P2128

Diagnostic Chart:

Schematic:

The accelerator pedal assembly contains two accelerator pedal position (APP) sensors with two independent 5 volt supplies, two independent grounds, and two independent signal circuits that vary resistance according to changes in accelerator pedal position. The ECM measures the signal voltage from each APP sensor, which are reduced values of the ECM 5 volt references. As the accelerator pedal moves from the rest to full position, the voltage on APP sensor 1 signal increases from 0.98 to 4.16 volts (+/-0.1), while the voltage on APP sensor 2 signal increases from 0.49 to 2.08 volts (+/-0.1). The ECM monitors each APP signal circuit for faults as well as a performing a comparison check between the sensor 1 and 2 signals. DTC P2128 will set if APP sensor 2 signal voltage at the ECM is below the calibrated voltage value.

DTC PARAMETERS
DTC P2128 will set if APP sensor 2 signal voltage is greater than 2.41 volts when:
^ Condition exists for longer than 140 ms
^ Accelerator pedal position must be changing
^ Main relay voltage is greater than 7.0 volts
^ Ignition is On

DTC P2128 diagnostic runs continuously once the above conditions have been met.

P2128 is a type A and C DTC.

NOTE: The MIL will only illuminate if the fault is present for longer than 5 seconds.

DIAGNOSTIC AIDS
To locate an intermittent problem, use Scan tool to monitor APP SENSOR 2 voltage with ignition On, engine Off. Wiggling wires while watching for a change in APP SENSOR 2 voltage may locate the area where an open or short to voltage in the wiring may exist.

If an APP sensor 2 signal circuit fault is detected, the ECM will default to one of the two limp home modes (limited pedal range with slow acceleration) and sensor 1 will be used. NOTE: The ECM will remain in this condition for the entire ignition cycle even is the fault is corrected.

Circuit 2701 (TP sensor 1/TP sensor 2) and circuit 1274 (APP sensor 2) share the same 5 volt reference supply (5 volt Ref-B).