I have a '03 S. During driving several lights came on, the yellow triangle with the arrow around it, the yellow EML light and the yellow tire sensor. and of course the check engine light. The car went into safety mode and ran at a limited throttle (48 MPH max.) to limp home. I have an OBD Bluetooth module interface that tells me I have a P0642 error which is Sensor Reference Voltage "A" Circuit Low. Is this something that can be checked? I have pulled all fuses, checked and reseated them. Pulled the battery for about 15 minutes. Error keeps coming back. So, before I spend $200 on a used ECU computer is there anything else I can check that may be causing this. Thanks in advance for any help.
AJ

 

I hate to make it sound simple.... fix the issue....a different computer will give you the same issue....sounds like the fix is beyond just "resetting" something....

 

Thats what I am trying to find out. Is it a ECU problem or an input to the ECU.

 

Could just be a part, a wire, etc....
The code just points you in a GENERAL direction of a fix....where to start looking.
on SOME items it leads you directly to a specfic part, but often the code is just telling you something upstream or downstream is broken....
So the troubleshooting can begin....anything else is just tossing parts at the car hoping for the best...often a waste of $$.

 

https://www.northamericanmotoring.co...limp-mode.html

 

How old is the battery? When lots of idiot lights start blinking plus an obvious hint in the direction of electrical issues that is a good place to start. Are there things going on as well like windows going up or down by themselves or other such silly stuff? Just disconnecting and reconnecting the battery won't have much of an affect except to make you have to reset the clock. If the battery is 4 or more years old, I'd look in that direction.

 

FWIW my list of things to check carefully. Battery voltage; battery connections, cables and earths; charging voltages on and off load. Under bonnet electrical connections for corrosion and security. Your fault seems voltage related but affecting a number of circuits so it has to be 'supply' rather than 'user'.

 

Battery is only two years old. No other weird stuff going on. I reseated the connections on the ECU just in case some corrosion set in and I've inspected best I can all the wiring under the hood and don't see anything obvious. Battery connections are good. I've seen some various post that indicate I could have a knock sensor, spark plug or wheel speed sensor problem. Not sure where to start looking.

 

What ended up fixing your problem? I am currently having the same problem.
Thanks!

 

I pulled all the sensors out and cleaned them off. I had some rust build up on one of them and that may have been my problem. The sensors are magnetic. I haven't had a problem since I cleaned them. They are easy to get out, just one bolt and they slide out.

 

When you say "all the sensors" which ones did you pull?
Best regards!

 

There is one sensor for each wheel. I pulled all four because the error code doesn't point to any one in specific so its basically an easter egg hunt.

 

At least on my model there are 4, I don't know if that is true for all models.

 

Unplug the button that is located under the emergency brake that is the tire pressure switch. Mine had a short that caused this same code and issue. I used a volt meter to locate the resistance and there was my voltage drop. the switch doesn't get pressed enough or something can get spilled on it or in it. Just saying it fixed my situation. Mine would go less than a mile or two after reset and it would go into limp mode and always had a code of P0642. I hope this helps anyone with the same problem