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8.1 random dies help please .

sweetk30

sweetk30

Back to play nice .
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My 2002 c3500hd 8.1 / 4L80-e truck gmt455 body has been randomly stalling but fires up .

It finally set 3 codes for p1516/1517/1518 for throttle / tac .

I know these trucks use a 2 year only tb before they updated them but my trucks last year for body style is 02 .

Any help would be great thanks .
 
left the shop this morning . stalled 4 times in 2 blocks . then over a lot more as i tried to go down the road . had to turn around and head back couldnt trust it .

also was cranking like it had out of timing problems . but when it fired it run smooth . set the 3 codes again and also went in reduced power and limp mode .

checked my 01 truck and different tack mod on firewall so cant even swap that over for testing .
 
I have no 8.1 exp. but sounds like a bad connection/ chaffed wire. Always fun to troubleshoot…
 
Check your grounds on the block. It’s not an 8.1 specific thing, but a smart starting point for diag.

I will say this I did have a random stall issue after my 8.1 install and it ended being the ground on the back of the head not being tight.

As far as the Tac/dbw codes, those don’t normally result in a stall. Reduced power for sure but not a stall. Things to check would be the throttle body itself. Carbon buildup causing the throttle blade to hang will set correlation codes.

Check connections and the pedal assembly, Tac module and throttle body. Keep in mind correlation codes set because there is a difference between the Tac circuit “a” and “b”. Any time there is a difference between the two percentages the fail mode is to set the code and drop the engine to idle. It you have any scan tool you can watch the values and see which side is off. Between the pedal and Tac module or Tac module and throttle body.

In my Workhorse days it was pretty common to have techs shotgun a pedal or Tac module at a unit and still had a problem which would usually lead to a wiring issue. It’s worth your time to pull up the diagnostic charts for the codes and run the testing down.
 
sweetk30 said:
My 2002 c3500hd 8.1 / 4L80-e truck gmt455 body has been randomly stalling but fires up .

It finally set 3 codes for p1516/1517/1518 for throttle / tac .

I know these trucks use a 2 year only tb before they updated them but my trucks last year for body style is 02 .

Any help would be great thank
Click to expand...
 
Truck is now out of service .

Swapping all the stuff off the flatbed over .

Not safe to drive and just need a truck that works . So old blue is back in service . Time to row gears in the other c3500hd 8.1 .
 
Did you upgrade to the newer crank position sensor?

It's possible you have a bad ground or intermittent power connection, and the throttle codes are just the first thing to log.
 
Blue85 said:
Did you upgrade to the newer crank position sensor?

It's possible you have a bad ground or intermittent power connection, and the throttle codes are just the first thing to log.
Click to expand...
Agreed !
A bad crank sensor would cause random stalls and or hard starts, among other symptoms.
Wes probably has more info on this.
 
I wish. Am kearning 8.1 stuff. Most of the throttle codes Ive been privy to ended up being bad terminals, or wire.
The crank sensor if old style is certainly suspect.
 
Has single o-ring crank now .

Talked with a friend who was 20+ year gm dealer tech . Now he has his own shop at home and works on stuff . He told me before i bring it to him swap crank and cam sensors for new with gm / acdelco / delphi units ONLY .

I hit up rockauto today for a gm crank and acdelco cam and be here friday .
 
I couldn't find a gm cam sensor for mine, has a Standard products cam sensor atm @ 10k miles on it.
 
A bad cam sensor will cause some issues/codes, but usually not stalling/dying.
 
sweetk30 said:
Has single o-ring crank now .

Talked with a friend who was 20+ year gm dealer tech . Now he has his own shop at home and works on stuff . He told me before i bring it to him swap crank and cam sensors for new with gm / acdelco / delphi units ONLY .

I hit up rockauto today for a gm crank and acdelco cam and be here friday .
Click to expand...
Good move :)
 
Can’t offer much help but to say that I knew of two guys from work who had new 2001 3500 8.1 and a 2002 2500 8.1 and both had issues with intermittent engine dying and in each case it was the crank sensor.
Both trucks had the same issue repeated after replacing the sensor about a year later.

As far as I know GM eventually upgraded the sensor and all was well the next time they were replaced.
 
i did the cam sensor = easy one and ZERO change in problem dead in home parking lot . when i get time i will do the crank sensor . but now its mad dash to the end of asphalt sealer season for me under 2 months till the end . and making up for super rainy 1/2 half .
 
did the cam sensor = easy the other day no change .

today was rain day left over from yesterday so no real work . swapped crank sensor .

so far it fires up and runs good . 5 miles local around house test drive no problems . had a random cam sensor code p0342 . cleared it and not back yet . just fired up after 2hr no run and back up . thinking of swapping back old sensor from original build from gm and try it .

side note : starting it under those bad conditions got the starter or flex plate all goofed up and now it has noise starting but fires up . . might have to swap out flex plate this winter .
 
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Try a little dab of Dielectric grease in the pins of the cam sensor. Just incase there is any “loose-ness” in the connector.

Short of connecting an “oscilloscope” to the cam sensor signal wire and monitoring it while driving. I know Snap-on made a scanner that had that capability. It’s called the “Vantage” it had a dual screen capability so you could look up specs and run the Oscilloscope at the same time. I had to go out and look at it, I haven’t used it in so long I had forgotten about it.
Just my two cents.
I really hate shotgunning parts at something without knowing what’s happening.
 
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BoondocK5 said:
Try a little dab of Dielectric grease in the pins of the cam sensor. Just incase there is any “loose-ness” in the connector.

Short of connecting an “oscilloscope” to the cam sensor signal wire and monitoring it while driving. I know Snap-on made a scanner that had that capability. I don’t remember its name though.
Just my two cents.
I really hate shotgunning parts at something without knowing what’s happening.
Click to expand...
Gona swap old back in and try . And warranty this new sensor .
 
I’ve caught more than one Chevy crank sensor that’s gone away using the oscilloscope while driving. Use the record function and you can actually watch the signal go away
 
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