wheelin today and a couple of issues

[f5fstop]

Dealer can reset codes with a Tech 2. If he is trying to duplicate the problem, he might have to go on a high-altitude trip.

Didn't see the codes earlier.

P0068 Poor flow (with this code, the airflow is actually larger than expected)
P0171 Lean Code Bank 1 (Do you have an aftermarket air filter?)
P0121 Throttle Position Sensor Performance (TP sensor 1, and is related to a larger than expected intake of air)
P0016 Map Sensor (This code is set due to a camshaft position sensor pulse occurs during the incorrect crank position).
Either 68 or 121 can cause the PCM to go into reduced power mode. I'm guessing, and that is all it is, the PCM got a bit mixed up for some reason. One of the sensors that the PCM uses to monitor airflow (TP/BARO/MAP/IAT/MAF/RPM) could be failing, but not sure which one; it should set a code.

However, I do not see how a cat-back exhaust would cause any of these problems. If you had installed headers...maybe. But a new lower restricted exhaust and new pipes after the muffler should not cause any of these problems. I would ask the dealer to substantiate why he even thinks the exhaust will cause this problem.


How is your idle now that you have returned to the 6K range? That P0016 is out of place. If you had that one, and some P0300+ codes, along with a rough idle, I might suggest a cylinder head issue. But the cylinder head issue does not shut down the vehicle, it only causes a rough idle and sets codes.

I can find nothing in preliminary reports or in bulletins; other than for 171 where it states the air filter can be restricted, or PCV hoses kinked.

I will print this off tomorrow at work, and if the programming dude is around I will show them to him and see what he thinks.
I know he is hot and heavy on a new chassis cal that has to be released, but it outputs chassis codes when the condition happens, and so far, only a half-dozen complaints from customers, but quite a few from some engineers running the trails somewhere in the US.

DTC P0016
Circuit Description
The powertrain control module (PCM) uses the crankshaft position (CKP) sensor and the intake camshaft position (CMP) sensor information to monitor the correlation between the crankshaft and intake camshaft position. If the PCM detects a CMP sensor pulse occurs during the incorrect crank position DTC P0016 will set.

DTC P0068
Circuit Description
The powertrain control module (PCM) uses the following information to calculate an expected airflow rate:

? The throttle position (TP)

? The barometric pressure (BARO)

? The manifold absolute pressure (MAP)

? The intake air temperature (IAT)

? The mass air flow (MAF)

? The engine RPM

If the PCM detects the airflow rate is more than expected, DTC P0068 sets.

DTC P0121
Circuit Description
The powertrain control module (PCM) uses the following information to calculate an expected airflow rate:

? The throttle position

? The barometric pressure (BARO)

? The manifold absolute pressure (MAP)

? The intake air temperature (IAT)

? The mass air flow (MAF)

? The engine speed (RPM)

If the PCM detects the airflow rate is more than expected, DTC P0121 sets.

[timgco]

stock air filter. The only mods done to engine would be the cat back B&B Exhaust. This truck has also had a trans replaced. I'm not sure on the air filter hose/ intake being kinked or blocked. I honestly have neverr had the aibox open yet.

They arer still blaiming the exhuast.

[f5fstop]

Not saying this is it, but you mentioned trans replacement....

Subject: P0101 P0106 P0121 Poor Acceleration and Detonation in Gear - keywords chuggle converter drive forward fuel hesitate idle information launch load low misfire miss performance power reverse stall surge #PIP3144A - (11/22/2005)



Models: 1996-2006 All General Motors Passenger Cars and Light Duty Trucks




--------------------------------------------------------------------------------

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
Customer concern of poor acceleration, detonation or "ping" at idle in drive or reverse, and/or possible DTC P0101, P0106 and/or P0121 set in the PCM. The vehicle will perform properly after attaining a speed of about 30 - 40 mph. The condition may also be described by the customer or the dealer as a hesitation, stall when putting into gear, surge on accel (similar to hitting fuel cut or rev limit). The ultimate cause may be a non-holding torque converter stator or damaged stator support shaft within the automatic transmission.

Recommendation/Instructions:
The following checks should be performed in the event that normal engine driveability checks have not resolved the detonation or "ping" at idle in drive or reverse, lack of power from a stop, stall, surge on accel and or hesitation complaint.

The transmission oil cooler outlet line (line to the cooler) should be checked for excessive heat. The Tech II scan tool may be helpful on vehicles equipped with the transmission fluid temperature sensor in the cooler line (mainly front wheel drive). On vehicles that do not have the temperature sensor in the cooler line a temperature probe should be used to check the temperature. The temperature readings should be compared to a like vehicle with the same powertrain option content.

In the event the engine is not producing sufficient power the transmission oil temperature at the outlet cooler line will not be excessive and should compared closely to the like vehicle.

In the event the transmission torque converter stator or stator support are damaged the transmission oil temperature at the outlet cooler line will be excessive to that of a like vehicle.

A stall test (brake torque) may point to a damaged torque converter, the stall RPM speed will be lower then a like vehicle. However, poor engine performance will also produce a lower stall speed RPM.

If the torque converter stator or stator support is suspect, the transmission should be removed and the stator support inspected for spline damage. If the stator support splines are damaged the transmission should be repaired and new torque converter installed. If damage is not present on the stator support the concern is either internal to the torque converter stator or an engine performance concern.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

Hitting a fuel cutoff limit will be like your symtoms, floor the accelerator but nothing happens, vehicle slows.

[HummBebe]

By jove I think he's got it

[f5fstop]

Originally Posted by timgco

stock air filter. The only mods done to engine would be the cat back B&B Exhaust. This truck has also had a trans replaced. I'm not sure on the air filter hose/ intake being kinked or blocked. I honestly have neverr had the aibox open yet.

They arer still blaiming the exhuast.

Have them give a definite reason why the exhaust would cause this problem. Dealers are notorious at blaming something on an aftermarket item, with no proof or experience when they fail to find the true problem. They may not be able to find the real problem, not due to their incompetence, but due to the fact that once in a while these new vehicles will exhibit a behavior that can't be explained.

I will check today, in case I'm wrong, but I have never in my life heard of a cat-back exhaust causing any problems with the engine or trans, and even early in the AM, I cannot conceive of what the exhaust would do to cause the problems you stated. If the exhaust was clogged, yes, but if it was clogged, it would not run ok afterward either. And what normally clogs exhaust systems, catalyst material discharged from the catalyst due to backfires. This you don't have, so I rule out the exhaust.

The exhaust is a static device, if it was causing problems, it would cause problems all the time at high altitudes, a restart would not fix the problem. (Just my opinion.)

I'm still thinking the PCM or a sensor "farted" and the restarts fixed the problem, similar to my 4-wheel drive problems on the trip. The trans bulletin is just a "maybe" since it does show some of you symptoms. Problem is you have those other codes too.

[h2co-pilot]

F5 is a such a Sweetheart - always helping out.

Hope you get it straight Tim.

[Ipedog]

All hail F5

[f5fstop]

You have an interesting PM that includes some information .
Again, if you want to show them the write up to the dealer, feel free, just remove any identification of who sent it.

[timgco]

Originally Posted by f5fstop

You have an interesting PM that includes some information .
Again, if you want to show them the write up to the dealer, feel free, just remove any identification of who sent it.

Thank you. I just called the service dept. They drove it last night and couldn't duplicate the problem. no $hit!

So I told him word for word what "my source" had said. I also answered one of the two questions. Reduced engine powere was present until the egine was turned on and off. I'm getting you the other info as well.
Thank you.

[usetosellhummer]

ddaammmnnnn you man f5, I vote you as a Hummer god.

[f5fstop]

New information. The way John phrased it is it could be a brain fart that could become a stroke. He is thinking there computer program, for some reason, could have become confused by certain inputs, and one of those inputs may have failed temporarily, and could fail totally later.
He is the first person who I have talked to made a statement about the exhaust. The engine parameters are looking for a specific back pressure; usually a small amount of change makes no difference. But, at this altitude, and you possibly doing something normal but strange to a sensor (such as momentarily lifting off the accelerator, then flooring it, or just the opposite),the computer reacted with a reduced power mode. Resetting it by turning it off/on made it reboot, similar to a Windows Brain Fart.
Just another opinion. But he wants to know the final conclusion if there is one.
First guy is still waiting for any information he can get. He is also very curious.

[timgco]

F5- i want to thank you for your efforts on this!!!!!!!!!!!!!!!!!!

You are a huge asset to this forum.

The dealer is reaplacing the TPS due to the "higher up" recomendation.

I smiply stated that this came from someone on a design/ engineering team for these truck and names/ positions were withheld.

After i told them of my connections, they did not hesitate to take the advice and run with it. So we'll see.

I fully plan on running McCalister's gulch this weekend on Sunday and will see what happens @13,000ft.

Thanks again for your help!!!!!!!
Tim.

[f5fstop]

I really hope that it was the problem. Everything seemed to lean that way, but it was just some educated guesses from miles away.
Glad to be of some help and good luck running the pass.