# Looking for a Gm 6.0l gas expert



## Husky gas axe (Sep 8, 2018)

Hey everyone I have a 2003 chev 2500 HD. Been a great truck. It developed an intermittent starting issue. It always starts, but takes a few times. Code shows to replace cam sensor. I did that. Still the same. I also did the complete fuel system new. Starter is new. The truck always starts but it’s aggravating. Thanks for input. 
6.0l gas, auto, 100 000 miles
Kyle


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## 1Alpha1 (Sep 9, 2018)

I own a 2002 *1500* HD. Bought it used @ 104K miles back in late 2005. It was spotless, inside and out. I now have 150K miles on it, and no issues at all. Same engine as yours. 

Hope that someone will come along and be able to help you. I'm curious as to the problem.


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## s sidewall (Sep 9, 2018)

Did you perform crank/camshaft correlation relearn after installing new cam sensor?

Steve


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## s sidewall (Sep 9, 2018)

When you said codes says to replace cam sensor, that was after running diag chart, and what code is setting?

Steve


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## s sidewall (Sep 9, 2018)

What part of the fuel system did you replace, pump assembly, pressure regular. Let me know so I can check it out at the shop at lunch tomorrow if I don't have a lot on my schedule. 

Steve


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## Husky gas axe (Sep 10, 2018)

Fuel pump,regulator and filter got replaced. The dealer did the sensor so I assume the did the correlation.


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## s sidewall (Sep 10, 2018)

Did he diag it as being the sensor or just install and setup?

Steve


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## Husky gas axe (Sep 10, 2018)

It was diagnosed at that. Installed and when he puts the scanner on, code still apears.


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## s sidewall (Sep 10, 2018)

Sounds like he needed to have dug deeper. If you have the code, I'll put the service manual on my pc.
Is it P0341?
Steve


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## Husky gas axe (Sep 10, 2018)

Sorry Steve I don’t remember right now. I am taking the truck to another gm tech in the next town over. I will keep you posted. He thinks possible bad wiring to the sensor? He also asked if the timing chain has ever been changed.


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## s sidewall (Sep 11, 2018)

That's why I asked did he did deeper. Been seeing a lot of wiring damaged from mice at the dealership lately. Keep us posted. 

Steve


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## alleyyooper (Sep 11, 2018)

Some of those codes will remain after a fix for 20 to 40 cranks(attempt to start). Should have had the battery disconnect to clear the code after the sensor was replaced.


 Al


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## s sidewall (Sep 11, 2018)

GM scan tool should clear everything, both of mine do.
If code resets, it's a hard failure. 
Steve


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## alleyyooper (Sep 11, 2018)

Yes the scan tool will clear the code if you tell it to.

 Al


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## s sidewall (Sep 11, 2018)

All I use now is my laptop and GM MDI module. Now and then I'll pull out my Tech2.

Steve


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## Greaser007 (Sep 16, 2018)

Hey Sidewall,
What do think may be the culprit of why there is intermittent start-up issues ?
Does the 6.0 liter engine have an "Oil Pressure Sensor Switch" to go bad. My old '95 6.5 turbo diesel had these fail often. The oil-pressure-sensor switch shuts off fuel in the event of a roll-over accident. May this be a possible culprit ?

I have a 2007 Chevy 2500 4x4 Suburban with the 6.0 engine. I have only owned it for 1-1/2 years, and put 30k on it in that time. I use it to haul my flatbed trailer and 16-foot Stock trailer. ( it is the 'wife's' car ) What I am concerned about with this engine is that I truly believe I need to find someone who can richen-up the fuel-air ratio.
What I am feeling is a "lean-miss" on a hard long pull up a grade on the expressway. I have taken it to the best shops in my area and both the GMC dealer and GM dealer.
They all keep telling me "all-is-OK" with my engine, but they are not "Feeling-It", and I wish there was a setting on the ECU where when I set my transmission to Tow-Haul mode, that would also richen the mixture to a richer setting to squelch the lean "stumble" which is aggravating.

I drove a -95 GMC 2500 4x4 Suburban with 6.5 Turbo Diesel for 15-years and the electronic injection-pump controller (PMD - pump-driver-module) goes bad and causes stumbling and stalling and all kind of codes to be thrown, which in my opinion is "default" stuff which may not identify the "culprit."
After installing my 3-rd PMD, for 3-years following, my cruise control was intermittent, and I kept getting a check-engine light which I ignored, because I kept getting a Injection Pump code thrown. (there is nothing to rebuilding a pump except new Seals). So I take the rig to the shops, and they want $4k to replace the injection pump. B.S. to that. I finally found that the "Injection-pump" Code being thrown, was because of a Vacuum leak in the waste-gate circuit ! 
Why couldn't the mechanics have told me this ? ….. I am just the Consumer with the "deep-pocket"
The demise of the vehicle is that the freeze plugs began rusting trough at 280k miles, and the shop wanted $4.4k dollars to pull the engine and replace all the freeze plugs. Just before selling the vehicle, I discovered that I had a leaking vacuum line fitting supplying vacuum to the Turbo waste-gate controller. The fitting looked tight, but leaked. After correcting the vacuum leak, the engine ran like brand new, and in a 500-mile journey, the cruise control never missed a beat, and the check-engine light never came on. Simple little things ……. that an engine analyzer won't tell you. This is why a good Diagnostic Techie is hard to find, when you must go beyond the Codes.

The odometer had 295k on it when I sold it. In the 15-years of ownership I faithfully ran Marvel Mystery oil in with the fuel to assist in lubing the injection-pump, and to also keep the Optical-Sensor clean inside the injection-pump. I never had a valve-cover off of that engine nor did I ever change injectors, or glow-plugs or injection-pump.
The engine oil consumption never changed in those 15-years either, and consumed 1-quart of oil in 400-miles. A Great work truck !

I have to laugh at myself when guys tell me how wonderful their fuel mileage is with their Super-Duty diesels. It is a proven fact that is takes "X" amount of fuel to build "X" amount of Horsepower. You just cannot get 19-miles per gallon driving a 7k lb pickup pulling a 9k lb trailer up into the 6k elevation from sea-level. hahaha


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## s sidewall (Sep 17, 2018)

If the oil sender goes out, only low oil pressure light will come on, will still run. If fuel pump won't deliver the correct fuel pressure, will cause had starts, if fuel pressure regulator stick open some, it will bleed off fuel pressure. On the tow/haul, all I can tell you is to use 3rd gear. To richen up fuel, aftermarket programmer. Some times you do have to think outside the box, especially when GM gives the wrong information in the service manual and you replace a good part that tests show is bad, cause they list the wrong voltage reading. Been there two weeks ago on a Magna Ride suspension system. Tests showed control module was bad. Replaced and programmed it and still same issue. So I ran jumpers from one side of the car to the other. My test showed be a bad shock, replaced it and fixed the problem. Sent GM a reply about the voltage being listed wrong, waiting on their reply.

Steve


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## Greaser007 (Sep 21, 2018)

Steve, thanks for the tip on the Oil Pressure Sensor.
I have a thought for Gas Axe: have you rechecked the plug in the crank sensor wire ? I forgot to completely seat the plug one time, and I chased the 'no-spark' problem until I got to item #13 on the troubleshooting list, and the connection had lost continuity.
Does the 6.0 liter have a fuel shut-off solenoid that could be a culprit for Husky gas axe, if the wire circuit had a intermittent break ?

Sometimes I wonder how long troubleshooting before I have a "hard-failure" ! hahahaha ….. good thing they have sedatives like fishing or the wife's cooking.

Where someone mentioned the mice and wiring, I moved into a home that had sat vacant for a few years with 'doors' open. The first night stay, a rat chewed through 2-fuel hoses and 3-coolant hoses in my '02 Subaru ! It totally disabled my car for 3-weeks because the molded coolant hoses were Dealer-only parts which takes time. After the first repair, that booger took out 3-more coolant hoses.
That rodent didn't like having intruders in his space. I have never had any problems since trapping that rat. pesky rodents.


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## s sidewall (Sep 21, 2018)

Forgot to mention, on the newer model, around 2014 and up, with Displacement on Demand, they put a filter under the sender. I've seen those clog up and sender would lose oil pressure causing oil light to come on and pressure to drop to 10 psi or less. Should set a code for intermittent crankshaft position. Rats and mice love wires. I make good money fixing those but can be I nightmare. Especially when you're chasing a dtc. Guy last week chased a code for an hour til he came got me. I looked at the wiring diagrams for his concern. Told him where I would go and check and make sure a connector was good. As soon as he pulled the fuse box cover I saw rat droppings. I told him to pull fuse box and check for wire damage. Didn't chew up but 4 harnesses and two connectors. 

Steve


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## Greaser007 (Oct 1, 2018)

alleyyooper said:


> Yes the scan tool will clear the code if you tell it to.
> 
> Al


 What component do you think may likely be the culprit of a continuity problem (intermittent at start-up) ?
I watched a YouTube video where the guy did the "pull-test" on the wires going into the plug to the throttle positioning sensor He said he sometimes finds where someone prior had pulled the wire loose from the clip, but the insulation was holding everything in position. He warmed up the wires with blow-dryer and then pulled carefully on each wire individually to see if the wire pulled away from the pin clip and with the insulation stretching on one, it indicated a fractured connection. 
Do these efi ignitions have any kind of an "exciter" to go intermittent ? Honda civics had issues with exciters.

Len


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## s sidewall (Oct 1, 2018)

Just crank and cam sensor, throttle body connection and mass air flow sensor. Should set code.

Steve


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## blades (Oct 2, 2018)

lean miss - up a hill under load -- coil on plug, plug or coil going south, dielectric integrity of boot, plug, coil could be breaking down, plug loose or cracked. also seen this with a pcv leak ( vacuum) if 4x4 with auto hubs vacuum leak there. because something isn't firing all the time other sensors say too rich computer leans out mix- sneaky as sin.


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## s sidewall (Oct 2, 2018)

Forgot to mention, inspect the ground wire on the right rear of the cylinder head, make sure the bolt is tight and the wire isn't damaged, it's known to cause problems. 

Steve


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## Greaser007 (Oct 2, 2018)

blades said:


> lean miss - up a hill under load -- coil on plug, plug or coil going south, dielectric integrity of boot, plug, coil could be breaking down, plug loose or cracked. also seen this with a pcv leak ( vacuum) if 4x4 with auto hubs vacuum leak there. because something isn't firing all the time other sensors say too rich computer leans out mix- sneaky as sin.


Sneaky as Sin yes !
Those little gremlins that we chase. I am going to inspect vacuum hoses, and as Steve suggests too, I am going to check that head ground. thanks
Yes, this is a 2500 4x4 Suburban with dash control so probably Vacuum control front axle lock. This thing has the strange T-case with internal clutches. Np 246 I think.
I had my mech install new GM plug wires at 90k and the odo is on 100k currently, and he said the Coils were "fine" _ _ _ according to him.
(with these newer fuel injected engines all the intake plumbing must fit tight with no leaks or we get a no-start) vacuum and electrical issues can cause hair-thinning.

Blades, like I think I had mentioned earlier about the waste-gate vacuum leak problem with my -95 Suburban 2500 4x4 with the 6.5 TD, The vacuum fitting was glued together with Locktite Gasket-maker, and didn't discover the leak until I pressure washed the engine and it blew the plastic fitting from the hose.
( some earlier mech had put a hose clamp on a small plastic fitting, and it caused the nipple to Taper, and hose to fall loose, but looked snug ) Even with trying to glue the two together with Loctite gasket-maker, it separated. And at that time, I had not noticed the slight Taper. The little gremlins that challenge us right ! 

Len


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## s sidewall (Oct 2, 2018)

Front axle is engaged by an electric motor, no vacuum. An intake leak will makem run lean, always the red intake gaskets that caused problems, never the green. I do like the clutches in the transfer case. Is yours full time? That's where I mostly see the clutches in the transfer case.

Steve


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## s sidewall (Oct 2, 2018)

Only thing vacuum that I remember is brake booster, unless you got hydo-boost, pvc system on those trucks, GM done away with vacuum controls long time ago, early 90's. My 94 Silerado 3/4 4x4 was all electric. Just had vacuum for brake booster and pvc system. 

Steve


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## blades (Oct 3, 2018)

hate to tell you this Vacumm controls - their back yep electric motor engages transfercase- if you have auto hubs vacumm engagement on some makes. don't think newer stuff has pvc any more it is pcv fed into intake manifold. on indirect fuel inject not too much of a problem but on direct injection loads up the valves.


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## s sidewall (Oct 3, 2018)

Newer stuff, GM wise, still has pvc systems, metering system built into valve/camshaft covers piped over to intake. Trucks have a belt driven vacuum pump for the brake booster now also.

Steve


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## Greaser007 (Oct 14, 2018)

s sidewall said:


> Newer stuff, GM wise, still has pvc systems, metering system built into valve/camshaft covers piped over to intake. Trucks have a belt driven vacuum pump for the brake booster now also.
> 
> Steve


Hey Steve,
Do you see intake manifold leaks with the 2007 era 6.0L engines ? I know that the buick 3.8L V-6 plastic intakes are troublesome.

4-wheeler magazine awhile back had an article on the different new process transfer-cases, and that was where it mentioned the 246 having internal clutches, and I think they are electronically controlled is my guess with solenoids maybe, and the ABS wheel sensors may control the clutches. 
The 4x seems to work very well, as I backed the stock trailer down through a swale to load up fir rounds, and I was actually surprised the suburban pulled the trailer up and out without fuss. It was several months after that test that the wife was reading through the 'build-sheet' that was with the vehicle when we bought it "used" and the doggon thing has an optional Locking Differential in the rear. That is why it didn't fuss much pulling that trailer out of the swale.

Fuel-trim …………. hmmm …….. a new arena for me. 

It would be cool to be smart enough to just plumb-in a manual (milliamp) rheostat controller to adjust on-the-fly the fuel-air ratio while watching the f/r gauge to fatten-up the mixture when feeling the Lean-miss. But I am not an electrician.
I wonder if relocating the O2 sensor to a hotter location would fool the ECU into fattening up the f/r ratio ?
And, too, I wonder if my mechs are looking at the individual injector data to check the pulse data of each. I doubt that I have a partially plugged injector, but I don't know who had their hands on this engine for the first 70k miles, or what the original owner put it through towing in the 112 degree summers here.

The 4L80E automatic transmission behind the 6.5 td free-wheeled in direct, and really needed an exhaust brake or something to help slow it down on descent pulling a trailer. ( I know, just burn the trailer brakes  I think TDI offered a kit to reprogram the shifting which may have incorporated the lock-up in the torque converter for descent. I don't know, because rather that buy the kit for $1200, I just cussed a lot whenever I had to go to the Pacific Coast and back to the Sacramento Valley pulling a trailer.


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## s sidewall (Oct 15, 2018)

On the intake leak, if it has/had the red seal intake gaskets, they leak, the green seal intake gaskets fixed the problem. I think it was different materials on the change. Only wau to know which one ya got is pull intake, but I'd spray some carb cleaner around it and see if RPM changes. If it dont, it's not leaking.
The 02 sensors read how much oxygen is in the exhaust, more oxygen it will richen, less it will add more fuel. ECM tries to keep it around 0 fuel trim, -3 or +3 is ok. 
Steve


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## Greaser007 (Oct 28, 2018)

Steve,
Yes, I believe my wife's Suburban is full-time with a knob on the dash to select 2x or 4x ( I think ). With her Suburb being a 2500 series, it has pretty stiff suspension, but rides nice for a 3/4-ton truck, and it has the light corp. rear end with 3.73 gears.
The local GM dealer said our transmission needed replacing, and we did have extended warranty, so they installed a GM refurb auto trans. The GM parts guy said the GM no longer has new replacements, but refurbs now. That was new news.
Whew, just finished splitting and stacking our firewood for the winter. 7-chords worth. My splitter got a good workout and me too. Thanks to this Arboristsite forum, I was able to diagnose a problem when my hydraulic fluid began belching out the hyd fluid tank vent. The union coupler on the intake hose to the pump had loosened.
That was an easy fix, after pumping $30 worth of fluid into the dirt, and I hadn't noticed. We have an abundance of Digger Pine in our area, so I watch the local Craigslist ads to scarf-up free wood.
When you look at all the work involved to maintain equipment and fuel costs, it really is Not-Free. hahaha, but lots of Isometrics and pulled muscles.

( I am currently wrestling with replacing hydraulic lifters on a '95 Honda Passport with the 3.2L Isuzu V-6 engine. The Honda service manual says to clean and inspect the lifters to see if they pump-up properly before replacement ). Hmm, and am about ready to remove timing belt and then the SOHC cams and rocker assemblies.
I wish there was adjustable rockers for this 3.2 engine, but I haven't found any in my travels. This hobby project will be my "holiday-puzzle" for the next several weeks.
Personally, I don't prefer engines with non-adjustable lifters like the early Olds engines, where the valve stem height determines the hyd lifter pre-load. This is because if using too thick of a head gasket (aftermarket), the pre-load may not be enough to prevent noisy Lifters ! a real PIA I prefer not to deal with.

Happy holidays coming up !


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## s sidewall (Oct 28, 2018)

Be glad it doesn't use shims on top of lifters to adjust valve slash, those are a paiiiiin.

Steve


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## Greaser007 (Dec 7, 2018)

s sidewall said:


> Be glad it doesn't use shims on top of lifters to adjust valve slash, those are a paiiiiin.
> 
> Steve


Do you think my 2007 6.0L may have the red intake gaskets ? I am not familiar with what years the red was used.

Blades has some real good points. As he mentions the direct injection loads up the intake valves _ _ _ he is Correct because that is what I have also noticed with the direct injection Suzuki, Honda, Toyota and Isuzu engines that I have torn down. And too, the oil rings are stuck-tight in the piston ring glands with Carbon ! hmm, were the previous owners driving the engines low on oil and way-beyond normal service intervals ?

Fuel-Trim _ _ _ a new animal for me to digest ! and it really makes my brain 'foggy' too. like mush trying to absorb all that technical data.

I am just finishing up with a Isuzu 3.2 liter V-6 intake rocker-shaft and intermediate rocker-arm replacement.
When re-furbishing the engine the "first-go-around" I had overlooked that the intermediate rockers (which open the exhaust valves) had worn into the intake rocker shaft by about 0.040" and caused the exhaust tappets to be LOOSE with the 0.040" clearance with the hydraulic lash adjusters fully extended. Go Figure ! _ _ a good thing this is my project and not a clients.
The exotic valve train on this engine reminds me of working on a motorcycle engine but on a larger scale.
This engine is in my 1995 Honda Passport, which is like a scaled-down version of the Chevy Surburban, but with all aluminum engine and transmission / T-case. And I like the torsion-bar front suspension and the Dana 44 rear-end. The length to width ratio should make it pretty stable on the snow covered roads.

I sure have enjoyed this Forum for learning some good pointers on keeping my three Husky chainsaws operating reliably.
My oldest "old reliable" is a 1984 Husky 2100 cd, then there is the 394 XP which year I am not so sure, but about tweaked my pull-wrist trying to start the engine without the comp. release, until I finally figured out it would work. And then my little general-purpose yard saw which is the Husky 142 with 16-inch bar. great working saws.

You guys have a very Happy Holiday through the end of the year !

Len


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## gmule (Jun 15, 2019)

Have you checked fuel pressure?


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