Reduced Engine Power Mode on '03 Burb

[MASTERBrian]

For about 3 years I've been dealing with this issue on our 2003 Suburban with 5.3L Flex Fuel . I've gotten about any and every engine code from this and I've read the service bulletins and such, but the issue keeps popping up.

So far, what I've done in order as best as I can recall...
1) Cleaned Throttle Body, Related Sensors, etc, helped but issue returned in about month or two.
2) Replaced the Throttle Body with an A1 Cardone, as it's what I could locally get. Problem went away immediately and stayed away for several months.
3) Replaced Pigtail at TB and soldered each connection and used heat shrink tape to help water proof and protect. Also used Di-electric grease at fittlings.
4) Replaced Hood to firewall ground strap, unhooked and cleaned the ground strap on Left side of engine to frame(?), same for both ground straps under driver door on frame. Maybe one other ground point, I forget, it's been two years for this, but they were all cleaned, inspected and I used Di-electric grease at each connection to help seal out moisture, etc.
5) Couldn't easily get to the straps on rear of heads, so took to shop and they inspected each of these grounds and said everything looked good on them. I believe they then fogged the system to do a deep clean of the intake and TB....this step as well as grounds might actually have been done before 1st TB replacement.
6) Got codes pointing to throttle position sensor at pedal. I replaced that. Again, this helped for a couple of months.
7) more codes, pointing to TPS at TB. I had the A1 Cardone TB warrantied out for another unit. Actually tried to get refund, but they refused said needed to try another one first. Issue went away until this spring. That was last fall or late summer.
8) started happening again, more codes, etc and this time the truck started actually stalling out at times. Found an AC Delco TB on Amazon and ordered that....locally those seem hard to find and I've had good luck on Amazon with parts and they are fast with Prime Shipping. **ACDelco 217-2293 GM Original Equipment Fuel Injection Throttle Body with Throttle Actuator** This was done in mid-late May.
9) in the last few days the issue is creeping back in. Today I stopped at a shop I use that is heavy into GM engines and spoke with them about possible flash of PCM. The Tech, whom is the son of the Owner and slated to take over the business and seems very knowledgeable, said that since the codes seem to go away within a drive or two that it's most likely NOT the PCM and more than likely in the TB and because I haven't bought one from a GM parts department. His belief is that not all AC Delco's are created equal.

My question is this, can anyone confirm or deny that if I bought an AC Delco from Amazon that it might be different than if I had bought from a GM Dealer. Does it also seem likely that if the code goes away that it would in fact be the TB and NOT the PCM? When I did the pigtail at the TB the wires ended up a bit longer than I would like, but I left them. I'm thinking of now going back and shortening them to be 100% certain there isn't a fault in there, but I highly doubt it. I've also read one guy said he was about in the same boat as me and finally just replaced a ground at the head that looked good and issue seems to be staying away.

I've asked somewhere about replacing these grounds and I believe there are 2-4 on the back of the head....2 on driver side and 1-2 on passenger side. They are a nightmare to get a wrench on, from what I've noticed, which is why I paid the shop to inspect and hopefully replace. I'm debating taking it to an electrical repair shop to see if they can check and replace the grounds as well as the other issues with voltage, but afraid I'll be throwing hundreds down the drain. I've also considered just figuring out what those grounds go to and duplicating them elsewhere on the block. ie....if it goes from head to frame, just pick up an easier to access spot on head and frame and run a completely new strap. Some have suggested that might work and I should leave the old in tact as well.

Any suggestions here? I'm going to call a guy in a few that flashes PCM's to see what he says. Might try that as well.

[edhtrd71]

Hey, sounds like a real pain. I don't think you have a bad throttle body. A delco throttle body is a delco throttle body. They are quite reliable and I would bet your original one is still good. At the dealership 99% of throttle codes were caused by wiring issues. I would order a new connector and pigtail. You have to wire them in right though. Use as much length of the new wires as possible and cut back as far into the original wires as you can. Don't make the new harness any longer than stock. Also make sure all of your wires are the same length. You can't have one longer than the rest. Make sure your soldering is really good and connections are tight. Don't reuse the same connector because it has been disconnected to many times and terminal tension is prolly week. Also some terminal fretting has probably already started. Good luck.

[LEEVON]

Question, do you trust your shop? Are they strong on diagnostics? Do they have GM software? If so, why not let them have a crack at it? It would require simply stating the problem and let them find the conclusion though, not directing the process...let them start from the top. We deal with issues like this all the time and they almost always get resolved. Fact is a GOOD driveability technician will make us all feel inadequate when it comes to diagnosing this issue.

[MASTERBrian]

Originally Posted by edhtrd71

Hey, sounds like a real pain. I don't think you have a bad throttle body. A delco throttle body is a delco throttle body. They are quite reliable and I would bet your original one is still good. At the dealership 99% of throttle codes were caused by wiring issues. I would order a new connector and pigtail. You have to wire them in right though. Use as much length of the new wires as possible and cut back as far into the original wires as you can. Don't make the new harness any longer than stock. Also make sure all of your wires are the same length. You can't have one longer than the rest. Make sure your soldering is really good and connections are tight. Don't reuse the same connector because it has been disconnected to many times and terminal tension is prolly week. Also some terminal fretting has probably already started. Good luck.

The pigtail was replaced, but I did leave the wires longer than factory. I've thought about shortening them, if you think that might help, I'll do sooner than later. Everything was the same length, even though longer.

[MASTERBrian]

Originally Posted by LEEVON

Question, do you trust your shop? Are they strong on diagnostics? Do they have GM software? If so, why not let them have a crack at it? It would require simply stating the problem and let them find the conclusion though, not directing the process...let them start from the top. We deal with issues like this all the time and they almost always get resolved. Fact is a GOOD driveability technician will make us all feel inadequate when it comes to diagnosing this issue.

Yes and no....They build lots of race engines and such and are pretty heavy into GM stuff. I do believe they have gm software, but not 100%. I'd take to a seller, but everything I read had people saying they did this and still had the issues after hundreds and hundreds of dollars spent, since reaching into thousand or more.

My shop said they have fought others as well. Their last suggestion was maybe flashing the computer, thinking maybe it's had the code so much that it just needs a flash to get cleared up. Right now it is mainly doing at startup, but it has happened while driving once or twice.

As far as trouble shooting it, they all seem to say can only test voltage while it's happening, which is needle in haystack thing.

So frustrating....

[MASTERBrian]

Just a follow up on this. I took to a shop that specializes in electrical. This problem hadn't presented since about early Sept, when it was going crazy. On the day I took to shop it presented twice, in fact once during the 1 mile drive to the shop. He kept it and put a few hours of driving for parts and even home and on errands over the weekend with his scanner hooked up and nothing. His recommendation was maybe to re-build the wire harness, but at a tune of about $500. I was ready to just go ahead and do this, but he talked me out of it because he didn't feel good about throwing parts at something he couldn't get a live capture of what was going on.

Someone recommended EFI Connections for the connectors for the harness, I called them and for about $110 they built me the complete harness, with Delphi Parts and crimped to spec, for between throttle pedal sensor and TAC module, then also the harness for between the TAC and Throttle body. Even the electric tech said go for it, he can't build it that cheap. That said EFI is possibly going to start building the harness for stock, but prices might be different than what I paid, since I provided some info on lengths, etc.

Now if the postal service can figure out where my package that has been sitting in town since Sunday and out for delivery since Monday is, maybe I can get them installed. They are now showing as delayed with nothing else given. Waiting on a call from them as I type.

My questions on this now are is it worth it to pay the electrical guy $75 p/h to wire the harness between the TAC and the Throttle Body in? 8 wires of the 16 wire harness are just plug and play the other 8 need to be spliced into the existing harness(s). The harness between the TAC and Throttle Pedal is probably a 10 min swap, if that. To get my lengths I went to the salvage yard and took some measurements off a like year burb with half of the stuff already out of my way. In fact I grabbed the newer version TAC module and Throttle Pedal sensor from that truck, may go back for the Throttle body, but I'm told not really important to have matching parts as they are all interchangeable.

I can do wiring, BUT, so far I don't have a diagram, which I wish I had. EFI Connections is producing the wiring in same color and size as factory schematic, so they say just match wires and solder in place. The harness goes up under the fuse panel on driver side fender. I want it to look as factory as possible when complete, so no one looks at it down the road and says....WTH!! I also worry that if this system is that picky, that if I do something just a little off, I'll have other issues with it, but EFI Conn says, these other wires should have NO EFFECT of the drive by wire/reduced engine power issues. All of those wires are in the plugs they crimp to spec.

So I'm wondering do I replace the wires myself, just solder and heat shrink the 8 wires myself. I'd use silver solder and try to locate some good quality heat shrink to seal out any moisture, etc. Then bundle it all back in the factory loom.

EFI also says if I have issues AFTER the wire change, the issue is elsewhere, which means back to electrical shop or another shop. I do have the E series TAC off a 2005 Burb...mine is the A series. Should I swap them when I do the wiring or wait and see?

[MASTERBrian]

Doesn't appear I updated this ever, so wanted to say....

I had the electrical repair guy, that suggested the harness might be the issue, install the EFI Connections Harness's. Main reason being there were a few wires that needed soldered and I just plainly didn't want to mess with that.

So far, all has been going well. Time will only tell!

[Palf70Step]

Glad she is working for ya now!