2020 Silverado Accessories Wiring Help Needed

Transient · February 1, 2021

It's quite possible for you to have a faulty battery. It happens quite often. Have you got a volt meter that you can see how many volts the battery is putting out? Shold be around 12.4 without the engine running and around 14 with engine running.

I have this. It was given to me by my brother several years ago. He's a mechanic, but lives in another state. He's also whiteout major health issues and is in no condition to help me. I've never used it, and don't know how to use it. I also have the wires/probes it came with. Just didn't take a picture of them. Sorry, but sure if that's what you're referring to.

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20gmctruckguy · February 1, 2021

Yes, that's the toold you need. Set the dial 3 clicks to the left (on the 20) which should read up to 20 volts DC. Put the black wire probe into the bottom hole and the red one into the hole directly above it. Black is negative (-) red is positive (+). Touch the probes to the corresponding battery posts and see what reading you get. Not sure if your multimeter needs a battery, but probably make sure it has a fresh one in it.

Transient · February 1, 2021

Thanks. The device turned on. I did as instructed and it read 0.00, and a "-" symbol flashing in front of the number. The probes were placed directly on the battery posts. However, in an attempt to rule out a battery issue with the multimeter, I went to change it out afterwards only to find out I don't have any spare square batteries. As soon as my wife gets home I'll get some new batteries and check again.

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20gmctruckguy · February 1, 2021

15 minutes ago, Transient said:

Thanks. The device turned on. I did as instructed and it read 0.00, and a "-" symbol flashing in front of the number. The probes were placed directly on the battery posts. However, in an attempt to rule out a battery issue with the multimeter, I went to change it out afterwards only to find out I don't have any spare square batteries. As soon as my wife gets home I'll get some new batteries and check again.

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Okay, do the same test on another car battery if you have one around. That will confirm the multimeter is working.

Transient · February 1, 2021

Okay, do the same test on another car battery if you have one around. That will confirm the multimeter is working.

I was able to test the multimeter on my wife's Traverse when she got home tonight. She been driving the car throughout the day with trouble, so I think it's safe to say the battery was good. Unfortunately, the same can't be said about the multimeter. It read 0.00 on her car, too. I'll get a new battery for the multimeter in the morning. I have a market behind my house that I can walk to while my kids are doing their schoolwork on the computer. I'll report back when I have info.

The working theory in my head right now is one of the cells in the truck battery no longer works. It's the only thing I can think of. Battery can't crank the starter, but the truck runs perfectly once it has been jump started. Battery gauge gives no indication of trouble. No lights, codes, etc. Even the cruise control works. Only thing I've noticed is the Auto Start/Stop is turning off the engine at traffic lights.

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PhilB · February 1, 2021

The battery in the meter is for measuring resistance when in the ohms function or test continuity. You should not need a battery to test the truck's battery. You could have faulty testing leads or a bad meter. To test your leads put the dial in the continuity check mode (just to the right of the 6 o'clock position). Your test leads should be in the same position on the meter as when testing the voltage. Now touch the test leads together. You should get a tone, and the meter should read '1'. If that happens, then your test leads are functional.

To test the DC voltage function, put the dial back on the 20. Get a good battery (AA, AAA, 9V) and touch the leads to it (red/positive, black/negative). You should read 1.5v or 9v, depending on the battery.

Transient · February 2, 2021

The battery in the meter is for measuring resistance when in the ohms function or test continuity. You should not need a battery to test the truck's battery. You could have faulty testing leads or a bad meter. To test your leads put the dial in the continuity check mode (just to the right of the 6 o'clock position). Your test leads should be in the same position on the meter as when testing the voltage. Now touch the test leads together. You should get a tone, and the meter should read '1'. If that happens, then your test leads are functional.

To test the DC voltage function, put the dial back on the 20. Get a good battery (AA, AAA, 9V) and touch the leads to it (red/positive, black/negative). You should read 1.5v or 9v, depending on the battery.

I did a instructed, but it read "1" before I touched the leads together. No tone, even when I touched the leads together. I'll go buy another multimeter and see what happens from there. Right now I'm thinking I damaged the battery with the way I connected the wires. My bad. Stupidity is about to run me over $200. Oh well. At least it wasn't worse.

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Transient · February 3, 2021

I bought this multimeter last night. Moved it 4 clicks to the left for V. Black lead was in the center hole, red lead in the right hole. Checked the battery. With the truck off I got 12.4 on the reading. With the truck running I got 14.6. Then checked the alternator by putting red on the large cable running from the battery and black on battery ground while truck was running. Also got 14.6. Alternator is good? Battery is good? What could be the issue that's keeping my truck from starting without the assist of a jump box?

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20gmctruckguy · February 3, 2021

28 minutes ago, Transient said:

I bought this multimeter last night. Moved it 4 clicks to the left for V. Black lead was in the center hole, red lead in the right hole. Checked the battery. With the truck off I got 12.4 on the reading. With the truck running I got 14.6. Then checked the alternator by putting red on the large cable running from the battery and black on battery ground while truck was running. Also got 14.6. Alternator is good? Battery is good? What could be the issue that's keeping my truck from starting without the assist of a jump box?

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Looks like the voltages are spot on. I checked mine today just for my own curiosity and had 12.4 and 14.6.

So even with your light bar disconnected the truck will not start without the jump box assist? That is strange, and all I can think is to take the truck to a good mechanic. Maybe the cable to the starter is loose, but not too likely.

Transient · February 3, 2021

Looks like the voltages are spot on. I checked mine today just for my own curiosity and had 12.4 and 14.6.
So even with your light bar disconnected the truck will not start without the jump box assist? That is strange, and all I can think is to take the truck to a good mechanic. Maybe the cable to the starter is loose, but not too likely.

I have absolutely 0 electrical power with the lightbar disconnected. I can't unlock the doors, no readout on the DIC, no engine startup, etc. Reconnect the lightbar and everything works, except for the truck being able to start without a jump. Working theory in my mind is the battery is damaged internally and unable to product the required cold crank amps to start the truck.

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20gmctruckguy · February 3, 2021

12 minutes ago, Transient said:

I have absolutely 0 electrical power with the lightbar disconnected. I can't unlock the doors, no readout on the DIC, no engine startup, etc. Reconnect the lightbar and everything works, except for the truck being able to start without a jump. Working theory in my mind is the battery is damaged internally and unable to product the required cold crank amps to start the truck.

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I'm starting to wonder if you might have disconnected a ground wire by mistake. Earlier on you mentioned disconnecting the main power wires from the light bar and then had no power. Battery should be fine if it shows 12.4 with engine off. Reconnecting the light bar wires might be giving just enough ground for most electrical things to come to life but not enough for the starter. Check the ground cables wherever you have been working. A light bar just cannot provide power because it is not a battery.

20gmctruckguy · February 3, 2021

On 1/31/2021 at 4:41 PM, Transient said:

This just keeps getting more "interesting", and I'm even more stumped. I just disconnected both the positive and negative cables at battery for the light bar only. Prior to doing this everything worked, except for the starting not turning over and the lightbar not turning on. Now that I disconnected both the positive and negative connections to the lightbar from the battery, and disconnected the harness used to connect the auxiliary switches from the light bar main harness, I have no electricity in the truck. Jump box didn't detect the battery when I placed the positive clamp onto the positive terminal and negative clamp on the chairs ground post near the hood strut mount next to the battery. I moved the negative clamp to the negative post and it detected the battery, but still no electricity to the truck. Essentially, the lightbar is completely disconnected electrically, but it's the truck that has no electricity. It's as if the lightbar is supplying electricity to the truck. Here's what the fuse block on top of the battery looks like.

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Can you post a pic of the positive and negative cables from the lightbar that you said you disconnected? Not sure why there would even be any. How many wires or pins are in the plug that is closest to the actual light bar? I'm thinking there should only be 3. One for full power, another for ground and the third to control the low power feature. There shouldn't be any need for more wires going to the battery if you are connecting to the gm upfitter switches by the steering wheel. The gm upfitter switches have relays built in.

Edited February 3, 2021 by 20gmctruckguy

Transient · February 3, 2021

Pic of positive connection to battery. This is where the dealership installed the lightbar, so I left it alone. Only thing I did was reroute the wire due to the auxiliary switch install (200 amp fuse, 60 amp fuse, and bolts and plate) taking up the space where the fuse originally was. It's a tight fit, but it works.

Pic of negative connection for light bar

I'm only running the 2 connections because I'm only running the light on 1 switch at full power.

Transient · February 7, 2021

First, I want to say thank you to @20gmctruckguy for helping with the issue where my truck wouldn't start.

Second, my lightbar still doesn't work. Baja Designs has been trying to be helpful, but I just discovered they don't know which of their products they sold GM for the T1 trucks. They told me it was the ONX6 lightbar. I just discovered it is actually their S8 lightbar. I compared the lightbar on my truck to the pictures on GM Accessories. Those checked out. I then compared them to the products on Baja Designs website. It may seem like a non-issue, but it makes all the difference in the world due to 1 wire. ONX6 is a 3-wire cable. S8 is a 2-wire cable. Over a week of trouble because of this. To their credit, Baja Designs did send me new harnesses at no charge. They are trying to fix the problems, and have been very accommodating. Hopefully I'll have this all sorted out soon.

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Transient · February 10, 2021

Hoping to finally come to the end of this dilemma. On Monday I spoke with Baja Designs and discovered some interesting info. They confirmed the lightbar they sold to GM is in fact the S8. However, they said their normal S8 is a 3-wire, just like their ONX6 lightbar. The reason being is the S8 has amber LEDs in the lightbar that are on when the main lights aren't on. This would be a cool feature to have, but it's useless to me due to being in California. They have a stupid law where an offroad light must be covered while the vehicle is on the road if it's more than 40 inches from the headlights. This same law is also why you can't buy a 2500HD or 3500HD with roof mounted clearance markers in California. Therefore, GM wanted the lights without the amber LEDs, and because the S8 is cheaper than the ONX6 lightbar. Thus, the S8 lightbar sold through GM Accessories became a 2-wire setup. Baja Designs Technical Support wasn't aware of the differences. It took me pulling apart everything and providing pictures for them to see what was going on. I offered to bring my truck to their shop several times since I'm only 30 minutes away, but they never accepted the offer.

If anybody else has attempted to install the lightbar they'll find GM requires you to buy an additional wire harness to make the lightbar work. This wire harness has a relay, connects to the truck battery, has a key fob remote, and a remote signal receiver box that plugs into the wire harness. Baja Designs claims they made the wire harness only, and not the key fob and remote signal receiver box. When I examined both of these items I noticed there wasn't a single Baja Designs marking on them, so this seems to be true. It should also be noted this harness also has a connector for the a-pillar lights, which are another add on through GM Accessories.

At the end of the day it was decided that portion of the harness that connects to the a-pillar lights is not needed. If I choose to add the lights later I'll probably wire them to a separate switch. I'm not sure if I even want them, or if it's rather have them on the same switch as the lightbar. If I choose to go with the same switch I can simply order a Y-harness Baja Designs already makes and sells, thus making it a simple plug and play option. I'll need to review data to make sure I'm not overloading a switch if I opt for this.

Baja Designs has sent me a 2-wire harness for connecting the lightbar to an auxiliary switch. I think this will finally put to bed all the issues this project has experienced.

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