Hi all,
I have just become a H2 owner, 2003 with 41000 miles. Great thrill to drive so far and thoroughly enjoying the experience, however a few things need attention which is difficult as I am in the UK and not many garages here have experience with Hummers;
Here goes;
Speedo needle is playing up, sometimes gives up and starts again next journey, perhaps speedo sensor on gearbox end?

The engine management light is on and during a 6 hour drive back after collecting the car, about 2 hours into the journey I felt a loss of power and the engine light flashed instead of staying permanently on. I pulled in and restarted the engine and haven't had the problem since.

I have a whipple supercharger fitted but with the engine light on I am keeping very light on the gas just in case, I have no idea if the supercharger is related to the engine light being on and Im unsure on how the performance would be because this is my first hummer. Hoping someone can recommend a diagnostics kit I could purchase or a garage in the uk who could help? The journey home sitting st 60 to 70 mph achieved around 14 to 17 mpg which I was happy with do hoping that sounds like everything is running normally. Having read that the transmission is under greater strain with a supercharger am I better off removing this for the long term? Original manifold Needed

 

Any GM aka Chevy dealer should be able to help you out, as they are a GM product and can be serviced and scanned with the normal GM tools.

If you want to get your own, you can either find a "tool" that allows the J2534 pass through and find a "free" copy of TECH2Win which emulates the factory GM Tech2 scan tool. Or search ebay.co.uk for a Tech2 clone tool with good reviews.

Usually when the engine light flashes it's due to the engine computer detecting misfires, which is not a good thing. But hard to tell without having codes to go by. It could also be related to your speedo issue...

 

Here in the uk we just have Vauxhall dealerships owned by GM but I'd be very surprised if they had ever seen a Hummer in for a service! But you never know! They may be able to help! I can't sense any misfire in the engine and it's interesting that the speedo may be causing it. The engine light flashing happened just once in a long journey and was fine straight after but the light is permanently on. I have a friend with a snap on computer which is an American company I think so I'm hoping it will read the Hummer. Thanks for the info on the Tech2.

 

The Snap-On Scanner should be perfect for your H2. Let us know what the codes are.

 

Will be having a go tomorrow at reading the codes, fingers crossed.
I had the mot today which was all good and underneath is fine, no leaks etc

 

Don't not spend money on a expensive code reader . I have 2 and I don't used
Only reader u need is Torque app and a $10 boxes Bluetooth pcm readers
Also Very helpful to use daily

 

Are you referring to the 30 day free trial software, or sw that doesn't have a countdown timer? If you have a trusted site for the sw without the countdown timer, can you share it?

 

Hi, codes were as follows:
P0174 System too lean bank 2
P0327 Knock/Combustion vibration sensor 1 Curcuit low bank 1 or single sensor
P0332 Knock/Combustion vibration sensor 2 Curcuit low bank 2

We reset the codes and have driven 5 miles home and engine light has stayed off, maybe it's going to be ok, otherwise lambda sensors?

When I had left the headlights on without engine running for five mins my battery mustn't be that great as it struggled a little to start and threw another code up which was P1516, but we reset again and put the battery boost on and it started fine without any engine light again, it also stated 'reduced engine power' when we had the struggle starting which I'm guessing is something relating to the poor battery limiting things

 

I would venture that your intake gaskets are leaking. The good news is you need to remove it to replace the knock sensors anyway. Not a hard job just time consuming.
Fel Pro intake gaskets are better than the OEM gaskets.

 

Thanks Calif, I'll wait for the engine light to return and read again to see if all three codes comeback and go from there.
In your experience does the h2 go into 2nd gear fairly quick? Mine kind of holds in first too long unless I ease off the gas pedal to encourage it to go to second gear (all other changes seem fine), is this normal in the 4 speed auto? Also today I tried the heated seat button which seemed to work for a bit but now doesn't switch on, just flashes for a second and that's it, perhaps a fuse blown.