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Old 01-20-2018, 03:06 PM   #4
fdryer
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Join Date: Jan 2006
Location: NYC
Posts: 40,237
 

2003 L-Series 3.0L Sedan
Default Re: 2003 Ion starting then immediately stalling

Engine computers are far more rugged than home PCs, laptop, Ipads, tablets and cellphones. Try leaving any of them outdoors all year and see if they still work. EFI systems have been around for several decades without reported failures of pcm or ecm. If they do fail, it would be major news all over the world. They don't and the few that do fail are the exception to the rules. Its understandable to relate computers with plug n' play but not with automotive computers. As you know, some require a security relearn procedure to marry ECMs to BCMs GM uses (Passlock). Performing a successful Passlock relearn with security turning off means security isn't the problem. Unfamiliarity with EFI systems gets many into trouble.

Did you check for blown fuses?

Presuming security is disabled to allow starting and running, all EFI systems still run with three necessary items - air, fuel and spark. If the engine turns over (cranks) but doesn't run or runs briefly, checking for fuel and spark might be some first steps in troubleshooting. Fuel and pressure can be checked by depressing the fuel test valve on the fuel rail (black cap covering a tire valve) after ignition is turned on. Fuel should spray out. Spark to each plug can be difficult to test but an alternative method may help; spraying starting fluid into throttle and starting - if spark is generated then starting fluid will ignite in each cylinder to get the engine running.

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