8.1L/496 Tech

Learned from watching south main auto repair on youtube, disconnect both ends of the harness, put 12v and ground on one end, and the bulb on the other. If its dim, the wiring is bad. Just make sure the sensor and abs module are disconnected. Using a headlight bulb as a load instead of a test light allows more current to flow, so if theres any resistance in the wires the bulb will be dim, just dont beat up the terminals in the connectors
 
oh yeah, I've seen him do that. Smart.

I'll try to give it a shot. Thanks for the idea.
 
BDK said:
Swapped out the oxygen sensors. Cleared the codes. Let it idle for 30 minutes, took it for a drive. Runs great. It had Denso sensors in it, unknown if they are OEM. I'm impressed with that motor. In limp mode, 4500RPM up a 8 mile grade with the AC on and it never got over 210*. 18,000lb RV with a 3500+lb toad.
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Next time...look at the CTS data on your scanner instead of the temp gauge. I was suspicious towing across the desert one day and plugged in, CT on the scanner was 247, intake air temp 142, temp gauge on the dash said 195.
 
Jmmorriso said:
Learned from watching south main auto repair on youtube, disconnect both ends of the harness, put 12v and ground on one end, and the bulb on the other. If its dim, the wiring is bad. Just make sure the sensor and abs module are disconnected. Using a headlight bulb as a load instead of a test light allows more current to flow, so if theres any resistance in the wires the bulb will be dim, just dont beat up the terminals in the connectors
Click to expand...

Still haven't done that.
Crap ton of other **** to do.

Put 1000ish mi on the truck since I swapped the MC. Brakes haven't locked back up since. I think that issue is fixed.





One thing to note about the ABS problem is that if I hit a pothole or a hard bump, the ABS light will blink.
I'm thinking there has to be a bad connection.
 
Bebop said:
Still haven't done that.
Crap ton of other **** to do.

Put 1000ish mi on the truck since I swapped the MC. Brakes haven't locked back up since. I think that issue is fixed.





One thing to note about the ABS problem is that if I hit a pothole or a hard bump, the ABS light will blink.
I'm thinking there has to be a bad connection.
Click to expand...
The amber ABS light or the red brake light or both?

These have an issue with vibrations from the solenoids cracking some solder connections for the main power relays in the EBCM...I usually remove the EBCM from the ABS unit, remove the torx screws and use a razor blade to slice through the sealant to pull the lid off, then look it over with a magnifyling glass....I usually find 3 or 4 connections that look a bit "foggy" and reflow them, then everything works as it should again.

There is also a ground on the frame toward the front of the drivers door that is ****ty....clean everything up and use a bolt and nut instead of the self tapper that GM used that was probably stripped during assembly at the factory.
 
Amber light.

What you're saying is very interesting.

I'll look into all of that.

Thank you !
 
Bebop said:
Amber light.

What you're saying is very interesting.

I'll look into all of that.

Thank you !
Click to expand...
Usually the scenario I described brings on the red light AND the amber light...

Find a scan tool that can pull ABS codes. That's your starting point
 
Lbhsbz said:
Usually the scenario I described brings on the red light AND the amber light...

Find a scan tool that can pull ABS codes. That's your starting point
Click to expand...

Oh...

Never seen the red light. Ever.

Scan tool shows missing communication with pass sensor and that's it. See a few posts above.
 
Been driving it around quite a bit this month.

Brakes have never locked up again. Soooo I'm gonna say that the master cylinder was the original issue.

ABS light still flickers from time to time, haven't had time to dig in.
 
Drove 450 miles on flat highway, thought the gas gauge was broke. Got 13 MPG hauling ass at 80.

Empty 2wd CCLB. Full tuneup, cleaned the throttle body (probably the first time ever since ‘02), new K&N cone filter, cleaned MAF grid (also first time ever).

She’s peppy as hell now.
 
Lbhsbz said:
The amber ABS light or the red brake light or both?

These have an issue with vibrations from the solenoids cracking some solder connections for the main power relays in the EBCM...I usually remove the EBCM from the ABS unit, remove the torx screws and use a razor blade to slice through the sealant to pull the lid off, then look it over with a magnifyling glass....I usually find 3 or 4 connections that look a bit "foggy" and reflow them, then everything works as it should again.

There is also a ground on the frame toward the front of the drivers door that is ****ty....clean everything up and use a bolt and nut instead of the self tapper that GM used that was probably stripped during assembly at the factory.
Click to expand...
I've actually had the bad ground on the frame in that spot before. Also if one of your wheel bearings are on the way out I've seen them set ABS codes for air gap.
 
shortbus4x4 said:
Also if one of your wheel bearings are on the way out I've seen them set ABS codes for air gap.
Click to expand...
I've actually seen this before. 2wd 2500, neighbors truck. "Oh well, I ain't need no annie locks anyways..." A month or two later the wheel folded up into the fenderwell backing out of the driveway.
 
45acp said:
I've actually seen this before. 2wd 2500, neighbors truck. "Oh well, I ain't need no annie locks anyways..." A month or two later the wheel folded up into the fenderwell backing out of the driveway.
Click to expand...

Same here, have saw that a few times. Last one was an ol boy at work. He mentioned the light popped on. We jacked it up in the air and both wheels were just flopping around!:shaking:
 
Bebop how's the abs issue?

Buddy of mine described same issue as what we have and he re-solder parts of the abs module. I'll have mine done hopefully this month. I'll take pics of process so it should help out for everyone since it'll be free and takes bit of time
 
A couple months ago, as I was driving it, the front right wheel locked up at 70mph while on the highway. I almost crashed bad.

After I took it apart, the pad had worked itself sideways, like the caliper was only using one of the 2 pistons, then the pad fell out of the groove and wedged itself between the mount and the rotor, thus locking it.
When I swapped the previous caliper, it was kinda doing the same thing too.
This car was crashed on the front right and I'm kinda wondering if the upright is tweaked and the caliper is not centered. It's weird.

I slapped a new caliper and pad and it drives around but I don't trust the vehicle anymore.



I don't have any of the signs of a bad ABS module (like the code C0265 "EBCM Relay Circuit Low"). The only ABS code happens when the front right wheel speed suddenly drops like I posted above. It does it every so often. I tried a new wheel bearing, new ABS sensor, nothing. I don't think it's a sensor distance thing (VR sensor too far from the teeth) because the speed randomly drops out when you're at 4mph, the same way it does it when you're on the highway at 70mph. Might be a wiring thing but I can't figure out where.

I also have a lot of other **** to do in life and since I haven't needed to tow anything so it just sits.
 
Someone decided the new corvette needed an 8.1
20240516_140541.jpg

20240516_140551.jpg
 
Larry Hofer? Those are custom heads to get direct injection.
 
Mine has been driven 80 miles in the past 6 months.
It's kinda sad really, but I don't really need it at the moment.
 
Bebop said:
Mine has been driven 80 miles in the past 6 months.
It's kinda sad really, but I don't really need it at the moment.
Click to expand...

I’ll be honest, prior to buying mine, I started scoping out these GMT800’s local to me. I see TONS of these trucks in great condition, just sitting. Seriously, I think 90% of owners just keep them for towing and hauling.

Some I have been seeing for over 10 years. Sitting outside, and apparently just keeping on. Don’t feel bad. I only drive mine to blow the cobwebs out. But there will be plenty of times it’ll be nice to have.
 
FleshEater said:
I’ll be honest, prior to buying mine, I started scoping out these GMT800’s local to me. I see TONS of these trucks in great condition, just sitting. Seriously, I think 90% of owners just keep them for towing and hauling.

Some I have been seeing for over 10 years. Sitting outside, and apparently just keeping on. Don’t feel bad. I only drive mine to blow the cobwebs out. But there will be plenty of times it’ll be nice to have.
Click to expand...

The clear coat is starting to go and I don't want to park it inside and loose room in the shop. That's what's annoying really.

RunningProblem said:
Do you guys with broke fuel gauges need to replace the stepper motors?
Click to expand...

I had to replace a fuel level sending unit but that's it. Knock on wood but the gauges on both trucks are fine.
 
RunningProblem said:
Do you guys with broke fuel gauges need to replace the stepper motors?
Click to expand...

Does your cluster have other issues?

My 03 started doing crazy **** including alien hieroglyphics on the DIC. The fuel gauge and Speedo still worked so I never got it fixed. :laughing:

Mine did have the oil pressure and volt meter steppers going nuts at times. I found a guy that rebuilds clusters for reasonably cheap, but smoked the trans and parted it out before I got there.
 
RunningProblem said:
Do you guys with broke fuel gauges need to replace the stepper motors?
Click to expand...
irate4x4.com

GM cluster issue

2003 2500HD LT, key on, comes as scrambled like atari game centipede game or random special chracter instead of X in a Box This occur when key is on, it would from outside to inside before normal spec comes up. After that, all works good as it should Wondering if any, the common issue for...
irate4x4.com irate4x4.com

Mine still good since the repair
 
What? said:
Ever get the brake figured out?
Click to expand...
Nah.
I removed the fuses for the ABS pump and module and put a new caliper and so far so good.
But again 80 miles.
 
I replaced just the lights. Thankfully I haven’t needed a stepper motor yet.

www.gmgaugerepair.com

DIY LED Light Kits – GM Gauge Repair

DIY Bulb to LED Conversion Kits, LED gauge lights, & all LED gauge needs are provided. We lead in rebuild & repair of LED instrument panel lights, LED gauge lights.
www.gmgaugerepair.com www.gmgaugerepair.com

I ordered the white ones. It’s nice to have the gauge cluster actually light up.

The light for trans temp, and speed above 60 mph were burnt out.
IMG_1314.jpeg



The LEDs work with the dimmer too. It is nice.
 

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