Will not start or crank please help me!

shane777

Original poster
Member
Oct 25, 2022
1
Tennessee
I have a 2004 trailblazer, 4.2, 250,000 miles. Was a daily driver and always kept maintenance and serviced. For the miles it has, it runs (or did) great!! One day on way to town the motor died on my while driving down the road. I rolled into a driveway and kept turning key on and off until it finally started again. Took to mechanic immediately and they said their scanner could not detect anything wrong. Went home. Next morning needed to run errand and it wouldn't start not matter what I did. I've owned this truck for about 10 years and the only thing that weird has happened is the headlights would sometimes go out on me while driving, then come back on. Then that wouldn't happen for another 2 or so years. So anyways, I had truck halled to a mechanic. After a week of looking they said it is the ecm or (brain) so they put a new one in and said Chevy dealership will have to program it. Then, dealership said they couldn't program new brain because there is a short somewhere and it could take years to find? I don't know what to do. I have tried jumping the starter relay with wire and I can get it to crank but it won't start. But the key does nothing but make fuel gauge and temp gauge move. I also don't hear fuel pump come on. Someplace please help me with your knowledge!
 

Chickenhawk

Member
Dec 6, 2011
779
It is always best to start with the most common (and easiest to fix) problem and work from there. Once we eliminate those, then we can zero on other possible causes.

PCMs rarely fail. By far, the most common problem for these platforms is the ignition switch. In fact, many of us carry a spare switch in the glove box; that's how common it is. If your ignition switch has never been replaced, start with that and let us know the result.

The headlights is a separate issue. Change the headlight relay in the underhood fuse box. Also, if it ever fails at night, switch the fan and headlight relays and that will get them back up and working temporarily.
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
When you say it fails to start, what do you mean exactly? It cranks and doesn't start? Or it doesn't crank at all? Your answer will dictate which direction to take, which are very different.
 

TollKeeper

Supporting Donor
Member
Dec 3, 2011
8,047
Brighton, CO
I think I would be trying to get the PCM back from the shop that replaced it.. Why replace something you cant program... Idiotic!
 
Dec 5, 2011
574
Central Pennsylvania
If the truck does ANYTHING when you turn the key, a video with audio may help us diagnose what's going on. The possible causes are many and varied. Giving a full list of them would be of little help to someone who's not mechanically inclined and versed in these trucks. A good place to start is the ignition switch as mentioned above... but first (for me anyway) is a complete check of every fuse. Admittedly, most of the fuses won't cause the engine to die, but to list the ones that can would also not be useful and any decent mechanic should've run through the possibilities related to fuses anyway. My "engine dying" problems were related to a LOOSE (not blown) fuse and fixing it was as simple as slightly bending the legs of the fuse at fault.
 
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