The accelerator pedal position (APP) sensor system consists of two independent sensors that read differently scaled values of one another in order to command the throttle butterfly to a particular position. The APP sensor signal circuits are monitored continuously. This DTC will set if APP Sensor 1 signal voltage should exceed a calibratable upper limit.

DTC P1278 will set if APP Sensor 1 signal voltage greater than 4.82 volts when:

P1278 is a (type A) DTC.

To locate an intermittent problem, use the scan tool to monitor APP Sensor 1 with ignition On, engine Off.

Wiggling wires while monitoring APP Sensor 1 may locate the area where an open or short to ground exists.