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Discussion Starter #81
Thanks for the recommendation on the Hantek scope.

That is one that frequently came up in my searches.

I like that it is computer based, but also wonder if handheld would be more convenient.

The Hantek software has presets for various car specific tests, correct? How do you like that feature?
 

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LOL! I'm still in the learning stage with this thing. I know it has preset tests for the charging system, as well as ignition, etc. My use of it has been just to learn some of it's capabilities. Haven't had to troubleshoot with it yet. I've used presets to check the High Speed Data Circuit, the starting circuit and injector circuits. Next on the list is sensors as I think it will be especially useful there. Right now I'm looking for a small inexpensive tablet running Windows. The laptops I have are a bit unwieldy.
 

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Discussion Starter #83
I am more confused now.

I disconnected the gray wire (Field Duty) for my drive to and from work. The voltage seemed to be a bit more stable, buy it would still fluctuate w applied throttle. It did not climb as high, but would get to upper 15's w moderate acceleration. I had to basically completely floor it to get it to hit 16volts and go into fail safe mode.

So, it appears the problem exists w out the second wire just not as severe. I don't know if that means the problem is red computer connection or something else (ground...)

So tired of this $#!t.
 

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Discussion Starter #84 (Edited)
Well, I can now confirm it is NOT the ECM.

More #@$&ing wasted money!!!

I tried using a Scope Also. W out knowing what a good signal trace looks like, using a Scope is quite useless.

Maybe it's time to dump this freaking truck. It just doesn't make sense.

New ECM, new alternator, new battery, new battery cables, cleaned every ground point...

I quit.
 

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Wow... My typos, I'll try again.

Oh man, I was hoping you would find the solution. But, nope, just a quitter. ;-). Just kidding Ken. We certainly gave it our all. I am a EE and I packed it in long before you. I do love my new Tacoma though, I must say.

There... All fixed. Sorry you couldn't figure it out. If you go for a new truck, the 2019 Tacomas are marked down, also, the Silverados are at 30k last I checked. Great deal of you can still trust Chevy.
 

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Discussion Starter #88
Bumping the thread hoping someone will read that might have insight.

Right now, w nearly freezing temperatures, the problem almost never happens.

I took a long drive this weekend... After a long time and afternoon temps rising, the fluctuating voltages w throttle application started.

Recap: new ECM, new battery, new alternator, ground splice packs removed and redone w ring terminals, new +/- battery cables, ground connections on engine block cleaned/tightened...

At a loss...
 

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Just guessing, but have you checked out the throttle wiring?

I'm not sure what you'd look for other than a chafed/loose wire...then again, my BlueDriver OBD2 scanner lets me watch live data, and there are 4 or 5 different data channels for the drive-by-wire throttle system...perhaps you could get ahold of a similar scanner, watch the data stream for a spike or something?
 

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Discussion Starter #90
Thanks, Jamyers.

I looked at wiring harness from PCM to fuse box and to coils. I don't think I opened the portion at the throttle body.

I have a tech2 clone and have monitored many things, but not the drive by wire stuff.

That gives me a couple other (and free) things to look at.

With the problem only occuring while driving and only once "something" is heated up, it has not been possible to do a wiggle test on wires or signal trace .

I will look into that this weekend.

Keep the ideas coming.
 

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Just curious, what Tech2 do you have, and how do you like it?
 

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Discussion Starter #92
I have one that most refer to as a Chinese Clone. I have not used a "real" one, but I am not sure what the difference would be.

My only complaint is that I was cheap, and did not order one that came w the molded carry case. I really wish I had gotten the case. I have not been able to find any place to get just the case.

The new GM system is MDI. There are copies of them too. I wouldn't mind finding out about them... They work on much newer vehicles, so more likely will support my next vehicle.
 

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Discussion Starter #93
Might have success... Reluctant to say, though.

I replaced the ignition coils.

Temperatures here no higher than 60, so it might just be too cold to set condition for the problem.

But, I had 2 separate drives today each about an hour long, and not any indication of the voltage problem starting.

My thoughts were that the coils would work much harder under acceleration. Nothing else electrical really does anything different while accelerating other than the injectors. The injectors just turn on longer during acceleration but they don't "work harder".

Brand new coil packs are likely due after 25 years... $115 for AC Delco from RockAuto. If they didn't fix the electrical issue, this was the cheapest "mistake" but likely still needed
 

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Discussion Starter #94
This problem is still haunting me. Now that the temperatures are constantly best 100 here, the electrical gremlin is back w a vengeance.

Slightest acceleration causes the fail safe mode to kick in on BCM. The main complaint for me, is this is turning off the HVAC and my truck won't keep cooled down. If cruising steady speed she blows down to 40 degrees.

Someone has to have some insight on this.

HELP!!!
 

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Discussion Starter #95
I am fairly certain that I have figured it out, finally. I reread all my rambling posts and saw one about possible problem w engine paint on my replacement engine that might interfere w good grounding of the Alt to the block/cylinder head.

I bought a 18" battery cable and connected it from one of the alternator mounting bolts and the (-) battery terminal.

341249


341250


That seems to have fixed the problem.

I checked for voltage drops across each battery cable, the Alt and the battery and every combination I could think of. The issue only happened during acceleration, so I'm thinking the coils using more power while accelerating would draw more electricity and the mount between the Alt and engine caused resistance that caused the Alt voltage to climb upwards of 19 volts.

The engine block was painted w cast aluminum color paint, so it's hard to see if all the paint is removed from the mounting points. I should remove the Alt and grind the mounts... But it is really hot and the added cable seems to work.

Bottom line, be careful w paint on the cylinder head, block or alternator.
 

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Discussion Starter #96
Adding a ground wire for the Alternator definitely fixed my electrical problem.

At some point, when the weather is cooler and I have the time, I will pull the Alternator, grind down the mounting bosses for the alternator. Of course, when it is cool, the problem doesn't happen so it would take a while to see if engine paint on the alternator mount is the issue... but it would help make it more "correct".

Still cannot believe I spent so much time and money trying to figure this out...
 
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