Diagnostic Aids

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

Blower motor input circuit.
Daytime Running Lights (DRL) input circuit.
Headlight input circuit.
Rear window defrost input circuit.
ECA.

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

Fig 1: Electrical Load Input Circuit

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 ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Turn ignition on. Turn climate control motor switch to low-speed position "1" or "2". Measure voltage between test pin No. 14 at breakout box and chassis ground. If voltage is not 10-17 volts, go to step 13). If voltage is 10-17 volts, go to step 11).

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 test pin No. 14 at breakout box and chassis ground. If voltage is less than 1.5 volts, replace ECA and confirm idle speed fault has been corrected. If voltage is 1.5 volts or more, go to step 12).

12) Check Blower Circuit For Short To Power Turn ignition off. Disconnect blower motor relay. Measure resistance between test pin No. 14 and pins No. 37 and 57 at breakout box. If resistance is more than 10,000 ohms, check for damaged blower motor or relay. If resistance is 10,000 ohms or less, repair short circuit.

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. If resistance is less than 5 ohms, go to step 14).

14) 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. 40, 46 and 60 at breakout box. If resistance is more than 10,000 ohms, check for damaged blower motor or relay. If resistance is 10,000 ohms or less, repair short circuit.

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 ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Apply parking brake. Turn ignition on. Turn headlights on. Measure voltage between test pin No. 42 at breakout box and chassis ground. If voltage is not 10-17 volts, go to step 23). If voltage is 10-17 volts, go to step 21).

21) Check DRL Circuit Voltage (Headlights Off) Turn headlights off. Release parking brake. Turn ignition on. Measure voltage between test pin No. 42 at breakout box and chassis ground. If voltage is less than 1.5 volts, replace ECA and confirm idle speed fault has been corrected. If voltage is 1.5 volts or more, go to step 22).

22) Check DRL Circuit For Short To Power Turn ignition off. Disconnect DRL relay. Measure resistance between test pin No. 42 and pins No. 37 and 57 at breakout box. If resistance is more than 10,000 ohms, check daytime running lights module for malfunction. If resistance is 10,000 ohms or less, repair short circuit 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 and confirm idle speed fault has been corrected. If resistance is less than 5 ohms, go to step 24).

24) Check DRL Circuit For Short To Power Turn ignition off. Disconnect daytime running lights relay. Measure resistance between test pin No. 42 and test pins No. 40, 46 and 60 at breakout box. If resistance is more than 10,000 ohms, check daytime running lights module for malfunction. If resistance is 10,000 ohms or less, repair short circuit 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 and all accessories off. Remove ECA 60-pin connector, and inspect it for damaged terminals. Repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Turn ignition on. Measure voltage between test pin No. 45 at breakout box and chassis ground. If voltage is 1.5 volts or more, go to step 34). If voltage is less than 1.5 volts, go to step 31).

31) Check Headlight Circuit Voltage (Headlights On) Turn all accessories off. Turn ignition on. Turn headlights on. Measure voltage between test pin No. 45 at breakout box and chassis ground. If voltage is 10-17 volts, replace ECA and confirm idle speed fault has been corrected. If voltage is not 10-17 volts, go to step 32).

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 and confirm idle speed fault has been corrected. If resistance is less than 5 ohms, go to step 33).

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 each resistance is more than 10,000 ohms, check headlight switch for malfunction. If any circuit resistance is 10,000 ohms or less, repair short circuit 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 pins No. 37 and 57 at breakout box. If resistance is more than 10,000 ohms, check headlight switch for malfunction. If resistance is 10,000 ohms or less, repair short circuit 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 ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Turn ignition on. Measure voltage between test pin No. 15 at breakout box and chassis ground. If voltage is 10-17 volts, go to step 41). 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 test pin No. 15 at breakout box and chassis ground. If voltage is less than 3 volts, replace ECA and confirm idle speed fault has been corrected. If voltage is 3 volts or more, go to step 42).

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 resistance is more than 10,000 ohms, check DEF switch or relay for malfunction. If resistance is 10,000 ohms or less, repair short circuit 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 step 44). If resistance is 5 ohms or more, repair open circuit 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 each circuit resistance is more than 10,000 ohms, check DEF switch and relay circuit for malfunction. If any circuit resistance is 10,000 ohms or less, repair short circuit and confirm idle speed fault has been corrected.