Brake light on - Rear Speed Sensor RH circuit

Happened to me in the front. Probably need a new wheel bearing hub as the sensor is integrated into the hub assembly. Use a Timken or OEM. The cheaper alternatives will fail in a year. Maybe $300 installed if you shop.

 

Moog is bad. Only Timken or OEM! No they do not have to be replaced in pairs for this issue.

 

There could be a few things noted in the repair manual for you to check before condemning the bearing hub.

The computer setting this code is up in the front of the car under the hood. It can set the code because the signal it receives from the right rear wheel sensor seems weird, but it has no way of leaving its post to go back there and find out why. All of the wiring and connections between that sensor and the computer are included in what the computer 'sees'.

The cause can turn out to be the sensor in the bearing hub. But it can also be frustrating to spend $300 changing the bearing hub, find out you still have the code, and then get around to checking the wires.

 

Foreign object on speed sensor code.

 

... as surmised by a computer that's 20 feet away from the sensor, based on a pattern of electrical noise.



There are 13 pages of workup steps given (shared by this code and the ones for the other three corners) to help pin down which of those possible trouble areas really has caused the code.

 

Check the electrical plug connection first, at the back of the bearing. Think this can be done without even raising the rear, but it does make it easier.

 

Where you find the workup steps for different trouble codes is in Toyota's Repair Manual for the car, and we have a wiki page that Elektroingenieur kindly assembled with a lot of information on ways of accessing it, including the direct way with a small subscription fee to Toyota, and some other ways that might be available to you through existing agreements with libraries, etc.

So you open the manual and you search up the section about the C1238 code, and there you are.

Different people on PriusChat have different levels of comfort around how big a part of Toyota's manual they're comfortable copying and posting. In a way, that just fits the way US copyright law works, which doesn't give any simple clear rules for what counts as fair use; it just comes down to "do whatever you feel you could defend in court if it came to that." For me, I put the line somewhere between pasting a small selected bit that goes directly to a question in a thread (which I do a lot, like in #7) and wholesale copying a 13 page section, which I generally avoid. But there are other members here who do feel comfortable pasting whole sections, and if one of them drops by this thread you might end up with a copy here, or if you search the forum for C1238 you might find another thread where somebody already did.

If neither of those pan out, you can always go right to the source. Even paying the $20 to Toyota usually isn't unreasonable for the info you get to fix your car. (Some of us had older cars where we paid hundreds of dollars to get those manuals printed on trees.)

As for talking to the repair shop, you can probably just say you have a code where the ECU gets a funny signal from that sensor, and you'd hope to rule out any cheap reasons the signal could get funny on the way to the ECU, before settling on the expensive hub bearing with the sensor. Really, that ought to be the way a tech in a repair shop thinks anyway (not that it always is). The little bit I clipped in post #7 ought to be enough to suggest what the possibilities are.

 

This might be what you're looking for. @ChapmanF 's "bread crumbs" helped:

 

I don't know. See if they will give a year warranty. NSK are not the cheapest.

https://www.timken.com/resources/timken-ball-bearing-wheel-hub-units_11234/

 

Chapman.. I am trying to learn HOW he ABS system works.
I am feeding the signal from the front ABS sensor into the rear sensor feed.

It not working..

Why?

 

What are you trying to accomplish by doing that? And in what generation car (this is a Gen 3 forum, but I see a Gen 2 in your profile)? I'm pretty sure Gen 3 uses a Hall-effect-like sensor (square pulses of constant amplitude, only their width and frequency change with speed) and Gen 1/2 used simpler sensors (sine waves, frequency and amplitude increasing with speed). There might be different pulse counts per revolution for front and rear, I don't know.