For 1990-2009 cars

### DTC P1816 - Transmission Range Switch - Park/Neutral With Drive Ratio

### Circuit Description

The powertrain control module (PCM) determines if the transmission is hydraulically in drive with the transaxle range switch in Park or Neutral. As long as the PCM receives a valid transaxle range switch combination, the PCM will run a diagnostic to determine if the vehicle is in drive hydraulically. The PCM under normal conditions, should detect the input shaft spinning greater than a calibrated value (ISS/Engine Speed > .86). This indicates there is no load being applied to the transmission. DTC P1816 sets when a hydraulic drive ratio is detected when the transaxle range switch has Park or Neutral selected and then later determines a valid ISS signal has been received.

### DTC Parameters

DTC P1816 will set when a drive ratio is detected when transaxle range switch is in Park or Neutral when:

• | The condition exists for longer than 1 second

• | The input speed is NOT present

• | The vehicle speed is NOT present

• | The transaxle in Park or Neutral for a minimum of 3 seconds to start test

• | The engine is running

• | The TFT is above 0°C (32°F)

• | No ISS, transaxle range switch or vehicle speed DTCs have been set

Once the above conditions are met, then:

• | The vehicle speed is above 5 km/h (3 mph)

• | The input speed is greater than 100 RPM

• | The ratio of input speed-to-engine speed is less than 0.75 for longer than 1 second

DTCP1816 is a type B DTC.

### Diagnostic Aids

This DTC sets when a hydraulic drive, gear ratio, is detected when the transaxle range switch indicates Park or Neutral.

Under normal conditions, the ratio of input speed-to-engine speed should be greater than 0.86 with the engine running and the transaxle in park.

The PCM will boost line pressure if this DTC is active.

The PCM will command 2nd gear starts if this DTC is active.