No High resolution signal from ECM

10-14-2010, 11:08 AM
I have a 94 Firebird Trans AM 107k miles, 5.7 Litre LT1.

One day it would not start. Cranked good but would not fire up.

Long story short I replaced the ICM, Coil and Optispark.

The car would crank strong but would take about 5 seconds to fire up.

Finally took it into a reputable mechanic. He did his diagnostic and determine the the low resolution signal was not going from the ECM to the ICM/Coil. So I got a new manufacture ECM. The ECM came pre-programmed. Installed it.

The car fires right up like she use to the first time when the engine is cold. But after the motor has ran and warms up the crank time is back to about 3 to 5 seconds. The mechanic says the high resolution signal is flat lining or there no high resolution signal when the motor is hot.

Any one have any idea of cause or have a diagnosing suggestions?


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