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Old 02-24-2021, 05:16 PM   #2
fdryer
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Join Date: Jan 2006
Location: NYC
Posts: 44,832
 

2003 L-Series 3.0L Sedan
Default Re: L200 2002 won't stay on running

Unfortunately, you may be describing another repair shop that simply replaces parts on your dime, hoping to hit the right solution while making money whether or not a solution is found. Sorry, but any time an engine computer is replaced and the engine still won't run simply says the repair shop is guessing. As a rule, engine computers rarely fail and experienced people can determine whether or not a computer failed. Extensive diagnostics are performed by experts to narrow a problem down.

EFI systems can be easy or difficult to diagnose/troubleshoot unless a person has knowledge of engines, EFI systems, how sensors work and the various symptoms that can mislead anyone........ to replace the engine computer yet not fix the problem. The key is diagnosing then troubleshooting. Diagnosing gathers symptoms, testing sensors, fuel pressures, inspecting spark plugs, checking for spark and having knowledge of factory anti theft systems and how they prevent a vehicle from being stolen by disabling the ignition system, injectors, starter or combination of all three. Idiot lights reveals where to go as well as any error codes whether from the engine or wrench light. Engine light codes are related primarily to emissions errors and easily decoded. Wrench light error codes cannot be decoded by generic readers. GMs Tech II scantool, high end aftermarket scantool or moderately priced Tech II scantool clones can decode wrench and many other proprietary GM codes.

The first thing is if either the engine or wrench indicator are on and decoding stored errors. Next might be following suggestions given above to determine if a fuel or spark problem exists. With the engine running only a few seconds, this might be a fuel issue requiring a fuel pressure gauge monitoring before, during and after starting. Fuel pressure should remain high at all times, even when the engine shuts off. Spark can be tested to ensure it doesn't cut out after long cranking cycles. If this isn't fuel or ignition related then determining if factory security isn't turning on the security light but disables injectors occurred. GMs Passlock security disables injectors during a theft attempt and can allow the engine to run for two seconds before shutdown. Repair shops with expertise would know this by referring to online manuals for info (alldata or Mitchell). Without service manuals, anyone can guess and replace parts without finding a solution. I prefer to know as much as possible about the problem and gather info then refer to manuals to bolster any knowledge I don't possess before making guesses on parts swapping. This usually means I don't rely on repair shops. The brains and answers resides in service manuals. Matching symptoms to service manual info tends to determine a solution.
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