2008 Prius ABS Control Module Failure - Questions w/ Diagnostic Screenshots

welcome!

idk if that reader can be trusted with a prius. how many miles on her?

would it be worth paying a dealer to get the correct codes?

 

Too funny ... his Autel gadget confuses the brake ACCumulator with "adaptive cruise control". Good luck solving that cruise control leakage there.

One thing worth knowing about the computers in a Prius is they talk to each other, and sometimes one computer will set a trouble code that's just for trouble it heard about from a different one. For example, you might have an engine controller code for some problem with the engine, and also a hybrid-control code saying the engine failed to start. That doesn't mean you've got any separate problem in the hybrid system too.

The B1421 is a code you will always have if strong light isn't shining on the solar sensor at the moment you have the codes read. So it's nothing to worry about (unless you know the car was in strong light at the time).

You have a code complaining about the voltage reaching the ABS controller. That does not always (or even most of the time) refer to the condition of the 12 V battery, but rather to the condition of wiring or connectors on the way to the ABS controller. But I won't say it's never the 12 V battery, either. You have two codes about lost communication with two different controllers. There will be somebody along sooner or later to suggest you should check the health of the 12 V battery, and this time I won't even object.

I see nothing in this group of codes to suggest any problem with the traction (big) battery, and if I had to guess why the mechanic might have thought so the first time, I'd probably say jumping to conclusions without looking up the codes much.

 

Hi Geedis,

I had the following errors and codes (C1256 - ACCumulator Low Pressure - is a match with yours) that was all solved by replacing the ABS actuator on my 2005. Might be worth checking with another mechanic for codes to make sure the right kind of diagnostics is performed, and the real issue identified.

 

x2 with Chap......with all the inconsistent and unusual codes in there, it would definitely be in your best interest to verify the 12v system/battery is good prior to any other "recommended repairs".

One thing to keep in mind is the Prius is sometimes more like a computer than a normal car. The 12v system does not start the engine, but instead boots up all the computers and electronics (and various pumps, like the ABS). A crappy 12v sometimes = a crappy boot up and a lot of chasing your tail for ghost faults.

 

Hope you found something useful - let us know in the end how it was solved. What I meant with checking with other mechanic is that replacing the ABS actuator might be costly and it is better to be on the safe side to replace something that is for sure broken.

 

Check the 12v voltage when the car has sat overnight, BEFORE you start it. You can do that yourself search the site and there are posts on how to do it. You don’t even need a meter, you can read it from the MFD.

As far as the reader it’s Autel software talking to Toyota software. Doesn’t always jive 100%. The basic emissions codes do by law but your codes are not emissions codes. Some of them at least. Chapman pointed out a glaring error. Was adaptive cruse control even an option in 2008?

 

The newest one has a different part number than the first 3. Don’t know it off the top of my head but you can find it here.

 

There is another way to access that menu also. You press the display button then press 2 points on the screen several times in succession. Saves on turning the headlight switch. If you look around you can find the two points. It would be hard to verbally describe them.

 

My guess involved some poor underpaid Autel employee trying to copy code definitions from some abbreviated cheat list found by google, seeing something about "acc leakage" and adaptive cruise was just the first thing that came to mind. Probably hadn't heard of a brake accumulator.

When I use the voltage shown in the MFD signal check, I typically find it to be a bit more than half a volt lower than measurements elsewhere at the same time. It's fairly consistent with itself, so I use it often enough, but I tend to avoid drawing dire conclusions when comparing it to anybody else's "your battery is done for if it's below x" charts.

 

True but it is something anyone can check themselves. 11.5v perhaps you investigate more, 10v and you pretty much know there is a problem. After that comes 2 groups of people. The chargers and the replacers. Toyota dealer always seems to say replace. As far as charging I would like to know how much the car is driven and time the car is in ready mode. 2-3 five minute trips a week won’t keep the charge up but if someone is driving 30 minutes or more 5 days a week my guess would be bad battery.

 

Can the car be driven in its current condition?
If it can be driven, do you find that the brake actuator pump is running more than normal? (this pump sounds like a rattlesnake when the pump is running. Repeatedly press the brake pedal to force this pump to run while the Prius is READY, so you can identify when it is running.)

If yes, that is an excellent indication that the brake actuator needs to be replaced and confirms that DTC C1256 and C1391 are correct.

If that does not seem to be a problem, DTC C1300 means that the skid control ECU needs to be replaced. If the 12V battery is not weak, it could be that errors within the ECU are causing the other DTC logged by that unit.

Besides that it appears that you need new TPMS sensors to be installed next time you buy tires, if not sooner.

 

I would not worry about the other fault codes besides the ones that relate to the TPMS system. The transmission control fault is just saying that ECU is aware of a hybrid system fault. The fault is that the braking system is impaired.