No high idle at start

GCCFZJ

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So the IAC was improperly wired on my vehicle and started. Had to have it wired correctly and replaced the IAC. Now there is no high idle start when cold, I have to give it gas and use the hand throttle till it warms up. Had a local mechanic pull code 43. Took the car to Toyota out here in Doha and they are telling me they can’t pull code 43, yet still no high idle at cold start. Any suggestion on where to go with diagnosis and fixing? I’ve read that code 43 essentially doesn’t allow the ecu to receive the starter signal which doesn’t allow the ecu to send additional
fuel during a cold start. Read lots of threads but ultimately no solutions. Was hoping the tech at Toyota would be able to find the problem but not yet.
 

ceylonfj40nut

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Have you tried disconnecting the positive terminal to reset the ECU and then fire it up?
 

GCCFZJ

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Yes, I’ve tried that. I also put another IACV in place and still have the cold start issue. Does anyone know what signals the ECU sends during cold startup to enable the high idle?
 

GCCFZJ

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Some great questions but an update to this post. Bad idle air control valve. Code 43 was resolved and related to a break in the speed sensor. The high idle issue remained even after swapping three different used IACV. A new aisin unit has been purchased and will update this thread with the results. A lot of these threads have mentioned that the IACV rarely goes bad but my situation, of swapping three, seems to differ.
 

GCCFZJ

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Solved my no high idle cold start…..ecu was damaged. Swapped a different ecu and I have high idle cold start again. I will be sending my damaged ecu for inspection and repair.
 

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