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Home >> Mazda >> 1999 >> B2500 TL, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 4 (Engine Controls - Self-Diagnostics - EEC-V - 6.8L (99S E Series & 99S F350 To F550)) >> System Tests >> Test DS: Air Conditioning Pressure (ACP) Sensor >> Diagnostic Aids

Diagnostic Aids

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

  1. 1) DTC P1461

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

    Turn ignition on. Using scan tool, select ACP V PID from PID/DATA monitor menu. If PID voltage is 4.9 volts or more, go to next step. If PID voltage is less than 4.9 volts, fault is intermittent. Go to step  18).

  2. 2) Check VREF & SIG RTN Circuit

    Turn ignition off. Disconnect ACP sensor connector. Turn ignition on. Measure voltage between SIG RTN and VREF terminals at ACP sensor wiring harness connector. See Fig 1. 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 .
    Fig 1: Identifying ACP Sensor Circuits & Connector Terminals
    G99A02099Courtesy of FORD MOTOR CO.

  3. 3) Induce Opposite Signal

    Turn ignition on. Using scan tool, select ACP V PID from PID/DATA monitor menu. If PID voltage is 4.9 volts or more, go to next step. If 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 .

  4. 4) Check ACP Circuit For Short To VREF

    Turn ignition off. Disconnect scan tool Data Link Connector (DLC). Disconnect PCM 104-pin connector. Measure resistance between ACP and VREF terminals at ACP sensor wiring harness connector. If resistance is more than 10,000 ohms, go to next step. If resistance is 10,000 ohms or less, 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. 5) Check ACP Circuit For Short To Power

    Turn ignition on. Measure voltage between ACP terminal at ACP sensor wiring harness connector and chassis ground. If voltage is less than one volt, go to next step (Escort and Tracer) or replace PCM (except Escort and Tracer). 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. 6) Check Circuit Resistance

    Turn ignition off. Leave ACP sensor disconnected. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure resistance between PCM connector pin No. 86 (ACP) 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 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 connector. Leave ACP sensor disconnected. Connect a jumper wire between PCM connector pins No. 86 and 91 (SIG RTN). Turn ignition on. Using scan tool, select ACP V PID from PID/DATA monitor menu. If 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 PID voltage is 4.9 volts or more or 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.
    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. 10) DTC P1462

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

    Turn ignition on. Using scan tool select ACP V PID. If PID voltage is .15 volt or less, go to next step. If PID voltage is more than .15 volt, fault is intermittent. Go to step  18).

  9. 11) Check VREF Circuit At ACP Sensor

    Turn ignition off. Disconnect ACP sensor connector. Turn ignition on. Measure voltage between SIG RTN and VREF terminals at ACP sensor wiring harness connector. 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 .

  10. 12) Induce Opposite Signal

    Turn ignition off. Connect a jumper wire between ACP and VREF terminals at ACP sensor wiring harness connector. Turn ignition on. Using scan tool, select ACP V PID from PID/DATA monitor menu.
    NOTE: If communication link error is displayed, remove jumper wire and go to next step.

    If PID voltage is 4 volts or less, go to next step. If PID voltage is more than 4 volts, replace ACP sensor. 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 Ground Or SIG RTN

    Turn ignition off. Disconnect scan tool Data Link Connector (DLC). Disconnect PCM 104-pin connector. Measure resistance between ACP and SIG RTN terminals at ACP sensor wiring harness connector. Also measure resistance between ACP terminal at ACP sensor wiring harness connector and negative battery terminal. If both resistance readings are more than 10,000 ohms, go to next step. If any resistance reading is 10,000 ohms or less, repair short circuit. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST .

  12. 14) Check ACP Circuit Resistance

    Measure resistance between PCM connector pin No. 86 (ACP) 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. 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, go to next step.

  14. 16) Check 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. 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 Wiring Harness & Sensor

    Turn ignition on. Using scan tool, select ACP V PID from PID/DATA monitor menu. 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 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, unable to duplicate fault at this time. Go to 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.

  16. 20) DTC P1463

    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 on. Possible causes for this fault are:
    • A/C system mechanical malfunction.
    • A/C system electrical malfunction (non-EEC related).
    • A/C clutch continuous engagement.
    • ACP or VREF open circuit.
    • Faulty ACP sensor.

    Turn A/C and defroster off. Start engine and allow to idle. Verify A/C clutch disengages. If A/C clutch disengaged, go to next step. If A/C clutch did not disengage, check A/C clutch circuit. See CLIMATE CONTROL (A/C ALWAYS ON) in TROUBLE SHOOTING - NO CODES - EEC-V article. Repair as necessary.

  17. 21) Check Power & Ground To A/C Clutch

    Turn ignition off. Disconnect A/C cycling switch. Connect a jumper wire between A/C cycling switch connector terminals. Disconnect A/C clutch. Connect non-powered test light between power and ground terminals at A/C clutch wiring 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, perform the following:

  18. 22) Check ACP V PID

    Start engine. Ensure A/C is off. Using scan tool, access ACP V PID from PID/DATA monitor menu. Note A/C V PID voltage reading. Monitor PID value and turn A/C on. Note PID voltage reading within 5 seconds of A/C clutch engagement and compare reading with PID reading noted previously. If PID voltage change is more than .3 volt, ACP sensor and PCM can detect change in A/C pressure. Check A/C system for proper operation and repair as necessary. If PID voltage change is not more than .3 volt, go to next step.

  19. 23) Check Refrigerant Charge

    Turn ignition off. Reconnect all components. Connect A/C manifold gauge set. With A/C off, note high pressure reading. Turn A/C on and within 5 seconds, note high pressure reading. If high pressure reading changes more than 30 psi (207 kPa), go to next step. If high pressure reading does not change more than 30 psi (207 kPa), service A/C system as necessary. Start engine and turn A/C on for 15 seconds. Turn A/C off and repeat QUICK TEST .

  20. 24) Check VREF Circuit At ACP Sensor

    Turn ignition off. Disconnect ACP sensor connector. Turn ignition on. Measure voltage between SIG RTN and VREF terminals at ACP sensor wiring harness connector. 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 .

  21. 25) Check ACP Circuit Resistance

    Turn ignition off. Disconnect PCM 104-pin connector. Measure resistance between PCM connector pin No. 86 (ACP) and ACP terminal at ACP sensor wiring harness connector. 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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