Intermittent (!) Warning light, DTC C1300. What type of Skid Control ECU issue?

It sounds like you have your finger on the pulse. The C1300 is a self-test failure, which means that internal routines are not finding what they should, such as the ROM check sum is bad, or something similar. Not much for it but to replace and see, IMHO. Let us know how it goes.

 

Hi there. I am from New Zealand and i recently had my 2005 Prius diagnosed and one of the DTC's was 1300 with a detailed freezeDTC of 1011. You say above that you were going to swap out the ECU. How did that go? Thanks

 

Hello. I am experiencing what may be the same issue with my 2008 Prius. The light came on and will go off and come on intermittently; it usually stays on for anywhere between 15-150 miles before going off and staying off for a few days (I drive 180 miles daily, at a minimum)-but it is never on when I am near a garage or have an appointment. Can you give me an idea as to where you purchased the replacement ECU and a rough cost (monetary and time to replace)? Thank you!

 

First get your fault codes read with Toyota hybrid capable scanner. Fault information stays in the memory even after light has cleared. If you want to read code yourself get techstream. Best if you can get both code and sub code (if there is).

 

Thanks for the replies-I do need to have the code read yet, it seems that every time I schedule an appointment, the light goes off and I didn't realize it would stay in memory. I'll check back in once I have the info.

 

Hello Speedy7, how did u do the re-calibration. If u can share some details it would be great. I got about 5 codes on ABS unit and C1300 is one of them, and I did notice with Dr.Prius that my charging amps do not go up while braking and my gas mielage dropped ever since these codes came on.

 

You could include all of the about 5 codes if you wanted to give us more complete information, but the C1300 generally indicates that the skid ECU has failed its self-test. The repair manual doesn't generally go into internal repairs of ECUs, but just recommends replacement. Before that, it might be good to look at the other codes and see if the manual indicates any way that they could lead to a C1300 also being posted.

It is common for the regenerative braking cooperation to be disabled when such brake system trouble codes are posted.

 

All 5 codes. C1241, C1242, C1256, C1300 & C1391. Attached are ffd as well.

 

All of those voltages in your freeze frames are really low, around seven volts or below. That's definitely low enough where you can start to see logic circuits doing weird things, because the strictly regulated 5 V that the circuits rely on comes from onboard regulators that can need a couple volts of headroom to do their jobs.

So I would grab a meter and focus on finding out why the voltages arriving at the brake ECU and actuator are so low, whether it's because of the aux battery or something dodgy in the wiring or connections.

Once that is resolved, I would clear the codes, find something wooden to knock on, and see if they come back.

 

Thank you Chapman, I pulled the ffd and I was like okay, what should I do now. I do not have a repair & troubleshooting manual, once I find that I guess I need to start checking what nominal range should be. The battery for the car is 1.5yr old at most.

 

Have we got a page for you:

Toyota Service Information and Where To Find It | PriusChat

The trouble codes you have refer to voltages arriving at the brake ECU or at the brake actuator. When they are low, it can be because of the condition of the car's 12 volt battery, but it doesn't have to be. You can also have situations where the 12 volt battery is just fine but there are connector or wiring problems dropping the voltage before it gets to these components.

If you have a multimeter, this is just a simple matter of making some voltage measurements, starting with the 12 volt battery itself, and following the wiring diagram until you see where the voltage stops being ok. If you don't have a multimeter, you have a preliminary problem to solve first.

Nominal ranges in a car's "12 volt" system are, by design, pretty broad. As low as 11 (and that's conservative!) or high as nearly 15 can all be seen without ill effect. (Toyota will tell you to charge the battery, if it's below 11, before spending much effort on other troubleshooting.) That's why the boxes, like ECUs, that are most voltage-sensitive contain their own regulators to make a strict 5 volts from whatever's coming in. But the regulators can struggle to make a stable output when the supply isn't at least a couple volts higher, so that's why the 7-ish supply in your freeze frames is Definitely Too Low.

 

Thank you Chapman, I found that page. I see the wire repair manual used for fixing pins and wiring on the vehicle. But anything else it points to TIS which is a subscription service from Toyota. Was hoping somebody got a pdf of the RM & EWD for my 2008 Gen2.

 

Just a brain fart, my lights flicker sometimes, and the driver side turns off after some time, so wondering if indeed is the wiring issue and may be both are related. I found a 2006 EWD RM01R0U, wondering if I could use it for 2008 as both are Gen2

 

That's probably the same 2006 pdf that a lot of people are referring to for their Gen 2s when they are not signed in to TIS.

It's ok until it isn't ... there can be minor differences between years, and also the manuals on TIS get updated/corrected, which doesn't happen to a downloaded pdf.

So of course you can look stuff up in the pdf as a first stop. If you run into something that doesn't make sense or is missing from that copy, you know where to go for the real deal.

Yes, TIS is a subscription service, but you can get two days' access for $20, which I seem to spend maybe once every year and a half or so. Not a whole lot of money, compared to paying shop rates, or having a car that doesn't work, or having one that I broke because I didn't look something up.

Also, that wiki page mentions several other access options that Elektroingenieur went to the trouble to explain there, such as through a local public library, which can be free.

 

Did not get very far. The Battery is good, 12.73V @ battery. Brake power supply output measured 11.7v (10-14v) is nominal. Ran into trouble trying to get to Skid Control Unit in the dash. Looks like I need to major disassembly of dash to get to it, I removed all panels/skins on driver side but still wont get enough access, looks like I have to remove the lower instrument panel sub assembly to get to it. All ABS fuses are good in engine compartment.