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03-10-2015, 03:08 AM | #1 |
Registered User
Join Date: Oct 2008
Location: los angeles ca
Posts: 210
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Engine light will not flash any code???
Friend has a 1990 GMC 2500 5.7 ltr. Th400 which has the engine service light on. A scan tool does not work and when I jump the a and b connections where you plug in the scanner to pull the codes, it just flashes once rather than flashing the 12 code which I believe tells you it is communicating correctly and then will spit any trouble codes thereafter.
I pulled a spark plug because the truck feels like it is skipping (engine still feels very strong) and the plug is black so I it seems like it is in a rich condition. Anyone have a problem like this or know of a thread that I could read for some ideas where to go? Thanks for any help. |
03-10-2015, 06:48 AM | #2 |
Registered User
Join Date: Jan 2006
Location: Smithfield, VA
Posts: 1,501
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Re: Engine light will not flash any code???
Start with an ignition tune up. At least look at the cap and rotor but suggest replacing it and wires as well.
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03-13-2015, 08:32 AM | #3 | |
Still plays with trucks
Join Date: Jul 2009
Location: Spokane, WA
Posts: 3,556
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Re: Engine light will not flash any code???
Quote:
My 91 had an ECM circuit board come loose inside the case and it would go from running normal to limp home mode randomly after hitting a bump. I figured it out when I pulled the ECM and heard the noise inside. I put my chip into a spare ECM I had sitting around and it fixed the problem.
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miSSed opportunity - ground up creation of an AWD 1994 454 SS that never was http://67-72chevytrucks.com/vboard/s...d.php?t=795577 69 C10 shortbed stepside 400 small block - built like what a super sport truck could have been 69 K20 lwb TBI 350 4L60E NP208 14-bolt Dana-44 w/disc 68 Camaro SS / RS 500hp 439 inch roller cam big block 4L80E 79 Malibu TPI 350 4L60 w/ Z28 steering & sway bars |
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03-13-2015, 09:21 AM | #4 |
Registered User
Join Date: May 2004
Location: Minnesota
Posts: 4,620
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Re: Engine light will not flash any code???
I agree it sounds like an ECM failure.
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For those of you that are wondering why you are not getting replies to your thread: Did you give the model, year, engine, fuel system type, and transmission information? If it is modified from what came stock from the factory, let us know that too. |
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