Limp Home U0101 et al...

Just doing my errands, heading home from the grocery store and what do I see but the return of the wrench and engine lights along with the RPMs leaping as the engine decides that limping home is the best way home. Fortunately, we were just a few miles from casa del 500 dinero coche, on roads where the top practical speed stays below 35MPH, so no biggie.  Can't say my passengers were all that happy, even though the car performs well most of the time, they expect to be stranded for every outing.

I was able to get the codes from the car using the Android “FordSys” program (more on that later), here’s what I have:

Code	Meaning
U0101	Lost communication with TCM (transmission control module)
P0641	Sensor reference voltage ‘A’ circuit open
U0415	Invalid data received from ABS (anti-lock braking system) module
U1900	No description
B1318	Battery voltage low
B1342	Electronic control unit is faulted

After letting things rest (and the super-cap drain so things reset), the engine started no problem, no wrench light and the check engine light turned off after the second engine running cycle, just like the last time this problem occurred.

Sometime a few months ago, I broke down and laid-out the $29, or something like that, for an AllData DIY subscription for the Freestyle. For the error codes in question, there’s a bunch of “pin point” tests to check for continuity and wiggle checks for the connectors.  What All Data doesn't provide the full schematics for the car, as I'd like to see where +5v circuit A goes, as I have an intermittent issue with some segment of that wiring it seems.

Looking at the codes above, I’m guessing a short or disconnect (somewhere?) resulted in a few components going into reset due to a voltage drop or the networking between the components failed due to signal integrity. Before replacing parts, I need to make sure the communication between said parts works properly, or I won't be fixing the problem by swapping what's at either end of a bad connection.  I’m presently replacing the brake lines on my kid’s Grand Am, so the actual checking will need to wait for a bit.

FordSys

All of the diagnostic information comes to me complements a program on my Android phone called FordSys. A regular code-checking program returns no problem codes, because what’s reported above aren’t in the standard inventory of codes for engine trouble a generic code reader reads. I very much like FordSys, I’m not so crazy about the intrusiveness of the ads.What was small ads on the bottom of the screen has morphed into full screen overlay ads. I’d much rather pay the developer, who deserves the money for his hard work, and not be bothered with ads at all.