Engine Control Module Code and Rough Idle

[rks171]

My 2007 Yaris has had a rough idle that comes and goes for over a year now. My attempts to fix it have included changing the spark plugs, cleaning the mass air flow sensor, and changing the air filter. I have changed the battery a year ago when the old one died. The car has about 140 k on it now. Within the last month, I've now been seeing the check engine light go on and off periodically. I had the car scanned and the error code is P0606, which says it's something related to the engine control module (ECM).

The guy at O'Reilly says it doesn't necessarily mean the ECM itself is faulty. He actually believes it isn't the ECM itself because the check engine light doesn't stay on all the time. He thinks it's something mechanical. From what I read, this error code can be a real pain to diagnose, as it can be caused by a lot of things from corroded wires, to faulty connected sensors, to the ECM itself. However, I'm wondering if that rough idle might give indication as to what is triggering the error code. What else could cause the rough idle that could also cause the ECM to complain? O2 sensors, MAF sensor?

My last resort is to take it to the dealer and have them try and diagnose it, but I hear that can get expensive fast. If they hook it up to their computer, is it going to tell them exactly what is at fault in the system?

[CTScott]

If it is an intermittent issue, having the dealer plug in the techstream tool won't tell them much.

You can pick up an ECM for under $50 off ebay or from a junkyard (just match the 89661-xxxxx part number). Since you have an 07, you don't have an engine immobilizer, so you can just swap in the replacement ECM for a quick and easy test.

[rks171]

Okay thanks. Is there anything special I need to do when I make the swap? I read that they sometimes need to be reprogrammed when installed or that there is a relearning period required.

[xdarkxfirex]

The dealer will charge you an arm an leg for everything. I got burned one time when my wheel cylinder threads were stripped $10-$15 for a new aftermarket, and they wanted to charge around $135 for an oem, plus 210 for labour to install. Ended up costing me around $286 for that and bleeding, plus around the same when I blew the fusable link on the positive battery terminal. The dealerships are plain crooks.


As for your ECU, I believe you can change it at home, fairly easy, I tried to remove one from the local yard here which wanted $22 for one, but I didnt bother getting one. Local yards, or many reman, used sellers sell with lifetime warranty. Dont buy a new one unless you want to pay a ton, maybe it needs a reprogram?

https://www.youtube.com/watch?v=pOSEJu7_Upc


"Possible causes
- Faulty Engine Control Module (ECM)
- Engine Control Module (ECM) Harness power supply circuit is open or shorted
- Engine Control Module (ECM) Programming

Tech notes
Check the ECM fuse, if fuse is OK try erasing the code first and if the code comes back you may have to reprogram or replaced the ECM.

There is a factory service bulletin for the following Toyota models:

Read more: http://engine-codes.com/p0606_toyota.html#ixzz3a4gCcPLx

[CTScott]

Originally Posted by rks171

Okay thanks. Is there anything special I need to do when I make the swap? I read that they sometimes need to be reprogrammed when installed or that there is a relearning period required.

Just install it. It may run a little rough for a few seconds, but then will be fine. There is no reprogramming required to test it. If your state does any type of inspection where they plug into the diagnostic connector, the replacement ECM will report the incorrect VIN, but that can be corrected using the TechStream tool (if the ECM solves your issues).