Occasional accelerator pedal position codes are not uncommon on the Saturn Astra. The system essentially runs 6 wires from the accelerator pedal (two sensors, two 5v, two grounds) As there are so many typical failures here, it is worth taking the time to try to diagnose before throwing parts at the problem.

Popular failures include:
- accelerator pedal,
- fuse box (UEC),
- ECU,
- throttle body,
- wiring

Water seems to migrate into the UEC, so that is worth an early check
https://www.vauxhallownersnetwork.co...fira-b.371985/

The accelerator pedal differs for the automatic & manual transmission cars.

I don't think the OEM are sold anymore but aftermarket parts are sold on ebay or Spareto directly. Aftermarket pedals are easy to get from Europe (we got hit with $18 in tariffs and $18 DHL tariff admin fees). There also is a replacement circuit board sold but that obviously would not address any issues with the contacts etc.

Some related codes -
P2122 Accelerator Pedal Position (APP) Sensor 1 Circuit Low Voltage
P2123 Accelerator Pedal Position (APP) Sensor 1 Circuit High Voltage
P2127 Accelerator Pedal Position (APP) Sensor 2 Circuit Low Voltage
P2128 Accelerator Pedal Position (APP) Sensor 2 Circuit High Voltage
P2138 Accelerator Pedal Position (APP) Sensor 1-2 Correlation

OUR PROBLEM AND FIX
We had periodic P2122 over time but recently P2138 popped up and the pedal went a bit wonky. Our quick diagnosis:

- We pulled the fuse box, visually inspected for damage or corrosion, sprayed with some contact cleaner.
- The UEC schematics on Chilton and Charm were completely "wrong" for our car so we bypassed some basic testing
- Pulled the 2 big cables to the ECU for inspection too.
- Pulled the pedal. The electrical connector showed 5v and grounds correct on the DMM.
- Connected the pedal to 5v power supplies. I think both channels should sweep from about 0.1v to 4.9v. One channel did not register and the other ranged from 1v to 3v.

So, given the pedal failures, we didn't continue testing the throttle body or system and just purchased a new pedal. Connected the pedal, connected the big battery, and started car. Check engine light disappeared and accelerator pedal works perfectly.

 

That's great information. I don't know how may Astra owners are on the forum, but maybe derf will make a sticky out of this. I'm sure you won't be the only one to have this issue.