2006 Hummer H2 Limited Edition
Late 2006 Hummer H2
Fusion Orange
Tires: 37x22x13.50

• 2nd Owner
• Running 93 Octane otherwise terrible power and acceleration???

(Don’t know if previous owner had a supercharger or reprogramed the ECU. GM Dealer tried to re-flash ECU 2 Times will not accept re-flash)

• Constant Knock Sensor Codes (P0032) Knock Sensor 2 Circuit Low Bank 2

(Replaced both Knock Sensors and Installed New Harness Twice still same Problem)

• Transmission Temperature (200*) during normal operation

• Engine Temperature (200*) during normal operation

(Replaced Radiator & Thermostat last week due to hairline crack in Radiator still running at same temperature)

• Feels like the transmission does not downshift when braking to a stop…Is this normal?

• When accelerating from Stop no power until 3500 RPM

• Cannot maintain 4th Gear over 75mph will downshift to 3rd Gear and remain until pedal is released.

• 3rd Gear power is almost non existent when on highway to pass another vehicle

• Once in overdrive 4th Gear slightest acceleration of throttle will cause immediate downshift.

• Fuel Economy is horrible 7.5 mpg ( How can this be increased?

• Water Leaks into Cab of vehicle in 3 Locations Drivers Side & Passenger Side Front near A-Pillars headliner corners are saturated in heavy rains and also rear Passenger Side in trunk notice water in storage cutout above wheel well

(Have inspected Marker Lights for possible leaks and found them all to be tight and ran a bead of Urethane around the lights to ensure no leaks are possible however still have the water issue)

Thinking of Re-Gearing the truck… anyone have any suggestions of what to run?
Truck is used On-Road 80% of the time for Highway driving my normal running speeds are
80MPH to 90MPH

Regarding the vehicles running issues acceleration power knock sensor codes I have heard the following from GM MasterTechs and Independent Mechanics.,,,,

Possible Torque Converter Issue…..
Possible Timing Chain Issue….
Possible ECU Programing for SuperCharger that has since been Removed….

I am at a loss here… I love this Truck but need to fix the Power concerns.
It truly feels like the truck is bogging down almost as if there is a restriction. I even went so far to remove the exhaust from the back side of the headers to see if it was an exhaust restriction… only difference was the truck sounded like a car at Daytona 500 lol …. Lots of noise and still same power issues and bogging down So I ruled out exhaust restriction as a culprit.

The spedo is off by about 5-7mph due to the larger wheel and tire size
My Fuel economy is absolutely horrible which makes sense since the vehicle is always running in 3rd gear above 3500 RPM.

Any help or recommendations from others that have experienced similar issues is greatly appreciated.

 

Maybe you are in tow mode but the tow mode light is out. I would push the the tow mode button to make sure you aren't in tow mode.

 

Curious how you came by a truck with this many issues, must have been damn cheap. Was it this way when you got it?

Engine temp is reasonable, 210º is fairly normal. Tranny temp is pretty high, have you checked the fluid for water since your radiator was cracked? Does the truck coast okay if you drop it into neutral, no dragging brake? And how many miles on the truck? Might be worth it to pony up for a Carfax.

 

Thanks for the comments...
I am curious if anyone has had these similar issues after going up to 37's prior to regearing the truck and if so what gear ratio did you go with on your truck?

2003hummerH2:
Maybe you are in tow mode but the tow mode light is out. I would push the the tow mode button to make sure you aren't in tow mode.

Never thought of that... but I tried the button Light Works fine when engaged.. no changes in the drive.

flyday58:
Curious how you came by a truck with this many issues, must have been damn cheap. Was it this way when you got it?

I have owned the truck for going on 3 years now. I bought it with 53K miles roughly.. Wasnt damn cheap lol and didnt have these issues until the last 6 months...

Engine temp is reasonable, 210º is fairly normal. Tranny temp is pretty high, have you checked the fluid for water since your radiator was cracked?
Checked the Tranny Fluid and it is normal no water in the fluid.. might be time for a Tranny Flush though..

Does the truck coast okay if you drop it into neutral, no dragging brake?
Truck coasts fine in neutral

And how many miles on the truck? Might be worth it to pony up for a Carfax.
I currently have 78K miles on the truck now.

 

So was it fine, normal ops, then suddenly or slowly started doing this 6 months ago? If so I would have to rule out the supercharger bit as it should have been doing it all along.

Can you maually shift from 1st to 2nd then drive? If it doesn't downshift it should really lug, depending on the gear.

What do you mean by no power till 3500 rpm? Is it really slow to accelerate and then takes off? And when trying to pass does it just make alot of noise but barely speed up?

On the roof leaks I have to assume you checked the drains for the sun roof, made sure they drain. Should come out behind the fender wells near the tires. The bung plugs for the corner marker lights are hard to seal with silicone, gotta be careful with those.

I was gonna suggest catalytic converter but if you disconnected both exhausts at the headers I don't see that as a possibility.

 

Definately check into regearing. Anyone i've seen on here with 37's has claimed the truck was a slug and would hop back and forth between 3rd and fourth.

Have you tried cleaning or replacing your MAF sensor? i was having problems with a intermittent misfire. The truck had been to the garage many times. The mechanic was stuck on the MAF saying it was weak but within tolerances. So he cleaned it and the truck ran strong all the way home. Unfortunately i had him do a smoke test because iwas convinced it was the intake gaskets. He also soaked the motor with a hose which leaked into my knock sensors and the truck really had no power. I know you've replaced all that twice with no luck. My truck ran great after i did the intake gaskets, knock sensors and harness.

I see where flyday was going with coasting the truck in neutral for drag. I had a seiZed caliper on the rear. My gas mileage was horrible and power was down. You couldnt really tell by coasting because the truck carries so much momentum. Drive the truck for a while and get out and touch the center of the rim ( careful it may be hot). Use a temp gun if you have one and make sure that at the rim center they are all around the same temp. If one is hotter that'll be the one.

The gm techs most likely checked the MAF. But its all i can think of.

 

A plugged Catalytic converter will produce a lot of those symptoms. You need to find someone with a back pressure gauge. It screws into an 02 sensor port and give you a real good idea if your exhaust is flowing as it should.

 

you should not have to run 93 in these trucks especially with how bad the gas mileage is lol. ive had a few mail order tunes and in person tunes done on my vehicles. most tuners will lock the pcm so nobody can tamper with there tune and blame them for power train failure. or so a dealer cant re-flash it and the customer will lose the tune.
which is why the dealer cant reflash it. and only the tuner that locked it can unlock it. but reading above you stated the issue just started after 3 years of ownership. that makes this HIGHLY unlikely.

if you still want to pursue the issue look for an unlocked oem pcm and swap it out.

do you have any engine codes? pending codes? hook your truck up to a code reader you could have a few pending codes that haven't thrown the light yet which could help steer you in the right direction.

torque converter or timing chain sound like a possibility but before going that deep into the truck i would rule out all other options.

both the H2's ive owned had leaks from the roof. both had sun roofs also. the issue was with the silicone around the lights on the roof weathered away and was letting water in. just had to re apply silicone around the lights and for insurance put some around the weather stripping on the front doors. the sun roofs are very well known to leak tho.

 

If the pcm cant be programmed I would start right there. First make sure there is no aftermarket devices that splice into data lines as this can cause programming errors. When knock sensor codes are setting this retards timing to try and eliminate "perceived" knock. I would check circuits from knock sensor harness to pcm for opens and shorts to ground. then test knock sensor side of harness and each knock sensor should read between 93k ohms to 107k ohms. If those test good and circuits to pcm test good id replace pcm

 

I had a superchips tune on my 2003. I sold the truck and put the ecm back to stock. I didn't try starting it since I've never had an issue removing the tune and reloading stock file. Ship truck to buyer and truck doesn't start. Long story short I had to send the ecm to superchips for them to wipe their software from it and reload the stock file. GM had tried to reflash it before sending the ecm to superchips but it will fail during download. Just a thought.