[RobertFB]

My GEMS P38 has been having idle problems off and on. I let it sit fo 3 or 4 months and now it won't idle at all. Started to do some basic diagnosis - the nanocom says TPS voltage is only .02v. Basically 0. So I back probe the TPS connector, and realize it's not getting 5V at the connector. Figuring a problem with the harness or connector, I checked at the ECU connector. No dice - there's not 5V there either.

I disassembled the ECU and found only one through-hole 5v regulator but I'm seeing 5v on the output leg of it. I'm totally stumped here. Is the out-going 5V always present at the connector? Or is there internal ECU control of the voltage? Because if it's the former I'm thinking it's a bad solder joint somewhere and I can jumper the 5V direct to the TPS connector.

Or should I be looking for another ECU?

 

[RobertFB]

Figured it out - on NAS models from 98.5 and up there is a fuel tank pressure sensor. On Gems models, this is fed by the same 5V as the TPS.

I recently had a fuel pump fail and the wires for the fuel pump heated up and melted together, shorting the pressure sensor to ground. The lack of TPS voltage was due to the ECU having an over current protection circuit internally. Fixed the wires and back in business.