On the 2005 Pontiac GrandPrix,the P1125 and P2138 and directly related. These codes are pointing to a problem with the Accelerator Pedal Position Sensors. These sensors are built into and part of the accelerator pedal assembly. Carefully inspect the electrical connector and wire harness for any loose, broken or damaged wires. Inspect the sensors for any signs of water intrusion. If the inspection checks ok, the accelerator pedal assembly will need to be replaced.
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