Factory or not?

[RichLo]

I see a 'Starter Inter.' wire on that last picture you posted so thats a combination alarm and remote starter aftermarket unit. I bet everything your experiencing is caused by that box.

RanchWelder gave you some great guidance. Take that post seriously! I would carefully inspect everything that's been done without cutting anything, take lots of pictures and then bring it to a highly reputable local 'owner/operator' mechanics shop. Not a big brand shop that hires high-school kids to install car stereos. It wont be cheap but it also wont be a never-ending problem when its done correctly.

 

[1998_K1500_Sub]

The GMT400 electrical systems are not very complex (nothing like we have in automobiles in recent years). Each wire has a function, and each function has a wire, for the most part.

You’ll do fine with some common sense and, if you need clarification on a wire’s color / purpose, a service manual.

Be methodical! Remove it wire by wire; work with only one wire at a time… remove whatever they have spliced to each OE wire, and then reestablish that OE wire’s connection to its corresponding mate. Don’t go in there and cut everything out first, and then try to put it back together that’s a recipe for failure.

Respect the airbag wiring, as you have already been advised.

I removed a Lo Jack that someone had installed in my 1995 S-10 Blazer, and its electrical system is pretty similar to the GMT400 for all years.

The Lo Jack wasn’t confusing to remove… most time was spent simply doing a good job of reconnected wires that they had spliced.

Finding where they hid the radio transmitter and back-up battery was probably the most difficult part. They stuffed them away in a corner of the truck that I didn’t know existed.

 

[97Kharon]

**UPDATE**
As of this morning the system was remove, it wasn’t too terrible although it was spliced in numerous power wires and had three ground points in various locations under the dash. The main wiring harness was tucked up into the cavity by the driver kick panel it took a a few tugs to get it out as it was packed tightly into the cavity. Truck starts and runs fine now, i will have to rewire my fog lights as the system utilized it’s ground. I did discover three connectors packed in foam tucked and hidden under the dash panel I managed to cut the zip tie and pull them up towards the cluster for a photo.

 

[97Kharon]

**UPDATE**
As of this morning the system was remove, it wasn’t too terrible although it was spliced in numerous power wires and had three ground points in various locations under the dash. The main wiring harness was tucked up into the cavity by the driver kick panel it took a a few tugs to get it out as it was packed tightly into the cavity. Truck starts and runs fine now, i will have to rewire my fog lights as the system utilized it’s ground. I did discover three connectors packed in foam tucked and hidden under the dash panel I managed to cut the zip tie and pull them up towards the cluster for a photo.

Functionally wise the truck starts better and regained horn usage however i lost power to the overhead console and middle console i’m sure it’s the secondary fuse box or the relay powering it that’s the issue.

 

[Orpedcrow]

You must be registered for see images attach

The plugs in foam appear to be factory. The ones that were plugged into them look like t-harnesses maybe. I don’t have a manual in front of me but that might be where you’re fog light and overhead console issues are.

 

[97Kharon]

You must be registered for see images attach

The plugs in foam appear to be factory. The ones that were plugged into them look like t-harnesses maybe. I don’t have a manual in front of me but that might be where you’re fog light and overhead console issues are.

Currently scouring the internet and going though the service manual trying to figure out what connecters are possibly for. Once it cools down a bit or first thing tomorrow morning i’ll be retracing my steps to see what i overlooked.

 

[RanchWelder]

Good job.

Some of the under dash harness is for a factory towing controller for trailer brakes and signals wiring.
The harness may also contain provision for air bag suspension controls for trucks with added dealership installed features.
You may not need them for anything if your truck was not the loaded version.

The glove box will show you the codes for the options you may or may not have.
Chances are the voltages screwed up the fly back zener diodes within the cotrol switches in the overhead systems.
One sure way to know if you have power is by pulling the overhead control panels and testing the tiny light-bulbs, if they do not light up when you turn on the headlights or interior lighting.

If the tiny bulbs are good (ie: they have continuity when tested with an ohm meter when removed from the control panels), and they light up with separate 12v testing power, then your controllers no longer have power and ground. The switch panels are for sale on AZ if yours is blown.
Now you know why buying a used unit from ebat can be a rip off, if they are selling a blown unity for $65.00 or around half of what a new replacement costs.

Voltage spikes from the alarm could have ruined the expensive sensitive switch controllers, by allowing back flow of voltage through the ground circuits and destroying the single direction zener/resistor circuits designed to limit fly back effect. Several systems can be effected, making diagnostic very difficult.
You are correct presuming the relays also have a resistor for fly back and could also be blown, however, if other fly back's are ruined, swapping relays may not fix the issue... You see how this can be running in circles?

Check all your grounds and fuses before you mess with anything. Verify the lights work and if they are blown bulbs, if they do not.

If this does not fix anything and your controller(s) still malfunctioning:
It is possible your head light switch is ruined and causing the other systems to mal-function too.
Everything is switched in the most confusing way through the headlights switch... (don't argue with this logic... it is a fact).

The headlights and wiper circuits are very difficult to explain to a non-automotive electrician. The wiring diagram will confuse you for months if you cannot understand the methods the engineers used and the math required to make it a dealership repair, (***all on purpose, so when it breaks you buy a new truck after your local mechanic cannot find the issue to fix it).

When you add a system disrupt-er like the alarm you cross connect the sensitive confusing voltage systems GM has designed.

You're lucky if your wiper control module is not blown or the headlights switch has not burned up the circuit which routs power the controllers you are having issues with.

Verify the wiring colors at those black factory connectors and I'll bet you find they are for factory trailer brakes, air bag suspension, the more advanced radio / GPS audio video system, etc... may not not be your issue. Search the web for the super expensive options packages this truck could have come with, rear A/C and heater, heated seats, supreme audio, full trailer controls... before you jump to conclusions what they do.

Does your cluster work correctly now and do you still have a working battery after 3-4 days of sitting without running?

The diode in your dash is what I am most concerned with... $350 is a lot of money.
It it's blown and you do not find the other issues, it can blow a new rebuilt replacement if all the possible fly-back issues are not found and repaired...

Good luck.

 

[97Kharon]

Good job.

Some of the under dash harness is for a factory towing controller for trailer brakes and signals wiring.
The harness may also contain provision for air bag suspension controls for trucks with added dealership installed features.
You may not need them for anything if your truck was not the loaded version.

The glove box will show you the codes for the options you may or may not have.
Chances are the voltages screwed up the fly back zener diodes within the cotrol switches in the overhead systems.
One sure way to know if you have power is by pulling the overhead control panels and testing the tiny light-bulbs, if they do not light up when you turn on the headlights or interior lighting.

If the tiny bulbs are good (ie: they have continuity when tested with an ohm meter when removed from the control panels), and they light up with separate 12v testing power, then your controllers no longer have power and ground. The switch panels are for sale on AZ if yours is blown.
Now you know why buying a used unit from ebat can be a rip off, if they are selling a blown unity for $65.00 or around half of what a new replacement costs.

Voltage spikes from the alarm could have ruined the expensive sensitive switch controllers, by allowing back flow of voltage through the ground circuits and destroying the single direction zener/resistor circuits designed to limit fly back effect. Several systems can be effected, making diagnostic very difficult.
You are correct presuming the relays also have a resistor for fly back and could also be blown, however, if other fly back's are ruined, swapping relays may not fix the issue... You see how this can be running in circles?

Check all your grounds and fuses before you mess with anything. Verify the lights work and if they are blown bulbs, if they do not.

If this does not fix anything and your controller(s) still malfunctioning:
It is possible your head light switch is ruined and causing the other systems to mal-function too.
Everything is switched in the most confusing way through the headlights switch... (don't argue with this logic... it is a fact).

The headlights and wiper circuits are very difficult to explain to a non-automotive electrician. The wiring diagram will confuse you for months if you cannot understand the methods the engineers used and the math required to make it a dealership repair, (***all on purpose, so when it breaks you buy a new truck after your local mechanic cannot find the issue to fix it).

When you add a system disrupt-er like the alarm you cross connect the sensitive confusing voltage systems GM has designed.

You're lucky if your wiper control module is not blown or the headlights switch has not burned up the circuit which routs power the controllers you are having issues with.

Verify the wiring colors at those black factory connectors and I'll bet you find they are for factory trailer brakes, air bag suspension, the more advanced radio / GPS audio video system, etc... may not not be your issue. Search the web for the super expensive options packages this truck could have come with, rear A/C and heater, heated seats, supreme audio, full trailer controls... before you jump to conclusions what they do.

Does your cluster work correctly now and do you still have a working battery after 3-4 days of sitting without running?

The diode in your dash is what I am most concerned with... $350 is a lot of money and it it's blown and you do not find the other issues, it can blow a new rebuilt replacemnt if all the possible fly-back issues are not fixed...

Good luck.

Prior to uninstalling it i had the truck sitting with the battery disconnected for a full day. The same day i looked at the schematics and wrote down what wires were what till i was certain i covered everything needed for the job ahead however i didn’t expect the harness from the module to be spliced into so many different power and ground wires as if they wanted to be certain the module would work not matter what. My suburban has the travel time package, it was shocking it still had the tv and vhs player from back then. They were powered by a few wiring harness that led to a separate fuse block and relay that’s attached to the firewall by the brake pedal. I removed everything temporarily till everything power wise was fixed but i’m liking the space it was once took. I’m planning on getting a smaller console and using the power wires for a auxiliary switch panel. I haven’t had any issues since i removed it. Next weekend i plan on working on it again, reconnecting the fog light wiring and looking into the other disconnected ground wires that i found which were wrapped around the wiring for the airbag leading up and behind the radio which is why i left for next weekend. I’m curious to know about the connectors that were wrapped in foam padding.

 

[RanchWelder]

I'm rooting for you.

I'm going to ask you to consider this post important.

Clean every ground. Grease every connector with dielectric grease after cleaning with contact cleaner spray.
The big gray tube at the parts store...

Carefully pull EVERY connector on your engine, spray with electronics contactor spray or brake clean and use dielectric grease on every connection under your hood. All of them everywhere. You are likely to see corrosion on the plugs to your ignition module inside your distributor and coil wires as well.

Replace your damaged battery. All that blinking has done some damage, no matter what anyone tries to tell you with the tester at the store. Save what you have for a spare and/or have it deep cleaned at a golf cart repair shop, using their $1400 deep cycle anti-corrosion machine or trade it in.

Replace your primary ground wires from your battery to your frame and starter.
Don't even think about it, for $25 buy new ground wires, scrub the corrosion from where they have been arcing and do not make yourself sick doing so. The dust is toxic and corrosive. There will be dust everywhere they are bolted.
If you get it on your fingers and rub your eye you'll need to seek medical attention or go blind, so pay attention.
The insides of the black casing is probably full of green or white dust. You cannot re-use them.
Rub your hands on your pants and they will rot through and you'll cross contaminate everything you touch in the house.

If you fill a gallon bucket with water and add a little baking soda for a portable paw wash, you'll have clean hands before you pet your dog or cat. Don't contaminate your wash bucket. If you get it in the eyes you'll need the bucket water reasonably clean to wash your face.

Do not dump baking soda water onto your battery. Boom.

Locate the grounds inside the cabin bolted to the side walls and dash. Scrub clean and grease everything.
Don't forget your head lamp connectors, while you fix your fog lights. Grease away and try not to break anything.

You should plan on removing your door panels and doing the same to the connections at your window controls and motors.
You also have a date with your starter and alternator wiring harness. Pull every nut and bolt and keep cleaning until you find every positive and negative connection.

The more grounds you clean under the dash the better. There's a bunch of them. Every one is suspect to failure now.
If your red battery wires look lumpy or bent up in weird shapes under the casing, they are bad too.

Have fun and document everything you find and replace.