A tale of woe and OBD codes.....

Hi All,

We've owned our 2005 gen 2 prius for nearly 4 years. For the first 3 years it gave stirling service with very few issues (Tyres, exhausts, normal wear and tear stuff) however we then started getting the engine light come on with code for lambda sensors.

We changed one lambda sensor, then the other, the exhaust (with cat again) and the MAF sensor. ENgine light stayed on, but it worked just fine so it wasnt a priority so we just carried on tinkering whenever trying to work it out.

We then got some very odd behaviour after a fortnight in an airport carpark. 50 miles into the journey the dashboard lit up like a christmas tree with brake codes at 2 in the morning. I believe this was the small battery which has now been replaced with a gel battery.

We were worried by this new behaviour and we took the car to the local auto electricians showing a AFR sensor code and P0606. I was able to deduce that the AFR sensor was not getting voltage to it's heating element but it was a new lambda sensor so it didnt make much sense.

THe autoelectricians checked continuity in all the wiring, and put another new lambda sensor on. This didnt fix it. After this and after confering with the local toyota dealership for whom they do work, they decided to put on an entire new set of ECUs. This has removed the AFR sensor code but still leaves the P0606. It may be my imagination but i think the braking is now always jerky even on smooth surfaces coming to a complete stop, and often shows the tyre tracks symbol on the dash. No codes are thrown on this though.

I have now managed to obtain a usb interface and a copy of Techstream.

This provides a more verbose freeze frame than my generic reader did, but i'm really stumped as to where to go with this.

Can anybody advise please? I'd be eternally grateful as it seems the experts are stumped and I really dont know where to turn.

I've attached a zip of the csv file exported for the freeze frame from techstream in case anybody has any ideas from that!

Thanks,

Rich.

 

Hi Patrick - thanks for your response. All of the ECUs on the car have been replaced. I'll take a good look at the wiring harness and the throttle motor i guess then!

Thank you, i sincerely hope there's something there.

 

Yes it was a used set.

I had an electrician change all the ecus. Do they have to be matched parts for me to do it as an entire set? If i was to change a single ECU i'd have to recode it if i've understood correctly?

I'm happy to chance a few more quid on it before I give up if this sounds like the most likely fault!

THanks,

Rich

 

OK brilliant. That's got to be worth the 30 quid or so they go for on ebay

I'll let you know how i get on!

Thanks,

Rich.

 

Just to confirm, I'm looking at what's referred to as the ECM?

Thanks

Rich.

 

brilliant thank you. I guess i'll find out if they swap the sides for right hand drive models in the next day or two

 

Another 89661-47110 is ordered and is now on it's way.

Have you ever seen the issue with the skid display coming on when coming to a halt and a jerk - like it's disengaging the drive or the brakes or something? Maybe if the throttle sensor is misreading this could be the issue?

Thanks

Rich

 

Hi guys,

Well I finally got round to trying a third ECU. It also gives the P0606.


My lashup to go for a ride without having to actually swap the ecu out of the car... - for owners looking in the future, this means the ECM is on the passenger side in right hand drive cars.

So, given everything else that's been tried already and the odd braking behaviour, is there anything else that could cause this P0606?

Thanks for your answers, they really are appreciated, and hopefully if this can be fixed it saves a car from the scrap yard. I cant let anybody drive this just because with the braking behaviour it feels unsafe.

Rich

 

Yes, the one with the picture of 2 tyre tracks. It comes on just as the car is coming to a halt. There's a kick through the brakes where it feels like it's not going to stop but then it does then stop.

I've only driven about 5 miles this afternoon after changing the ECU. I have driven lots of miles before the previous reset, but got nothing but a P0606.

My gut feel is that whatever is happening is going to be something to do with the braking issue with what I've read about current draw or shorts causing 0606s on numerous vehicles. I'm definitely out of my depth but then the autoelectricians who have consulted toyota are also out of ideas.

Thanks,

Richard.

 

Hi Valde,

I purchased a workshop manual online last night. It has some interesting information in it, which i think may be key. According to the manual the 0606 can also be tripped by the throttle position monitor being faulty. On that basis i'm going to get another one off ebay and give that a try next. Maybe that could also tell us why the brakes misbehave if the throttle is perhaps still on a little as well as the brakes? What do you think on this? I'm also wondering whether the actual sensor on the accelerator pedal could be at fault...

The code only comes on after you've been driving for a while. it doesnt come on if the car is left idling afaik,

The manual also has a list of what ecus and wires talk to which other wires and ecus. I do have toyota techstream so i'm thinking i should be able to record the sensors and what they're expecting in terms of values and what they're getting.

Otherwise i think i'm going to have to do exactly as you suggest.

Thanks for the reply!

Rich

 

Well throttle sensor ordered. I'll post details of the 0606 tonight. If nothing else somebody else may find it useful in the future.

 

MONITOR DESCRIPTION The ECM continuously monitors its internal memory status, internal circuits, and output signals to the throttle actuator. This self-check ensures that the ECM is functioning properly. If any malfunction is detected, the ECM will set the appropriate DTC and illuminate the MIL. The ECM memory status is diagnosed by internal "mirroring" of the main CPU and the sub CPU to detect random access memory (RAM) errors. The two CPUs also perform continuous mutual monitoring. The ECM sets a DTC if: 1) output from the 2 CPUs are different and deviate from the standards, 2) the signals to the throttle actuator deviate from the standards, 3) malfunction is found in the throttle actuator supply voltage, and 4) any other ECM malfunction is found.