The accelerator pedal position (APP) sensor system consists of two independently scaled potentiometers (APP sensor 1 and APP sensor 2), that vary resistance according to the changes in the throttle position. The ECM measures the signal voltage from the two sensors, which are a reduced value of the ECM 5 volt reference. The voltage for APP sensor 1 and APP sensor 2 range from 0.4 - 3.8 (+/-.1) volts and 0.2 - 1.9 (+/-.1) volts, respectively. The APP sensor signal circuits are monitored continuously for an open, short to ground, or short to voltage condition. DTC P1271 will set if the ECM determines APP sensor 1 and APP sensor 2 signal inputs are in disagreement.
DTC PARAMETERS
DTC P1271 will set if the ECM determines APP sensor 1 and APP sensor 2 signal inputs are in disagreement when:
| • | Condition exists for longer than 140 milliseconds |
| • | Battery voltage is greater than 7.0 volts |
DTC P1271 diagnostic runs continuously with ignition On.
P1271 is a (type A) DTC
Diagnostic Aids
To locate an intermittent problem, use the Scan tool to monitor APP SENSOR 1 and APP SENSOR 2 with the ignition On, engine Off and:
| • | Accelerator pedal at normal rest position. |
| • | Accelerator pedal pressed completely to floor |
Voltage should be within 0.1 volts of:
Rest | Accelerator Pedal to Floor | |
|---|---|---|
APP SENSOR 1 | 0.40 | 3.80 |
APP SENSOR 2 | 0.20 | 1.90 |
If no other DTCs have been set and the voltage readings are not as indicated above, replace APP sensor assembly.
If both P1271 and P1516 are set, circuit 486 or 1274 may be shorted to voltage.
If DTCs P0102, P0108, P0533 and P1271 are set, there may be a short to voltage on circuit 1164.
If DTCs P0103, P0108, P0113, P0118, P0123, P0223, P0341, P0406 and P1271 are set, there may be an open circuit in the 5-volt reference return circuit 652.
