DTC P1599: A/C Pressure Sensor Volts Too Low

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

NOTE: A/C pressure sensor voltage is monitored with ignition on, engine 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 less than .5 volt. Possible causes are; defective A/C pressure sensor, defective PCM, or defective connectors or wiring. The A/C pressure sensor may also be referred to as A/C pressure transducer.

Turn ignition on with engine off. Using scan tool, read A/C pressure sensor voltage. If A/C pressure sensor voltage is more than .2 volt, go to next step. If A/C pressure sensor voltage is .2 volt or less, go to step 4 .
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, just above A/C compressor, near dipstick. See Figure . PCM is located at driver's side front corner of engine compartment, just below air cleaner assembly. 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 .
Turn ignition off. Disconnect A/C pressure sensor connector. A/C pressure sensor is located on A/C refrigerant line, just above A/C compressor, near dipstick. See Figure .
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 4.9 volts, go to next step. If voltage is 4.9 volts or less, repair open on Violet/White wire between A/C pressure sensor and PCM. PCM is located at driver's side front corner of engine compartment, just below air cleaner assembly. Perform TEST VER-2A .
Ensure ignition is on with engine off. Using scan tool, read A/C pressure sensor voltage. If A/C pressure sensor voltage is 4.5 volts or less, go to next step. If A/C pressure sensor voltage is more than 4.5 volts, replace A/C pressure sensor. Perform TEST VER-2A .
Turn ignition off. Disconnect PCM connectors. PCM is located at driver's side front corner of engine compartment, just below air cleaner assembly.
Using ohmmeter, check resistance between ground and terminal No. 3 (Dark Blue) wire on A/C pressure sensor connector. This wire comes out of A/C pressure sensor connector as a Dark Blue wire and changes to a Dark Blue/Yellow wire at connector near rear of PCM and goes to terminal No. 42 on PCM connector C2. If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair short to ground on Dark Blue and Dark Blue/Yellow wire between A/C pressure sensor and PCM. Perform TEST VER-2A .
Ensure PCM connectors are still disconnected. Using ohmmeter, check resistance between terminals No. 1 (Black/Light Blue wire) and No. 3 (Dark Blue wire) on A/C pressure sensor connector. The Dark Blue wire comes out of A/C pressure sensor connector as a Dark Blue wire and changes to a Dark Blue/Yellow wire at connector near rear of PCM and goes to terminal No. 42 on PCM connector C2. If resistance is 5 ohms or more, replace PCM. Perform TEST VER-2A . If resistance is less than 5 ohms, repair Black/Light Blue wire, Dark Blue wire and Dark Blue/Yellow wire between PCM and A/C pressure sensor as they are shorted together. Perform TEST VER-2A .