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

asked by on August 23, 2017

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.

Check Engine Light is on Inspection $79.99 - $99.99 Get a Quote

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.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing


Experienced Mechanic?

Earn up to $65/hr

What others are asking

2008 jeep grand Cherokee keeps going into limp mode

It's possible that water or dirt has infiltrated an electrical connection to a key sensor. That could cause the vehicle to go into limp mode or reduced power. The issue you are writing in about is common enough that a...

2006 Jeep Grand Cherokee 3.7l has a rough idle when stopped. I can be at a stop sign, red light, or just parked with the engine ru

You may have a bad spark plug or ignition coil and will need to have the computer tested for misfires. If you get misfire codes it will identify what cylinder is misfiring and will need to replace the plugs and...

I brought a 2006 Infiniti g35 coupe. When I start it up it sounds like a race car, when I press the gas it gets louder until I let

The previous owner might have modified the air intake (a box like component holds the intake filter) but the noise you are referring to is probably caused by a defective exhaust and/or aftermarket exhaust parts which result in excessive noise....

My manual car starts but will not move on any gears.

What you are describing sounds like potentially a worn out clutch. As you know, the clutch transmits engine power to the gearbox, and allows transmission to be interrupted while a gear is selected to move off from a stationary position,...

How long does it take to remove and replace a throttle?

Hi there If the throttle sensor is not working, it's most likely caused by an electrical issue; as opposed to a mechanical problem with the throttle body or other components. The best thing to do is have a professional mobile...

clicking popping sound when turning sharp left

Hello there. Is your Jeep four-wheel-drive? A clicking or popping noise can come from a CV joint with a torn grease boot. The boot develops a tear or leak and the grease will leak over time until the joint is...

Jeep shutting down below 1,000 RPMs

Your issue could have countless causes, from a vacuum leak to a faulty fuel pump. If the Check Engine Light is on, the first step is to retrieve the associated diagnostic trouble codes (DTCs). These codes serve as a starting...

Car vibrates while accelerating

You might have a bad engine mount. Vehicles with transverse engines usually have 3 engine mounts and 2 transmission mounts. Some also have torque mounts. The mounts isolate the engines vibrations. When the insulator on the mount tears, the engine...

Power steering assist fault

Interestingly, there is an identical report of this fault, for your year, make and model, in the NHTSA database. It's probably not the battery, although you should still go ahead and load test the battery. Once the car engine is...

Related articles

How to Choose a Jeep Grand Wagoneer
Due Due to a recent surge in popularity, the Jeep Grand Wagoneer is making a comeback. Since the vehicle was manufactured only throughout the sixties, seventies, eighties, and the early nineties, most Jeep Grand Wagoneers are no longer on...
The Top 5 Selling Cars in Alaska in 2012
Alaska Alaska requires a different kind of vehicle to handle both the terrain and the wintery conditions. While some of the most popular options for the Alaskan terrain in previous years included options such as the Subaru Forester and the...
The Best Used Cars to Buy to Maximize Resale Value
A A car is not an investment. An investment, by definition, increases in value. A car is a necessary purchase, and it will never appreciate in value, with the possible exception of classics and antiques. So, as a used car...