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Test DS: Air Conditioning Pressure Sensor: Testing

    NOTE: For additional testing information, see DIAGNOSTIC AIDS .

  1. 1) For KOEO, KOER & Continuous Memory DTC P1461: Check ACP V PID
    This DTC indicates PCM has detected high voltage in ACP circuit. Possible causes for this fault are:
    • ACP Sensor Circuit Short To PWR
    • ACP Circuit Open
    • Faulty Powertrain Control Module (PCM)
    • ACP Circuit Shorted To VREF Or SIG RTN
    • Faulty ACP Sensor

    Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Turn ignition switch to ON position. Using scan tool, access ACP V PID from PID/DATA MONITOR & RECORD menu. If ACP V PID voltage is 4.9 volts or more, go to next step. If ACP V PID voltage is less than 4.9 volts, fault is unable to be duplicated at this time. Go to step  18).

  2. 2) Check Voltage Between VREF & SIG RTN Circuits To ACP Sensor

    Turn ignition switch to OFF position. Disconnect ACP sensor connector. Turn ignition switch to ON position. Using a DVOM, measure voltage between SIG RTN and VREF circuits at ACP sensor harness connector. See Figure. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, VREF is out of range or SIG RTN circuit is open. Go to TEST C, step  1).

  3. 3) Induce Opposite ACP Signal

    Turn ignition switch to ON position. Using scan tool, access ACP V PID from PID/DATA MONITOR & RECORD menu. If ACP V PID voltage is 4.9 volts or more, go to next step. If ACP V PID voltage is less than 4.9 volts, replace ACP sensor. Refer to appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST .

  4. 4) Check ACP Circuit For Short To VREF In Harness

    Turn ignition switch to OFF position. Disconnect scan tool from DLC. Disconnect PCM connector(s). Using a DVOM, measure resistance between ACP and VREF circuits at ACP sensor harness connector. See Figure. If resistance is more than 10 k/ohms, go to next step. If resistance is 10 k/ohms or less, repair short to VREF in ACP circuit. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST .

  5. 5) Check ACP Circuit For Short To Power In Harness

    Turn ignition switch to ON position. Using a DVOM, measure voltage between chassis ground and ACP circuit at ACP sensor harness connector. See Figure. If voltage is less than one volt, go to next step (LS, Marauder, Thunderbird and ZX2), or replace PCM (all others). Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST . If voltage is one volt or more, repair short to VPWR in ACP circuit. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST .

  6. 6) Check For Open ACP Circuit In Harness

    Turn ignition switch to OFF position. Leave ACP sensor and PCM disconnected. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure resistance of ACP circuit between PCM harness connector and ACP sensor harness connector. See Figure. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in ACP circuit. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST .

  7. 7) Check PCM

    Reconnect PCM harness connector(s). Leave ACP sensor disconnected. Connect a jumper wire between ACP and SIG RTN circuits at ACP sensor harness connector. See Figure. Turn ignition switch to ON position. Using scan tool, access ACP V PID from PID/DATA MONITOR & RECORD menu.
    NOTE: If scan tool is now unable to communicate, replace PCM. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST .

    If ACP V PID voltage is 4.9 volts or more, replace PCM. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST . If ACP V PID voltage is less than 4.9 volts, replace ACP sensor. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST .

    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 7) to step 10). No test procedures have been omitted.
    8. NOTE: For additional testing information, see DIAGNOSTIC AIDS .

  8. 10) For KOEO, KOER & Continuous Memory DTC P1462: Check ACP V PID
    This DTC indicates PCM has detected low voltage in ACP circuit. Possible causes for this fault are:
    • ACP Circuit Open, Or Shorted To GND Or SIG RTN
    • VREF Circuit Open
    • Faulty Powertrain Control Module (PCM)
    • Faulty ACP Sensor

    Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Turn ignition switch to ON position. Using scan tool, access ACP V PID from PID/DATA MONITOR & RECORD menu. If ACP V PID voltage is .15 volt or less, go to next step. If ACP V PID voltage is more than .15 volt, fault is unable to be duplicated at this time. Go to step  18).

  9. 11) Check Voltage Between VREF & SIG RTN To ACP Sensor

    Turn ignition switch to OFF position. Disconnect ACP sensor connector. Turn ignition switch to ON position. Using a DVOM, measure voltage between SIG RTN and VREF circuits at ACP sensor harness connector. See Figure. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, VREF is out of range. Turn ignition switch to OFF position and go to TEST C, step  1).

  10. 12) Induce Opposite ACP Signal

    Turn ignition switch to OFF position. Connect a jumper wire between ACP and VREF circuits at ACP sensor harness connector. See Figure. Turn ignition switch to ON position. Using scan tool, access ACP V PID from PID/DATA MONITOR & RECORD menu.
    NOTE: If a scan tool communication concern exists, remove jumper wire and go to next step.

    If ACP V PID voltage is 4 volts or less, go to next step. If ACP V PID voltage is more than 4 volts, replace ACP sensor. Refer to appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST .

  11. 13) Check ACP Circuit For Short To PWR GND Or SIG RTN

    Turn ignition switch to OFF position. Disconnect scan tool from DLC. Disconnect PCM connector(s). Using a DVOM, measure resistance between ACP circuit, and SIG RTN circuit at ACP sensor harness connector, and negative battery terminal. See Figure. If both resistance measurements are more than 10 k/ohms, go to next step. If either resistance measurement is 10 k/ohms or less, repair short to ground in affected circuit. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST .

  12. 14) Check ACP Circuit For Open In Harness

    Using a DVOM, measure resistance of ACP circuit between PCM harness connector and ACP sensor harness connector. See Figure. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in ACP circuit. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST .

  13. 15) Check For The A/C Clutch To Engage

    Turn ignition switch to OFF position. Reconnect ACP sensor. Turn ignition switch to ON position. Turn A/C switch to ON position while listening for A/C clutch engagement. If A/C clutch engages when A/C is turned on, replace PCM. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST . If A/C clutch does not engage when A/C is turned on, go to next step.

  14. 16) Check A/C System Refrigerant Charge

    Reconnect all components. Connect A/C manifold gauge set and check if A/C system has correct refrigerant charge. Service A/C system as necessary. For additional information, see appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST . If A/C system has correct refrigerant charge, replace PCM. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 16) to step 18). No test procedures have been omitted.

  15. 18) Check For Intermittent ACP Circuit Fault

    Turn ignition switch to ON position. Using scan tool, access ACP V PID from PID/DATA MONITOR & RECORD menu. While observing ACP V PID, lightly tap on ACP sensor and wiggle and bend ACP, SIG RTN and VREF circuits between ACP sensor and PCM to simulate road shock. A fault is indicated by a sudden change of ACP V PID voltage. If fault is indicated, isolate and repair as necessary. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST . If no faults are indicated, fault is unable to be duplicated at this time. Go to TEST Z, step 1) .
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 18) to step 20). No test procedures have been omitted.
    16. NOTE: For additional testing information, see DIAGNOSTIC AIDS .

  16. 20) For Continuous Memory Only DTC P1463: Verify A/C Clutch Can Disengage
    This DTC indicates PCM has detected that ACP sensor did not detect sufficient change in A/C system pressure when A/C switch was turned to ON position. Possible causes for this fault are:
    • A/C System Mechanical Malfunction
    • Open ACP Or VREF Circuit
    • Faulty ACP Sensor
    • A/C System Electrical Malfunction (Non-EEC Related)
    • A/C Clutch Continuous Engagement

    Ensure A/C and defroster are off. Start engine and allow to idle. Verify A/C clutch is disengaged. If A/C clutch is disengaged, go to next step. If A/C clutch is not disengaged, diagnose by symptom. See CLIMATE CONTROL (LACK OF A/C COOLING, A/C ALWAYS ON OR A/C INOPERATIVE) under SYMPTOMS in TROUBLE SHOOTING - NO CODES - CNG, FLEX-FUEL & GASOLINE article. Repair as necessary.

    17. NOTE: If voltage and ground to A/C clutch have already been confirmed okay with a non-powered test light in TROUBLE SHOOTING - NO CODES - CNG, FLEX-FUEL & GASOLINE article, or if A/C clutch can be heard clicking on when A/C is turned on, go to step  22).

  17. 21) Check For Voltage & Ground To A/C Clutch
    Turn ignition switch to OFF position. Disconnect A/C cycling switch. Connect a jumper wire between A/C cycling switch harness connector terminals. Disconnect A/C clutch. Connect non-powered test light between power and ground terminals at A/C clutch harness connector. Start engine and allow to idle. Turn A/C switch on. Monitor test light for 15 seconds. If test light comes on or A/C clutch can be heard clicking, go to next step. If test light does not come on or A/C clutch cannot be heard clicking, see appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.

  18. 22) Check If A Sufficient A/C Pressure Change Can Be Detected By The ACP PID

    Start engine and allow to idle. Ensure A/C is off. Using scan tool, access ACP V PID from PID/DATA MONITOR & RECORD menu. Note A/C V PID voltage reading. Monitor ACP V PID value and turn A/C on. Note ACP V PID voltage reading within 5 seconds of A/C clutch engagement and compare measurement with ACP V PID reading noted previously. If A/C clutch does not engage, or if ACP V PID voltage change is .3 volt or less, go to next step. If ACP V PID voltage change is more than .3 volt, ACP sensor and PCM can detect a sufficient change in A/C pressure. If directed here by DTC P1463, diagnose by symptom. See SYMPTOMS in TROUBLE SHOOTING - NO CODES - CNG, FLEX-FUEL & GASOLINE article. Repair as necessary. For all others, see appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. Check A/C system for proper operation and repair as necessary. After servicing A/C system, start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST .

  19. 23) Check A/C System Pressure & Pressure Change

    Turn ignition switch to OFF position. Reconnect all components. Connect A/C manifold gauge set. Start engine and allow to idle. With A/C off, note high pressure measurement. Turn A/C on. Wait 5 seconds and note high pressure measurement again. Turn A/C off. If high pressure measurement changes more than 30 psi (207 kPa) within 5 seconds of clutch engagement, go to next step. If high pressure measurement does not change more than 30 psi (207 kPa) within 5 seconds of clutch engagement, A/C system pressure did not change as expected. Service A/C system as necessary. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. After servicing A/C system, start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST .

  20. 24) Check Voltage Between VREF & SIG RTN Circuit To ACP Sensor

    Turn ignition switch to OFF position. Disconnect ACP sensor connector. Turn ignition switch to ON position. Using a DVOM, measure voltage between SIG RTN and VREF circuits at ACP sensor harness connector. See Figure. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, VREF is out of range. Go to TEST C, step  1).

  21. 25) Check ACP Circuit For Open In Sensor

    Turn ignition switch to OFF position. Ensure ACP sensor harness connector is disconnected. Disconnect PCM connector(s). Using a DVOM, measure resistance of ACP circuit between PCM harness connector and ACP sensor harness connector. See Figure. If resistance is less than 5 ohms, replace ACP sensor. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST . If resistance is 5 ohms or more, repair open in ACP circuit. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST .
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