2009 chevy Colorado electrical gremlin

ID Status Date Year Make Model Transmission Type A/C Controls Public/Private
#15013 Closed 2009 Chevy Colorado wt 2wd public

Hello, and thanks for doing what you do.
I have a 2009 chevy colorado wt 2.9l 2wd, auto transmission. No modifications other than an autostart.
A few years back when the weather got really cold, I driving and suddenly lost the following
Heater(blower on all speeds)
Windshield wipers
Turn signals
Headlights(when in automatic mode, I’ve found putting the switch to the On position will thankfully keep my headlights on even when this happens)
Also, my abs light comes on, yet the abs continues to work.
And somewhere along the way my traction control light came on and is on all the time, yet my traction control works fine, just adding this tidbit of information in case it helps determine a path of logic.
This scenario happens constantly ever since, once the weather gets cold, so I put the truck in neutral, and shut the ignition off, the back on again and everything instantly begins working again, then will just all fail again repeatedly. Eventually usually after a few miles everything typically returns to working again. The only issue I have is my heat blower motor stopped working on #4, but always works on the other 3 speeds, so I eliminated the resistor issue as a cause and am fine with only 3 speeds.
I removed the passenger side ground block and it is working , as when off my heater and directionals failed only, then when bolted back on they both returned.
I am lost as to where to look next, there is very little corrosion under the hood, what do you suggest?
Thanks for your consideration in helping me!


I always prefer to divide and conquer when multiple symptoms present at one time. Since the blower motor is likely the easiest component to access it is where I would start.  I would test to see if the power or the ground signal goes missing when the problem presents itself. Once you know that we could work out a deeper strategy.

Thanks. Unfortunately it was warm enough out that it didnt fail so I couldn’t test as you asked YET.
But while I was there
I took the kick panel off to inspect the wide white connector as i saw in another
Helpful article, then proceeded to drop my glovebox door, and found the black
Molex connector where the wires drop down to the resistor. I had power on the orange wire on the right side/ incoming, but no power on the side feeding the fan, since setting 4 on the fan selector bypasses the resistor and I havent had speed 4 function for awhile
I ended up jumping it around the connector and all 4 speeds now work. Only reason I jumped was because I tried everything but the connector would not come apart I’m assuming its welded or damaged inside. I can cut and solder all the wires that are in that connector to eliminate it if you think something in there may be causing all the other things that suddenly stop working. But for today before doing anything all worked normal, typical when it’s not too cold out.
At least I have the fan working on all 4 speeds now. Thank you

I have been driving another car meanwhile
So I disconnected the battery for a few days.
Yesterday I cut and soldered every wire in the black connector right behind the glovebox.
Everything was working fine.
Today, not cold out, everything failed again
Headlights when in auto
Hazzard lights
And all 4 speeds on blower.
So in that state, I removed the 2 wire blower plug from the blower and checked for voltage there with the fan switch on 1,2 3 or 4, and found no voltage there at all.
I then ran a jumper cable from my positive terminal on the battery and did have 12
6 volts between the battery jumper, and the orange wire in the connector going to the blower, so apparantly when things fail I am losing the positive somewhere.
Any suggestions?
Thanks again

Sorry typo I meant to say 12.6 volts

positive terminal on the battery and did have 12.6
volts between the battery jumper, and the orange wire in the connector going to the blower, so apparantly when things fail I am losing the positive somewhere.
Any suggestions?
Thanks again

Went out again now after disconnecting battery cable for over an hour.
Started truck and had all new weirdness
Wipers came on by themselves and the directionals were clicking and flashing what seemed about twice their normal speed, then both at once then engine would stall.
I restarted and it did all this craziness and stalled a couple more times. After about 4 restarts all for the moment is working , except I’m noticing the wiper intermittent dial seems funky.
When I rotated to the first intermittent (int) position and second, it goes inconsistent and faster than it should
Then on the 3rd int. Position it almost seems normal
But while I leave it in say 1, and there not moving, every time i press either the brake pedal, or tap the turn sign, or hazards button the wipers definitly move, and sometimes the abs light flashes for a second then goes off again
During this all my traction control light went off for the first time in years, but then came back on, what the?

One other thing, a couple times the horn did a double toot on it’s own in case that means something
Thanks again

Crap, after all that today, I realized the drivers side grounding block was loose,
And I drove to test out when all hell broke loose I guess it jiggled around
I tightened it and I’m back to everything working accept having traction control light on, but definitly was missing the positive when it first failed today, any idea on positive being lost at fan connector ?


There is a possibility that the loose ground could have also been causing the lack of power. Accessory power on your truck is relay controlled and relays cannot work correctly without  a good ground. Back to driving and testing if the problem comes back.

This morning all was failing again, in that state I checked for voltage and had nothing at the fan plug itself.
I checked from the orange wire in the fan connector to the frame and had a circuit.
I ran a wire from the positive battery terminal and had 12.6 volts between the orange and that direct positive jumper .
I dont get any circuit between the brown in the connector to the jumper direct from the battery positive though, seems the positive feeding all the nonworking accessories etc is missing somewhere.
Thanks again


Go to the underhood fuse box and check to see if the Blower fuse (30 amp) is powered when the problem is present and you are finding no power on the brown wire at the blower motor.


If the fuse is powered and good then we have three connection points to check for a breakdown. If it is not powered then we have to go backwards and find out why the Ign 3  HVAC relay is not working properly. Please see the attached diagram.

Thanks so much I will do that when I get home, thanks again.

So this morning first start all worked,
I shut off and restarted and everything failed, I pulled the 30 amp blower fuse and checked the power feeding it and there was no power there, the fuse itself did check good though.


Glad you found power at the fuse terminal but try not to remove the fuses to test. You may have had to if it was a PAL style fuse. Moving things around can affect intermittent problems and skew testing. The next time the problem occurs test for power at the horn, fog lamp or stoplight fuses. If  there is power at any of those fuses and there is no power at the blower fuse I would recommend replacing the IGn 3 relay. There may be a same part number relay in a different location that is not for something important that you can test with. Please see the attached diagram.

Thanks, to be clear there was No power feeding the 30 amp blower fuse, and I did have to remove it to get down to the blades to test, but again no power there.
I’ll look at horn, fog lamp or stoplight fuses to see how I can possibly check without pulling them, and see about a swappable ign3 relay


Wow, sorry I left the very important  word “no” out of the first sentence of my last reply.  “Glad you found (no)power at the fuse terminal”  However the same follow up test for power at the horn, fog lamp and stoplight fuses still applies.

Whew, thanks for clearing that up,
Meanwhile she hasnt failed, I try every morning and night, the one thing that’s always wacky is my wiper speeds even when everything else is functioning.
My low and high always work correctly
But my intermittent speeds are off, for instance my lowest intermittent speed is about 3 times too fast, and goes double time, then the delay is longer etc. All the intermittent speeds are definitly off in case this means anything relevant.
I’ll keep trying and next time she fails I’ll check what you said
Thanks again

One thing also maybe to narrow it down,
Whenever it does fail, if I turn my headlight switch to on instead.of the auto position, they will work every time even when all else is failing, that’s how I get home from work most nights,
And to get everything back in, I keep putting it neutral, turn off key, then restart and hope and usually eventually everything works again


After trying day and night all week it finally failed again this morning.
It was pouring rain but I immediately put a meter into the pins of the foglight relay after having to pull it out. She remained in failed state and I did get 15 volts when probing the slots where the fog relay was to battery ground, and truck was still in failed state when done. Hopefully I did something right, I’m not sure how I was supposed to check things without removing them. Btw, shut off, then turned back on and everything was working again


The fog lamp relay did not need to be pulled. Simply test for power at the test points in the top of the fuse. That aside, I would recommend replacing the ignition 3 relay as the likely cause of your concern.

Thank you
Stupid move by mean, shoulda realized checking at top of fuses, never realized they weren’t sealed up there duh.
Im going to buy that relay, I dont have part number so I’ll have to look at one in truck tonight to get correct one.
If next time it fails with old ign3 relay in, can I pull it out and replace with new one with engine still running? Or is that a no no,
Just thought if I do and all suddenly works then it’s a definite find?
Thanks again


Although I would prefer for the ignition to be off  it is okay to change that relay with the ignition on. Just make sure you are replacing the correct one. It could set a code in the BCM but should cause no other issues.

Temperatures have been above freezing all week and it hasnt failed, today temps are in single digits and it failed within a minute of turning engine on.
I shut off key, restarted everything worked fine then it failed again.
I replaced the ign3hvac relay with engine of with brand new one, restarted and it failed in a minute or so, so I left engine running and check all the standard fuses in that state
The following fuses did Not have power to them…
Frt park lamp
Rear park lamp
Rear park lamp2
Backup lamp
Rt hdlp
Lt hdlp
The only other larger style fuse I did pull to check was the blower which also had no power.

Note that the turn frnt hazzard front and rear Did have power in failed state, but they didnt actually function
For what it’s worth every time it fails I get an Abs, and brake light on my dash, and with low temperatures it fails consistently every few minutes.
Hope this means something and again I Thank you.


Based on your latest test information I researched the wiring diagrams further and suspect one of a few things could be happening.

A poor ground connection at the driver’s side grounding tree G105. The ground bolt could be loose or there could be terminal damage inside the connector.

A poor harness connection under the underhood fuse box.

A faulty Body Control Module (BCM).

Thank you ,
I pulled apart the ds grounding block and was gonna just solder every wire together and connect back solid to eliminate any possibility of bad connections within the block itself,
But I decided to check all the pins inside to a chassis ground first. 2 of the wires never read back to a ground though .I turned every switch on I could think of but dont get a circuit, not sure if I should?
I also pulled the fuse box and pulled all the connectors and reassembled, it was squeaky clean connections all around [i did not split the box] but just in case I unplugged and reseated them all, Il try attaching picture marking the 2 wires that I get no ground circuit through shouldn’t I get a ground to them all?
Wishful thinking,
Thanks again


The ring terminal to bolt connection is the ground for all of those circuits so you should not expect to see a substantial ground circuit on those wires. The image is a little blurry but it appears to me that many have white corrosion on them and the one on the end that is highlighted with a red dot is compressed.

The picture is bad, all connections are very clean, the one was pushed from me testing.
Just so I dont confuse things, I clamped one side of my meter to a good chassis ground and every wire did read some ohms but
Those two particular ones read nothing, same as when I wasn’t even touching the meter lead to them, shouldn’t there be something there, I’m asking because if theres a possibility that those 2 are broken somewhere up in the harness I’ll go on a mission trying to track them down and repair them.
Thanks again


Your testing method is flawed.  All components on those wires are seeking a ground from the attaching bolt. They are not supplying a ground to anything unless all components including the ground bolt are attached.  Also an ohms test for wiring condition is about one of the worst tests that can be done.

You will need to fix the damaged terminal.

If the terminals are clean and not corroded as they appeared in the picture I  would have to be leaning towards a faulty BCM. Unfortunately that would  not be a DIYer diagnosis or repair.

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