SOLVED - Big 3 upgrade, EVERY warning light on immediately after.

[Tyrant]

Update:

4WD (4 high/auto/2 high, NO low) still works, ABS/traction control are completely non functional, and it randomly goes into limp mode on start-up.

There's no rhyme or reason to it... It'll refuse to downshift, won't rev past ~2,000 in Drive (but will in lower gears), and it's gutless. If it wasn't supercharged, it probably wouldn't even be drivable.

I can park, shut her down, and fire her up with no limp mode. Sometimes it'll take 2-3 restarts, sometimes it'll stay for the entire day.

It happens when it's 80° out, 30°, and everywhere in between.

I found a guide that suggested measuring resistance at the diagnostic port a while back, but misplaced the link before I could get to it. I snagged a new multimeter, as my old one finally bought the farm. Do you guys have any info on which pins I'd need to test and how much resistance I should be looking for?

Thank you again!

 

[HACK BLOCK]

might be worth it to take it to a professional now

 

[Tyrant]

Unfortunately I'm beginning to think the same. I'll give it one more whirl by trying to test the modules, I hate paying "diagnostic" fees that are easily inflated.

 

[CaptainAmerica1]

Seems you’re in over your head. Take it to a professional. I know what they’re gonna find. But you do you homie….

 

[Tyrant]

Update:

Went to a local shop, worked with the techs there for a few hours to try and narrow it down.

They are convinced that the ABS module is the root cause of the issue. Voltage and resistance measured at the ABS plug is as it should be.

After I got home, I measured resistance between pin 6 and 14 of the DLC and what did I find - 120 ohms.

The rear terminating resistor reads 120, so that's a no go. From what I'm reading, the other resistor is actually in the ECU.

 

[CaptainAmerica1]

Keep ignoring the obvious. I’m sure you’ll burn it to the ground in no time…

 

[George B]

Did you and the shop confirm a handshake from each of the modules with a scan tool? How did they come to the conclusion it’s the ABS module?

I am still of the opinion some module is fried unintentionally.

 

[petethepug]

ARES Technologies No1 Reman Pre-Programmed Engine Computer PCM ECM ECU

If you need an engine computer, we are here to help you to identify the right module for your car.

arestechnologies.com

$129 for a new BCM coded to the truck.

 

[Tyrant]

Did you and the shop confirm a handshake from each of the modules with a scan tool? How did they come to the conclusion it’s the ABS module?

I am still of the opinion some module is fried unintentionally.

The measured resistance at the DLC tells me you're probably right. The shop tech I worked with's explanation for the ABS module suspicion was basically that it interprets the readings from the hall/wheel speed sensors at each wheel, then sends the data to the other modules.

That would explain the absolute disappearance of the ABS module in the Tech 2 and the Snapon readers, as well as the traction control.

It doesn't explain the TCCM and FPCM codes, to which I think your suggestion is more appropriately linked.

Thank you!

 

[Tyrant]

Keep ignoring the obvious. I’m sure you’ll burn it to the ground in no time…

Alright, I'll humor you since you're so insistent - ripping out 0 awg wire and replacing it with stiff, pre-moulded 4 awg will magically fix the canbus? Are you volunteering to pay Stealership prices for the wire and then reimburse me for the time when the obvious occurs?

Nothing is disconnected. I've gone over every single connector in the vehicle, including those behind the dash, blown them out w/ compressed air, and slathered them with dielectric grease.

I've replaced every J case and mini blade fuse. I bought Tech2Win and ran through the diagnostic protocol with that, followed the TSB for these issues, and then doubled down on the diagnostic with somebody more acquainted with GM electrical than myself.

I'll appreciate any constructive criticism, but I don't personally care if you have a vendetta against "Big 3 upgrades", so I'm directly asking you to keep the glaring negativity to yourself. I don't have a tantrum when people stuff 22" chrome wheels on their SUVs or lower them, even if it isn't my cup of tea. I addressed constant headlight dimming and very rough starts in -20° weather by choosing to decrease the resistance between my battery and the starter/distribution block. On the plus side, it worked - on the down side, I inadvertently stumbled upon something else in the process. Whether or not I caused a short inadvertently or simply unmasked an existing issue doesn't change the fact that I'm trying to address it now.

I appreciate your earlier, more constructive input and I'm not saying "Boo, go away" - I'm only asserting that I don't care for the constant sarcasm and negativity. I'll welcome any reasonable attempt to help, as I hope people can tell from my interactions thus far.