P2138

Wiring Diagram:

P2138- APP SENSOR 1 - 2 CORRELATION
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 3.68 volts (+/-0.1), while the voltage on APP sensor 2 signal increases from 0.49 to 1.84 volts (+/-0.15). 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 P2138 will set if APP sensor 1 and APP sensor 2 signals are out of correlation with each other for a certain length of time.

DTC PARAMETERS
DTC P2138 will set if APP sensor 1 and APP sensor 2 are out of correlation when:
^ APP sensor 1 and APP sensor 2 signal voltages are out of correlation by greater than 0.27-0.99 volts based on position of sensor 1 and throttle angle
^ Condition exists for longer than 140 ms
^ Accelerator pedal position must be changing
^ Battery voltage is greater than 7.0 volts
^ Ignition is On

DTC P2138 diagnostic runs continuously once the above conditions have been met.

P2138 is a type A and C DTC

NOTE: The MIL will illuminate 5 seconds after the DTC has been set with the fault still occurring.

DIAGNOSTIC AIDS

IMPORTANT: If a low or high voltage APP sensor circuit fault also sets, diagnose that DTC first. An intermittent circuit fault may also set this DTC.

To locate an intermittent problem. use Scan tool to monitor APP SENSOR 1 and APP SENSOR 2 with ignition On, engine Off. Press accelerator pedal very slowly from the rest to full position, while monitoring each sensor voltage range. Watch for a sharp change in each of the voltage ranges which would indicate a problem.

Make sure each APP sensor harness connector terminal is not spread and the connector is free of corrosion or foreign material.

APP sensor 2 should always be one half the voltage value of APP sensor 1 (+/-0.1 volts) during the entire pedal travel range.


REST POSITION FULL TRAVEL

APP SENSOR 1 0.98 3.62

APP SENSOR 2 0.49 1.84

Replace the accelerator pedal position sensors if a problem was found.