Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum banner

02 trailblazer cranks but won't start

613 Views 28 Replies 5 Participants Last post by  Ravalli Surfer
I unhooked the wire harnesses from the pcm to clean them with electrical cleaning spray. Plugged everything back in... cranks but won't start.
Before, it started instantly.
No codes...
1 - 20 of 29 Posts
Welcome to the Forum!

OK, so you have a 2002 TrailBlazer that you cleaned the contacts in the PCM connectors. What did you use to clean them? Are you sure you did not bend any pins?

Awaiting your reply.
  • Like
Reactions: 1
But why? "Before, it started instantly"... before you flushed out the connectors? Were you trying to fix a no-start by cleaning the pcm connectors, or was it fine but you decided it seemed like a good idea then it wouldn't start afterwards?

Start by double-checking your work:
Maybe pull the connectors again, and check to make sure you didn't bend any pins, then reseat them carefully but firmly. Maybe someone will chime in here and instruct you as to whether or not the battery should be disconnected (use a keep alive device, battery back-up of sorts) or not while doing this.

Then check the basics:
Check for fuel pressure and check for spark. You may need to buy/rent/borrow a fuel pressure gauge and a spark tester if you don't already have them.
Welcome to the Forum!

OK, so you have a 2002 TrailBlazer that you cleaned the contacts in the PCM connectors. What did you use to clean them? Are you sure you did not bend any pins?

Awaiting your reply.
I used electrical contact spray... and carefully plugged in, and tightened up the bolts.
I'm a fair mechanic, and am stumped by this one
Not all electrical contact cleaner spray is created equally. Some of them will actually melt or swell the connector plastic. I got nailed once on a burglar alarm system I was servicing. Sprayed all the mechanical window contacts with a contact cleaner and then would up having to replace them a week later because the cases swelled and would not let the contacts move.

I would double check the contacts and use some isopropyl alcohol as a "rinse".

The next thing I would do is to check the fuses, and then make sure you have spark and fuel pressure.
  • Like
Reactions: 2
I will give it a try.
It fired once, but that was it.
Are there any electrical breakers? Or reset buttons?
Are there any electrical breakers? Or reset buttons?
I do not believe there are any.
It sounds like it's not getting any fuel.
Can it simply lose fuel pressure when the battery is out?
Well, if the fuel injectors are leaky or the check valve in the fuel pump assembly is defective, yes, the engine could lose fuel pressure. You need to connect a fuel injection system pressure gauge to the test port (which is located adjacent to the fuel filter underneath the vehicle) to see if the fuel pump is making the required 50 - 57 psi.
  • Like
Reactions: 2
Fuel delivery was proper before I unhooked anything.
Now, suddenly, it sounds like it's not getting any fuel.

I'm not usually stumped on trouble shooting
One thing to check would be the 125 Amp MEGA Fuse to make sure it did not blow. It's located where the positive battery cable connects to the underhood fuse panel.

Start with the simple stuff. Is it getting fuel? Do you have spark? Any chance you forgot to plug something back in or together?
I replaced the 125 amp fuse in the front of the fuse box.
I don't have an assistant to check spark.
I'll try starter fluid tomorrow in case it somehow lost it's prime.
All your suggestions are greatly appreciated
You are quite welcome.

What, no buddies in the area that are thirsty for a beer?

That is what we are here for.

You might want to swap the fuel pump relay with another relay with the same numbers printed on it to rule that out.

I just thought of something. Since you were playing around with the PCM, you might have "corrupted" the security sync between the PCM and the BCM. I would suggest doing a security relearn to allow the PCM and BCM to "reintroduce" one another. Here is the link on how to perform it, and you are looking for post #7:

Just make sure your battery is fully charged before doing the security relearn.
See less See more
  • Like
Reactions: 1
Sure sounds complicated.... but I'll do it.
I got beer if that helps
I sprayed starter fluid directly into the intake and it almost ran.
I cannot find a fuel pump relay anywhere.
Where is the relay?
Got er started!
The fuel pump relay was not in it...and it ran that way before!
How can that be?
I didn't remove that relay.
Thanks for getting me on the r
One more thing.
The dash lights flicker when I let off the accelerator...
I heard it's common.
I don't suppose you know the cure?
Look for a missing dashboard light relay 😅
I'll look.
  • I talked to a guy with an 05 and an 06... Trailblazer and both of them ficker on the dash
1 - 20 of 29 Posts