Bad FICM, replaced... now runs but dies after 30 seconds. - Chevy and GMC Duramax Diesel Forum
04.5-05 LLY Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

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post #1 of 2 (permalink) Old 10-18-2019, 06:19 AM Thread Starter
Join Date: Oct 2019
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Bad FICM, replaced... now runs but dies after 30 seconds.

Hey guys, so if anyone could let me know what the difference is between the Engine Family 4SZXH06.63AK and 4SZXH06.63AW (obviously the last character being different) it would be greatly appreciated.

For a back story, my FICM is bad on my 04.5 LLY, yes I already checked the wiring harness in the known issue areas. It was popping the EDU 1 fuse every time you turned the key on resulting in a no-start situation. My buddy had another LLY FICM that I installed and now the truck starts, however it runs great for 30 seconds and then shut off completely (no codes to help diagnosis either which is super helpful). After re-inspecting the old and the replacement FICM I noticed that the model numbers (8GF1XS) are exactly the same however the engine family number above are one character off. Have googled extensively and all it brings up is EPA data when searched.

My (hail mary) thinking is that my truck may be California compliant as it was bought out west and if this is the case that maybe there were some discrepancies in the programming and now the ECU and replacement FICM are incompatible or fighting each other.

Any help would be generously appreciated. Thanks
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post #2 of 2 (permalink) Old 10-18-2019, 07:19 AM
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Join Date: Aug 2012
Location: New Hampsha'
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Perhaps it's pulling air in at the fuel line connections to the ficm. Did you use new copper washers on the banjo fittings? Or at least inspect them if reused?

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