TPS 5V Dropping after 15-20mins running

[Mikkson99]

Hi. I've got a m50 turbo, with VEMS v3.

I got a problem; After 15-20 minutes the TPS 5V supply will drop to around 2.6-2.7v and the ECU don't get the rigt readings.
Happens every time. Taught it may be the low voltage, when I didn't hav an alternator yet, but that did not help. Testet latest today, with 14.v on the system.

Measured same voltage both at TPS connector and EC36/29, so I guess the wire is fine. Also measured the wire end to end, 0.7ohm, and to ground - OL...

Also I was suspicious that the TPS itself where bad, as it was a "UAES" china copy thing. Got hold of an OEM BOSCH, but that didn't help neither.

Does anybody have a clue at what is happening/wrong?

Best Regards /Sondre Mikkelsen

[jrussell]

Had some good discussion on this in the VEMS Users Group facebook group, but summarizing here for history/search purposes.

Pin 29 is a voltage divider. It shouldn't drop voltage unless there's a significant current draw on it. Is the TPS the only device on pin 29?

Does pin 28 (a 5v voltage regulator, not voltage divider) exhibit the same? Are there devices on pin28 now? If not, you could use that to see if the behavior follows.

I have seen where a bad (non-compliant) USB to serial cable pulled pin9 low on the db9 port... after 5-15 minutes. This is used for 5v power for the bluetooth devices and is standard in the rs232 spec. This is verified to not be the case in this instance, but just pointing out the possibility.