase new keys/visit a dealer for reprogramming keys. This truck has 280,000 miles on it and I mainly just use it for hunting and driving back and forth to work occasionally so the cheaper the repair, the better. I'm not against bypassing the PATS system completely if possible.

Any help would be appreciated.

 

If none of the gauges are working, you don't have a PATS issue (it's secondary), something else is wrong. Check for proper operating power and good grounds to both the cluster and to the PCM.

 

I don't think the PATS would give speedo, rpm and other electrical problems.. Just the THEFT light and no start... Since it has been raining, I would guess your windshield leaked water and dripped on the GEM in front of the driver seat, behind the steering wheel, behind the dash........ Not a "common" problem, but has happened to many people on 1999- 2002 trucks.

 

maybe read post #5

https://www.ford-trucks.com/forums/1...gone-wild.html

 

Honestly you have not narrowed it down to any specific cause.
From the description given, I would first look for a harness issue a 'Critter' thought was good to eat, first.
If the PCM does not function, the Pats has nothing to communicate with and will react leading to a false conclusion.

 

Ok, didn't have much time this afternoon but I started with the PCM. Pulled it out and plugged it up under the hood where I could see it a little more easily. Used a voltmeter with the red wire on the battery and the black on the case of the PCM to verify Ground is good. Wasn't sure about exactly how to check voltage going into the PCM but I spot checked a couple (red) wires going into it and had 12 volts on everything I checked. I'm sure this is far from proper procedure but a proper procedure for checking it out would be beneficial if anyone has it.

Also, I have a cheap OBD-2 scanner that works with an app on my phone. It has worked before on this truck on multiple occasions but today it said it couldn't pull codes from the vehicle. Related to my current problem I'm guessing.

Where do I go from here? Certainly there's a better way to check the status of my PCM than the redneck check I did this afternoon.

 

I believe the scanner plug is powered by a fuse that also feeds the cigarette lighter plug... Either the fuse is blown, or you have a power problem feeding it........ that's just a start.

 

There's way more going on than a blown fuse to the cigar lighter. If the PCM doesn't power up, for example, you'd have pretty much the same effect (at the phone) of an unpowered OBDII port.

OP:
1. Does the check engine light come on when the key is turned to RUN?
2. Mechanical or digital odometer? If digital, what does it do hen the key is turned to RUN?..

 

The OBD-2 port powers up, the app connects with the scanner. But the app says the scanner can't pull codes. How can I verify whether the PCM is good or not? Or should my next step be something else?

 

1. CEL bulb is blown and has been for a while. I can replace and check but won't be today. Other lights in the dash are working normally when turned to RUN.
2. Digital odometer which ordinarily is intermittent anyway is not working at all. (Usually a couple light taps on the dash or pressing the trip button will make it light up. But not now.) I think it's safe to say it is doing nothing when the key is turned to RUN.

 

Sounds like you have a a real cluster you-know-what on your hands.

 

Didn't have to come here to figure that out... ...but hey, what do you expect. I've had it 12 years and it's had a rough life, time for something to really screw up on it.

Let's say the CEL is on, then what?
Let's say the CEL is off, then what?

 

The PATS module lives in the instrument cluster. Your instrument cluster is acting up. I would be looking at the instrument cluster. You say the odometer isn't working but used to be fixed by tapping it - that is a classic sign of cold solder joints which is a fairly common problem on these clusters. Look at the youtube videos on re-flowing the problem connectors.

 

Looked at this again today. GEM module shows no sign of moisture. I guess that means it's good. Is there a way to check it out?

Replaced the CEL bulb and it doesn't come on. Odometer not working still so I'm assuming it's not just the bad solder joint.

Where does the ignition switch fit into all this? Possible that's gone bad?

How can I verify whether or not my PCM and/or GEM module is good?

I'm about fed up with it. Mechanical issues are usually pretty easy to me but electrical... I'm ready to pull my hair out.

 

Problem is your not understanding the relationships that exist.
The Ignition switch supplies fused power to a number of systems and relays.
The PATS gets it power through the ignition switch, coils and injectors, the PCM is powered through a relay, the dash power is separate but through the ignition switch...
You have to sort out what is and is not powered.
The Gem has nothing to do with all this. It lights dash lamps for the functions it performs such as 4x4 hi, lo etc. and does interior light timing control, power window control, wiper control etc. Nothing to do with dash control other wise.
You have to get a lead on what part is having an issue and work from that point and direction.