2003 6.0 throttle body question

[rod7515]

I have a 2003 Yukon Denali with a 6.0. There I a plug for the wiring harness that pushes in the front corner of the throttle body. About every 100 miles or so while driving my traction control light will come on and I loss all power. The vehicle goes into creep mode. I will pull over, shut off the vehicle, open the hood and jump up on the bumper and wiggle that connector. Clos the hood and start it back up. Traction light will be off and everything is back to normal. Now it will set a throttle/pedal position sensor switch A/B voltage correlation when this happens. I’ve gone to the salvage yard and found another plug but off an 5.3 and cut off about 4” of harness with it but the wires look slightly smaller. The plug looks identical. Should I worry about the wire size or go ahead a splice it in.
My other issue is a code PO300 which is a random misfire. This will set only when pulling a trailer and going up a fairly long incline with slight acceleration. I can not feel the misfire at all. Anyone else ever had this. Should I start another tread on that code issue? I want to correct these issues as I get tired of the check engine light on. I do plan on checking the plugs as I don’t know how long they’ve been in. The previous owner did change out all injectors, wires, plugs but it’s been 40k miles ago. I’ve only had this vehicle for about 5k.
My last code is a P0420 which is car system efficiency below threshold bank1. I am changing out all 02 sensors tomorrow.
When I bought this it was setting a lean bank 1 and bank 2 but I corrected that with a new MAF. All other codes were in it as well when I bought it.
Thanks for any help
Rod

 

[strutaeng]

I have a 2003 Yukon Denali with a 6.0. There I a plug for the wiring harness that pushes in the front corner of the throttle body. About every 100 miles or so while driving my traction control light will come on and I loss all power. The vehicle goes into creep mode. I will pull over, shut off the vehicle, open the hood and jump up on the bumper and wiggle that connector. Clos the hood and start it back up. Traction light will be off and everything is back to normal. Now it will set a throttle/pedal position sensor switch A/B voltage correlation when this happens. I’ve gone to the salvage yard and found another plug but off an 5.3 and cut off about 4” of harness with it but the wires look slightly smaller. The plug looks identical. Should I worry about the wire size or go ahead a splice it in.
My other issue is a code PO300 which is a random misfire. This will set only when pulling a trailer and going up a fairly long incline with slight acceleration. I can not feel the misfire at all. Anyone else ever had this. Should I start another tread on that code issue? I want to correct these issues as I get tired of the check engine light on. I do plan on checking the plugs as I don’t know how long they’ve been in. The previous owner did change out all injectors, wires, plugs but it’s been 40k miles ago. I’ve only had this vehicle for about 5k.
My last code is a P0420 which is car system efficiency below threshold bank1. I am changing out all 02 sensors tomorrow.
When I bought this it was setting a lean bank 1 and bank 2 but I corrected that with a new MAF. All other codes were in it as well when I bought it.
Thanks for any help
Rod

1. I would just get a new throttle body connector and solder it in. Check Rockauto. They are probably not that expensive and you get a new plug and wires. Any time there's even a slight lost on contact on that circuit the ECU will detect it and throw it into limp mode. I believe there was like a TSB to address the issue and it involved replacing the connector.

2. Random misfire? That definitely needs to be fixed.

3. Has it been run a while with the apparent misfire? If so, your catalytic converter has been damaged. Probably by the previous owner since you mentioned you bought the truck. Items 2 and 3 may be related. If there's a misfre, the system will likely run lean because the fuel is not ignited properly.

 

[S33k3r]

Any time there's even a slight lost on contact on that circuit the ECU will detect it and throw it into limp mode. I believe there was like a TSB to address the issue and it involved replacing the connector.

Would you have any idea where I might look and find that TSB? Our throttle body loses connectivity when it gets warm/hot, causing the aforementioned problems. I, too, have a 6.0, but this is our 2005 Suburban 2500. My maine mechanic can duplicate the problem, but is not an electrical specialist and so didn't trace it down (plus he left the day after we dropped it; he's a good guy -- this is not a ding against him).

If anyone has anything on how the throttle body is connected, electrically, please share it. We had originally taken it to a transmission shop, they replaced the throttle body and... Yeah. THAT wasn't the problem.

 

[strutaeng]

Would you have any idea where I might look and find that TSB? Our throttle body loses connectivity when it gets warm/hot, causing the aforementioned problems. I, too, have a 6.0, but this is our 2005 Suburban 2500. My maine mechanic can duplicate the problem, but is not an electrical specialist and so didn't trace it down (plus he left the day after we dropped it; he's a good guy -- this is not a ding against him).

If anyone has anything on how the throttle body is connected, electrically, please share it. We had originally taken it to a transmission shop, they replaced the throttle body and... Yeah. THAT wasn't the problem.

I was trying to remember where I had seen that TSB being mentioned. I'm certain it was here on this site...of course, now I can't find it. :-(

 

[S33k3r]

I was trying to remember where I had seen that TSB being mentioned. I'm certain it was here on this site...of course, now I can't find it. :-(

If I just had a nickel for every time that happened to me! Maybe that should be a dollar, these days; you know?

 

[rod7515]

I would be interested in seeing that bulletin as well.
Today I replaced all 4, 02 sensors. Hoping that will take care of the 0420 cat code.
I then took the plug I got at the salvage yard and spliced it into the harness for the throttle body.
Also went and got 8 AC Delco spark plugs and installed them. Those old plugs were close .100 gap. Hoping that may have been causing the misfiring code.
Bad thing is with no rain in the last 3 weeks here I’m not going to be pulling the trailer with mowers for the next week or 2 so it may be a while until I know. I don’t use the Yukon for anything else.
I did clear all the codes so now I just need to drive.
Thanks for all the help and anymore you can throw my way.

 

[strutaeng]

Just an FYI: Every time I rewrite (reflash) the tune on my 06 Suburban 2500 LQ4 with HP Tuners I get a message about reduced power. The first time it happened I freaked out. I messaged my buddy that does a bit more tuning than me and he said just clear the code, and I did. I can't recall the code right now.

I'm guessing the reflashing the tune breaks the communication ever so slightly, such that the code is triggered. I haven't tried reflashing my 2004, so I don't know if that's normal on the P59 ECUs.

My 99 Silverado doesn't do that, but that one has the older ECU P01 operating system. It's drive by cable, so I guess it doesn't even have that code, LoL.

 

[rod7515]

Forgot to mention a few things. First I was able to get in touch with the guy I bought this from last May. He told me he had replaced the throttle body with a new one about a year before that. Someone had already replaced the connector and they thought that would cure it but it’s apparent it did not.
I would love to see that service bulletin to see what the options repair is. When I have to stop and go out under the hood I can’t even see that connector move when I push it back on. I don’t quite know understand why that fixes anything it temporarily.
Does anyone know f this was just a couple year issue and was it just on the 6.0 engines?
Thanks Rodney

 

[NardDog]

I would be interested in seeing that bulletin as well.
Today I replaced all 4, 02 sensors. Hoping that will take care of the 0420 cat code.
I then took the plug I got at the salvage yard and spliced it into the harness for the throttle body.
Also went and got 8 AC Delco spark plugs and installed them. Those old plugs were close .100 gap. Hoping that may have been causing the misfiring code.
Bad thing is with no rain in the last 3 weeks here I’m not going to be pulling the trailer with mowers for the next week or 2 so it may be a while until I know. I don’t use the Yukon for anything else.
I did clear all the codes so now I just need to drive.
Thanks for all the help and anymore you can throw my way.

I think someone mentioned this already but the cats probably need to be replaced, especially if the code come back. There is a hack for the o2 sensors that you can try, google 02 sensor hack involves an adapter you drill out and it moves the 02 sensor away from the pipe, anyway it worked for me for a few years but eventually i replaced the cats and actually gain a few hp, thats how bad mine were clogged.

 

[OBSalsoNNBS]

@rod7515
Did you figure your truck out? My '12 Tahoe 5.3 is at the dealer now. I had similar problems, replaced the TB and pedal sensors, connectors, TB, but it seems like it's a wiring issue.
Hope your truck had a happy ending