[mvidlak]

Hi,

I posted while ago about similar issue (used to have loss of comm codes). Problem went away eventually for like a year (can't really connect it to any fix attempts). 2007, i5, 4x4, ext cab

now I'm back to intermittent no power to radio, dash and occasional no start. No codes other than p0411 and p0172.

What's happening (all this while driving)

1) radio loosing power for few minutes at the time, always turns back on eventually. this happens very often. Sometimes it turns back on in a second or two. If the radio is dead for longer than couple seconds dash follows and dies too. Eventually, everything turns back on.

2) when dash dies everything is off except CEL.

3) when everything turns back on, probably 90% of time passlock turns on (solid). not every time though. usually goes to normal after restart.

4) lately, sometimes after loosing power to radio and dash for a while, when everything turns back on I have battery light and sometimes airbag light on top of pass lock.

5) truck never died on me while driving but sometimes won't start (its a daily driver and this only happens about once in 2-3 months) when this happens it doesn't click or crank. everytime it happened it started fine after few attempts. (in less than 10 mins)

What I did

all electronics are stock

I got rid of ground packs above wheel wells and grounded all wires directly to chasis.

tested power to fuse box and ran new ground to chasis. only inspected grounds to block - seems ok but I'm ready to just start replacing all main wires from battery at this point.

Checked, cleaned grounds in cab under seats, rewired bcm ground as it seemed pinched a little - used same location under seat for now, I'll probably ground it somewhere else at some point.

I have newer battery and tested it to double check. All numbers seems to be normal.

I didn't have chance to test voltage when this is happening because of course everything is always back to normal by the time I get home. But when the radio and dash die I can hear that blower is loosing little bit of power too. still blows at all settings but I can hear it slows down a little. I'm pretty sure A/C stops working when it happens too.

Everything else keeps working.

Anyone has an idea what should be the next step? I just wanted to check as there's always ton of good info here.

I don't have issue with anything else other than what I mentioned above so I'm assuming BCM is probably ok and lower on my list.

I feel like my next step should be ignition switch because of the passlock light. It's weird that I'm loosing other things at the same time but I guess it can all be connected somehow? I will probably run all new wires from battery too (both 12v and grounds) just to rule that out.
Anything else I am missing?

Thank you!!!

 

[mvidlak]

So, I just drove around with voltmeter to see if I can confirm voltage drop. Radio and dash went dead (only CEL on) and sure enough, voltage was down to 13.6V. After restarting everything back to normal and >15V. Normally I'd just keep chasing main wires but I can't wrap my head around how intermittent this is and that most of the time everything comes back to normal after restart...

 

[cart7881]

I sent you a message. It looks like the ground side of the circuits is pretty well covered so I looked at the power side. The cluster and the radio each have their own fuse and circuit. The circuits do, however, come close to each other in an inline connector. Maybe access that connector and check the wiring and terminals. It is connector C200, located "behind the I/P left side above brake pedal assembly on lower A pilar" It is a Black 40 terminal connector

 

[cart7881]

Power to the HVAC control and ignition switch also goes through that connector.

 

[mvidlak]

Thanks for digging into this for me!!

I just took a quick look at the connector and everything seems ok. Moved harnesses around and couldn't replicate the issue. So I don't think that's my problem but I'll still test the suspected pins to make sure.

Also, when I thought about the voltage drop again I was wondering if the regulator module behind battery could have anything to do with that. I tried to unplug it to see what happens. Voltage drops to 13.8 - similar to what happens when my dash and radio die, but everything still worked fine. I do not have any loss of communication codes right now. Even unplugging the regulator didn't set any - I expected to see some U codes but maybe I just didn't run it like that for long enough or it needs to do it couple times before triggering the CEL.

Anyway, I remember when I was dealing with similar issues for the first time about 2 years ago. I did have these:
U1016 loss of pcm communication
U1064 loss of body control module, dash integration module, sbm communication

I do not have those codes now, but issues are back. I'm kinda just running in circles with this thing - maybe I should drop 5.3 in it and start over haha

 

[cart7881]

Well, other than what I mentioned, the symptoms seem to go back to the power source. Other than that, nothing else seems to be related to all of those systems. Fuse box, maybe. Have you checked the contacts of the maxifuse?

 

[mvidlak]

I did check and cleaned contacts on fuse box.

Yeah... I think I just need to focus on basics again. I didn't pay too much attention to this yesterday but I just noticed again that my voltage was up to 15.4V with truck running, which seems way too high. Drops down to 13.8 with regulator unplugged. I've had these issues for a while and it comes and goes all the time so for now I'll assume that it's not alternator/regulator issue. (also can't replicate issues with regulator unplugged) To me it still looks like a poor connection somewhere.

I'm not best with electrical... but I guess voltage drop somewhere could cause reading that creates overcharging condition? I'll test voltage drop on everything I can again. I know there's the regulator module on grounds behind battery, do we have a regulator built in the alternator too? Anywhere else where could be truck reading voltage for charging? knowing where is ecm taking readings from could point me right direction...

 

[cart7881]

I think 15.4 volts is within limits, but barely. Maybe something is causing an excessive current draw with the engine running.

 

[JonRado]

Hi,

I posted while ago about similar issue (used to have loss of comm codes). Problem went away eventually for like a year (can't really connect it to any fix attempts). 2007, i5, 4x4, ext cab

now I'm back to intermittent no power to radio, dash and occasional no start. No codes other than p0411 and p0172.

What's happening (all this while driving)

1) radio loosing power for few minutes at the time, always turns back on eventually. this happens very often. Sometimes it turns back on in a second or two. If the radio is dead for longer than couple seconds dash follows and dies too. Eventually, everything turns back on.

2) when dash dies everything is off except CEL.

3) when everything turns back on, probably 90% of time passlock turns on (solid). not every time though. usually goes to normal after restart.

4) lately, sometimes after loosing power to radio and dash for a while, when everything turns back on I have battery light and sometimes airbag light on top of pass lock.

5) truck never died on me while driving but sometimes won't start (its a daily driver and this only happens about once in 2-3 months) when this happens it doesn't click or crank. everytime it happened it started fine after few attempts. (in less than 10 mins)

What I did

all electronics are stock

I got rid of ground packs above wheel wells and grounded all wires directly to chasis.

tested power to fuse box and ran new ground to chasis. only inspected grounds to block - seems ok but I'm ready to just start replacing all main wires from battery at this point.

Checked, cleaned grounds in cab under seats, rewired bcm ground as it seemed pinched a little - used same location under seat for now, I'll probably ground it somewhere else at some point.

I have newer battery and tested it to double check. All numbers seems to be normal.

I didn't have chance to test voltage when this is happening because of course everything is always back to normal by the time I get home. But when the radio and dash die I can hear that blower is loosing little bit of power too. still blows at all settings but I can hear it slows down a little. I'm pretty sure A/C stops working when it happens too.

Everything else keeps working.

Anyone has an idea what should be the next step? I just wanted to check as there's always ton of good info here.

I don't have issue with anything else other than what I mentioned above so I'm assuming BCM is probably ok and lower on my list.

I feel like my next step should be ignition switch because of the passlock light. It's weird that I'm loosing other things at the same time but I guess it can all be connected somehow? I will probably run all new wires from battery too (both 12v and grounds) just to rule that out.
Anything else I am missing?

Thank you!!!

Thanks for getting this started. My 2006 I-5, Z71 Crew cab does the same thing. How many miles are on your Colorado? Mine has 185+K. Intermittent gremlins are a bitch. This has happened to me twice of late, truck still runs but all gauges, radio, and lights drop out with passlock light on.. I haven't found anything like you to put my finger on and say "this is it". But I'll keep looking too.

 

[mvidlak]

Thanks for getting this started. My 2006 I-5, Z71 Crew cab does the same thing. How many miles are on your Colorado? Mine has 185+K. Intermittent gremlins are a bitch. This has happened to me twice of late, truck still runs but all gauges, radio, and lights drop out with passlock light on.. I haven't found anything like you to put my finger on and say "this is it". But I'll keep looking too.

Hey, yeah still can't figure it out, I went through all grounds, wanna look behind dash and at ignition switch now. It's hard to track it down. Now it sometimes happens like 10 times during 15 minute drive...
At least it never dies on me completely
I have close to 250k miles on it. It's been super reliable other than this.

 

[mvidlak]

So just an update. Went through all the wiring I could see related to this, checked harnesses to dash, radio, new ignition switch. Problem still comes and goes. I'm starting to think it's BCM.

 

[cart7881]

After looking back at all the info here, it seems that you might, in fact, have a communication problem. When you are driving and the radio shuts off, does the clock still show? When the cluster fails, do the turn signals still work? As you probably already know, both the radio and cluster are on the Serial Data Bus and almost all of the cluster functions are bus controlled. There is a separate battery feed to the radio for the time and memory and the turn signals are hard wired to the cluster.

It's possible to lose comm between the BCM, Radio and Cluster and still have the engine running because communicatiuon between the ECM and the BCM is a different wire. Have you had a close look at the connectors for the BCM? There could be some fretting corrosion forming there or high resistance melting.

I'll send you some more info.

 

[mvidlak]

Thank you! I didn't see anything obvious around BCM but I'll look at the pin out and double check.

When radio shuts off the clock is gone too. Sometimes it remembers time when it turns back on sometimes it completely resets.

Never noticed turn signals not working when cluster fails. When cluster fails check engine light is only thing that's on. After it comes back to life it's always different - sometimes it comes back with just passlock light, sometimes with error message on display, sometimes battery, airbag light and sometimes all of the above. I also know my ac compressor stops working when radio and cluster goes. (can't say if every time but know it happened few times)
It only happened handful of times in couple years that after these issues truck wouldn't start - not cranking. Always started after few cycles...

 

[mvidlak]

So, while chasing more wires I found shredded pieces of paper towel or something and just a mess in the dash. So I'll pull the dash and I'm hoping to find some wiring that's been chewed on!

 

[cart7881]

This is getting interesting!! Keep us posted. Thanks.

 

[mvidlak]

I will! I really hope I find something. Pulled the dash, I'll get back to it tomorrow. I wonder how many screws and nuts I'll have extra when I put the dash back in :-D

 

[cart7881]

Contact me if you need any info.

 

[mvidlak]

So again, nothing obvious behind the dash. But it's nice to have that harness exposed now. I just plugged in cluster, radio and 2wd/4wd switch bc we have lot of snow and of course everything works fine now. So I'll drive it like this for a while, that way when radio and cluster dies I have good access to all connectors to troubleshoot.

 

[cart7881]

Sounds like a plan. Keep us updated. Thx.

 

[JonRado]

Thanks for getting this started. My 2006 I-5, Z71 Crew cab does the same thing. How many miles are on your Colorado? Mine has 185+K. Intermittent gremlins are a bitch. This has happened to me twice of late, truck still runs but all gauges, radio, and lights drop out with passlock light on.. I haven't found anything like you to put my finger on and say "this is it". But I'll keep looking too.

On a whim, I had a new key made to replace my really worn original key. My thinking, after doing all the grounds, etc., was that something in the ignition switch would drop out parodically from worn or sticky parts causing a loss of signal to the BCM. My engine always kept running and all power would come back after on the next "start try" I used the new key with a liberal amount of dry graphite and a lot of in and outs and on and offs. I'm still monitoring and waiting for the anomaly to re-appear, but so far - since before Christmas - so good.