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By AlexP, June 19, 2018

Hello Corolland  

Error code: P1656; Oil Control Valve Circuit

What I've done: changed out solenoid with AC Delco, replaced ACD with Toyota genuine, still issue...

Last august, we had a new motor put into our beloved 2000 Toyota Corolla. House issue, work travel etc have kept me from driving it too much. 

Fast forward from august to January, I noticed the CEL is on. Good thing we have a 1 year warranty on this baby. Take it back to mechanic, he keeps it for a week and does some diagnosing. Asks me if CEL was on previously? I can't recall, and he says all his work and his technicians diagnostic work points to a bad ECM/ECU. I take him at his word. Take care home, and just last week, took it to another mechanic I trust for some more diagnostic work. He verifies that he thinks its the ECU/ECM. Said that "we don't see a signal from that circuit at the ECM/ECU, that circuit is dead." 

Second mechanic knows that I sometimes do my own work, so he knows that its not guaranteed I'm going to pay him a large sum of money to do this job. I don't believe he is out just to make a buck. To be frank, I trust his judgement. 

His charge for 3 hours of diagnostic work was $120. Said if job to replace ECM/ECU would be 280 for labor (minus 120 for diagnosis) plus parts. He found a new OEM part for 390. OUCH. Ebay has tons of the computer I need (89661-02691). But all the ads say 1999+ cars "MAY" need to be reprogrammed. Therein lies my question:

If I buy a used ECU/ECM, will I need to reprogram it so that my vehicle will work? I'm aware that VIN is embedded in the code, and perhaps that would prevent me from passing SMOG in CA? But will my vehicle systems work properly as a drop in replacement?

  • 320 posts

You will need to reprogram it to make the odometer accurate and possibly to avoid having the stereo shut down (not sure when that was introduced as an ant-theft measure). Legally, yes, you may need to reprogram for the VIN too. I suspect it would work. I don't know why it would not. I'm not an expert, though. 

I would still test the circuit yourself for a bad ground or broken wire. 

Sorry for the delay in replying, I didn't see the post for whatever reason!

  • Like 2

Thank you for the feedback guys. i'll report back with what I find this upcoming weekend.

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