On Board Diagnostics II PCED

1999 PCED On Board Diagnostics II

SECTION 5: Pinpoint Tests

KM: WOT A/C Cutoff Relay, A/C Circuits

KM1 KOEO/KOER DTC P1460: VERIFY ACCS PID IS OFF

Note: Verify A/C and defrost were off during KOEO/KOER Self-Tests. If the vehicle is not equipped with A/C, the WOT A/C Cutoff (WAC) circuit is not used and the DTC P1460 can be ignored.

Start engine.
A/C and defroster off.
Access ACCS PID.

Is the ACCS PID off?

Yes	No
KEY OFF. GO to KM2 .	GO to KM22 to check A/C circuits for short to power.

KM2 CHECK VPWR VOLTAGE TO WOT A/C CUTOFF RELAY

Disconnect WOT A/C cutoff relay.
Key on, engine off.
Measure VPWR circuit voltage at the WOT A/C cutoff relay harness connector.

Is voltage greater than 10.5 volts?

Yes	No
KEY OFF. GO to KM3 .	For LS6/LS8 : GO to Pinpoint Test Step B5 . All others : REPAIR open circuit. START engine. Turn A/C on, WAIT 15 seconds. A/C off. Key off. RERUN Quick Test.

KM3 CHECK WOT A/C CUTOFF RELAY

Refer to pin numbers molded on WOT A/C cutoff relay. There will be either a Pin 1 or Pin 85.
Measure resistance between either Pin 1 or Pin 85 and all other pins of the WOT A/C cutoff relay. One measurement must be between 40 and 120 ohms, with the other measurements being greater than 10,000 ohms.

Are all resistance checks OK?

Yes	No
GO to KM4 .	REPLACE WOT A/C cutoff relay. START engine. TURN A/C on, WAIT 15 seconds. A/C off. Key off. RERUN Quick Test.

KM4 CHECK WOT A/C CUTOFF (WAC) CIRCUIT FOR SHORT TO POWER IN HARNESS

Disconnect PCM.
Key on, engine off.
Measure voltage between WAC circuit at WOT A/C cutoff relay vehicle harness connector and ground.

Is voltage less than 1.0 volt?

Yes	No
KEY OFF. GO to KM5 .	REPAIR short circuit. START engine. Turn A/C on, WAIT 15 seconds. A/C off. Key off. RERUN Quick Test.

KM5 CHECK WAC CIRCUIT FOR SHORT TO GROUND IN HARNESS

Disconnect scan tool from DLC.
Measure resistance between WAC circuit at WOT A/C cutoff relay vehicle harness connector and ground.

Is resistance greater than 10,000 ohms?

Yes	No
GO to KM6 .	REPAIR short circuit. START engine. Turn A/C on, WAIT 15 seconds. A/C off. Key off. RERUN Quick Test.

KM6 CHECK WAC CIRCUIT FOR OPEN IN HARNESS

Note: Refer to the PCM pin numbers at the beginning of this pinpoint test.

Measure resistance of WAC circuit between PCM harness connector and the WOT A/C cutoff relay harness connector.

Is resistance less than 5.0 ohms?

Yes	No
REPLACE PCM (refer to Section 2 , Flash EEPROM). START engine. Turn A/C on, WAIT 15 seconds. A/C off. Key off. RERUN Quick Test.	REPAIR open circuit. START engine. Turn A/C on, WAIT 15 seconds. A/C off. Key off. RERUN Quick Test.

KM8 LACK OF COOLING (A/C)/A/C NOT FUNCTIONING: CHECK FOR VOLTAGE TO A/C CLUTCH

Note: If the A/C clutch will engage, follow the "Yes" Action To Take of this test step. If not, or unsure, continue with this test step.

Key off.
Disconnect A/C cycling switch.
Install a jumper wire in the A/C cycling switch harness connector (to complete the circuit).
Disconnect A/C clutch.
Connect digital multimeter between the power pin and ground pin at the A/C clutch vehicle harness connector.
Start engine.
Turn A/C on, wait 15 seconds.
Check voltage reading.
After testing, turn key off and reconnect A/C clutch.

Was voltage greater than 10.5 volts?

Yes	No
REMOVE jumper. RECONNECT A/C cycling switch. For Contour/Mystique/ Cougar with symptom "poor A/C system performance in hot ambient temperatures": GO to KM55 to check A/C high pressure switch input to PCM. All others: GO to the Climate Control System - General Information Section 412-00 in the Workshop Manual to diagnose symptom.	No voltage to A/C clutch. GO to KM9 .

KM9 CHECK ACCS INPUT TO PCM WITH A/C ON

A/C cycling switch disconnected and jumper wire installed in the harness connector.
Start engine.
A/C on.
Access and view ACCS PID.
After testing, remove jumper reconnect A/C cycling switch and turn key OFF.

Was the ACCS PID "ON"?

Yes	No
GO to KM15 .	The PCM is not receiving the ACCS signal, and as a result will not allow the A/C to turn on. GO to KM10 .

KM10 ACCS PID OFF WITH A/C ON: CHECK FOR VOLTAGE TO A/C CYCLING SWITCH

Key on, engine off.
Disconnect A/C cycling switch.
A/C demand switch to A/C on.
Measure voltage at the A/C demand switch side of the A/C cycling switch harness connector.

Is voltage greater than 10.5 volts?

Yes	No
KEY OFF. GO to KM11 .	KEY OFF. GO to the Climate Control System, General Information Section 412-00 in the Workshop Manual to check A/C demand switch operation, applicable fuses, wiring to A/C cycling switch or other checks as directed.

KM11 CHECK IF A/C CYCLING SWITCH CONTACTS ARE CLOSED

Measure resistance of the A/C cycling switch contacts at the A/C cycling switch connector.

Is resistance less than 5.0 ohms?

Yes	No
RECONNECT A/C cycling switch. GO to KM12 .	GO to the Climate Control System, General Information Section 412-00 in the Workshop Manual to check for causes of A/C cycling switch being open (such as low refrigerant charge). REPAIR as necessary.

KM12 CHECK FOR VOLTAGE TO A/C HIGH PRESSURE SWITCH FROM A/C DEMAND SWITCH

Disconnect A/C high pressure switch.
Key on, engine off.
A/C on.
Measure voltage at the "from A/C demand switch/A/C cycling switch" pin of the A/C high pressure switch harness connector.

Is voltage greater than 10.5 volts?

Yes	No
KEY OFF. GO to KM13 .	REPAIR open between A/C cycling switch and A/C high pressure switch.

KM13 CHECK CONTINUITY OF A/C HIGH PRESSURE SWITCH HIGH PRESSURE CONTACTS

Measure resistance of the A/C high pressure switch high pressure contacts (these are the normally closed contacts).

Is resistance less than 5.0 ohms?

Yes	No
RECONNECT A/C high pressure switch. GO to KM14 .	Go to the Climate Control System, General Information Section 412-00 in the Workshop Manual to check for overpressurized A/C system, etc. If OK, REPLACE A/C high pressure switch (REFER to instructions in Climate Control System, General Information Section 412-00 in Workshop Manual).

KM14 CHECK ACCS CIRCUIT VOLTAGE TO PCM

Disconnect PCM.
Key on.
A/C ON.
Measure voltage at PCM harness connector pin 41.

Is voltage greater than 10.5 volts?

Yes	No
REPLACE PCM (refer to Section 2 , Flash EEPROM).	REPAIR open circuit between the A/C high pressure switch and PCM.

KM15 NO/LOW VOLTAGE TO A/C CLUTCH (ACCS PID ON WITH A/C ON): CHECK A/C DEMAND SWITCH VOLTAGE TO WOT A/C CUTOFF RELAY

Key off.
Disconnect WOT A/C cutoff relay.
Key on.
A/C demand switch to A/C on.
Measure voltage at the A/C demand switch input pin at the WOT A/C cutoff relay harness connector.

Is voltage greater than 10.5 volts?

Yes	No
KEY OFF. A/C off. For Contour/Mystique/Cougar (w/o returnless fuel system): GO to KM35 . For all others: GO to KM16 .	REPAIR open in A/C demand circuit between WOT A/C cutoff relay and ACCS circuit splice to PCM.

KM16 CHECK A/C CLUTCH PWR AND A/C CLUTCH GROUND CIRCUITS FOR OPEN IN HARNESS

Disconnect A/C clutch.
Disconnect scan tool from DLC.
Measure resistance of the A/C clutch PWR circuit between the WOT A/C cutoff relay harness connector and the A/C clutch harness connector.
Measure resistance of the A/C clutch ground circuit between the A/C clutch harness connector and ground.

Is each resistance less than 5.0 ohms?

Yes	No
REPLACE WOT A/C cutoff relay.	REPAIR open circuit.

KM19 DTC P1464: CHECK ACCS PID

Note: Verify A/C and defrost were off during Self-Test. If A/C or defrost were on, turn off and rerun Self-Test.

Key on, engine off.
A/C and defrost off.
Access ACCS PID.

Is ACCS PID on?

Yes	No
GO to KM22 .	The ACCS PID indicates that the ACCS input to the PCM is low. VERIFY test results. With A/C and defrost off, RERUN Self-Test where P1464 was received.

KM20 A/C ALWAYS ON: CHECK FOR VOLTAGE AT A/C CLUTCH WITH A/C OFF

A/C and defroster OFF.
Disconnect A/C clutch.
Connect a digital multimeter between the power pin and ground pin at the A/C clutch harness connector.
Start engine.
Monitor voltage.
After testing, turn key off and reconnect A/C clutch.

Was voltage less than 2.0 volts?

Yes	No
The electrical portion of the A/C system is not at fault. GO to the Climate Control System, General Information Section 412-00 in the Workshop Manual.	A fault is indicated in the A/C electrical system. GO to KM21 .

KM21 CHECK ACCS INPUT TO PCM WITH A/C OFF

Key off.
Connect scan tool to data link connector.
Start engine.
A/C and defrost off.
Access ACCS PID (Powertrain Menu).

Is the ACCS PID "OFF"?

Yes	No
KEY OFF. For Contour/Mystique/Cougar (w/o returnless fuel system): GO to Pinpoint Test Step KM50 . All others: GO to the Climate Control System, General Information Section 412-00 in the Workshop Manual.	KEY OFF. GO to KM22 .

KM22 ACCS PID ON: DISCONNECT A/C CYCLING SWITCH AND CHECK IF ACCS PID TURNS OFF

Disconnect A/C cycling switch.
Key on, engine off.
Access ACCS PID.

Is ACCS PID off?

Yes	No
VERIFY operation of A/C demand switch (REFER to the Climate Control System, General Information Section 412-00 in the Workshop Manual). If OK, REPAIR short to power in A/C Demand circuit to A/C cycling switch.	KEY OFF. For applications without WOT A/C cutoff relay: GO to KM24 For Contour/Mystique/Cougar (w/o returnless fuel system): GO to KM45 . All others: GO to KM23 .

KM23 CHECK A/C CLUTCH PWR CIRCUIT FOR SHORT TO POWER IN HARNESS

Disconnect WOT A/C cutoff relay.
Key on, engine off.
Measure voltage between A/C Clutch PWR circuit in harness connector and ground.

Is voltage less the 1.0 volt?

Yes	No
KEY OFF. GO to KM24 .	REPAIR short circuit.

KM24 CHECK ACCS CIRCUIT FOR SHORT TO POWER IN HARNESS

Disconnect PCM.
Key on.
Measure voltage between PCM harness connector pin 41 and ground.

Is voltage less than 1.0 volt?

Yes	No
KEY OFF. For applications without WOT A/C cutoff relay: REPLACE PCM (refer to Section 2 , Flash EEPROM). All others: GO to KM25 .	REPAIR short circuit.

KM25 CHECK ACCS CIRCUIT VOLTAGE TO PCM WITH WOT A/C CUTOFF RELAY CONNECTED

Reconnect WOT A/C cutoff relay.
Key on.
Again, measure voltage between PCM harness connector pin 41 and ground.

Is voltage less than 1.0 volt?

Yes	No
REPLACE PCM (refer to Section 2 , Flash EEPROM).	REPLACE WOT A/C cutoff relay.

KM26 NO WOT A/C CUTOFF: DOES THE A/C TURN OFF WHEN THE A/C DEMAND SWITCH IS TURNED OFF?

Does the A/C turn off when the A/C demand switch is turned off?

Yes	No
GO to KM27 .	GO to KM20 .

KM27 CHECK IF A/C CUTS OFF DURING WOT

Start engine.
A/C on.
Initiate a brief Wide Open Throttle (WOT) and return to idle. Listen for the A/C clutch to disengage during the WOT, then re-engage a few seconds after returning to idle (a "click" sound will be heard when the clutch re-engages).

Note: If the clicking sound cannot be heard, disconnect the A/C clutch. With a test lamp connected between the A/C clutch PWR pin and ground pin of the A/C clutch vehicle harness connector, observe the test lamp while performing the brief WOT. The test lamp must go off during the brief WOT, then come back on a few seconds after returning to idle.

Repeat test, if necessary, to verify results.

Does the A/C clutch or test lamp operate as indicated?

Yes	No
KEY OFF. RECONNECT A/C clutch (if necessary). The WAC circuit is operating properly. At this time the A/C will cut-off during WOT.	GO to KM28 .

KM28 NO WOT A/C CUTOFF W/NO DTCs: CHECK WOT A/C CUTOFF RELAY

Reconnect A/C clutch and WOT A/C cutoff relay (if disconnected).
Key on, engine off.
Access Output Test Mode on Scan Tool.
A/C on.
While listening to the A/C clutch, command the outputs off and on a couple times.

Does the A/C clutch engage and disengage when the outputs are cycled off and on?

Yes	No
KEY OFF. The Electronic Engine Control system is operating properly. If symptom is intermittent, GO to Pinpoint Test Step Z1 . Otherwise, testing is complete. Key off. RETURN to Section 3 to service any other symptoms.	VERIFY that the A/C clutch was engaged during testing. If not, REPEAT test with clutch engaged. If clutch was engaged, REPLACE WOT A/C cutoff relay.

KM30 CONTINUOUS MEMORY DTC P1460: CHECK WAC CIRCUIT FOR INTERMITTENT CONCERNS

Note: If the vehicle is not equipped with A/C, the WAC circuit is not used and the P1460 can be ignored.

Note: Refer to the beginning of this pinpoint test for PCM pin numbers and to determine if relay is normally open or closed.

Key off.
For normally closed relays, disconnect A/C cycling switch. Install a jumper wire in the A/C cycling switch harness connector (to complete the circuit).
Key on, engine off.
A/C demand switch on.
Check WAC circuit for short to ground (open or short to power for normally closed relays) while completing the following (the A/C clutch will click on when a fault is detected):

Shake, wiggle and bend the WAC circuit between the PCM and the WOT A/C cutoff relay.
Lightly tap on the WOT A/C cutoff relay (to simulate road shock).

Is a fault indicated?

Yes	No
KEY OFF. ISOLATE fault and REPAIR as necessary. REMOVE jumper wire. COMPLETE PCM Reset to clear DTCs. START engine. Turn A/C on, WAIT 15 seconds. A/C off. Key off. RERUN Quick Test.	GO to KM31 .

KM31 CHECK WOT A/C CUTOFF CIRCUIT FOR INTERMITTENT CONCERNS

Key on, engine off.
For normally closed relays, jumper wire installed in A/C cycling switch.
A/C demand on.
Access Output Test Mode on scan tool.
For normally open relays :
Turn outputs on.
For normally closed relays :
Turn outputs off.
Check WAC circuit for open or short to power (short to ground for normally closed relays) while completing the following (the A/C clutch will click off when a fault is detected):

Shake, wiggle and bend the WAC circuit between the PCM and the WOT A/C cutoff relay.
Shake, wiggle and bend the VPWR circuit to the WOT A/C cutoff relay.
Lightly tap on the WOT A/C cutoff relay (to simulate road shock).

Key off, A/C off.

Is a fault indicated?

Yes	No
ISOLATE fault and REPAIR as necessary. REMOVE jumper wire. COMPLETE PCM Reset to clear DTCs. START engine. Turn A/C on, WAIT 15 seconds. A/C off. Key off. RERUN Quick Test.	Unable to duplicate or identify fault at this time. GO to Pinpoint Test Step Z1 .

KM35 CHECK NORMALLY CLOSED CONTACTS OF THE WOT A/C CUTOFF RELAY

Measure resistance of the normally closed contacts of the WOT A/C cutoff relay (Pins 3 and 4 of relay.)

Is resistance less than 5.0 ohms?

Yes	No
GO to KM36 .	REPLACE WOT A/C cutoff relay.

KM36 CHECK IGNITION RUN VOLTAGE TO A/C CLUTCH RELAY

Disconnect A/C Clutch relay (refer to pinpoint test schematic and, if available, the Wiring Diagram Manual).
Key on, engine off.
Measure ignition run circuit voltage at the A/C clutch relay harness connector.

Is voltage greater than 10.5 volts?

Yes	No
KEY OFF. GO to KM37 .	CHECK condition of related fuse. If OK, REPAIR open circuit. If fuse is damaged, verify ignition run circuit is not shorted to ground.

KM37 CHECK FOR OPEN GROUND CIRCUIT TO A/C CLUTCH RELAY

Measure resistance of the ground circuit between the A/C clutch relay harness connector and ground.

Is resistance less than 5.0 ohms?

Yes	No
GO to KM38 .	REPAIR open circuit.

KM38 CHECK A/C DEMAND CIRCUIT FOR OPEN BETWEEN WOT A/C CUTOFF RELAY AND A/C CLUTCH RELAY

Measure resistance of the A/C demand circuit between the WOT A/C cutoff relay and A/C clutch relay harness connectors.

Is resistance less than 5.0 ohms?

Yes	No
GO to KM39 .	REPAIR open circuit.

KM39 CHECK A/C CLUTCH PWR AND A/C CLUTCH GROUND CIRCUITS FOR OPEN IN HARNESS

Disconnect A/C clutch.
Disconnect scan tool from DLC.
Measure resistance of A/C clutch PWR circuit between A/C clutch relay and the A/C clutch harness connector.
Measure resistance of A/C clutch ground circuit between A/C clutch harness connector and ground.

Is each resistance less than 5.0 ohms?

Yes	No
REPLACE A/C Clutch relay.	REPAIR open circuit.

KM45 DISCONNECT A/C CLUTCH RELAY AND CHECK IF ACCS PID TURNS OFF

A/C high pressure switch disconnected.
Disconnect A/C clutch relay (refer to pinpoint test schematic and, if available, the Wiring Diagram Manual).
Key on, engine off.
Again, access ACCS PID.

Is ACCS PID now off?

Yes	No
KEY OFF. REPLACE A/C clutch relay.	KEY OFF. GO to KM46 .

KM46 CHECK A/C DEMAND CIRCUIT BETWEEN WOT A/C CUTOFF RELAY AND A/C CLUTCH RELAY FOR SHORT TO POWER

Disconnect WOT A/C cutoff relay.
Key on, engine off.
Measure voltage between the A/C demand to A/C clutch relay circuit at the WOT A/C cutoff relay harness connector and ground.

Is voltage less than 1.0 volt?

Yes	No
GO to KM47 .	REPAIR short to power.

KM47 CHECK ACCS PID WITH WOT A/C CUTOFF RELAY DISCONNECTED

Key on, engine off.
Again, access ACCS PID.

Is ACCS PID off?

Yes	No
REPLACE WOT A/C cutoff relay.	KEY OFF. GO to KM48 .

KM48 CHECK ACCS CIRCUIT TO PCM FOR SHORT TO POWER IN HARNESS

Disconnect PCM.
Key on.
Measure voltage between PCM harness connector pin 41 and ground.

Is voltage less than 1.0 volt?

Yes	No
REPLACE PCM (refer to Section 2 , Flash EEPROM).	REPAIR short to power.

KM50 VOLTAGE ALWAYS AT A/C CLUTCH (ACCS PID OFF): CHECK FOR A/C CLUTCH RELAY CONTACTS STUCK CLOSED

Disconnect A/C clutch.
Disconnect A/C clutch relay (refer to Pinpoint Test Schematic and, if available, the Wiring Diagram Manual).
Key on, engine off.
Again measure voltage between the A/C clutch PWR pin and ground pin at the A/C clutch harness connector.

Is voltage less than 2.0 volts?

Yes	No
REPLACE A/C clutch relay.	REPAIR A/C Clutch PWR circuit short to power.

KM55 CHECK A/C HIGH PRESSURE SWITCH MEDIUM PRESSURE CIRCUITS

Note: An A/C high pressure switch medium pressure circuit concern can result in the high speed cooling fan not coming on when the A/C refrigerant pressure becomes high. In hot ambient conditions, this may result in the refrigerant pressure continuing to increase until the A/C high pressure switch high pressure contacts open, shutting off the A/C until the pressure drops to an acceptable range.

Key off.
Disconnect A/C high pressure switch.
A/C off (to prevent chance of short circuits).
Connect a jumper wire between the A/C high pressure switch circuit and ground circuit at the A/C high pressure switch harness connector.
Start engine, wait 15 seconds.

Does the high speed fan come on?

Yes	No
KEY OFF. A/C high pressure switch medium pressure circuits are OK. REMOVE jumper. RECONNECT A/C high pressure switch. GO to the Climate Control System, General Information Section 412-00 in the Workshop Manual to diagnose symptom.	An A/C high pressure switch medium pressure circuit concern may exist. GO to KM56 .

KM56 CHECK FOR OPEN GROUND CIRCUIT TO A/C HIGH PRESSURE SWITCH

Key on, engine running.
Connect jumper wire between the A/C high pressure switch circuit at the A/C high pressure switch harness connector and the battery negative post.
Wait 15 seconds.

Does the high speed fan come on now?

Yes	No
KEY OFF. REPAIR open ground circuit to the A/C high pressure switch. REMOVE jumper wire. VERIFY a symptom no longer exists.	KEY OFF. REMOVE jumper wire. GO to KM57 .

KM57 CHECK FOR OPEN A/C HIGH PRESSURE SWITCH (ACPSW) CIRCUIT BETWEEN A/C HIGH PRESSURE SWITCH AND PCM

Disconnect PCM.
Measure resistance of the ACPSW circuit between the PCM harness connector pin 86 and the A/C high pressure switch harness connector.

Is resistance less than 5.0 ohms?

Yes	No
REPLACE PCM (refer to Section 2 , Flash EEPROM).	REPAIR open circuit.