Check engine light comes on several minutes after starting engine

toyota
start
driving
engines
lights
supra

#1

toyota supra turbo 1987 good condition with new rebuilt engine about one since engine put in by auth toyota mechanic. recently check engine light would come when driving then go out about 1-2 seconds after coming on. Now the light comes on about 2-3 minutes after start driving and stays on until engine ignition turned off.

On restart light remains off, but again will come on shortly after start driving. Took to Toyota dealer and mechanic check codes and felt oxygen sensor bad. This was replaced by mechanic and toyota dealer, and light stayed off when drove home, then several days later about 20 miles from home light comes back on and stays on until engine ignition turned off. Back to dealer, and mechanic check wires, and apparently could not find reason for abnormal codes. light comes on normally at ignition on, and then goes off when engine started. Stays off for a few miles and then comes on and stays on again until engine ignition turned off. Problem with light which has never happened before, (I am original owner, and have taken good care of the car). Help if anyone has suggestion ! I do not want to ruin this new rebuilt engine or other parts that may be bad sending check engine through the ECU (Electronic control Unit)



















































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