Replacing Skid Control ECU of Prius Gen 3

Background

It started with three dash lights [yellow brake, ABS, VSC] and sometimes four including the red brake. Then with the proper diagnosis with techstream and repair manual lead me to calibrate the linear solenoid valve, which refuses save calibrated data. Then skid control ECU had to be replaced.

At this point, apart from above dash lights,

1. I had to be careful since I had no ABS, Toyota informed me I could even lose electronic brake assist [but never happened],

2. my MPG was significantly low since my regeneration does not happen well [brake rotors are very hot even after a small trip].

3. Sometimes power steering assist feels to be odd

4. And time to time my cruise control would not work, and the dash light would blink when I try to lock the speed

As in my country its Toyota directly do the repair and maintenance. With few dealers. I just went to Toyota for repair and they would ask me $3000 for the replacement. I never expected “Toyota” to have that high repair cost just 4 years after production. And explained my disappointment and worked away.

Then to find out these ECUs were quite available in the market in recycling centres. So I got one and replaced from a very skilled technician. This way replaced 4 times didn’t work any. Final one worked for few weeks until I saw the fluid leak.

So then with the help of community here I found the repair manuals, tech stream and mostly the guts to do the replacement by myself.

Then got an ECU from Ebay, with the same part number and photo matching. But then to find out it’s a LHD [Left Hand Drive] since its from USA. And my car is a JDM which is RHD. But with few modifications it fitted well enough. There would not be a major difference, so I didn’t mention it in the title

How did I do it

my apologies not being able to post any photos. This was since I had to do the entire thing at night since I was busy at office during the time and my photos were not clear enough.

Firstly, removed the firewall [can find video instructions on the web], it was simply removing the wiper blades and two lock pins in top plastic part. Then remove wiper motor assembly. Then un screw 12 bolts to remove steel cover.

Then ECU can be seen parallel to the brake pedal.

Before dealing with the ECU it’s a good idea to remove the negative terminal of battery. [or you can keep the drivers door open during the process and keep the key far away from the car so there is no brake pressuring during the time. Yes, car has to be off during the time.

Remove two bolts in the brake fluid reservoir bracket and clear the way to ECU.

Remove the communication cable connected to the ECU.

Remove two hoses from brake reservoir to ECU. It’s a good idea to block the hose, while its disconnected. And the un screw the brake 4 distribution steel pipes using 10’ key and the pressure line [red pipe].

Now dip below the steering wheel and remove the below plastic cover. And unscrew the 4 bolts around brake pedal. These bolts attaches the ECU to the chassis. This is the most time consuming and toughest work out of all, required lot of patience.

Remove the brake light switch and then remove the pin and the, which goes across the brake pedal lever. Now we can take the ECU out.

Now go in the reverse order to fix the new ECU.

I faced the difficulty since it was a LHD ECU and the car is RHD. It was the drivers side front wheel brake pipes giving problem to fix. But go ahead and bend the pipe if you face the same situ.

Prior connecting the Communication cable, make sure your reservoir has fluid at least to mid level. This level will come down soon, since ECU has to be filled with fluid.

After everything is fixed. And making sure hoses and pipes are properly tightened. Switch on the car [not ready mode] check for any DTCs. Clear them if theres any. You’ll have to calibrate the linear solenoid valve. Before resetting as in instructions make sure you run the test mode [unless this can cause a huge problem, you might have to look for another ECU].

If its other side ECU [as I experienced] DTCs will say “wrong ECU connected” don’t worry. Switch off the car and restart the calibration. You might have to do this few times. But it should work.

Check the fluid level during the process and refill if it goes below mid level. Finally release air from brake lines.

Take the car for a test ride. Do some panic brakes straight and while turning to each side. And get comfortable with braking.

Monitor the MGP gains and rotor heating for some time, just to ensure its working perfect.

 

47210-47130 is the part no. I know even in Sri Lanka gen 2 ECU is being replaced more and more. Where are you from and how much dealer says it is?