High Idle caused by incorrect TPS wiring.
09-01-2017, 02:47 PM
#1
Rennlist Member
Thread Starter
High Idle caused by incorrect TPS wiring.
I have been plagued with a high (1400-1500) idle since my intake refresh but haven't had a chance to do much about it until this week. That did give me time to ruminate on what I did to cause it, and I finally decided it was something to do with the TPS circuit. I had eliminated the TPS to LH harness during the refresh - it all checked out, along with vacuum leaks, other sensors, and simple mechanical stuff like throttle cables. But I kept thinking about the fact that I had refreshed the connectors on the main-to-TPS harness.
Yep, that's where the problem was, and here is what happened. First, putting a new connector on the engine side harness, I interpreted the diagram in the WSM "geometrically", i.e. the central connector in the diagram is the central connector in the plug. Wrong. The central connector in the diagram is labeled as "1", and it goes into the plug in that position. The same with the other two: follow the numbering and color coding in the WSM wiring diagram and locate the wires in the plug accordingly.
But still no joy, high idle persisted. Then I remembered I had removed the connectors in the TPS harness plug for some reason, and that when I reinserted them I didn't feel entirely sure I had remembered their positions correctly. As others have found, the short TPS harness wires are NOT color-coded the way the engine harness wires are, and this is not noted in the WSM. In the former it is 1/brown/ground, 2/white/idle, 3/white with red stripe/WOT, but the TPS short harness are white/blue/black. It took a little work with the DMM to determine that this is 1/white/ground, 2/black/idle, 3/blue/WOT (white might be yellow, not sure).
BTW, before I made the corrections, there were no connections at all between the TPS and the engine harness, which was confirmed by disconnecting the TPS while the engine was running- no change in the high idle.
Anyway, all is fine now. In searching RL for help on this I noted a few others have had similar probles, and I hope this helps those trying to figure out the TPS wiring.
Yep, that's where the problem was, and here is what happened. First, putting a new connector on the engine side harness, I interpreted the diagram in the WSM "geometrically", i.e. the central connector in the diagram is the central connector in the plug. Wrong. The central connector in the diagram is labeled as "1", and it goes into the plug in that position. The same with the other two: follow the numbering and color coding in the WSM wiring diagram and locate the wires in the plug accordingly.
But still no joy, high idle persisted. Then I remembered I had removed the connectors in the TPS harness plug for some reason, and that when I reinserted them I didn't feel entirely sure I had remembered their positions correctly. As others have found, the short TPS harness wires are NOT color-coded the way the engine harness wires are, and this is not noted in the WSM. In the former it is 1/brown/ground, 2/white/idle, 3/white with red stripe/WOT, but the TPS short harness are white/blue/black. It took a little work with the DMM to determine that this is 1/white/ground, 2/black/idle, 3/blue/WOT (white might be yellow, not sure).
BTW, before I made the corrections, there were no connections at all between the TPS and the engine harness, which was confirmed by disconnecting the TPS while the engine was running- no change in the high idle.
Anyway, all is fine now. In searching RL for help on this I noted a few others have had similar probles, and I hope this helps those trying to figure out the TPS wiring.
Last edited by M. Requin; 09-01-2017 at 07:32 PM.
09-02-2017, 07:30 AM
#4
Rennlist Member
Thread Starter
The S3 has two switches, correct, which means three wires. I don't know about other models, but in perusing wiring diagrams (trying to find those non-listed wire colors) I did see some two wire units which appeared to be not switch but rheostat based. I don't recollect which models they were for, though.
