DTC C1231 Help

Hello,



Long time lurker, new at posting.

I have a 2010 Prius III (nav, JBL, sunroof, solar roof) and currently trying to diagnose a DTC C1231.

I am the second owner (first hybrid) and have had her since January 2015, she had 15k on the clock when I bought her.

It was a real gem to find her with such low miles, she is my daily commuter car only, 57K on the clock now.

Anyway, on to my issue.

A few weeks before xmas, all was normal as has been in the past 3 years, when all the sudden I get in the car and get the dreaded "Check Hybrid System" error on the MFD and car will not go ready. Immediately turned to PriusChat. Tried everything described here in PC including, battery disconnects, 3 times on the start button, etc. Nothing got the car to ready.

Towed her home and began diagnosing her. Got the Techstream out, scanned it, and the only DTC that was displayed was P3004. New 12v battery was installed, all fuses checked, plug/unplug hybrid battery, etc. etc, to no avail. More research here in PC and found this DTC to be an issue related to the inverter and the TSB for it.

Towed it to closest dealer (I'll withhold name). Drop it off in the morning, told service manager I scanned it and found the DTC P3004, a few hours later he called and told me that it was the inverter and I was lucky that it was covered under warranty. 2 days later, I get the "car is ready" call. They inform that TSB-0036-16 was performed and all was good, car is running. Also performed, was a recall on the airbag system, where they install airbag brackets (CGG50A), not sure what this entails, but I think it is related to the whole airbag Tanaka fiasco, I received a recall letter in the mail, so they performed it.

Anyway, I go and pick up the car and they now tell me that there are 3 issues that they found that I need to decide on what they should do. None of the 3 are related to the inverter and/or TSB-0036-16. 1- NAV system has error of no DVD map, 2- power window auto function not working, 3- a code of C1231 is now coming up. My answers to the service manager where: 1- I took the DVD out before I disconnected the battery, so I have it, 2- "did you perform the reset procedure when you disconnected the battery?" (He was oblivious to this procedure!), 3- That code was not there before, why is it there now (his answer is "now it is showing up").

When the "Check Hybrid System" event happened the VSC light was ON along with the rest of the MFD lights, so I couldn't tell the service manager that they caused the VSC light to come ON and the C1231 code to trigger, even though when I first scanned it the code was not there. I think they may or may not have done something when they performed whatever they did for the airbag recall. I can’t' prove anything, so off I go back home. Anyway, issues 1 and 2, where not an issue after all, as you all know. It seems that they somehow "forgot" there was a power window reset procedure. Now for #3, their proposal was to replace the steering angle sensor at a total cost about $1,000. I responded with "can it wait?", since the service manager advised that the car would drive just fine even with the issue.

Go back home and back to PC, where I find lots of info to the steering angle sensor, zero point calibration, info on the clockspring (spiral cable), etc. Using Techstream I tried to erase the code but it kept coming back. Measured voltages at the connectors and followed the repair manual to reset the memory, and perform the zero point calibration. Rescan car and still DTC C1231 keeps popping up.

More research on PC leads me to think the steering angle sensor may have gone bad. New part (#86245-74010) cost about $400. Note the sensor and clockspring are 2 separate parts. They do install together, the sensor attaches to the clockspring.

Anyway, not wanting to spend the $400, I turn to Ebay and find a used one for less than $100.

A week later, I go and install it (again using PC for info on steering wheel removal and such). Key point here is to keep the clockspring centered and not to turn it any way.

All seems ok with the physical install of the "new" sensor, reset the memory, redo calibration, etc, but C1231 continues to pop up.

I highly doubt that the original angle sensor was bad at all, then the second one also bad? What are the odds?

One thing to note here, is that when you do the ZPC, you need to have the parking brake OFF, if not the brake system calibration does not happen and you will lose regenerative braking. It feels really weird if you don’t properly calibrate the brakes.

Car drives fine now, but the VSC light is always ON and the C1231 code has not gone away.
Don’t know if VSC really works as I have no way on testing that.

Anyone have any clue what else it could be?

I am researching whether this could be caused by something in the braking system since brakes and VSC seem to share the same computer module.

Sorry for the long post.

Any help is highly appreciated.

Thanks.

 

The airbag explanation makes a lot sense. I admit I didn't road test the car as it is stated. Fuses checked and voltages checked. Gonna try it again this weekend following procedure attached by padroo and will post my findings. Thank you all for the replies.

 

Hello again all,

Once again I tried the procedures to try to clear up the DTC. This time I followed the words to the teeth including test driving the car. DTC C1231 will not go away. One thing I noticed is that the steering angle sensor and steering angle values in the data list do not change while road testing. If I steer right or left, I assume these values would change. Mine are set to 850.5 degress. Is that normal? Thanks.

 

Hi all,

I have finally fixed the issue. I got around to buying another used steering angle sensor from ebay. This time I found a set that had both the sensor and the clockspring pulled from same car. Installed it, did the ZPC, cleared all codes, and no more codes. Skid control light is OFF. Car test drove OK. I must have purchased a bad unit initially as the second time around it worked. Thanks to all for your insights and help.