What causes the diagnosis of going in and out of limp mode?

Asked by Jun 28, 2012 at 10:33 AM about the 2008 GMC Sierra 1500 SLT Ext. Cab

Question type: Maintenance & Repair

I have had my vehicle to 3 different dealers to diagnose the problem for a fix. No error codes are being stored is one issue and the service engine light is not on. here is what happens, while drving at any speed, the truck seems to feel like it stalls. All indicator dash lights come on, (service engine, ABS, etc as well as park assist). After a brief second or so, all clears and truck resumes. I was told it is going into limp mode briefly but they cannot diagnose since there are no codes and the service engne light does not stay on. Acts like a huge hiccup. Lose everything. At high speeds, the truck will just roll through it and only the dash lights alert you it happened. Slower speeds can really be felt. I am afraid this could become a safety issue. Does anyone have any idea where to begin. I would think someone would know at the places I have been. Come back when the light stays on is what I am told. Maybe someone here can provide some input....please


2 Answers


sounds like some sort of pcm issue maybe, i work for an expert diag shop and alot of issues similar to urs, no codes stored, intermitant issues that sort of thing get traced back to a pcm flash or pcm replacment. best place to take is is not the deal because they just go by a computer screen, alot of independent shops use a program called all data that will alert them to any pcm updates or anything that should be done, dealers also have this but tend to ignore it becuz the comouter has no codes. try a local guy but make sure he's reputable this kind of stuff is very tricky to diag and the shop may have ur truck for quite some time hope this help

I think i know what you problem is go under the accelerator pedal and there is a sensor connected to it i believe a throttle position sensor or something like that this sensor replaced the wire from back in the days anyways disconnect the sensor when this happens for a minute with car off then plug it back in and start it see if it fixes the issue this sensor is around $250 this happened to me more than 5 times i hope you resolve it good luck

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