Quote:
Originally Posted by b08b
Rod,
My son has 04 ls V6. Autozone scan codes p0352,p0353, p0355. changed plugs on 4,5,and 6. Swapped coils on 4 and 5, had codes cleared, #5 still showed bad. Took to mechanic. He checked codes, tested coils, checked plugs,& did compression test. He replaced coils 4,5,6. (I furnished O'Reilly coils.) After driving a couple miles, "cel" again with same miss. Mechanic scanned again and got p0300, p0316 & p0355. His conclusion after talking to a former ford dealer mechanic is flash pcm driver. Took to dealer who said it had been flashed previously. New consensus is bad pcm. Took to autozone just for kicks and code p0352 was there as well. ...
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It's not unheard of for the PCM to fail in this way. Leaving bad coils in for far too long can cause PCM output driver failure. That said, it really doesn't happen that often. Before you condemn the PCM, carefully check the wiring between the coils and the PCM, including the coil end connectors and the PCM end connector. The service manual gives the steps to take and electrical measurements to make to verify the wiring harness.
BTW, simple resistance checks on the coils do not detect the most common failure mode (internal HV breakdown) of the coils of the LS. Ford has a TSB out that explains how to stress the coils and take readings using an oscilloscope to determine if the coils are good or not.