Diagnostic Aids
WARNING: This page does not describe the selected car, but rather 26 other vehicles, including the 1999 Mercury Tracer, 1999 Mercury Sable, 1999 Mercury Mystique, 1999 Mercury Mountaineer, and 1999 Mercury Grand Marquis. However, it is still accessible from the selected car via links, so may be relevant.
Perform this test when instructed during QUICK TEST or if directed by other test procedures. This test is used to diagnose the following:
- Wiring harness circuits (ACCS, ACPSW, VPWR and WAC). See Fig 1-Fig 5 .
- Faulty Wide Open Throttle (WOT) A/C cutoff relay.
- Faulty Powertrain Control Module (PCM).
Fig 2: Identifying WAC Circuits & Connector Terminals (Crown Victoria, Expedition, Grand Marquis, Navigator, Pickup F150 & F250 Light-Duty)
- 1) KOEO & KOER DTC P1460: Verify ACCS PID Is Off
These DTCs indicate a WAC circuit fault or A/C was on during self-test. Possible causes are:- A/C on during self-test.
- Open or shorted circuit.
- Faulty WOT A/C cutoff relay.
- Faulty PCM.
Ensure A/C and defroster were off during KOEO ON-DEMAND SELF-TEST and KOER ON-DEMAND SELF-TEST. If vehicle is not equipped with A/C, ignore P1460. If A/C or defroster was on during self-test, turn system off and repeat self-test. If vehicle is equipped with A/C, start engine and allow to idle. Using scan tool, select ACCS PID. If PID value indicates OFF, go to next step. If PID value indicates ON, go to step 22).
- 2) Check VPWR Circuit
Turn ignition off. Disconnect WOT A/C cutoff relay connector. Turn ignition on. Measure voltage between VPWR terminal at WOT A/C cutoff relay wiring harness connector and chassis ground. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, repair open in VPWR circuit. - 3) Check WOT A/C Cutoff Relay
Turn ignition off. On WOT A/C relays that terminals are numbered 1-5, measure resistance between relay terminal No. 1 and all other relay terminals. Resistance should be 40-120 ohms between terminals No. 1 and 2 and more than 10,000 ohms between terminal No.1 and other relay terminals. On WOT A/C relays that terminals are numbered 30, 85, 86, 87 and 87A, measure resistance between relay terminal No. 85 and all other relay terminals. Resistance should be 40-120 ohms between terminals No. 85 and 86 and more than 10,000 ohms between terminal No. 85 and other relay terminals. On both relays, if resistance is as specified, go to next step. If resistance is not as specified, replace relay. - 4) Check WOT A/C Cutoff (WAC) Circuit
Turn ignition off. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Turn ignition on. Measure voltage between WAC terminal at A/C cutoff relay wiring harness connector and chassis ground. If voltage is less than one volt, go to next step. If voltage is one volt or more, repair short to power in WAC circuit. - 5) Check WAC Circuit For Short To Ground
Turn ignition off. Disconnect scan tool. Measure resistance between WAC terminal at A/C cutoff relay wiring harness connector and chassis ground. If resistance is more than 10,000 ohms, go to next step. If resistance is 10,000 ohms or less, repair short to ground in WAC circuit. - 6) Check For Open WAC Circuit
Measure resistance between PCM connector pin No. 69 (No. 70 on Contour 2.5L, Cougar 2.5L and Mystique 2.5L) and WAC terminal at WOT A/C cutoff relay wiring harness connector. If resistance is less than 5 ohms, replace PCM. If resistance is 5 ohms or more, repair open in WAC circuit.NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 6) to step 8). No test procedures have been omitted. - 8) Lack Of Cooling: A/C Not Functioning
Turn ignition off. Disconnect A/C cycling switch. Connect a jumper wire between A/C cycling switch wiring harness connector terminals. Disconnect A/C clutch. Connect a DVOM between power and ground terminals at A/C clutch wiring harness connector. Start engine. Turn A/C on and wait 15 seconds. If voltage is not more than 10.5 volts, go to next step. If voltage is more than 10.5 volts, turn ignition off. Reconnect all connectors. On Contour, Cougar and Mystique, go to step 55). On all other models, check and repair A/C system as necessary. - 9) Check ACCS PID Value
Ensure jumper wire is still connected between A/C cycling switch wiring harness connector terminals and A/C is on. Using scan tool, select ACCS PID from PID/DATA monitor menu. If PID value indicates ON, turn ignition off. Remove jumper wire. Reconnect A/C cycling switch, and go to step 15). If PID value indicates OFF, PCM is not receiving ACCS signal. Go to next step. - 10) Check For Voltage To A/C Cycling Switch
Turn ignition on. Disconnect A/C cycling switch. Turn A/C switch on. Measure voltage between A/C Demand Switch input terminal at A/C cycling switch wiring harness connector and chassis ground. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, check for fault in A/C demand switch, related fuses or related wiring harness. See appropriate article in AIR CONDITIONING & HEATING. - 11) Check A/C Cycling Switch Contacts
Turn ignition off. Measure resistance between A/C cycling switch terminals. If resistance is less than 5 ohms, reconnect A/C cycling switch and go to next step. If resistance is 5 ohms or more, check for low refrigerant charge. - 12) Check For Voltage To A/C High Pressure Switch
Disconnect A/C high pressure switch connector. Turn ignition and A/C switch on. Measure voltage between chassis ground and A/C demand switch input terminal at A/C high pressure switch wiring harness connector. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, check for open circuit between A/C cycling switch and A/C high pressure switch. Repair as necessary and verify symptom no longer exists. - 13) Check Continuity Of A/C High Pressure Switch Contacts
Turn ignition off. Measure resistance of high pressure contacts at A/C high pressure switch. If resistance is less than 5 ohms, reconnect A/C high pressure switch and go to next step. If resistance is 5 ohms or more, check for high pressure (refrigerant overcharge). Service A/C system as necessary. If A/C system pressure is okay, replace A/C high pressure switch. Verify symptom no longer exists. - 14) Check Voltage To PCM
Ensure ignition is off. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Turn ignition on. Turn A/C on. Measure voltage between PCM connector pin No. 41 (ACCS) and chassis ground. If voltage is 10.5 volts or less, repair open circuit between A/C high pressure switch and PCM. If voltage is more than 10.5 volts, replace PCM and verify symptom no longer exists. - 15) Check A/C Demand Switch Voltage
Turn ignition off. Disconnect WOT A/C cutoff relay. Turn ignition on. Turn A/C on. Measure voltage at A/C demand switch input terminal at WOT A/C cutoff relay wiring harness connector. If voltage is more than 10.5 volts, go to step 35) (Contour and Mystique) or go to next step (all other models). If voltage is 10.5 volts or less, repair open in A/C demand circuit between WOT A/C cutoff relay and ACCS circuit splice to PCM. Verify symptom no longer exists. - 16) Check A/C Clutch PWR & A/C Clutch Ground Circuits
Disconnect A/C clutch. Disconnect scan tool. Measure resistance of A/C clutch PWR circuit between WOT A/C cutoff relay wiring harness connector and A/C clutch wiring harness connector. Also measure resistance of A/C clutch ground circuit between A/C clutch wiring harness connector and ground. If both resistance readings are less than 5 ohms, replace WOT A/C cutoff relay. Verify symptom no longer exists. If any resistance reading is 5 ohms or more, repair open in appropriate circuit. Verify symptom no longer exists.NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 16) to step 19). No test procedures have been omitted. - 19) DTC P1464: Check ACCS PID
This DTC indicates ACCS input to PCM was high during self-test. Ensure A/C and defroster were off during KOEO ON-DEMAND SELF-TEST and KOER ON-DEMAND SELF-TEST. If A/C or defroster was on during self-test, turn system off and repeat self-test. Turn ignition on. Using scan tool, select ACCS PID. If PID value indicates ON, go to next step. If PID value indicates OFF, verify self-test results. Leave A/C and defroster off and repeat QUICK TEST . - 20) A/C Always On
Turn A/C and defroster off. Disconnect A/C clutch. Connect a DVOM between connect a DVOM between power and ground terminals at A/C clutch wiring harness connector. Start engine. If voltage is 2 volts or more, go to next step. If voltage is less than 2 volts, no fault is indicated at this time. If symptom still exists, check A/C system and repair as necessary. See appropriate article in AIR CONDITIONING & HEATING. - 21) Check ACCS PID
Turn A/C and defroster off. Start engine. Using scan tool, select ACCS PID. If PID value indicates ON, turn ignition off and go to next step. If PID value indicates OFF, go to step 50) (Contour and Mystique) or check A/C system operation (all other models). See appropriate article in A/C HEATING & SERVICE. - 22) ACCS PID Indicates ON
Ensure A/C and defroster are off. Turn ignition on. Using scan tool, select ACCS PID. If PID value indicates OFF, verify A/C demand switch operation. Repair as necessary. See appropriate article in A/C HEATING & SERVICE. If A/C demand switch operation is okay, repair short to power in A/C demand circuit to A/C cycling switch. If PID value indicates ON, proceed as follows: - 23) Check For Short To Power
Turn ignition off. Disconnect WOT A/C cutoff relay. Turn ignition on. Measure voltage between chassis ground and A/C clutch PWR terminal at WOT A/C cutoff relay wiring harness connector. If voltage is less than one volt, go to next step. If voltage is one volt or more, repair short to power in A/C clutch PWR circuit. Verify symptom no longer exists. - 24) Check ACCS Circuit For Short To Power
Turn ignition off. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Turn ignition on. Measure voltage between PCM connector pin No. 41 (ACCS) and chassis ground. If voltage is one volt or more, repair short to power in ACCS circuit. Verify symptom no longer exists. If voltage is less than one volt, proceed as follows:- On models without WOT A/C cutoff relay (Econoline 6.8L, F250 Super-Duty & F350 Super-Duty 5.4L), replace PCM.
- On all other models, go to next step.
- 25) Check ACCS Circuit Voltage To PCM
Turn ignition off. Reconnect WOT A/C cutoff relay. Turn ignition on. Measure voltage between PCM connector pin No. 41 (ACCS) and chassis ground. If voltage is one volt or more, replace WOT A/C cutoff relay and verify symptom no longer exists. If voltage is less than one volt, replace PCM and verify symptom no longer exists. - 26) No WOT A/C Cutoff
Check if A/C turns off when A/C demand switch is turned off. If A/C turns off, go to next step. If A/C does not turn off, go to step 20). - 27) Check If A/C Cuts During WOT
Start engine and turn A/C on. Briefly snap throttle to wide open position and return to idle. Listen for A/C clutch disengagement during WOT, then re-engages after a few seconds of returning to idle. A click noise will be heard when A/C re-engages. Repeat test several times. If A/C clicking noise cannot be heard, disconnect A/C clutch. Connect a test light between A/C clutch power and ground terminals at A/C clutch wiring harness connector. Again, briefly snap throttle to wide open position and return to idle. Test light should be off during WOT and on after a few seconds of returning to idle. If A/C clutch or test light operates as specified, WAC circuit is functioning properly at this time. If A/C clutch or test light does not operate as specified, go to next step. - 28) Check WOT A/C Cutoff Relay
Reconnect A/C clutch and WOT A/C cutoff relay. Turn ignition on. Using scan tool, access OUTPUT TEST MODE. Turn A/C on. While listening to A/C clutch, command outputs ON and OFF several times. If A/C clutch engages and disengages when outputs are cycled off and on, system is functioning properly. If symptom is intermittent, go to TEST Z . If A/C clutch does not operate as specified, replace WOT A/C cutoff relay. Verify symptom no longer exists.NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 28) to step 30). No test procedures have been omitted. - 30) Continuous Memory DTC P1460
This DTC indicates WOT A/C cutoff relay circuit failure. If vehicle is not equipped with A/C, disregard this DTC. Turn ignition off. On models with normally closed A/C cutoff relay (Contour, Cougar, Econoline 4.2L and Mystique), disconnect A/C cycling switch. Connect a jumper wire between terminals of A/C cycling switch wiring harness connector. On all models, turn ignition and A/C switch on. Check for indication of fault while performing the following:- Wiggle and bend WAC circuit between WOT A/C cutoff relay and terminal No. 69 (No. 70 on Contour 2.5L, Cougar 2.5L and Mystique 2.5L) at PCM.
- Lightly tap on WOT A/C cutoff relay to simulate road shock.
- Check connectors for clean tight connection.
Fault will be indicated by A/C clicking on. If any faults are found, isolate fault and repair as necessary. If no faults are found, go to next step.
- 31) Check For Intermittent
Ensure jumper wire is still connected between terminals of A/C cycling switch wiring harness connector. Using scan tool, access OUTPUT TEST MODE. Command all outputs off. Check for indication of fault while performing the following:- Wiggle and bend WAC circuit between terminal No. 69 at PCM and WOT A/C cutoff relay.
- Wiggle and bend VPWR circuit to WOT A/C cutoff relay.
- Lightly tap on WOT A/C cutoff relay to simulate road shock.
- Check connectors for clean tight connection.
Fault will be indicated by A/C clicking on. If any faults are found, isolate and repair as necessary. If no faults are found, fault cannot be duplicated at this time. Go to TEST Z .
NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 31) to step 35). No test procedures have been omitted. - 35) WOT A/C Cutoff Relay
Turn ignition off. Ensure WOT A/C cutoff relay is disconnected. Measure resistance between normally closed contacts (terminals No. 3 and 4) at WOT A/C cutoff relay. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, replace WOT A/C cutoff relay. Verify symptom no longer exists. - 36) Check Voltage To WOT A/C Cutoff Relay
Disconnect A/C clutch relay. Turn ignition on. Measure voltage between IGN RUN terminal at A/C clutch relay wiring harness connector and chassis ground. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, check condition of related fuse. If fuse is blown, check for short to ground. Repair as necessary. If fuse is okay, repair open in IGN RUN circuit. Verify symptom no longer exists. - 37) Check For Open Ground Circuit
Turn ignition off. Measure resistance of ground circuit between A/C clutch relay wiring harness connector and ground. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in ground circuit. - 38) Check For Open In A/C Demand Circuit
Measure resistance of A/C DEMAND circuit between WOT A/C cutoff relay wiring harness connector and A/C clutch relay wiring harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in A/C DEMAND circuit. - 39) Check A/C Clutch PWR & A/C Clutch Ground Circuits
Disconnect A/C clutch. Disconnect scan tool. Measure resistance of A/C clutch PWR circuit between A/C clutch relay wiring harness connector and A/C clutch wiring harness connector. Also measure resistance of A/C clutch ground circuit between A/C clutch wiring harness connector and ground. If both resistance readings are less than 5 ohms, replace A/C clutch relay. Verify symptom no longer exists. If any resistance reading is 5 ohms or more, repair open in appropriate circuit. Verify symptom no longer exists.NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 39) to step 45). No test procedures have been omitted. - 45) Check ACCS PID (Contour & Mystique)
Turn ignition off. Disconnect A/C high pressure switch. Disconnect A/C clutch relay. Turn ignition on. Using scan tool, select ACCS PID. If PID value indicates OFF, replace A/C clutch relay. Verify symptom no longer exists. If PID value indicates ON, go to next step. - 46) Check A/C Demand Circuit
Turn ignition off. Disconnect WOT A/C cutoff relay. Turn ignition on. Measure voltage of A/C demand-to-A/C clutch relay circuit (Violet wire) between WOT A/C cutoff relay wiring harness connector and ground. If voltage is less than one volt, go to next step. If voltage is one volt or more, repair short to power. Verify symptom no longer exists. - 47) Check ACCS PID With WOT A/C Cutoff Relay Disconnected
Using scan tool, select ACCS PID. If PID value indicates OFF, replace A/C clutch relay. Verify symptom no longer exists. If PID value indicates ON, go to next step. - 48) Check For Short To Power
Turn ignition off. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Turn ignition on. Measure voltage between ground and PCM connector pin No. 41. If voltage is less than one volt, replace PCM. Verify symptom no longer exists. If voltage is one volt or more, repair short to power in ACCS circuit. Verify symptom no longer exists.NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 48) to step 50). No test procedures have been omitted. - 50) Check A/C Clutch Relay
Turn ignition off. Disconnect A/C clutch. Disconnect A/C clutch relay. Turn ignition on. Measure voltage between A/C CLUTCH PWR terminal (Violet/Blue wire) at A/C clutch wiring harness connector and ground. If voltage is less than 2 volts, replace A/C clutch relay. If voltage is 2 volts or more, repair short to power in A/C CLUTCH PWR circuit. Verify symptom no longer exists.NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 50) to step 55). No test procedures have been omitted. - 55) Check A/C High Pressure Switch Circuits
Turn ignition off. Disconnect A/C high pressure switch. Turn A/C off. Connect a jumper wire between ACPSW terminal and ground terminal at A/C high pressure switch wiring harness connector. See Fig 6. Start engine and wait 15 seconds. If high speed fan does not turn on, go to next step. If high speed fan turns on, no problem is indicated at this time. Reconnect all components. If A/C related symptom still exists, see appropriate article in A/C HEATING & SERVICE. - 56) Check For Open Ground Circuit
Start engine and allow to idle. Connect a jumper wire between ACPSW terminal at A/C high pressure switch wiring harness connector and chassis ground. Wait 15 seconds. If high speed fan is still off, remove jumper wire and go to next step. If high speed fan is on, repair open ground circuit to A/C high pressure switch. Verify symptom no longer exists. - 57) Check For Open ACPSW Circuit
Turn ignition off. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure resistance of ACPSW circuit between PCM connector pin No. 86 and A/C high pressure switch wiring harness connector. If resistance is less than 5 ohms, replace PCM. Verify symptom no longer exists. If resistance is 5 ohms or more, repair open in ACPSW circuit. Verify symptom no longer exists.
NOTE:
To identify WOT A/C relay terminals, refer to numbers molded on relay. Two different numbered relays may be used. WOT A/C relay terminals may be numbered 1-5 or terminals may be numbered 30, 85, 86, 87 and 87A. On relays that are numbered 1-5, terminals for relay coil are terminals No. 1 and 2. On relays that are numbered 30, 85, 86, 87 and 87A, terminals for relay coil are terminals No. 85 and 86.