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Gm Tech (Cam)
Gm Tech (Cam), GMC Mechanic
Category: GMC
Satisfied Customers: 1667
Experience:  GM Grand Master Technician 2007. 14 year experience.
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Chevrolet gmc: i have a 2003 gmc 2500 6.0 and get reduced engine

Customer Question

i have a 2003 gmc 2500 6.0 and get reduced engine power at random times, it might happen two times in a row or once and then nothing for weeks or months . i have a check engine light on that says mass air sensor light comes and goes i tried cleaning mass air sensor and didnt help , recently replaced knock sensors harness and intake gaskets ,cleaned throttle body , checked fuel pressure its good drove around with gauge on for awhile trying to get it to do reduced engine power but was unable to get it to do it . i have had scanner on it and throttle body is reading open 9 % at idle and only opens to 87%at wide open throttle not sure if thats correct . if i start it up warm or cold and try to go its sluggish for a couple seconds then is fine also while driving keeping at steady speed can feel it get sluggish and then better again doesnt do it all the time . in all its low on power . it has 170,000 miles on it
Submitted: 1 year ago.
Category: GMC
Customer: replied 1 year ago.
it was doing the reduced engine power before i did the knock sensors and intake if when it does it i have to pull over shut truck off for a couple seconds the start it up and it goes away i have also checked the ground wire on the back of the block .have not put a fuel pump in it since i have owned it bought it with 150000 miles not sure the throttle response seems to not always be there not sure if it could be tps or the throttle body as its electronic .would appreciate any info on where to start . thanks
Expert:  Gm Tech (Cam) replied 1 year ago.
Hi there, I am Cam. I don't suppose you have any codes from the system?
Customer: replied 1 year ago.
there was one that said mass air sensor i cant remember it exactly at the moment have had this problem for awhile ill go scan it and get back to u
Customer: replied 1 year ago.
it was p0606
Customer: replied 1 year ago.
im going to go scan and see if any others have come up as thats one i had written down
Expert:  Gm Tech (Cam) replied 1 year ago.
Ok, the P0606, what module was that stored in?
Customer: replied 1 year ago.
sry about that the p0606 was a different car the ones that are on the truck are p0101 two times and p1516 and that one is new never had that one before
Expert:  Gm Tech (Cam) replied 1 year ago.
These years of trucks with the electric throttle have a couple of very common issues. First and in my experience most common is the ground wire. THe ground runs from the rear harness behind the top of the engine to the rear of the left cylinder head. It is attached at the same bolt as the ground strap at the firewall. I have always been able to find this by pulling on the black wire and see if it gives. The fault has been a conductor broken in the insulation at the crimp. The second issue is the wiring near the throttle body. The wiring tends to break a few inches from the connector. check these out and see. Another common issue is the wiring near the throttle body itself. There are some wires there that can break inside the insulation and cause this. Check the wiring carefully near the throttle and about 6" back.Also check the wiring at the pedal under the dash, micro corrosion in the connectors can cause issues and even unplugging and plugging the connector back in will correct, it so then put some electronics grease on the pins. Finally is a connector in the throttle body itself. It is common for the pins in the connector to fail and cause codes. The repair for this is the pigtail connector for that throttle body.
Customer: replied 1 year ago.
thanks cam ill have to check them tomorrow was pulling into the driveway coming to a stop and truck went to a really low idle and died on me . did not get a chance to look at it but tried to start it fires,spits and pops a little bit and dies .. hopefully whatever was causing the other problems is whats wrong
Expert:  Gm Tech (Cam) replied 1 year ago.
ok
Customer: replied 1 year ago.
hi cam got truck running again the fuel pump went out ,so now it has new pump have not had reduced engine power yet but engine lights still on and still feels sluggish when accelerating and it still cuts out a little bit at steady throttle going going to check wires on throttle body tomorrow is there any way to test with multi meter? or just inspect wires
Expert:  Gm Tech (Cam) replied 1 year ago.
There is no way to really test the throttlebody with a multimeter, anyway if it is not setting any codes then the throttlebody is operating properly. Given the necessity of the throttlebody, it's very sensitive to any fault.