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My Toyota Vitz 2007 idles roughly and I got advice to clean the throttle body and make the vehicle re-learn the idle by starting the engine and let it idle for some time.

My question is, is it necessary to instruct the vehicle in some way (disconnecting the battery may be) to start re-learning? Or does it keep relearning always so that it is unnecessary to trigger it?

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I know this vehicle as a Yaris; 1NZ-FE engine, and that is the vehicle I am commenting on.

Toyota does not mention a specific procedure for an idle relearn in their official service information. Even the procedure for throttle body replacement does not mention a relearn procedure. The info does not state that a procedure is not needed, it is silent on the subject. Experience has taught that when service info does not mention a relearn the PCM performs this task without intervention. Self learn is normal and has become the routine for most PCM relearns for throttles, crankshafts, camshafts, evaporative purge amounts, individual cylinder fuel control and others. Most of these are done with software based on neural network type algorithms.

For a standard idle relearn with no OEM specified procedure the best method is to drive the vehicle for a time with lots of stop and start cycles. This usually resolves idle irregularities. If not try, the next method.

Professional techs learn some tips and workarounds. One of them is this, to reset a PCM that is not performing as expected remove both battery terminals touch them together for at least thirty seconds. This can, but does not always resolve a problem. It is a last resort procedure because it resets all the memories in every computer in the vehicle so be prepared to reset everything. Make sure to have the radio security code. On a luxury vehicles this often requires owner input to reset owner preferences.

If this does not work seek professional diagnostic help.

A short term subscription for Toyota tech info is available here https://techinfo.toyota.com. This is available in the US, I do not know if such is available elsewhere. This material is copyrighted so I will not copy it here.

  • Nice nugget. I learned something today :) TY @FredWilson – Ppoggio Dec 30 '15 at 6:59
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It usually requires the negative battery terminal to be disconnected for 5 minutes. Everything else is done by the computer. It will self adjust rather quickly. If it does not adjust, have your mechanic check for any codes.

  • Do you have any references for this? On some (if not all) Toyota models, disconnecting the battery can actually cause it to run worse without a throttle position re-learn. I don't know if that is the case here, but before you go throwing this advice out there, having something to back it up would be a good thing. – Pᴀᴜʟsᴛᴇʀ2 Dec 15 '15 at 1:33
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I just have done the ETV relearning on an Axio 2012 with 1NZ engine. The car had rough idling, even engine stalled. So removed the throttle body and cleaned it up. After fixing back the throttle, the idle rpm went up to 2200! Kept the engine idling for more than 10 minutes, removed battery negative twice, but no change! Then took the car for a test ride. Speeded up, pressed hard brake, pressed up, again brake. Did it for around 10 minutes. Meanwhile stopped the engine few times and restarted. Everytime found the rpm going down and finally it was set at 800!

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1)If this Toyota is like most sold in the USA you need have the engine coolant at operating temp first.2)Shut the vehicle completely off remove key. 3)You push the clutch in if it is a manual transmission. 4) Insert key. 5) Without starting the vehicle turn the key until you are on the "ON" position for about a second. 6) Switch off and back to on then start car from that position. Leave it alone and let it run. It will go through the self learning phase now. You can see it done on youtube I am sure! I think it takes about 3 minutes. It is not an automatic function you have to trigger it and you do not need a specialized tool to do it. Every time you disconnect the battery for any length of time this is needed. My 2003 Camry can not make it around the block with out stalling when I disconnect the battery to work on it after I hook the battery up again. Now if you had a hi end professional scan tool and programmer I am sure you could trigger it that way too but who has a code reader that can do that at home? Cheers!

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I literally just did this. Start the car and make sure the heater gauge is at warm. Then shut off. Turn the key to on [dont start] then off. On again, then off. Start the engine. Engage the e-brake and put your foot on the brake. Put the car in drive and wait while the car adjusts to it's normal rev. Took me 5 mins. Switching the key on and off twice and starting engages the relearn mode.

protected by Community May 29 at 1:40

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