2003 hummer h2 hard to start engine when i try to start engine, it will crank over like normal, but doesn't start. Then i try it again, and it starts, and runs rough for a few seconds, and runs f

cranks fast every time , starter motor cranks the engine fast , not slow, or dead starter
or cranks fast, starts and stalls in 2 seconds
and fast right foot actions can not prevent the stall?
yes ,yes,, look at dash IP cluster see IMMO lamp
if IMMO lamp fails (security) then try the 2nd key Chevy gave you day 1 new. both keys fail>? oops

teeh guide is H2 ,free from Chevy
security key called PASS_LOCK(tm)
page 2-19 in the manual
read it.


https://experience.gm.com/bypass/pcf/gma-content-api/resources/sites/GMA/content/staging/MANUALS/0/MA358/en_US/2.0/2k03hummer.pdf




During normal operation, the security light will turn off
approximately five seconds after the key is turned to RUN.

beyond all that there are 50 things to make engine not run, GOT TOOLS> (lots of em)
? Ill not guess all 50 and post them but can.

Have you had the crankcase temp sensor checked. If this sensor fails the motor will not start. Hope this is of help.
John S.

I had this same problem with my 2003 H2, my mechanic found that the fuel diaphragm was cracked and this was allowing my truck to flood. If it was a cold start, the extra fuel would evaporate and it would start fine. It actually got to the point where I would stall at a stop light or stop sign at idle. The part was is the neighborhood of $175.00 and about 1 hour of labor to install.

takes cats off, it will run better,more power and better fuel. check eng. will remain though

2003 hummer
If you have trouble in fixing your vehicles, try this link. Very helpful

Hello Stacy, My name is Mike. I am thrilled that you choose me to help you with your problem. I am sorry, it took me a few hours to get back to you. I have been helping other customers. Here is where I am with this on your cranking and not starting issue. Oh, by the way great job on your part eliminating some of the other potential suspects.

First of all, I try and tackle the easiest things first,to see if we get lucky.

Pull the start/run relay out for a couple minutes, then put it back in and reset it might reset the passlock box and start right up.

Now, why did I say that? I believe your problem is with your Passlock indicator.( which has to do with your anti theft system)The way I just described is a 50/50 chance to have it work, but don't worry. I always have a plan B and C.

Here is some questions to your symptoms: Stay with me now, wait for it.

Perform the re-learning procedure

Turn ON the ignition, with the engine OFF.

Attempt to start the engine, then release the key to ON (vehicle will not start).

Observe the SECURITY light, after approximately 11 minutes the light will turn OFF.

Turn OFF the ignition, and wait 10 seconds.

Repeat steps 1 through 4 two more times for a total of 3 cycles/30 minutes ( the vehicle

is now ready to relearn the Sensor Data Code and/or passwords on the next ignition switch transition from OFF

to CRANK).

Important: The vehicle learns the relearns Sensor Data Code and/or password on the next ignition switch

transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.

Start the engine (the vehicle has now learned the Sensor Data Code and/or password).

Here is Plan C as promised, but I personally would not suggest, Even though GMC offers a bypass procedure.

Link for a Bypass Solution:

http://newrockies.com/installation-instructions/hummer/h2/2003-hummer-h2/

Plan D, would be have to check into possibility of bad ECM, but lets hope that is just a worst case scenario.

Thanks So Much,Mike. Please Keep Me Informed of progress.

A scan tool should be able to read the temp pids at operating temperature to see if they are "off" enough to cause problems . Check for fuel lines to close to heat sources as boiling of the fuel causing vapor lock may be happening after heat soaking .

If you mean that the engine cranks over for 6 seconds before it fires up, that sounds like a fuel situation. You would need to install a fuel pressure gauge and turn the engine off for several minutes and see if pressure drops. The pump has a check valve that keeps the fuel line pressurized until you start the engine again, if that valve is bleeding off pressure it takes longer for the pump to prime the fuel system, hence your long crank. Could also be a regulator or fuel injector bleeding pressure. Good luck!

disconnect harness to the pump and jump with test light, turn key on and the light should go on for a few seconds

What have you done so far? Is it a crank/ no start or a no crank? Do you have any active engine codes? Was it in the shop recently, and if so, for what? Do you have both fuel and spark? Were there any symptoms or signs before this? Don't touch the gas pedal while your trying to start it.