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Engine Problems, low power, peiodic check engine light. 2007 H3 SUV LUX/ADV

H32NV

Well-Known Member
Messages
309
Location
Golden, CO
Hey all,

I have a bit of a werid issue going on. During my trip from New York to Denver, I got a check engine light that I chocked up to "bad gas". The engine felt sluggish, although still attained

highway speeds. The light went away after another tank of gas, and power was restored. When I was heading into Neo's house in Moab, the light came back on again, and I got the same

symptoms, lower power and hard starts. I pulled over, and it seemed like the engine had to turn-over for a long time before it popped and then came to life. After leaving Neo's in Moab,

the light went off again, but the power didnt come back to 100% this time. Upon getting to Flagstaff, now the light is back on again, and I am thinking it might be an O2 sensor that is

giving me an incorrect fuel.air mix. Took it to Auto Zone to pull the code, of course, the light goes off, and their OBDII reader cannot retrieve codes from the computer history of the truck, it

only has the capability to retrieve current codes with a CEL active.


Took it to the Caddilac dealer here, they do not have any history of being a Hummer Dealer in previous years. The service manager told me that there is a $95 diagnostic that A) is not covered by the

warranty, and that B) sensors such as the O2 sensor are not covered by the 100k powertrain warranty. Does this make sense? Ive never paid a diagnostic fee in the past because it has all been

chocked up to warranty repairs. Also, shouldnt the powertrain on our Hummers cover all parts necessary to run the engine? less wearable parts like belts, and filters?


Kind of up against a wall, I dont have an OBDII reader of my own, so i agreed to let them run the codes for $95 but I am awaiting a $1000 no warranty estimate that I imagine they are cooking up right now at a Managers Desk...

Neo, Beebs, F5... HELP!!

-Rob
 

H32NV

Well-Known Member
Messages
309
Location
Golden, CO
good news

Good news, it was a Cam sensor, and they are going to cover the diagnostic with the Hummer Warranty! He said

that the truck has a lot more power now, I would naturally expect this to be the case with a timing issue.

Looking forward to bantering with you all in the threads of the new forum!

Thanks,

-Rob
 

alrock

El Diablo
Staff member
Messages
10,442
Location
Scottsdale
Glad to hear the good news! I've had a few camshaft position sensor error messages but they've gone away. It was too hot this summer to work on the truck and figure it out.
 

H3slate

Brush raked
Messages
983
Location
Tualatin, Oregon
I have had similar codes pop up this summer, from what I have been reading, testing those cam sensors is not hard, just need to check the resistance.

Sent from my DROIDX using Tapatalk
 

M22KLARS

Unsafe At Any Speed
Messages
2,315
Location
Minnesota
I've had these same problems a couple times through out the past three years or so. The problem only seemed to last a few minutes or one re-start so I never looked into it further.
 

DJinCO

Well-Known Member
I was at AutoZone today buying vacuum line and RV Antifreeze when I noticed the manager going to an H3 in the parking lot with the code scanner. While in line I asked the owner of the H3 what the problem was? He said "check engine light"; No code showed so the manager said it was probably a loose gas cap.

I told him about H40. He has 50K miles on his H3.
 

MaxPF

AGNTSA
Messages
1,394
Location
The dark side of the globe
I was at AutoZone today buying vacuum line and RV Antifreeze when I noticed the manager going to an H3 in the parking lot with the code scanner. While in line I asked the owner of the H3 what the problem was? He said "check engine light"; No code showed so the manager said it was probably a loose gas cap.

I told him about H40. He has 50K miles on his H3.

Gas cap would have shown up. Most cheapie code scanners (and many programmers) will only read codes from the PCM or ECM. They will not read codes from a TCM, BCM, or any other modules. The MIL could have been set by any of those modules, and the VatoZone scanner wouldn't tell you squat.
 

f5moab

Mr. Beretta
Messages
1,986
Location
Hiding in a potato patch in Idaho
Gas cap would have shown up. Most cheapie code scanners (and many programmers) will only read codes from the PCM or ECM. They will not read codes from a TCM, BCM, or any other modules. The MIL could have been set by any of those modules, and the VatoZone scanner wouldn't tell you squat.

Max, could you explain that a little better? On the H3, the BCM is the trigger module for codes. It retains all codes and outputs them via the DLC. So, if a scanner cannot read the BCM on the H3, they will get nothing. And, that is true for GM vehicle, at least up to 2009 (not sure after that).
 
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MaxPF

AGNTSA
Messages
1,394
Location
The dark side of the globe
All modules are connected to the GMLAN bus. When you scan the vehicle with a TECH II, it detects all modules and then polls each for any DTC's they have. Or, you can poll a specific module of interest. I have never heard of the BCM being the sole repository of DTC's in any GM vehicle.
 

alrock

El Diablo
Staff member
Messages
10,442
Location
Scottsdale
Reaper, I had a few error messages, not actual sensors. I'm more than willing to share the error messages for only a few bucks. :wink:
 

f5moab

Mr. Beretta
Messages
1,986
Location
Hiding in a potato patch in Idaho
Are we discussing poling modules or retaining codes? I was answering to your statement, “[FONT=&amp]will only read codes from the PCM or ECM. They will not read codes from a TCM, BCM, or any other modules…”

[/FONT]
[FONT=&amp]As the following schematic shows the DLC information comes from the BCM. So if a reader cannot read a BCM it cannot read the codes from another device. Now there are some codes that will not be sent to some readers but they are non-critical codes and not a requirement under the OBD II specs as set by the SAE, and it requires the programmer to have the software to read these non-OBD II required codes. So, if a reader is setup as an OBD II only reader it should be able to obtain all OBD II required codes.
[/FONT]

[FONT=&amp]I will agree that some cheap readers will not be able to read non-OBD II required codes; however, cam sensor codes starting with the numeral “0” should have no problem since these codes fall under OBD II requirements. [/FONT]
[FONT=&amp]Polling modules is a complete different scenario than reading stored codes. In fact in later model vehicles a reader needs to be able to read the controller area network (CAN) and even the Tech II requires the CANDi (controller area network diagnostic interface) module interface to perform this function.[/FONT]

[FONT=&amp]This is pretty common on the majority of GM vehicles with BCM. The BCM is considered the mother of the controllers. At start up, the BCM checks all modules for connectivity and for any problems. (For example, the BCM upon startup recognizes the passlock system and gives the OK for the PCM to turn on the injectors.)[/FONT]

GMDLC.jpg
 

MaxPF

AGNTSA
Messages
1,394
Location
The dark side of the globe
Are we discussing poling modules or retaining codes? I was answering to your statement, “[FONT=&amp]will only read codes from the PCM or ECM. They will not read codes from a TCM, BCM, or any other modules…”

[/FONT]
[FONT=&amp]As the following schematic shows the DLC information comes from the BCM. So if a reader cannot read a BCM it cannot read the codes from another device[/FONT]

No idea where you are getting this from, but it is incorrect. I can take a PCM, ECM, or TCM from any GM vehicle, power it up on the bench, and read any DTC's, pull the cal, flash it, etc. For that matter, I can pull the BCM from any GM vehicle and read DTC's from any other module. The BCM is the bridge between the high speed GMLAN and low speed GMLAN networks, but it is in no way needed to read DTC's or flash other modules. IF it is possible to pull DTC's from the low speed bus, then I can see where the BCM would be needed, but I have never communicated with modules on the low speed bus. Using either a Tech II (which requires a CANdi interface) or EFI Live, all comms are done on the high speed bus which is tied to all major modules. The BCM doesn't control or arbitrate anything in this case.

It is common for DMax guys to get a MIL for a trans problem and their programmers and cheap code readers only read a P0700 code (trans MIL request). They have to find someone with a Tech II or EFI Live to read the codes from the TCM.
 
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