Aaaaaaaargh, went out with my DMM ... door locks are working again. Intermittent issues are the worst.

 

Yes I know it's an old thread and I'm necroposting. But it's the same issue. Power door locks quit. Again.

Recap: I pulled the GEM and inspected for water damage. None. I cleaned its contacts. But they were already good. I pulled all four door switches, disassembled them, and they look excellent. I physically tested their operation, looking closely at the contacts snapping together. They're like new. I took a look at the driver door wiring loom and there is no visual suggestion of cracks in wire insulation.

Then, some weeks after I posted this thread, my power door locks started working again all by their lonesome. For 18 months, they worked fine.

Then, 3 weeks ago, they stopped again. I was dreading inspecting each wife in the door loom. I put off the job. We got pretty good at locking and unlocking by hand.

Today, they started working again. But, they did so oddly. They locked themselves, twice, with no button pushed. And at one point, the actuators seemed to be stuck forcing the locks on. Using the door unlock button cleared that. This unusual set of symptoms suggests to me that it could only be electronic in nature. I no longer suspect wires in the door loom. I already inspected the door switches.

I think it's the GEM. I'm going to order a rebuilt one from a quality rebuilder such as Reman Auto Electronics or Automotive Scientific Inc. But neither lists GEMs on their site.

Has anybody had similar symptoms of a GEM going bad? I know it can also do horrible things like spin the starter when the motor is already running. One guy even lost his truck to fire, iirc, from a bad GEM.

 

Based on the continued guessing, I’m thinking you don’t have ForScan. You need to get ForScan and scan for stored GEM codes which could begin to point you in the right direction or confirm that it’s a GEM problem. I’m not saying it’s impossible to have a bad GEM with only one symptom but it’s unlikely and like you keep saying it “looks fine”. The issue with these is normally water damage and that should be pretty apparent.

And I‘m pretty sure the GEM doesn’t have anything to do with the starter.

 

I do have FORScan but haven't run it on this truck because it has an Edge Console. But now I remember that not all modules get logged by the Edge. I will run FORScan on there.

The starter issue was another guy in another post, fyi.

 

As suggested by @burnthelight88 , @calvinhg and I just ran FORScan on that truck, with interesting results (we also updated Gearhead tunes how to do that). The first clue came before we'd even started, as we found the truck had locked itself in the carport. The alarm did not know, so it was not locked with the Viper keyfob. And during testing, we observed the truck lock itself again, then stick on actuating the door locks downward. Bad news. All actuators are new as of 2 years ago.

Anyway, FORScan shows three errors that don't make sense, C1446, B1352, B1575.

• C1446 but brakes and brake lights work fine, no LED bulbs, that could drive a fault.
• B1352 but there are no ignition key symptoms - that code may be because we defeated the open door dinger 3 years ago.
• B1575 but no parking lamp symptoms, no LED bulbs.

I got a pic of the GEM with its part number and will order up a replacement. My normal suppliers for rebuilt electronics don't offer this GEM, so I'm turning to fleabay. Now would be a great time to warn me of any particular fleabay GEM vendor that done you wrong in a sad country song, as it were, probably also involving a lonely train station, a whiskey bar, divorce, lost true love, and/or a dear family member in prison but they didn't do it. That way I won't have to play a country record backwards to get my money back. If anyone remembers records. Or jokes. Or country music.

 

I don’t believe you’ll find a “vendor” for GEMs that you give the code to. Not that I ever had to replace my own, but my understanding was always that you need the same code and it’s literally a matter of searching eBay, Amazon, and all your local junk yards.

I guess what I’m getting at, again as I understand it but with no personal experience, is that these cant be programmed to match yours, it’s literally a matter of finding the same one in another truck, and then hoping it is somehow in better condition than yours. Always sounded like a needle in a haystack to me.

 

My master tech buddy suggests that he scan and self test my GEM with his professional SnapOn diagnostics. FORScan did run a test on it, but my impression of FORScan is that it's more suited to newer vehicles.

So that's my next step. There is one fleabay vendor who put me on a waiting list for that pert number.

 

Not familiar with the snap on so I’m sure it can’t hurt to check, but ForScan is actually extremely useful for the 99 and newer diesels. Most basic scan tools will not work beyond simple OBD read outs with these trucks apparently. I’ve even been told the OBD errors with a regular scan tool can’t be trusted and you basically have to use ForScan to get accurate results because of the diesel aspect. You can do much of what the dealership can do with all of their electronic tools such as injector buzz tests. However, snap on makes good stuff, so like I said, can’t hurt to check out what it has to offer.

yes, it’s also nice for newer fords because you can actually change some of the module data yourself. I use it on my 19 F150 often.

 

In another thread, @SuperDutyScaler spurred me to re-check the door wiring loom where it enters the cab right above the left kick panel, because he found wire damage there on his truck.

We didn't find any damage to door loom wires there, but @calvinhg did spot some unrelated wires (or so we thought). He grabbed them and traced them back to the Viper alarm module. Checking that installation manual, he found they are associated with remote door lock function of the alarm. They had been haphazardly draped, no split loom or other protection, near the foot brake by Custom Sounds in Austin TX, 4 years ago. We rarely use the foot brake, but at some point we did and the wires got damaged in its mechanism.

Repairing the wires solved our 2yr-long running battle with intermittent failure of power door locks. All caused by incompetent installation of an alarm by a chain store with supposedly good reputation. My GEM/BCM is fine after all.

Caveat emptor.

 

Glad to hear you figured it out.

 

Glad you figured it out. At least someone listened to me for once LOL