GM Drive By Wire Issues

[johnnewcomb62]

Hey all, I have gotten the LS3 installed and everything done and she starts right up and idles
like a kitten. But there is no throttle response at all. Is there any electronic/auto folks out
there that could possibley help with a resolution? Or is there a local shop that may could help
work out the problem that anyone knows of? I would like to have the ECM checked and then
go from there.
Thanks in advance for any info.

John

[JohnW8]

Don't the GM fly-by-wire setup need to use the throttle pedal assembly for the input signal? What car is it in?

[johnnewcomb62]

Its my Porsche 911 project. It had a blown engine and I got with the folks out in Vegas
Renegade Hybrid and bought the kit to install and bought a brand new 480-hp LS3 with
all the electronics foot pedal ect.
The isssue is, it will start and run at idle but no throttle response. I put a code reader on it
and got two codes; P2128 and P2128 P/D been in contact with the GM tech dept. but they
don't want to give much information to a consumer. So having to kinda find for myself and
can always use a little help from my friends!!!!!

[engled]

http://engine-codes.com/p2128.html

P2128 - Throttle/Pedal Position Sensor/Switch 'E' Circuit High

Short in the wire from the potentiometer to the ECU?

Or maybe this.

DTC P2128
Circuit Description
The accelerator pedal assembly contains 2 accelerator pedal position (APP) sensors. The APP sensors are mounted in the pedal assembly and are not serviceable. The APP sensors provide a signal voltage that changes relative to the position of the accelerator pedal. The engine control module (ECM) supplies a separate 5-volt reference and low reference circuit for each of the APP sensors.

The APP sensor 1 signal voltage increases as the pedal is depressed, from approximately 1 volt at rest to above 2.5 volts when fully depressed. The APP sensor 2 signal voltage decreases as the pedal is depressed, from approximately 4 volts at rest to less than 1 volt with the accelerator pedal fully depressed.

If the ECM detects that the APP sensor 2 signal voltage is too high, this DTC sets.

DTC Descriptor
This diagnostic procedure supports the following DTC:

DTC P2128 Accelerator Pedal Position (APP) Sensor 2 Circuit High Voltage

Conditions for Running the DTC
DTCs P0601, P0602, P0603, P0604, P0606, P0607, P0641, P0651 are not set.
The ignition is ON.
The ignition 1 voltage is more than 5.23 volts.
DTC P2128 runs continuously when the above conditions are met.
Conditions for Setting the DTC
The ECM detects that the APP sensor 2 voltage is more than 4.2 volts for more than one second.

Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.
Conditions for Clearing the MIL/DTC
The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.
Diagnostic Aids
Use the J 35616-B Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
If DTCs P0700, P2122, P2128, and P2138 are set together in various combinations, inspect the APP sensor 1 and 2 signal circuits for being shorted together.
For an intermittent condition, refer to Intermittent Conditions .
Step
Action
Values
Yes
No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Control Module (ECM) Connector End Views or Engine Controls Connector End Views

1
Did you perform the Diagnostic System Check - Vehicle?
--
Go to Step 2
Go to Diagnostic System Check - Vehicle

2
Turn ON the ignition, with the engine OFF.
Observe the accelerator pedal position (APP) sensor 2 voltage with the accelerator pedal in the rest position, with a scan tool.
Is the APP sensor 2 voltage parameter more than the specified value?
4.2 V
Go to Step 4
Go to Step 3

3
Observe the Freeze Frame/Failure Records for this DTC.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the Conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?
--
Go to Step 4
Go to Intermittent Conditions

4
Turn OFF the ignition.
Disconnect the accelerator pedal connector.
Turn ON the ignition, with the engine OFF.
Measure the voltage of the APP sensor 2 5-volt reference circuit, with a DMM.
Does the DMM indicate voltage within the specified range?
4.8-5.2 V
Go to Step 5
Go to Step 10

5
Probe the APP sensor 2 signal circuit with a test lamp connected to ground.

Does the test lamp illuminate?
--
Go to Step 8
Go to Step 6

6
Observe the APP Sensor 2 parameter, with the test lamp still connected to the APP sensor 2 signal circuit.

Does the scan tool indicate voltage at the specified value?
0 V
Go to Step 9
Go to Step 7

7
Test the APP sensor 2 signal circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?
--
Go to Step 16
Go to Step 13

8
Test the APP sensor 2 signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?
--
Go to Step 16
Go to Step 11

9
Test the APP sensor 2 low reference circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?
--
Go to Step 16
Go to Step 12

10
Test the APP sensor 2 5-volt reference circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?
--
Go to Step 16
Go to Step 11

11
Test for shorted terminals and for a poor connection at the engine control module (ECM) harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?
-
Go to Step 16
Go to Step 15

12
Test for an intermittent and for a poor connection at the accelerator pedal harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?
--
Go to Step 16
Go to Step 14

13
Test for an intermittent and for a poor connection at the ECM harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?
Go to Step 16
Go to Step 15

14
Replace the accelerator pedal assembly. Refer to Accelerator Pedal Position (APP) Sensor Replacement .

Did you complete the replacement?
--
Go to Step 16
--

15
Replace the ECM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?
--
Go to Step 16
--

16
Clear the DTCs with a scan tool.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?
--
Go to Step 2
Go to Step 17

17
Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

[JohnW8]

Speedsouth may be able to help. They do a lot of work with GM products.

Looks like Darryl has been googling again.

[engled]

Looks like Darryl has been googling again.

A lot cheaper than Speedsouth

[johnnewcomb62]

Thanks for the info guys, I have found through some testing that I don't have the Low
reference on app 2. Working and going to school in the evenings are holding me back
from being able to do much till the weekend. I have plans to trace the wire that is in
question for that ref. and see if maybe it has been pinched, cut or if there is a problem
at the ECM plug and will post results.
Thanks,
John

[johnnewcomb62]

OK verified the loss of the low ref. on app 2 and traced wire back to the ECM plug. We took
the top of the plug and untaped the wires and found the wire in question and give it a tug
and guess what, it popped right out of the plug of course broken! Now we have to figure
out what we have to do to get it ( the female plug pin ) back in. I will call GM tech today
and explain issue and report back.

John

[johnnewcomb62]

OK guys got it! What we found was we had to take the bottom plate off the ecm plug and
pull the pin out and reattach the wire and I soldered it on and re-inserted in into the plug and that took care of the problem.
Thanks to all who chimed in to help take care!

John