2003 H2 Hummer Transmission

SOURCE: my 2003 h2 hummer will initally not shift from

Check the linkage that goes from the shift lever down to the transmission. It sounds like somewhere along the line, it has become disconnected or has broken.
if that parts are clean then It sounds like you have a shift control solenoid that has high resistance causing the hard shift you describe. Scan the PCM for trouble codes if none are present you could have a internal transmission problem.

SOURCE: hummer h2 idle rpm too low

I can't solve the problem but was hoping you found the answer. I have a 2003 Hummer H2 and I am having the same problems if started in park or Neutral it will idle fine but if I put it in drive or reverse it will not idle

Did you find the solution and if so could you email me the fix.

[email protected]

Thanks,

Troy

SOURCE: Hummer H2 2003, shifting problem

Yea, hummers are notoriously unreliable. They are gas gusslers too.
I'm assuming this is an automatic?
When the transmissions computer detects any malfunctions, it will give you a check engine light, or something along those lines.
Do the normal checks such as checking the transmission fluid level as per the user manual.

For further diagnostics you'll need to take it to a mechanic. It's impossible to diagnose a problem like this without driving the car and being able to reproduce the problem.

SOURCE: change light on 2006 hummer h2

it can be easily changed by removing the plastic cover then u will see the light bulb, don't try to change it from the back, it wont open :)

SOURCE: Hummer H3 Losing power when shifting from 1st to 2nd gear.

as odd as this may sound, try replacing the fuel filter.