2007 Chrysler Town and Country, ca. 188,000 miles:
While driving at steady highway speed, I noticed the speedometer fall toward zero; a moment later all the instrument panel’s warning lights came on, and a few seconds later everything was back to normal. The engine ran smoothly the whole time; the voltmeter in my lighter socket showed no change.
What could be the source of the problem, and a solution? Could this mean a more major disfunction is likely?
You may be facing an issue with the TIPM
Tester
I agree that this sounds like one more case of a Chrysler TIPM that is failing. However, I think that the OP should have his alternator’s output checked because a failing alternator can also produce some strange (and transitory) symptoms.
I would think a charging system problem would reveal itself.
Tester
Is the TIPM the same thing as the BCM (Body Control Module)? What diagnosis can a DIYer with an OBD2 scan tool do? And where are these parts located? Maybe it’s as simple as unplugging, cleaning contacts, and plugging back in (I wish.)
IIRC, that is Chrysler’s term for their BCM.
The TIPM is the fuse/relay box under the hood.
It requires a factory level scan tool to diagnose.
Tester
TIPM == totally integrated power module I think. Not the same function as a BCM. Certainly have been the culprit in a lot of Chrysler related posts here, especially cars in the 2006 - 2009 vintage.
A problematic vehicle speed sensor (VSS) could cause this as well. That’s probably where I’d be checking first.
Transmission’s primary input is vehicle speed, so if that isn’t reliable, yes, more dysfunction expected.
Not sure where that part is located on your car, but VSS is on transmission case in my Corolla, and on xfer case on my 4WD truck. (Actually the sensors are part of the speedometer, those above are the places the cable drive to the speedometer originates.)
The instrument cluster rebooted. Blame the TIPM? I don’t think so.
Your vehicle does not have that power module, the TIPM is used on vehicles with CAN bus communication systems, your T & C has PCI bus communication. The RS Caravan models have an Integrated Power Module with Front Control Module, not integrated.
The instrument cluster is switched on by a signal from the BCM but don’t assume one or the other is at fault.
Isn’t Allpar your go-to for Mopar questions?
Yes. There and here people have offered suggestions. Someone at allpar just posted the instrument cluster self-diagnostics procedure. That and other ideas seem worth investigating. I thank you and the others for their help.