Teamscss.com

Hello everyone.


My shop has just finished an LS2 with A4 out of 2006 GTO into a 68 Chevelle.
Some background: I am using stock PCM, TCM and wiring harness. ALDL is connected as well as all accessories minus the A/C.
The car starts and runs but I have no throttle response.
I can read the APP values but they do not change the TP values.
I can command the TP to open from Tech2 but it does not respond.
I tried a known good pedal as well as a know good TAC/TP with same results.
I am getting a P2176 code - Minimum Throttle Position Not Learned.

I have verified all of the wiring.
PCM gets Battery V @ pin C1 20.
Ignition1 @ C1 14
Ignition3 @ C1 19
Accessory @ C1 18
Crank @ C1 52
Ground @ C2 73

TCM gets Battery V @ pin 32
Ignition1 @ pin 31
Accessory @ pin 11

My Drive by wire throttle has all the wiring checked to the PCM, and from PCM all wires check out to the Throttle.

Now...@ key ON cycle the Throttle Actuator Control (TAC) blade has to move to 0% (closed location), register that, and return to 21% open. I am not getting that throttle blade movement. I checked the Voltage @ TAC motor on each side and I get 9.7V instead of 12V.
Doing the GM pinpoint Test leads me to replacing a PCM. This makes no sense because the place that I got this engine combo ran it on the video with this PCM. The only thing I had done to the PCM/TCM is delete the VATS. Could that have anything to do with it? I don't think so, and my tuner who cleared the VATS says the same thing.

I've seen similar swaps done, so I know they work.


What am I missing??
Where did I go wrong?
Where did I lose a ground or forget to connect a power?

Any help is appreciated.

Teamscss.com

help bump

pist0lpete

iTrader: (3)

I haven't personally dealt with the throttle by wire on my swap so the only help I can offer is to check your engine grounds. You should have at the least one from the block to the chassis and one from like the cylinder head to the firewall. You really need to have two of each.

Teamscss.com

Grounds are good.

anymore?

Jones'n

You say you are using the stock ECU and such, but what pedal are you using? Is it from the GTO as well?

rsz288

Ditto. It does sound a little like the incorrect pedal. A non GTO pedal in place of where a GTO pedal should be, does create odd ETC problems. Also it should not be an LS1 GTO pedal either.

Also what are you flashing with?

Cherez.

Teamscss.com

Pedal is from the same LS2 GTO.
I wonder if there is a way that a tuner could have turned off the TAC function when deleting VATS. Is that even possible? Is there a way that he could have accidentally done that? I am not sure what he used to flash it with, but is there a function in a stock PCM that can shut off TAC, or is that a function of the flash device?
I know he typically tunes with HP tuners.

rsz288

Generally only a GM/techII based flash will touch the pedal /throttle control area.

What's the part number on the pedal? 921883XX ?

And what is the VIN, and calibration part number?

Never seen VATs affect the pedal. Have seen a disconnected pedal do this though, but you aren't getting any APP codes.

ls1_chevelle

iTrader: (9)

I had the exact same issue. Your Throttle body is dead. Find another one. We data logged mine while it was idling and got the exact signs you did.

6spdgto

iTrader: (5)

I happen to have a brand new one for sale if needed.

Teamscss.com

OK so here are the updates:

I took this TB and put it into a 2005 GTO and it works fine. (btw 05 and 06 GTOs have same p/n fro TB) So the problem is not in the TB.
Next the p/n on the gas pedals are also the same in 05 /06 GTOs. So that checks out as well.
Here's a problem that I found that I am rectifying by replacing a PCM.
Two wires that alternate Voltage to the TAC to control the throttle blade carry correct voltage but insufficient current to move the stepper motor inside TB. I have verifyed this in few following tests:
Test 1: I used a test light. That light needs X amount of current to light up a bulb. Keep in mind that my Fluke DVOM shows voltage at both yellow and brown wires with key ON. The bulb does not turn on on my Snap On test light.
Test 2: I decide to try to amplify the signals that are being fed into a TAC by PCM by using a simple dual 5 wire relay setup feeding Battery and Ground Voltage (V alternates from +12 to 0 to either wires to open or shut the TB) to the TAC as relays receive a low current signal from PCM. Well, PCM can't even supply enough current to trigger the relays.

I think the problem is internal to the PCM TAC circuit, since there are ICs ( integrated circuits) that amplify the output current. I have seen this in the electronics when I was in that industry. Voltage will be there until a load is applied to it. That load being the TAC motor.
PCM has been ordered already.
But what do you guys think?

rsz288

The throttle motor is a stepper motor as you noted, so it will be pulsed open/closed as directed by the ECM. The ECM will maintain high impedance (very low current) voltage on the motor at all times so it knows it is there. Have you seen any pulsing coming out of the ECM while operating the pedal?

Are you sure your ECM came from a GTO? A Corvette ECM with a GTO pedal may cause this behavior (it does in E38's). Has it been reflashed by GM or anyone with a pass thru J2534 device in addition to the VATS removal via the aftermarket program? Was the tuner's flash a Corvette or a GTO calibration

Teamscss.com

No pulsing out of ECM while operating pedal or commanding with Tech2. I am sure that ECM is out of GTO(wrecking yard did the startup test and shipped the entire combo as an assembly, including PCM, TCM etc.). Also all of other engine functions operate as they should.
About the tuning: I am not sure how he reflashed it, I know that he has no access to TIS web nor a Tech2. He tunes many GTOs and I was specific that this setup I am installing is from 06 GTO. I have also sent him back a PCM/TCM to recheck if he shut something off, he since verified that all was OK.

rsz288

Sure sounds like everything is in line and your tuner is on top of things.

If you have a tech II, does it show the main calibration as either 12603159 or 12604792?

If it is the E40 hardware, it'll sure be an odd one.

Jones'n

I have found at times that if the engine computer is only getting power on pin 19 & 20, it will seem like everything should be working, but there is no Throttle body controls.
Double check that you are getting good voltage on 14 with the key on. From what I can tell, that is the power that the computer uses to actuate the throttle body.

Teamscss.com

Pin 14 is good on voltage!

Thanks to everyone,
looks like we are all in agreement that everything checks out.
I'll be getting a new PCM by Thursday so I will post new findings then.

Thanks again

jfg455

iTrader: (5)

I am a GM tech and found this tech bulletin. Read it and see if it applies to your issue. G



Subject: Diagnostic Information for LS2, LS4 and LH6 Engines for Diagnostic Trouble Codes (DTCs) P0606, P0689, P1516, P1682 and/or P2176 That May Have Set Due to Low Battery Voltage Condition


Models: 2005-2006 Buick Rainier

2005 Chevrolet Corvette

2005-2006 Chevrolet Impala SS, Monte Carlo SS, SSR, Trailblazer SS

2005-2006 GMC Envoy Denali, Envoy XL Denali

2005-2006 Pontiac Grand Prix, GTO

2005-2006 Saab 9-7X

with 5.3L or 6.0L V8 Engine (VINs C, M, H, U -- RPOs LS4, LH6, LS2)




--------------------------------------------------------------------------------

This bulletin is being published to aid technicians in the diagnosis of the following DTCs:

• P0606 -- Control Module Internal Performance

• P0689 -- Engine Controls Ignition Relay Feedback Circuit Low Voltage

• P1516 -- Throttle Actuator Control (TAC) Module Actuator Position Performance

• P1682 -- Ignition 1 Switch Circuit 2

• P2176 -- Minimum Throttle Position Not Learned

The above DTCs may have set under a low battery voltage condition during or prior to vehicle cranking, then starting. If these codes are present, and a low battery condition exists or the customer indicates that the vehicle has experienced a low battery voltage condition, the technician should do the following:

With a Tech 2®, observe the engine RPM and the control module voltage in freeze frame and failure records for the DTC(s) set. If the engine RPM is zero or lower than idle speed and the control module voltage indicates less than 9 volts, this may indicate a low battery condition had occurred to cause these codes to set. The low battery condition should be diagnosed and corrected. Refer to SI for Battery Inspection/Test and/or Charging System Test.
If the battery voltage is within the normal operating range, refer to the DTC(s) set in SI for further diagnosis.
After the low voltage concern has been identified and addressed, clear the codes. Do not replace the ECM for this concern or replace and ECM with any of the following part numbers:
• 12597883

• 12596679

• 12597191

Teamscss.com

So they are saying not to replace the PCM with listed numbers? I ordered a PCM with the number listed above, does that mean there's a different upgraded p/n to be used with this setup? and what is that replacement p/n?

BTW I re-ran the test with Batt. charger ON to isolate a poor batt. condition.

jfg455

iTrader: (5)

When I checked with parts I came up with 2 numbers; first is P/N 12597883 and is listed as an ENG control module. The second is P/N 92189621 and is listed as a powertrain control module. But the first number is on the list as well. When you read it, it does look like they don't want you to use the numbers on the list. Weird. I'll check out what I can. Do you have the VIN number from the PCM? Maybe I can look it up that way. G

The chart for the DTC is straight forward. Either PCM, throttle body, or wiring issues. Sounds like you are on the right track.

Side note: HPTuners has a window to shut off the TAC functions. This has to be selected before you flash the PCM so it wouldn't have been done on accident. You also won't see any "pulses" with a test light as the PCM pulses the circut like 50 (or 100 I can't remember)times a second. It will just show up as a dim light (slow pulse) and a brighter light (faster pulse). Same reason your relay test may note be accurate. It might not put out enough continuous current to trip the relay but it would be enough to move the motor. Just my thoughts. G

Teamscss.com

VIN: 6G2VX12U96L570214

I just tried to read the fault freeze frame on my tech2 and "control voltage" is nowhere to be found on that list. The p2176 is set as soon as the key is ON, without eng. running. Also I think P/N 92189621 you found is a PIM module (powertrain interface module)

"With a Tech 2®, observe the engine RPM and the control module voltage in freeze frame and failure records for the DTC(s) set. If the engine RPM is zero or lower than idle speed and the control module voltage indicates less than 9 volts, this may indicate a low battery condition had occurred to cause these codes to set."