no throttle

[tbrown5079]

Time to get serious on this issue. On the final install and want to solve this b efore I put the fenders on. Engine starts up fine and runs smooth. In default mode ( fast idle ). No throttle. Check engine light goes out. No codes. Multimeter shows proper reading at throttle body but all the terminals at the pedal coming from the TAC read 6.9 volts. All of them. Tomorrow I will check all the terminals coming out of the TAC to see if it's in the harness. Also, I put a mechanical oil pressure guage in and the plug going to the ECM is just hanging there. Would this have been deleted in the harness and ECM tune? Could this cause the problem? I emailed wait4me performance but didn't hear back from them yet. Any suggestions?
Thanks
tbrown

[Angryman117]

The engine will run just fine without the oil pressure sensor. Did the TAC module, pedal, throttle body and ECU come from the same vehicle?

[tbrown5079]

The supplier said they did. A local reputeable company. The owner delivered it himself, one butt ugly night.

[BR3W CITY]

Originally Posted by tbrown5079

No throttle.

NO throttle at all, like not even a single rev or anything?
Watch the throttle blades (intake off obviously). Do they click up and down to system-check when key on is applied?

Also, I put a mechanical oil pressure guage in and the plug going to the ECM is just hanging there. Would this have been deleted in the harness and ECM tune? Could this cause the problem?

I'd have to check HP tuners, most of the lights can be turned off... but all it does is trigger the oil light. It has no effect on anything mechanically of operationally speaking. If you don't have an oil light hooked up, you won't even know.

tbrown

I have a few suggestions above. Also tell me what year your engine is, and what style of DBW pedal you have (metal arm or plastic)

[tbrown5079]

Ok here we go. Thanks for the responses on the issue. It is what I thought a 2007 4.8 Sierra engine but the harness is 2006 style ( 8 pins at throttle body. The pedal is all plastic. No it doesn't set the throttle plate when you turn the key on. Pulled the plug for the pedal from the TAC and have 6+ volts on every pin. Eliminates the harness. Checked the plug from the main harness and I have 12v at pin 2 ( should be 5v reference). No other pins have voltage or ground ( pin 15 is G104 and should be ground? ). Should I not expect other readings since it is not plugged in?

[BR3W CITY]

Well 2007 is a GenIV which doesn't use a Tac, 2006 is a GenIII (usually, 06 was the transition year). Big difference in how this gets solved.

What ECM do you have? If its a GenIV setup that TAC shouldn't even be there.

[tbrown5079]

The ECM is a Delphi P26440. Server# 12602802

[tbrown5079]

Also, what is this plug for?

[BR3W CITY]

I can't see the attached images unfortunately, my setup doesn't like displaying non-embed stuff for some reason.

[ls1nova71]

2007 is the transition year. They had new body style trucks and what they called the Silverado classic which was the older body style. The classic will be a genIII and have a TAC module. Post a pic of your engine and one of your computer and we can tell exactly which one you have. But, that plug in the pic looks like a plug for the electric fans judging by the colors and since there are only two wires.

[tbrown5079]

Here they are. Like I said, I think it is like the 2006 Sierra because it has 8 pins at the throttle body.

[ls1nova71]

Does it have a 4 bolt throttle body??

Looks like a 3 bolt, so that would be a genIII. Are you sure you have 12v power to the TAC module? If it never moves, makes me think maybe you missed a power wire. Other than that, try wiggling the wires a couple of inches from the throttle body, they're known to break inside the insulation in that area

[Super73]

What is in the tune?
Is it 100% stock other than VATS?

Things like disabling MAF can cause no throttle if other things are not adjusted.
Reducing torque management can also result in no throttle.

They will start, run, and some times not throw codes with the above.

[tbrown5079]

Now that I think about it there was one wire that I thought was an option( besides the one 12v all time and 3 12v with the key). I will check that( out of town for the weekend) and let you know. That may be the power wire I missed.

[tbrown5079]

Just a very mild tune.

[Super73]

Find out if tq management was plaid with.

[tbrown5079]

Tuner says the reduced engine power mode is caused from a throttle issue, not torque management. I will double check to see that all components match and the wiring to TAC and throttle body. Any other suggestions?

[BR3W CITY]

What are you using to check codes? Usually a throttle mismatch or similar failure throws a TAC failure/throttle failure/component mismatch code. A dbw-tuned truck should throw that code on startup the second that the TB doesn't do the position check...and I wanna know why the ECM is essentially ignoring the TB/TAC/Pedal failed.

Does it run ok otherwise? There are certain idle settings that affect the TB% that wouldn't be working if that whole system isn't working.

[Super73]

Originally Posted by tbrown5079

Tuner says the reduced engine power mode is caused from a throttle issue, not torque management. I will double check to see that all components match and the wiring to TAC and throttle body. Any other suggestions?

Reduction of tq management can create a no throttle in a dbw vehicle. I have had to fix it when tuning several c5 vettes and my wife's tbss. Keep in mind I have been tuning the gen 3/4 stuff since 2001.

[tbrown5079]

OK, was in the garage tonight trying to make sense of this. It is a genIII, 3 bolts at throttle body and a TAC module. I have some pin outs I got from LS1 swap and I'm checking voltages and grounds at the plugs to the TAC. I have 12v at pin 7 like I should have but no ground at pin 15. Then I have 6.9 v at every pin coming out of the TAC going to the pedal except for 1. The ground is G104. Wouldn't this cause my problem? Or would it only be ground if it was plugged in? Where could I pick up a ground in the harness to jump to G104 to check to see if this helps? Just trying to get a direction here before I have to start buying parts to throw at it. It runs smooth but at fast idle. Nothing you do changes it. Thanks for your help!

[ls1nova71]

All the power in the world isn't going to help if you don't have a ground. Try grounding pin 15 and see what happens.

[tbrown5079]

Can I ground it anywhere or does it have to be in a harness ground to check?

[ls1nova71]

Ideally it should be grounded to the rear of the head with the rest of the engine harness, but it shouldn't really matter as long as it's a good ground.

[tbrown5079]

OK. Thanks. I will try it in the morning and let you know.

[tbrown5079]

Time for celebration. I spliced a wire onto the pin 15 ground to the TAC which is G104 and bolted it to the rear of the right head. The throttle body clicked when I hit the key and I knew I had it. Thanks to all of you who responded and gave suggestions and encouragement. I will sleep better tonight! Also thanks to LT1swap. I got the pin out for the EFI off their site. To anyone who is considering an LS swap get on the LT1swap site and read, and read, and read it again until you understand what you are dealing with. It is all there. I would have been better equiped if I had done that.
tbrown