Test NTC-18: Checking A/C Pressure Sensor Signal

NOTE: A/C pressure sensor may also be referred to as A/C pressure transducer. For connector terminal ID, see CONNECTOR IDENTIFICATION . For wiring diagram, see WIRING DIAGRAMS article.

Turn ignition on with engine off. Using scan tool, check for DTCs. If no DTCs exist for A/C pressure sensor, go to next step. If DTC P1598: A/C PRESSURE SENSOR VOLTS TOO HIGH or DTC P1599: A/C PRESSURE SENSOR VOLTS TOO LOW exists, go to DTC P1598: A/C PRESSURE SENSOR VOLTS TOO HIGH or DTC P1599: A/C PRESSURE SENSOR VOLTS TOO LOW .
Turn ignition off. Disconnect A/C pressure sensor connector. A/C pressure sensor is located on A/C refrigerant line on firewall, near front of generator. See Fig 1 .

Fig 1: Locating A/C Pressure Sensor
Courtesy of DAIMLERCHRYSLER CORPORATION
Turn ignition on with engine off. Using voltmeter, check voltage at terminal No. 2 (Violet/White wire) on A/C pressure sensor connector. If voltage is more than 4.8 volts, go to next step. If voltage is 4.8 volts or less, repair open on Violet/White wire between Powertrain Control Module (PCM) and A/C pressure sensor. PCM is located between driver's side front fender and power distribution center, near battery. Perform TEST VER-2A .
Ensure A/C pressure sensor connector is still disconnected. Turn ignition on with engine off. Using scan tool, read A/C pressure sensor voltage. If A/C pressure sensor voltage is more than 4.8 volts, test is complete. If A/C pressure sensor voltage is 4.8 volts or less, repair high resistance in Dark Blue wire between A/C pressure sensor and PCM. This is the A/C pressure sensor signal. Perform TEST VER-2A .