Engine Power Reduced

NYSpeed Automotive
1

Okay, so i just put my new trans in and my car is stuck in engine power reduced. I hooked my scanner up and its reading TPS circuit high voltage. I didn’t have this code before the i put the new trans in…any ideas? I tried clearing the code but it comes right back.

I only have the driver seat in and i dont have the connectors plugged in so the service airbag pops up…could this be putting it in limp mode? I’m stumped and really need to be able to drive the car by tomorrow lol. any input is appreciated, thanks!

anyone have a tech II i could possibly borrow for a few hours?

2

Airbag will not cause power reduce. What is the code number

3

i’ll go get it now…also when i hook the scanner up it reads the TPS % but when i take my foot of the gas it drops down to 20% and then goes up to 35.5% with my foot off and stays there. :gotme:

i’m really starting to get annoyed lol

4

unhook the tps and give it a shot?

5

the code is

P2128
Throttle/Pedal position sensor ‘switch E’ circuit high input

6

Dead spot in the throttle pedal sensor located above the gas pedal on GM drive by wire applications

7

can i check for a dead spot? is it like checking a TPS? thank you for the input!

Do you have access to SI? do you think you could get me a wiring diagram? thank you.

8

Yes I have access to SI, I will look for the diagram

9

good luck anthony, lmk how it works out. also turn your phone on

10

So here’s an update. I found a diagram for the pedal position sensor. It’s getting both 5v references from the PCM. There is 2 signals it puts out, i believe a high and low

the first one starts out at about .6 volts then goes up to a little over 2 volts as the pedal is pushed down

the second one starts out around 4 volts then goes down to .6 volts

now shouldnt the first one go up to around 4.5 volts? and should the second one start at about 4.5 volts?

:EDIT:

I forgot to mention, i cleared the code, started the car and let it warm up. It didn’t go into engine reduced power until i hit the gas pedal, and immediately the CEL came on and it went into reduced power.

11

you probably wont be able to see a dead spot with out an oscilloscope.

12

2128 refers only to the second sensor on the pedal. It starts near 5 volts and goes down as the pedal is pressed. If the second sensor is showing more than 4.65 volts with pedal resting it will throw the code. What is the exact voltage with it sitting at rest? If you unplug the connector and test the 5 volt reference to ground with KOEO what does it read? Def not a 2138 code? There’s a possibility of a short in the harness by the kick panel.

13

The sensor is a barely over 4 volts at rest, i’ll go unplug the connector and try it. thanks for the input! i’ll be back in a bit with more info.

14

the exact voltage at rest is 4.074 volts and it goes down to about .865 volts

15

now its reading P2138

Throttle/Pedal Position Sensor/Switch ‘D’ / ‘E’ Voltage correlation

16

check for a bad wire in the harness in the left side kick panel. There is a bad seal that lets water in and can possibly corrode. Trace those wires.

17

i’ll do that now…thanks for the help bud :tup:

18

anytime.

19

yea theres actually a tsb for that…

20

remove the switch and test using an analog ohm meter. slowly bring the switch from nil to max and back watching the sweep of the needle. it should sweep smoothly with no spikes in either direction. if it does spike in either direction then obviously its bad. a digital ohm meter jumps around too much and you will never see the spike. we had my wifes expedition in 4 different places and spent close to $3000 trying to remedy this. finally i had day off and started tearing off corresponding sensors and switches and figured it out after 3 hours and $30 for the tps