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Diagnostic Aids

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

Perform this test when directed by QUICK TEST, or if directed by other test procedures. This CIRCUIT TEST is intended to diagnose:

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 Circuit
G96I29130
  1. 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.
  2. 10) Check Blower Motor Switch (Low Speed)  Turn ignition and all accessories off. Remove PCM 104-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (014-000950), 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. 10 at breakout box. If voltage is not 10-17 volts, go to step 13). If voltage is 10-17 volts, go to next step.
  3. 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. 10 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.
  4. 12) Check Blower Circuit For Short To Power  Turn ignition off. Disconnect high speed blower motor relay connector. Relay is located behind right side of instrument panel on blower assembly. Measure resistance between test pin No. 10 and test pins No. 71 and 91 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.
  5. 13) Check Blower Circuit Resistance  Turn ignition off. Disconnect blower motor relay. Measure resistance between BLR terminal at power distribution box and test pin No. 10 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.
  6. 14) Check Blower Circuit For Short To Ground  Turn ignition off. Disconnect high speed blower motor relay. Measure resistance between test pin No. 10 and test pins No. 23, 76 and 91 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.
  7. 20) Check DRL Circuit Voltage (Headlights On)  Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (014-000950), leaving PCM disconnected. Apply parking brake. Turn ignition on. Turn headlights on. Turn accessories off. Measure voltage between chassis ground and test pin No. 14 at breakout box. If voltage is not 10-17 volts, go to step 23). If voltage is 10-17 volts, go to next step.
  8. 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. 14 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.
  9. 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. 14 and test pins No. 71 and 97 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.
  10. 23) Check DRL Circuit Resistance  Turn ignition off. Disconnect daytime running lights relay. Measure resistance between DRL circuit terminal at DRL wiring harness connector 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.
  11. 24) Check DRL Circuit For Short To Ground  Turn ignition off. Measure resistance between test pin No. 14 and test pins No. 23, 76 and 91 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.
  12. 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 (014-000950), leaving PCM disconnected. Turn all accessories off. Turn ignition on. Measure voltage between chassis ground and test pin No. 49 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.
  13. 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. 49 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.
  14. 32) Check HDL Circuit Resistance  Turn ignition off. Disconnect headlight relay. Relay is located in engine compartment relay box. Measure resistance between HDL circuit terminal at power distribution box and test pin No. 49 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.
  15. 33) Check HDL Circuit For Short To Ground  Turn ignition off. Disconnect headlight relay. Measure resistance between test pin No. 49 and test pins No. 23, 76 and 91 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.
  16. 34) Check HDL Circuit For Short To Power  Turn ignition off. Disconnect headlight relay. Measure resistance between test pin No. 49 and test pins No. 71 and 97 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.
  17. 40) Check Rear Window Defroster  Turn ignition off. Disconnect rear window defroster coil connector. Turn ignition on. Using DVOM, measure voltage between coil connector and defroster coil. If voltage is 10-127 volts when defroster on and less than one volt with defroster off, go to next step. If voltage is not as specified, repair rear window defroster.
  18. 41) Check DEF Circuit Voltage (Defrost Off)  Turn ignition off. Turn all accessories off. Remove PCM 104-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (014-000950), leaving PCM disconnected. Turn ignition on. Measure voltage between chassis ground and test pin No. 66 at breakout box. If voltage is 10-17 volts, go to next step. If voltage is not 10-17 volts, go to step 44).
  19. 42) Check DEF Circuit Voltage (Defrost On)  Turn ignition on. Turn rear window defroster on. Measure voltage between chassis ground and test pin No. 66 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.
  20. 43) Check DEF Circuit For Short To Power  Turn ignition off. Disconnect rear window defroster relay. Relay is located in left side of trunk. Measure resistance between test pin No. 66 and test pins No. 71 and 97 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.
  21. 44) Check DEF Circuit Resistance  Leave ignition off and rear window defroster switch disconnected. Measure resistance between DEF circuit terminal at power distribution box connector and test pin No. 23 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.
  22. 45) Check DEF Circuit For Short To Ground  Leave ignition off and rear window defroster switch disconnected. Measure resistance between test pin No. 66 and test pins No. 23, 76 and 91 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.
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