More check engine lights caused by wiring

[Paul Ruggles]

This isn't a TJ problem, just an example. This happened on my daughters 2005 Grand Prix today. She came home today, said check engine light was on and car was in 'reduced power mode' on the information center. Put the scanner on it, came up with a throttle position to accelerator issue. Car has drive by wire setup.

Did a quick google search, most people automatically buy a new accelerator pedal and it fixes it about half the time. The rest of the time people just start throwing parts at it, hoping to fix it.

Did another search for 2005 Grand Prix wiring problems. Came up with multiple threads about the engine harness rubbing on the front valve cover. So I look at the car and find this.

7 wires rubbed through. Spliced them back together with heat shrink splices, good to go.

Look at your wiring before you buy parts. This kind of crap happens all the time on all makes of makes and models.

 

[Chris]

Great post, and a great reminder of why throwing parts at something is a poor solution.

I personally believe wiring is one of the very last things people think to look at, when in reality it should always be one of the first. Manufacturers often times will put wiring in areas where it's going to rub on other stuff, and things like this happen with age.

Good diagnostic skills for uncovering this! Was that wiring easy to get to, or did you have to really hunt for it?

 

[Paul Ruggles]

Right up front under the engine cover. Cover pushes down on the harness, right into the corner of the valve cover.

Would have been more difficult without the Google search. Pretty common problem on that generation GPs.

Once you get through all the bullshit out there on the internet, there is a lot of great info out there. Too bad most of the interweb has turned into a shitshow. It was alot better in my opinion before everyone became an expert at everything.

 

[Chris]

The problem with the internet (and it's tremendously worse on social media) is that as the person seeking help, you have to go into it knowing that most people you are talking to aren't experts. So there's a bit of a "buyer beware" disclaimer, or whatever you want to call it.

A lot of things were better back then, that's just part of getting older. You get to see everything around you change, and realize that a lot of things used to be better than they are now.

The upside to this is that diagnosing an issue is now probably a million times easier than it was before the internet. You just have to wade through a lot of shit to find the right answer. But, that's still easier than it used to be.

 

[bedhed]

Great post, and a great reminder of why throwing parts at something is a poor solution.

I personally believe wiring is one of the very last things people think to look at, when in reality it should always be one of the first. Manufacturers often times will put wiring in areas where it's going to rub on other stuff, and things like this happen with age.

Good diagnostic skills for uncovering this! Was that wiring easy to get to, or did you have to really hunt for it?

I agree. Nice catch, man. Until someone has "been-there-done-that" it's easy to instantly assume the worst, or do a quick/lazy scan of the wiring paths without doing a thorough scan. This is a great reminder for sure.

 

[Paul Ruggles]

I have had a few like this. One that sticks out:

2015 Colorado, about 60000 miles. I get a check engine light, comes up about evap leak detection pump. I think, cool, that should be under the 100000 miles emissions warranty. Dealer says nope, only catalyst. So I start digging into it because I am not paying the dealer to troubleshoot. They for the most part, not all, are parts changing monkeys.

Download the service manual, find the pinout from the pcm to the leak detection pump. Make some 10 ft long jumper wires for my meter, and start checking wiring. One wire is no good.

Ok, there are 4 junction connections between the pcm and the ldp. Start at the pump to the 1st connection, no good. Now I know where the break is. Start looking at the wire harness, and see its routed over the body mount.....hmmm. Sure as shit, it rubbed through the harness covering and rubbed through the wire I was testing. 5 minutes later, a heat shrink splice is in and I am good.


That would have taken the dealer a day at 100 dollars an hr to find ( if they ever did find it) . They would have changed the leak detection pump first, then maybe would have changed the pcm before they ever checked wiring.

 

[Leahatrill]

This isn't a TJ problem, just an example. This happened on my daughters 2005 Grand Prix today. She came home today, said check engine light was on and car was in 'reduced power mode' on the information center. Put the scanner on it, came up with a throttle position to accelerator issue. Car has drive by wire setup.

Did a quick google search, most people automatically buy a new accelerator pedal and it fixes it about half the time. The rest of the time people just start throwing parts at it, hoping to fix it.

Did another search for 2005 Grand Prix wiring problems. Came up with multiple threads about the engine harness rubbing on the front valve cover. So I look at the car and find this.View attachment 141052

7 wires rubbed through. Spliced them back together with heat shrink splices, good to go.

Look at your wiring before you buy parts. This kind of crap happens all the time on all makes of makes and models.

Do you have a picture of where these wires are located ?

 

[Chris]

Do you have a picture of where these wires are located ?

It’s on his daughters 2005 Pontiac Grand Prix, so it won’t really help.