I soooo close!! I mounted my DBW pedal and TAC module. Checked all grounds, then actually started the car for the very first time. It idled ok (loud.no muffler yet) for having sat for 18months. When I blimped the throttle it reacted, but then stayed at around 1700rpm for 20 sec, then came down to idle and died. When I restarted it was like the pedal was dead. Idle stayed around 600rpm with no change when pressing the pedal?? After 10 minutes of waiting it started up fine, the pedal reacts once, then it's back to the same story.
I haven't got radiator, MAF or EVAP hooked up yet, but that shouldn't matter should it?

 

Are you using a vette setup? The pcm references the MAF for ETC diagnostics on a corvette. I bet if you hook a maf up, it'll probably be fine. If not, scan it for codes.

 

It's a 2006 Silverado setup. MAF is 5 pin setup.

 

See what codes it's setting. Is the entire setup from the same vehicle? Wiring harness and all?

 

Harness is from same vehicle, but TAC and pedal were sent to me later, as they forgot to put it in the crate with the engine.

 

update... I'm starting the car with just battery no belts etc hooked up. Could this be why my throttle body acts crazy? A few times it just clattered open/shut about twenty times when I turned the key to run. The next time in run I pressed the pedal and the TB followed perfectly. As soon as I started it was dead.
I rechecked everything and started and the pedal worked...but only once.
Will it go to reduced power mode if the alternator isn't hooked up??
I'm going nuts!

 

....nobody...?

 

I have a 2003 motor with a 2005 PCM and a TAC and pedal I bought off two different trucks.

There is a very friendly GM service adviser at a dealer near me and he told me that my best chance for the DBW working is to take the PCM, TAC and pedal from the same vehicle, or at a minimum, the same year. The parts guy confirmed that there were different pedal and TAC part numbers depending on the year.

I know the pedal I have is a six wire and there are others with 9 wires. My TAC module wants to see a 9 wire pedal. I'm screwed.

I'm going to look for a PCM, TAC and pedal assembly that I know is off the same vehicle.

Are you sure the TAC and pedal assembly they sent you are compatible with the PCM you have?

 

and.............

Hook up your MAF, like the guy says

The alternator running or not shouldn't make any difference

 

Got the MAF hooked up. The pedal worked great....one time. After that it went back to not working right.

 

Still need to know what dtcs it is setting to really know what is going on. Without knowing what the pcm sees wrong, you're just wasting your time guessing.

 

Hi like pdsq98gt had said you must check for DTCs but what you are describing is the ECM going into a safe mode because it sees a problem .Check all wires and connectors most of the time wires brake right by the connector.
John

 

Verify you have the right TAC module and pedal for your PCM. Street & Performance has a listing of the TAC modules part #'s and their corresponding years. Or Speartech can probably tell you if you have the correct setup.

I had the same problem when I put my 5.3 in, and it was because I had the wrong TAC module and cable.

 

The code I'm getting is U0107 (Communication with TAC lost). Can battery voltage cause problems? I'm running without belt just off of battery power (for testing purposes). After one or two starts I notice that when I go to the "run" posistion the throttle blade starts clattering open/shut several times before I start. Once I charge the battery it doesn't do that the first one or two starts. ???

 

Yes if the battery is low/not charging the throttle can die/go into limp mode.

Similar to a mismatch between TAC and pedal.

 

with ignition on and engine not running the throttle blade should follow the movements of the accelerator pedal... i know the Aussie Cars dont like having the wrong pedal fitted and this causes the ecu to set codes then the blade wont work.. but they dont even move.. usually fail straight after key on... maybe check that the pedal and TACM are the right ones

 

I think rsz288 is on to something! As soon as I start, the battery drops to around 11V. Prior to starting its around 11.8V and the TAC works great....until I start!

 

Prior to starting, fully charged the battery needs to be at least 12.5V. Preferably 12.8 - 13.5V.

In our experience the ETC swallows its tongue if the run voltage is down around 10V or below. But with GM anything is possible on when something goes into limp.

ETC mismatches can induce limp mode from key on as Doubledip rightly notes, or every second day, or every second week. And anything in between. LOL!

 

Yes the DBW stuff is very critical to everything.. one slight error and the whole thing shuts down... (which is a good thing considering it is controlling the go fast bits )

have never had the voltage problem but them my jump battery is alway full charged and all cars we have had ... have the alternator working...

 

GM writes their PCM software to be sensitive to fuel pump voltage. The pump is just an electric motor, so feeding it less voltage means it pumps less fuel. Very likely they configured it to drop into limp-home mode.

At this point your findings seem to be indicating that it's ready to run, just finish connecting the cooling and charging systems and then re-test. And charge your batt.