P1520

Circuit Description
The Park/Neutral Position (PNP) Switch contacts close the input circuit from the engine control module (ECM) to ground when the transmission range switch is in the park position. The PNP switch is open when a transaxle drive or neutral range is selected. The ECM uses the P/N position switch information to perform the following functions:
- Control idle speed using the Idle Air Control (IAC).
- Vehicle speed sensor (VSS) output.
- Speed sensor diagnostics.
- Ignition coil spark advance.

The ECM supplies 12 volts to the PNP switch signal circuit. The ECM senses a closed switch (PARK selected) when the voltage on the PNP signal switch drops below 1 volt.

Conditions for Setting the DTC
- DTCs P0106, P0107, P0108, P0117, P0118, P0121, P0122, P0123, P0336, P0337 and P0502 are not set.

Stuck in park (PNP Switch is ON)
- Vehicle speed is greater than 30 mph (48 kph).
- Engine Coolant Temperature (ECT) is greater than 50 °F (10 °C).
- Engine speed is greater than 2000 rpm.
- Throttle position sensor is greater than 10%.
- Manifold Absolute Pressure (MAP) is greater than 6.5 psi (45 kPa).

Stuck in gear (PNP Switch is OFF)
- Vehicle speed is greater than 2 mph (3 kph).
- Engine speed is less than 1100 rpm.
- Throttle position sensor is less than 1.1%.
- MAP is less than 5 psi (34 kPa) with A/C OFF or less than 6 psi (42 kPa) with A/C ON.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will not illuminate.
- The ECM will store conditions which were present when the DTC set as Failure Records data only. This information will be not stored as Freeze Frame data.
- A history DTC is stored.

Conditions for Clearing the MIL/DTC
- A history DTC will clear after 40 consecutive warm-up cycles without a fault.
- DTC(s) can be cleared by using the scan tool.

Diagnostic Aids
An intermittent may be caused by a poor wire connection, rubbed through wire insulation or a wire broken inside the insulation. Check for the following conditions:
- Misadjusted PNP switch.
- Poor connection with the ECM harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
- Damaged wiring harnesses.

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

Steps 1 - 10:

DTC P1520 Park/Neutral Discrete Fault