DTC P1598: A/C Pressure Sensor Volts Too High

NOTE: For connector terminal ID, see CONNECTOR IDENTIFICATION . For wiring diagram, see WIRING DIAGRAMS article.

NOTE: A/C pressure sensor may also be referred to as A/C pressure transducer. A/C pressure sensor voltage is monitored with ignition on, engine is running and A/C clutch relay is energized. DTC may be stored in Powertrain Control Module (PCM) if A/C pressure sensor signal at PCM is more than 4.9 volts. Possible causes are: defective A/C pressure sensor, defective PCM, or defective connectors or wiring.

Turn ignition on with engine off. Using scan tool, read A/C pressure sensor voltage. If A/C pressure sensor voltage is more than 4.6 volts, go to next step. If A/C pressure sensor voltage is 4.6 volts or less, go to step 9 .
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. 3 (Dark Blue wire) on A/C pressure sensor connector. If voltage is 6 volts or less, go to next step. If voltage is more than 6 volts, repair short to voltage on Dark Blue wire between 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 .
Turn ignition off. Connect jumper wire between terminals No. 1 (Black/Light Blue wire) and No. 3 (Dark Blue wire) on A/C pressure sensor connector. Turn ignition on with engine off. Using scan tool, read A/C pressure sensor voltage. If A/C pressure sensor voltage is one volt or more, go to next step. If A/C pressure sensor voltage is less than one volt, replace A/C pressure sensor. Perform TEST VER-2A .
Turn ignition off. Disconnect jumper wire from terminal No. 1 (Black/Light Blue wire) on A/C pressure sensor connector and reconnect to engine ground. Ensure other end of jumper wire is still connected to terminal No. 3 (Dark Blue wire) on A/C pressure sensor connector.
Turn ignition on with engine off. Using scan tool, read A/C pressure sensor voltage. If A/C pressure sensor voltage is one volt or more, go to next step. If A/C pressure sensor voltage is less than one volt, repair open on Black/Light Blue wire between 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 .
Turn ignition off. Remove jumper wire. Ensure A/C pressure sensor connector is still disconnected. Disconnect PCM connectors. PCM is located between driver's side front fender and power distribution center, near battery.
Using ohmmeter, check resistance between terminal No. 3 (Dark Blue wire) on A/C pressure sensor connector and terminal No. 42 (Dark Blue wire) on Gray PCM connector C2. If resistance is less than 5 ohms, replace PCM. Perform TEST VER-2A . If resistance is 5 ohms or more, repair open on Dark Blue wire between PCM and A/C pressure sensor. Perform TEST VER-2A .
Ensure ignition is on with engine off. Using scan tool, read A/C pressure sensor voltage while wiggling wiring harness and connectors between A/C pressure sensor and PCM. A/C pressure sensor is located on A/C refrigerant line on firewall, near front of generator. See Fig 1 . PCM is located between driver's side front fender and power distribution center, near battery. If A/C pressure sensor voltage does not change while wiggling wiring harness and connectors, go to next step. If A/C pressure sensor voltage changes while wiggling wiring harness and connectors, repair wiring or connectors as necessary. Perform TEST VER-2A .
Inspect wiring harness and connectors between A/C pressure sensor and PCM. If no problems exist, test is complete. If any problems exist, repair wiring or connectors as necessary. Perform TEST VER-2A .