P0708

DTC P0708 (Two Connector NSBU)

Circuit Description

The installation of a transmission mounted neutral start/backup switch is required. This switch, commonly called a park/neutral position switch (PNP), mounts directly onto the transmission housing from the outside and detects the angular position of the shift selector shaft. This position is communicated to the transmission control module (TCM) so that certain vehicle control functions can be coordinated with the position of the shift controls. The PNP switch has redundant circuitry to alert the TCM in the event of a single wire or switch failure.

The neutral signal output of the PNP switch is typically used as confirmation that the transmission is in NEUTRAL before the engine starter is engaged. The PNP switch is interfaced to the starter circuit with weatherproof electrical connectors. The reverse signal provision may be used to activate vehicle back-up lights and/or reverse warning devices.

DTC P0708 is a type A DTC.

Conditions for Running the DTC

- The components are powered and ignition voltage is greater than 9.0 volts and less than 18 volts.
- Engine speed is greater than 200 RPM and less than 7,500 RPM for 5 seconds.

Conditions for Setting the DTC

DTC P0708 sets when the TCM detects an invalid condition and parity error occurring over consecutive ignition cycles.

Action Taken When the DTC Sets

While diagnostic response is active, one of the following conditions can occur:

- The TCM illuminates the malfunction indicator lamp (MIL).
- The transmission fails to hydraulic default.
- DTC P0708 will be stored in TCM history.
- The TCM freezes shift adapts.
- The TCM inhibits torque converter clutch (TCC) engagement.

Conditions for Clearing the DTC

- A scan tool must be used to clear the code from TCM history.
- This DTC does not automatically clear from TCM history after 40 ignition cycles.

Diagnostic Aids

- Inspect the wiring for poor electrical connections at the TCM and powertrain control module (PCM). Inspect for the following conditions:
- A bent terminal.
- A backed-out terminal.
- A damaged terminal.
- Poor terminal tension.
- A chafed wire.
- A broke wire inside the insulation.
- When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
- You may have to drive the vehicle in order to experience a condition.
- If P0875, previously P1713, is shown in failure records as being set first on the failure list followed by P0872, previously P1711, combined with P0708, this generally indicates a PNP internal switch failure. Often, when the DTCs are cleared, they do not return. This may be due to moisture that was present at the time the DTC was set, causing a short internally.
- Inspect the PNP switch linkage carefully for proper adjustment and for signs of damage.

Test Description

The numbers below refer to step numbers on the diagnostic table.

3. This step tests TCM input response.
4. This step tests the wiring harness for opens or shorts.
6. This step tests the wiring harness for a short to voltage.