Hi, I'm getting a reoccurring U0100 and U0101 code on my 2010 Camry. It's only got 24k miles on it and I've only put maybe a thousand on it so far. Seems to run just fine with the codes - any guesses besides "bad ECU" ? I'm just wondering if this could leave me stranded someplace? Code comes back after a mile or two of reset. Seems to run just fine.

Some history. It was my mother-in-law's car, inherited, so not beat up or modified.

Car sat unused for about 6 months over the winter, seemed to recover fine after jumping.

I replaced the brakes, rotors and front struts, just fyi. ABS sensors seemed ok and in place.

I had a P0442 code thrown a few times, new gas cap fixed that.

I had the blinking window buttons, which meant they needed to be recalibrated up and down - went away after window calibration - maybe part of the CAN bus issue?

Fuses are all good, of course.

No collision damage ever

Nothing else seems out of line, everything works, drives and shifts smoothly. Starts right up all the time.

Any guesses? I'm going to start by just reseating connectors on the ECU, etc.

Thanks - sounds like a needle in a haystack.....

 

The codes only indicate there is a lock of communication between CAN and a module or sensor it should be linked with. One code is the transmission control module, the other for the engine control module.

The Toyota dealer would use their Toyota diagnostic tool to try to link to all systems and sensors on the CAN. Then check for which items could not link up. This narrows down the problem area.

Its possible for a "P" or other code in set by a sensor or module connected to CAN to set these "U" codes. How deep into the cars systems does your scanner go to find codes?

See private message.

 

JP, thank for your reply. Unfortunately, my scanner is just a basic version, and only pulls/resets codes. I did the ol' pull off the battery ground and reseat the two big ECU connectors under the hood. Ran for a test run of about 15 minutes last night, then threw the same 100, 101 codes after a mile. Resetting it again, I drove another 20 minutes with no codes.

I'd think if it were an ECU bug, it would be consistent. Perhaps connection / ground to ECU or TCU, being a northern car in the salt. I haven't gotten to the TCU yet, buried under the battery....

Yeah, I know they could just probably knock it out of the park with the Toyota scanner, but you can't roll a car in for less than a grand these days.

A better scanner would be a great investment, any recommendations or is this locked up by Toyota?

Dave

 

A bit more to the mystery U0101 / U0100 codes. I only get them on startup when I haven't driven the car for a day or two. If I start it daily, I never get the codes. Maybe some keep-alive part of the ECU is discharging or such? Basic battery and connections are sound.

 

Try cleaning the electrical harness connections to the trans. Spray contact cleaner then apply some kind of dialectical grease.