ECM communication circuit C1203

Did you ever get this figured out? I'm having this exact same issue.

 

And one more with exact same issue after replaced ABS Modulator brand new from dealer and got stuck with the same errors. It is not possible to do anything further because there are existing errors - calibration is impossible with them. 1203 doesn't allow it, I think.

 

C1203 is a weird 'un. What it mainly means is the skid ECU doesn't feel like it's installed in the right car model, based on ID information it is getting from the power management control ECU, the ECM, and the yaw/acceleration sensor. Which sounds like a pretty big headache.

But there's also a "HINT" in the manual that C1203 will be output in any case before the linear solenoid offset has been learned the first time. So it evidently isn't supposed to stop you trying the offset learning, and if that works, the code can go away.

 

Spent a lot of time yesterday. A new master cylinder was purchased from the dealer. Due to error C1203, I was forced to remove all ECUs from the car and check their P/N. Didn't find any problems. But I found the damaged wire from the parking brake switch at the moment when I removed the fuse box for inspection .
The alarm installers mistakenly put their clip on the wrong wire, and when they tried to remove it, they damaged the wire. I removed the alarm when I bought the car and did not notice the damaged wire. I don’t use the parking brake; I didn’t know that the light didn’t light up.
As a result, at 3 am I finally completed the calibration and everything is fine now.
It’s bad that Toyota’s good program doesn’t give any hints as to why it can’t perform the operation.

 

Are you saying you didn't need the brake parts? It was the wire???

 

I think the solenoid offset learning is sensitive to whether the parking brake is on, so a problem in that circuit may prevent completing the learning. And then the C1203 doesn't go away. Sounds like kind of a flukey story, but flukey things happen.

 

The short story is this: I bought a 2011 Prius with a big hole in the block. I installed a used engine from Ebay from 2021 Corolla HY engine. http://www.ebay.com/itm/256388551001 It's a long story, but everything worked out well in the end. Then it turned out that there were no codes, but the brake pump turned on every 10-15 seconds. I have come across this many times before - the master cylinder needs to be replace. I spent a month trying to buy a used cylinder on Ebay but only 1 seller from Colorado sent me the cylinder. The rest refused. After installation I got 1203. Spent a few days and couldn't get it to run properly. Next thing you know. I bought a new one from the dealer.

 

Okay, but what about the wire that was cut? What was/is that about?

 

From reading the posts, the car was repressurizing every 10-15 seconds, so there was a legitimate need to replace the unit. But the replacement unit was posting a C1203 code that wouldn't go away—because it doesn't, if the solenoid offset learning can't be completed, and that apparently couldn't be completed because of a faulty parking brake signal, because of a wire that had been damaged by alarm installers mistakenly attaching a tap connector and then removing.

Again, it sounds like the kind of flukey one-off story that isn't going to inspire choruses of "oh yeah, that's the exact problem in my Prius too!" (unless everybody takes their Prii to the same alarm installers, who never learn from their mistakes), but it seems to be the story for this one anyway.

 

Thank you ChapmanF. You are absolutely right.


This is, of course, a completely different discussion but I thought that there would be interest in the topic of replacing the engine from a ’21 Corolla. The engine had partially damaged or missing parts. And even when I solved this problem, I immediately could not solve the cooling issue and was forced to understand in detail the design of the cooling system and discovered a lot of new things.
As a result, I was forced to replace the main computer on this Prius due to incorrect data for the operation of the water pump. The pump speed was too high and the temperature was too low - which caused cavitation and circulation stopped. It took me a week to understand what was happening. But now I know everything))))

 

This has happened to when I used a Regular Prius abs Module on a Prius V model, used parts. Basically wrong part, Prius c also has its own part all look almost identical but they are different. Also I order to do linear offset calibration when the part is new you have to perform the air bleeding with the scanner in order for the computer to unlock the system and let you do the calibration. This is what I have experienced in my history of working on Prius.