Park / Neutral Position Switch (PNPS)

Fig. 1 PNPS Location:

Fig. 2 Component Detail:

Diagnostic Codes: P1514, P1516, P1517

Monitoring Procedure
The PNPS is tested for incorrectly indicating neutral by detecting gear changes in electronic automatic transmission or high load conditions. The PNPS is tested for incorrectly indicating drive, by cranking. If these tests are not passed then a fault event has occurred. When sufficient fault events have occurred then a fault is registered.

The strategy will report to the Diagnostic Status Manager (DSM) when a PNPS monitoring fault is present and the DSM will then decide whether to store a fault code and to illuminate the MIL Lamp.

Three tests check the operation of the Neutral 1 Drive switch.

- The Drive position test will check for engine conditions that indicate that the transmission is in Neutral while the switch indicates Drive.

- The high load test establishes that there is a false indication of Neutral from the Neutral I Drive switch by checking for high engine load whenever high engine speed is seen in Neutral; high load indicates that the transmission is in Drive and low load implies Neutral.

- The gear change test on an electronically controlled automatic transmission involves monitoring for gear change requests while the switch indicates Neutral.

If these tests are not passed then the appropriate fault count will be incremented.

High Load Neutral/Drive, P1514
Test checks whether the Neutral/Drive switch is incorrectly indicating neutral, by detecting high engine load conditions or gear changes (on automatic transmission vehicles).

In neutral if engine load up to 47.8 % and engine speed up to 1900 rpm then fault counter incremented.

Possible Causes:
- ECM signal is wrong but undetected
- Neutral/Drive switch falsely shows Neutral.
- Neutral/Drive wiring I connector short circuit to ground
- Neutral/Drive wiring pulled low by other ECM

Gear Change Neutral/Drive, P1516
Test checks whether the Neutral/Drive switch is incorrectly indicating neutral, by detecting high engine load conditions or gear changes (on automatic transmission vehicles). This test monitors for gear change request signals whilst the Neutral/Drive switch indicates neutral.

Possible Causes:
- Neutral/Drive switch falsely shows N
- Neutral/Drive wiring/connector short circuit to ground
- Neutral/Drive wiring pulled low by other ECM
- Transmission ECM fault - sending extra ignition retard requests
- Road speed sensor fault - but undetected
- Road speed signal pulled down by another consumer ECM - but undetected
- Road speed signal swamped by Radio Frequency Interference (RFI) - but undetected
- Road speed signal wrongly sent by other ECM - but undetected

Cranking Neutral/Drive, P1517
A test checks for whether the Neutral/Drive switch is incorrectly indicating drive by detecting cranking.

Possible Causes:
- Neutral/Drive switch falsely shows D
- Cranking inhibit not working with switch in D
- Neutral/Drive wiring/connector open circuit
- Neutral/Drive wiring pulled high by other ECM
- Neutral/Drive wiring/connector short circuit to voltage source
- ECM engine speed signal corrupted to look like cranking - Radio Frequency Interference (RFI)