Diagnostic Aids

WARNING: This page is about a different car, the 1994 Mercury Sable, 1994 Mercury Cougar, 1994 Lincoln Continental, 1994 Ford Thunderbird, and 1994 Ford Taurus. However, it is still accessible from the selected car via links, so may be relevant.

Electrical load inputs are used for idle speed control strategy so correct idle can be maintained regardless of electrical demands on engine. PCM uses 4 accessories to determine electrical load status: blower motor, headlights, rear window defroster, and daytime running lights (if equipped).

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

Blower (BLR) motor input circuit.
Daytime Running Lights (DRL) input circuit.
Headlight (HDL) input circuit.
Rear window Defroster (DEF) input circuit.
Powertrain Control Module (PCM).

SWITCH CIRCUIT LOGIC

Application	Switch Position	Voltage
Blower Motor	1 Or 2	10-17
Blower Motor	3 Or 4	Less Than 1.5
Daytime Running Lights	Off	10-17
Daytime Running Lights	On	Less Than 1.5
Headlights	Off	Less Than 1.5
Headlights	On	10-17
Rear Window Defroster	Off	10-17
Rear Window Defroster	On	Less Than 3.0

Fig 1: Electrical Load Input Ckt. (FE2 - All Models)

1) Isolate Faulty System If idle speed fault occurs when blower motor is on, go to step 10). If idle speed fault occurs when daytime running lights are on, go to step 20). If idle speed fault occurs when headlights are on, go to step 30). If idle speed fault occurs when rear window defroster is on, go to step 40).

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 1) to step 10). No test procedures have been omitted.

10) Check Blower Motor Switch (Low Speed) Turn ignition and all accessories off. Remove PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Turn ignition on. Turn climate control motor switch to low-speed position "1" or "2". Measure voltage between chassis ground and test pin No. 14 at breakout box. If voltage is not 10-17 volts, go to step 13). If voltage is 10-17 volts, go to next step.

11) Check Blower Motor Switch (High Speed) Turn ignition and all accessories off. Turn climate control motor switch to high-speed position "3" or "4". Turn ignition on. Measure voltage between chassis ground and test pin No. 14 at breakout box. If voltage is less than 1.5 volts, replace PCM and confirm idle speed fault has been corrected. If voltage is 1.5 volts or more, go to next step.

12) Check Blower Circuit For Short To Power Turn ignition off. Disconnect blower motor relay. Measure resistance between test pin No. 14 and test pins No. 37 and 57 at breakout box. If all readings are more than 10,000 ohms, check for damaged blower motor or relay. If any reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, and confirm idle speed fault has been corrected.

13) Check Blower Circuit Continuity Turn ignition off. Disconnect blower motor relay. Measure resistance between BLR terminal at power distributor box and test pin No. 14 at breakout box. If resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and confirm idle speed fault has been corrected. If resistance is less than 5 ohms, go to next step.

14) Check Blower Circuit For Short To Ground Turn ignition off. Disconnect blower motor relay. Measure resistance between test pin No. 14 and test pins No. 40, 46 and 60 at breakout box. If all readings are more than 10,000 ohms, check for damaged blower motor switch or relay. If any reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, and confirm idle speed fault has been corrected.

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 14) to step 20). No test procedures have been omitted.

20) Check DRL Circuit Voltage (Headlights On) Turn ignition and all accessories off. Remove PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Apply parking brake. Turn ignition on. Turn headlights on. Turn accessories off. Measure voltage between chassis ground and test pin No. 42 at breakout box. If voltage is not 10-17 volts, go to step 23). If voltage is 10-17 volts, go to next step.

21) Check DRL Circuit Voltage (Headlights Off) Turn headlights off. Release parking brake. Turn ignition on. Measure voltage between chassis ground and test pin No. 42 at breakout box. If voltage is less than 1.5 volts, replace PCM. Remove breakout box and confirm idle speed fault has been corrected. If voltage is 1.5 volts or more, go to next step.

22) Check DRL Circuit For Short To Power Turn ignition off. Ensure PCM is disconnected. Disconnect daytime running lights relay. Measure resistance between test pin No. 42 and pins No. 37 and 57 at breakout box. If all readings are more than 10,000 ohms, check daytime running lights module for malfunction. If any reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, and confirm idle speed fault has been corrected.

23) Check DRL Circuit Continuity Turn ignition off. Disconnect daytime running lights relay. Measure resistance between DRL relay connector and test pin No. 42 at breakout box. If resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and confirm idle speed fault has been corrected. If resistance is less than 5 ohms, go to next step.

24) Check DRL Circuit For Short To Ground Turn ignition off. Measure resistance between test pin No. 42 and test pins No. 40, 46 and 60 at breakout box. If all readings are more than 10,000 ohms, check daytime running lights module for malfunction. If any reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, and confirm idle speed fault has been corrected.

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 24) to step 30). No test procedures have been omitted.

30) Check Headlight Circuit Voltage (Headlights Off) Turn ignition off. Remove PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Turn all accessories off. Turn ignition on. Measure voltage between chassis ground and test pin No. 45 at breakout box. If voltage is 1.5 volts or more, go to step 34). If voltage is less than 1.5 volts, go to next step.

31) Check Headlight Circuit Voltage (Headlights On) Turn all accessories off. Turn ignition on. Turn headlights on. Measure voltage between chassis ground and test pin No. 45 at breakout box. If voltage is 10-17 volts, replace PCM. Remove breakout box and confirm idle speed fault has been corrected. If voltage is not 10-17 volts, go to next step.

32) Check HDL Circuit Continuity Turn ignition off. Disconnect headlight relay. Measure resistance between HDL terminal at power distribution box and test pin No. 45 at breakout box. If resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and confirm idle speed fault has been corrected. If resistance is less than 5 ohms, go to next step.

33) Check HDL Circuit For Short To Ground Turn ignition off. Disconnect headlight relay. Measure resistance between test pin No. 45 and test pins No. 40, 46 and 60 at breakout box. If all readings are more than 10,000 ohms, check headlight switch for malfunction. If any reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, and confirm idle speed fault has been corrected.

34) Check HDL Circuit For Short To Power Turn ignition off. Disconnect headlight relay. Measure resistance between test pin No. 45 and test pins No. 37 and 57 at breakout box. If all readings are more than 10,000 ohms, check headlight switch for malfunction. If any reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, and confirm idle speed fault has been corrected.

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 34) to step 40). No test procedures have been omitted.

40) Check DEF Circuit Voltage (Defrost Off) Turn ignition off. Turn all accessories off. Remove PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Turn ignition on. Measure voltage between chassis ground and test pin No. 15 at breakout box. If voltage is 10-17 volts, go to next step. If voltage is not 10-17 volts, go to step 43).

41) Check DEF Circuit Voltage (Defrost On) Turn ignition on. Turn rear window defroster on. Measure voltage between chassis ground and test pin No. 15 at breakout box. If voltage is less than 3 volts, replace PCM. Remove breakout box and confirm idle speed fault has been corrected. If voltage is 3 volts or more, go to next step.

42) Check DEF Circuit For Short To Power Turn ignition off. Disconnect rear window defroster relay. Measure resistance between test pin No. 15 and test pins No. 37 and 57 at breakout box. If all readings are more than 10,000 ohms, check DEF switch or relay for malfunction. If any reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, and confirm idle speed fault has been corrected.

43) Check DEF Circuit Continuity Turn ignition off. Disconnect rear window defroster switch. Measure resistance between DEF terminal at power distribution box and test pin No. 15 at breakout box. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and confirm idle speed fault has been corrected.

44) Check DEF Circuit For Short To Ground Turn ignition off. Disconnect rear window defroster relay. Measure resistance between test pin No. 15 and test pins No. 40, 46 and 60 at breakout box. If all readings are more than 10,000 ohms, check DEF switch and relay circuit for malfunction. If any reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, and confirm idle speed fault has been corrected.