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I have a 2003 Silverado with a electrical problem. I checked…

I have a 2003...

I have a 2003 Silverado with a electrical problem

Mechanic's Assistant: Are you fixing your Silverado yourself? What have you tried so far?

Yes i checked all the fuses and wires

Mechanic's Assistant: Most vehicles have two fuse panels. Have you located both?

Yes checked both

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Answered in 1 minute by:
3/23/2018
Dan
Dan, Technician
Category: Chevy
Satisfied Customers: 25,969
Experience: Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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Hello, my name is ***** ***** I'm here to help get your problem solved.

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What is the electrical problem you are having? Thanks.

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Customer reply replied 3 months ago
temp, oil, fuel, and battery gauges, odometer door locks and windows not working i have battery, abs and air bag lights are on interior lights not working
Customer reply replied 3 months ago
i bought a BCM and did not have to reprogram it, so i put my old one back in. but did not fix the problem

Have you tried checking diagnostic codes? It sounds like you may have a couple problems going on. The instrument cluster is known to have problems on these vehicles.

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Customer reply replied 3 months ago
i forgot the DLC has a fault as well not communicating
Customer reply replied 3 months ago
all of these thing stop working at the exact same time

Thanks, ***** ***** a few minutes to look into this.

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Do windows/locks work from passenger door?

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Customer reply replied 3 months ago
no
Customer reply replied 3 months ago
no broke wires in the door jam on either side
Customer reply replied 3 months ago
12v accessories works

Check the airbag module and connector located under drivers seat. CHeck to see if unplugging module helps anything, let me know.

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Customer reply replied 3 months ago
no change
Jerry Newton
Jerry Newton, Chevy Technician
Category: Chevy
Satisfied Customers: 5,694
Experience: ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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It sounds like there is communication problem within the truck. What's the problem with the DLC, how did you determine there's a problem there?

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Customer reply replied 3 months ago
i have a scanner and it says the communication error

OK, what kind of scanner do you have? Can it read body codes, ABS codes, etc? Or just engine codes?

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Customer reply replied 3 months ago
its a Konnwei KW850
Customer reply replied 3 months ago
not sure if it reads the code cannot get to comm.
Customer reply replied 3 months ago
the DLC worked last month autozone it for a throttle body fault

OK, there is a communication. I can help you try to work this out.

All of the computers talk to each other on a communications circuit, it's called class 2 data. Basically it's one circuit that connects to all of the computers, and splices together in one place. If any of the computers on that class 2 data bus pull the circuit low (ground), all communication stops and the vehicle won't run. So the trick is figuring out which branch of the class 2 bus has the problem.

GM made this easy for us in a couple of ways. One was by using the factory scan tool, but you don't have that, so we'll skip over it. The second way is that you can easily access this splice, take it apart, and try to talk to one computer at a time. That's what we're going to do.

Under the driver's side of the dash, there is a splice called SP205. It's taped to the wiring harness in the vicinity of the headlamp switch. It is taped up so you can't see it, you have to dig to find it. It looks like a connector with a bunch of wires going into it, but the wires only go into one side, and nothing comes out the other side, the wires just stop there. I think it has 12 wires going to it, see if you can locate that.

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Customer reply replied 3 months ago
the truck run fine no problem with the engine drives fine
Customer reply replied 3 months ago
i found a plug with a cap on one end and about 12 wires in the other

That's SP205. Let's back up, though. I got the impression the truck didn't run for some reason, probably because of the communication issue. Let's forget that for the moment.

Do you have a test light?

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Key on, touch the tops of the fuses, the two little tabs on each fuse. Verify power at both sides of each fuse, and let me know if you have any that have power on only one side (bad fuse) or any that have no power at all (there will be a couple that aren't supposed to have power, but let's see what you have).

Both fuse boxes, under hood and in the dash.

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Customer reply replied 3 months ago
already did that no bad fuses

And all fuses have power?

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Customer reply replied 3 months ago
the one that is suppose to have power

The gauges that aren't working are all driven by ECM information delivered over the data bus. Locks and windows also need the data bus to work, so I am back to a communication issue. I initially thought you had an engine running problem as well, but I must have read that wrong or something.

We do see a lot of issues with ignition switches causing the gauge issues, but if all of the fuses have power on them, then that's not it.

I am chalking up the DLC communication fault to the scan tool at this point, I would get a different scan tool. Not that yours is bad, but scan tools are funky and one might not communicate but the next one will, especially where inexpensive Chinese scan tools are involved. You have airbag and ABS lights on, I would want to get those trouble codes. Can you get a scan tool that is more capable than the one you have?

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Customer reply replied 3 months ago
no not at this time

I am convinced that this is a communication issue, and to resolve it, you'll need a diagnostic tool that can query these other computers. Getting to SP205 is a start, but it's technique that also requires the scan tool I mention. The idea is to isolate each comm circuit, say the ABS to start with, then see if the scan tool will talk to ABS. If so, disconnect that one and try another, maybe airbag, and see if scan tool will talk to that one. And you go through all of the circuits like that until you find the one that's not talking, and you diagnose from there. But without the proper scan tool, the testing won't work.

For that reason, I recommend getting this into a capable repair shop that has the right tools to pin this down. From a DIY perspective, this is not a very friendly system, and you can spend a lot of money on wrong guesses here (in fact, you have already). For the $90 or so that a shop would charge, I would have them look at it with their scan tool and tell you what's wrong with it, and probably have them repair it as well, since any computer that needs replacement will likely require programming that can only be done with specialized equipment.

Please take a moment to rate my answers by clicking on the stars at the top of the page, that's how I get compensated. If you need more help, just let me know, I am happy to follow up.

Jerry Newton
Jerry Newton, Chevy Technician
Category: Chevy
Satisfied Customers: 5,694
Experience: ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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