Diagnostic Aids

Perform this test when directed by QUICK TEST . This CIRCUIT TEST is intended to diagnose:

• ACP sensor.
• ACP wiring harness circuits (ACP, VREF and SIG RTN).
• Powertrain Control Module (PCM).

1. Step 1) DTC P1461  This code indicates PCM has detected high voltage in ACP circuit. Possible causes for this code are:
   • Faulty ACP sensor.
   • Open or shorted circuit.
   • Faulty Powertrain Control Module (PCM).

   Turn ignition off. Connect scan tester to DLC. Turn ignition on. Access ACP V PID. If ACP V PID voltage is more than 4.9 volts, go to next step. If ACP V PID voltage is 4.9 volts or less, fault is intermittent. Go to step 18).

2. Step 2) Check VREF & SIG RTN Circuit  Turn ignition off. Disconnect ACP sensor wiring harness connector. Turn ignition on. Measure voltage between SIG RTN and VREF connector terminals. 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 is open. Go to CIRCUIT TEST C.
3. Step 3) Induce Opposite Signal  Turn ignition off. Leave ACP sensor disconnected. Connect scan tester to DLC. Using scan tester, access ACP V PID. If voltage between ACP V 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 . If ACP V voltage is 4.9 volts or more, go to next step.
4. Step 4) Check ACP Circuit For Short To VREF  Turn ignition off. Leave ACP sensor disconnected. Disconnect scan tester from DLC. Disconnect PCM 104-pin connector. Inspect connector for damage and repair as necessary. Measure resistance between ACP terminal and VREF terminal at ACP connector. If resistance is 10,000 ohms or more, go to next step. If resistance is less than 10,000 ohms, repair ACP circuit short to VREF. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST .
5. Step 5) Check ACP Circuit For Short To Power  Leave ACP sensor and PCM disconnected. Measure voltage between ACP terminal at ACP connector and chassis ground. If voltage is less than one volt, replace PCM and repeat QUICK TEST. For all models, if voltage is one volt or more, repair ACP circuit short to power. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST .
6. Step 6) Check Circuit Continuity  Turn ignition off. Leave ACP sensor disconnected. Disconnect PCM 104-pin connector. Inspect connector for damage and repair as necessary. Install EEC-V Breakout Box (014-00950), leaving PCM disconnected. Measure resistance between test pin No. 86 (ACP) and ACP terminal of ACP sensor wiring harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST .
7. Step 7) Check PCM  Turn ignition off. Connect PCM to breakout box. Leave ACP sensor disconnected. Connect jumper wire between test pin No. 86 and 91 (SIG RTN) at breakout box. Connect scan tester to DLC. Using scan tester, access ACP V PID (if scan tester is unable to communicate, follow YES path). Turn ignition on.
   • 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 .
   • 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 .
   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. Step 10) DTC P1462  This code indicates PCM has detected low voltage in ACP circuit. Possible causes for this code are:
   • Faulty ACP sensor.
   • Open or shorted circuit.
   • Faulty Powertrain Control Module (PCM).

   Turn ignition off. Connect scan tester to DLC. Turn ignition on. Access ACP V PID. If ACP V PID voltage is less than .15 volt, go to next step. If ACP V PID voltage is .15 volt or more, fault is intermittent. Go to step 18).

9. Step 11) Check VREF Circuit At ACP Sensor  Turn ignition off. Disconnect ACP sensor wiring harness connector. Turn ignition on. Measure voltage between SIG RTN and VREF connector terminals. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, VREF is out of range. Go to CIRCUIT TEST C.
10. Step 12) Induce Opposite Signal  Turn ignition off. Leave ACP sensor disconnected. Connect scan tester to DLC. Connect jumper wire between ACP terminal and VREF terminal at connector. Turn ignition on. Access ACP V PID (if scan tester cannot access ACP V PID, go to next step). If ACP V PID voltage is less than 4 volts, go to next step. If ACP V PID voltage is 4 volts or more, replace ACP sensor. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST .
11. Step 13) Check ACP Circuit For Short To Ground Or SIG RTN  Leave ignition off and ACP sensor disconnected. Disconnect scan tester from DLC. Disconnect PCM 104-pin connector. Inspect connector for damage and repair as necessary. Measure resistance between ACP terminal and SIG RTN terminal at ACP connector. Measure resistance between ACP terminal at ACP connector and negative battery terminal. If both resistance measurements are 10,000 ohms or more, go to next step. If either resistance measurements are less than 10,000 ohms, repair short circuit. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST .
12. Step 14) Check ACP Circuit Continuity  Leave ignition off. Install EEC-V Breakout Box (014-000950), leaving PCM disconnected. Measure resistance between test pin No. 86 (ACP) at breakout box and ACP terminal at ACP sensor wiring harness connector. 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. Step 15) Check A/C Clutch Engagement  Turn ignition on. Reconnect ACP sensor. Turn A/C switch on while listening for A/C clutch engagement. If A/C clutch engages when A/C switch 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 ignition is turned on, ensure system has correct refrigerant charge. Service A/C system if necessary. If A/C system has correct refrigerant charge, replace PCM and repeat QUICK TEST .
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 15) to step 18). No test procedures have been omitted.
14. Step 18) Check Wiring Harness & Sensor  With scan tester connected, turn ignition on. Access ACP V PID. While observing ACP V PID, lightly tap on ACP sensor to simulate road shock. Wiggle sensor connector and wiring harness. A fault is indicated by a sudden change of voltage. If fault is indicated, isolate and repair as necessary. If no faults are indicated, go to CIRCUIT TEST Z.
    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.
15. Step 20) DTC P1463  This code indicates PCM has detected that ACP sensor did not detect sufficient change in A/C system pressure when A/C switch was turned on. Possible causes for this code are as follows:
    • A/C system mechanical malfunction.
    • A/C system electrical malfunction (non-EEC related).
    • A/C clutch continuous engagement.
    • ACP V or VREF open circuit.
    • Faulty ACP V sensor.

    Turn A/C and defroster off. Start engine and allow to idle. Attempt to disengage A/C clutch. If A/C clutch disengages, go to next step. If A/C clutch does not disengage, repair or replace A/C compressor.

16. Step 21) Check Power & Ground To A/C Clutch  Turn ignition off. Disconnect A/C cycling switch. Connect jumper wire between A/C cycling switch connector terminals. Disconnect A/C clutch. Connect non-powered test light to A/C clutch connector terminals. Start engine and allow to idle. Turn A/C switch on. Monitor test light for 15 seconds. Turn ignition off. If test light comes on or A/C can be heard clicking, fault mechanical, fault is mechanical and EEC testing is complete.