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Here's a stumper! ### ANSWER POSTED ###

Jeremy airjer W
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Jeremy airjer W Grand Master

Jeremy airjer W

Posted
Posted

2007 Chevy Colorado 3.7 liter

This one came in on a flat bed. The customer said it would not crank after stopping for fuel. It had done this one other time and a jump start worked that time but did not this time.

I walked out to the vehicle with a jumper pack in hand. Jumped in and turn on the key. Everything comes on bright as day. Turn the key and it started right up, OF COURSE!

I pulled it into the shop and shut it off. I then proceeded to start it again and bingo, no crank. Everything is still bright as day with nothing unusually except the starter will not engage.

The first thing I did was check the anti-theft light. It was not on. I tried starting it again to see if I heard the starter solenoid click and it did not. I decided to print off a diagram of the starting circuit. When i came back the vehicle started. At this point I'm scratching my head. I tried it several time and no issue. I decided to pursue other projects and let it sit for about 20 minutes.

When I came back to it it wouldn't start again. I decided to start by swapping relays. There is a crank/run relay and a crank relay both are the same. The RAP relay was also the same and decided to systematically replace the other two one at a time with the RAP relay. First try and still a no start, second try and now everything is dead, WHAT? No dash lights no headlights no running lights, etc!

I switch those to relay back and I have power to the dash but it still wont start. By accident I left the key on (which was the big break in this one) and swapped those two relays again (rap and the crank relay). as soon as I pulled out the crank relay everything went dead again. It was at this moment I figured it out.

So, What is it?

Its not the relays

Its not the fuse block

Its not the ignition switch

Its not the battery

Its not the connections at the battery

Its not the starter

Its not the wiring

Its not a bad ground

The vehicle had been in the body shop a week before with major damage to the drivers front of the vehicle!

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Macgyver55 Grand Master

Macgyver55

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I'll have to give this one some thought, but it sounds like the retained accessory power part of the BCM must be involved. To tell you the truth though, I've never even opened the hood on a Colorado pickup ever. This one is kind of intriguing... wink

When all else fails... blame the body shop! laugh

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CAMAN Grand Master

CAMAN

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The only thing I can think of, since you specifically stated it had some serious front end damage and this could possibly a manual trans, the clutch switch or wiring got damaged? But since you never stated it was a manual I will assume auto.

In that case all I can think of off the top of my head is the BCM or PCM is toast?

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Tom7227 Grand Master

Tom7227

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Some sort of foolishness with the key. My kid had a similar problem with her car and we had to do something like turn the key on/off 3 1/2 times, flick the lights and then say 3 Hail Mary's and it would start. We towed the dang thing to the shop at least 4 times before we learned this trick, and I think I got the answer right here on this forum.

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CAMAN Grand Master

CAMAN

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Is the fuse block located on the driver's side under the hood where the repairs were made? If so, was the fuse block replaced due to the accident?

Yes it is, right behind the drivers headlight. Yeah I'm thinking a wire was forgotten or placed into the wrong location on the fuseblock when it was replaced.

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LMITOUT Grand Master

LMITOUT

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Posted

If that is the case, my thought was that the crank and RAP wiring was flip flopped so the relay was pulled in until the RAP timer expired in the BCM, which would then allow the truck to crank.

Something like that...

Has to do something with the timer I would think.

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