Q: P0642 code, how do I know what sensors and wiring is associated with reference circuit "A"?

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I received an answer back to this question already about my p0642. Mechanic said to unplug sensors to see if code goes away. My issue is that I don't know which sensors are associated with circuit "A". It would be a lot easier to track down. Also if you know a good place to find wiring diagrams that would also be very helpful.

I have back probed map, tps, crankshaft and camshaft sensors and have detected the 5v reference and it stays exactly at 5v. I've also replaced the tps, camshaft sensor, alternator, and battery.

Is there fuses I can check or certain wiring? Car has not been in accident. I did get implausible codes for rear right wheel sensor and brake signal but they were deleted and haven't come back.

My car has 128900 miles.
My car has an automatic transmission.

The only way to identify the sensors is through the factory wiring diagram and that is way too detailed to reproduce here. To resolve this issue you must have both the factory wiring diagram AND the specific "diagnostic decision tree" for Code P0642 that is also published in the manual. There are a lot of potentially relevant sensors including climate control, proximity alert, traction control, cruise control, anti-theft features, fuel injection control, anti-lock brake control, and many others. A complexity is, and the reason you need to use the decision tree from the manufacturer, is the fault is not necessarily the sensors themselves but rather a short in the wiring or a bad ground, not to mention of course the PCM itself could be faulty (although rare) or connections at the PCM culd be bad. If you do not have the manual (they are costly but worth getting), you can request a check engine light diagnostic - Code P0642 and at least, in this instance, the mechanic can walk you through the process so going forward you can be informed if a similar issue arises. If you have further questions or concerns, do not hesitate to re-contact YourMechanic because we want you to make the most of your repair dollars and help you to get the best possible results.

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