Diagnostic Aids

Perform this test only when directed by QUICK TEST. Ambient air temperature must be at least 50°F (10°C) to receive valid input from IAT sensor. Engine coolant temperature must be greater than 50°F (10°C) to pass KOEO SELF-TEST and greater than 180°F (82°C) to pass KOER SELF-TEST. Voltage values in this test are based on a 5-volt VREF signal. Values may vary up to 15% due to sensor and VREF variations.

This circuit test is intended to diagnose the following components and circuits:

• Intake Air Temperature (IAT) sensor.
• Engine Coolant Temperature (ECT) sensor.
• Wiring harness circuits (IAT, ECT and SIG RTN).
• Powertrain Control Module (PCM).

To prevent replacing good components, ensure the following non-EEC areas or components are not cause of problem:

• Coolant level low.
• Cooling system, water pump or fan.
• Engine operating temperature.
• Engine oil level low.
• Thermostat.
• Air cleaner duct.
• Ambient temperature.

Fig 1: Temperature Sensor Circuits & Connector Terminal ID

1. 1) Code 21/116 Or 24/114  Code 21/116 (ECT) or 24/114 (IAT)indicates corresponding sensor is out of self-test range. Correct range for measurement is .3-3.7 volts. Check for following possible causes:
   • Low ambient temperature (less than 50°F).
   • Low coolant level.
   • Faulty harness connector.
   • Faulty sensor.
   • IAT sensor improperly mounted in air cleaner.

   If vehicle cannot be started, go to step 3). If vehicle stalls, go to CIRCUIT TEST S . Ensure upper radiator hose is hot and pressurized. Repeat QUICK TEST. If Code 21/116 or 24/114 is present, go to step 2). If none of these codes are present, service other codes as necessary.

2. 2) Check VREF Circuit Voltage At TP sensor  Turn ignition off. Disconnect Throttle Position (TP) sensor. Turn ignition on. Measure voltage at TP sensor wiring harness connector between VREF and SIG RTN. See Fig 2. If voltage is 4-6 volts, reconnect TP sensor and go to step 3). If voltage is not 4-6 volts, go to CIRCUIT TEST C .
3. 3) Check Temperature Sensor Resistance  Turn ignition off. Disconnect suspect sensor. Measure resistance between sensor signal circuit and SIG RTN circuit at sensor. If resistance is not within specification, replace suspected sensor. See ECT & IAT SENSOR SPECIFICATIONS  table. Reconnect wiring harness, and repeat QUICK TEST. If resistance is within specification, perform following step as applicable.
   • For diagnosing vehicles with ECT sensor and a no-start condition, DO NOT service Code 21/116 at this time. Go to CIRCUIT TEST AA .
   • For all others, go to step 4).
     ECT & IAT SENSOR SPECIFICATIONS
     
     

     Temperature °F (°C)	(1) Volts	(1) Ohms
     50 (10)	3.51	58,750
     68 (20)	3.07	27,300
     86 (30)	2.60	24,270
     104 (40)	2.13	16,150
     122 (50)	1.70	10,970
     140 (60)	1.33	7700
     158 (70)	1.33	7700
     176 (80)	0.78	3840
     194 (90)	0.60	2800
     212 (100)	0.46	2070
     (1) Values may vary by 15 percent.

     Fig 2: Identifying TP Sensor Wiring Harness Connector Terminals

     
4. 4)  Warm engine to normal operating temperature. Turn ignition off. Disconnect suspect sensor. Run engine at 2000 RPM for 2 minutes. Measure resistance between sensor signal circuit and SIG RTN circuit at temperature sensor. See ECT & IAT SENSOR SPECIFICATIONS  table. If resistance is within specification, replace PCM and repeat QUICK TEST. If sensor is not within specification, replace sensor and repeat QUICK TEST.
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 4) to step 10). No test procedures have been omitted.
5. 10) Code 51/118 Or 54/113: Induce Opposite Code (Code 61/117Or 64/112)  Code 51/118 (ECT) or 54/113 (IAT) indicates corresponding sensor signal is greater than self-test maximum. Maximum signal voltage for ECT and IAT sensor is 4.6 volts. Possible causes for excess voltage signals are:
   • Open circuit in wiring harness (IAT or ECT).
   • Faulty connection.
   • Faulty sensor.
   • Faulty PCM.

   Turn ignition off. Disconnect suspect temperature sensor. Connect a jumper wire between sensor SIG RTN terminal and SIG RTN terminal at temperature sensor wiring harness connector. Repeat QUICK TEST. If Code 61/117 or 64/112 is displayed, replace suspect sensor and repeat QUICK TEST. If Code 61/117 or 64/112 is not displayed, remove jumper wire and go to step 11).

6. 11) Check Continuity Of Sensor Signal & SIG RTN Circuits  Turn ignition off. Ensure suspect temperature sensor is disconnected. Disconnect PCM 60-pin connector. Check for damaged wiring, and repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance of sensor signal circuit between test pin No. 7 (ECT sensor) or test pin No. 25 (IAT sensor) at breakout box and sensor signal circuit terminal at sensor wiring harness connector. Also measure resistance between test pin No. 46 and SIG RTN circuit at sensor wiring harness connector. If both readings are less than 5 ohms, replace PCM and repeat QUICK TEST. If either reading is 5 ohms or more, repair open circuit. Remove breakout box and repeat QUICK TEST.
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 11) to step 20). No test procedures have been omitted.
7. 20) Code 61/117 Or 64/112: Induce Opposite Code (51/118 Or 54/113)  Code 61/117 (ECT) or 64/112 (IAT) indicates sensor signal is less than self-test minimum. Minimum signal for IAT and ECT sensor is 0.2 volt. Possible causes for this fault are:
   • Circuit grounded in wiring harness (IAT or ECT).
   • Faulty sensor.
   • Faulty PCM.
   • Faulty connection.

   Turn ignition off. Disconnect wiring harness connector from suspect sensor. Check for damaged wiring, and repair as necessary. Repeat KOEO SELF-TEST. If Code 51/118 or 54/113 is displayed, replace sensor and repeat QUICK TEST. If Code 51/118 or 54/113 is not displayed, go to step 21).

8. 21) Check VREF Circuit Voltage At TP Sensor  Turn ignition off. Disconnect wiring harness connector from suspect sensor. Disconnect TP sensor. Turn ignition on. Measure voltage between VREF and SIG RTN at TP sensor wiring harness connector. If voltage is not 4-6 volts, go to CIRCUIT TEST C . If voltage is 4-6 volts, connect TP sensor and go to step 22).
9. 22) Check Temperature Sensor Signal For Shorts To Ground  Turn ignition off. Disconnect suspect sensor. Disconnect PCM 60-pin connector. Inspect for damage and repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 7 (ECT) or 25 (IAT) and pins No. 40, 46 and 60. If any reading is less than 10,000 ohms, repair short circuit and repeat QUICK TEST. If all readings are 10,000 ohms or more, replace PCM and repeat QUICK TEST.
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 22) to step 90). No test procedures have been omitted.
10. 90) Continuous Memory Code 51/118, 54/113, 61/117 Or 64/112  A Continuous Memory Code 51/118 or 54/113 indicates sensor signal is greater than self-test maximum of 4.6 volts. Code is set during normal driving conditions. Continuous Memory Code 61/117 or 64/112 indicates sensor signal is less than self-test minimum of 0.2 volt. Code is set during normal driving conditions. Possible causes for these faults are:
    • Faulty sensor.
    • Open or grounded circuit in harness.
    • Faulty PCM.
    SENSOR CODES
    
    

    Sensor	Continuous Memory Code
    IAT	54/113 Or 64/112
    ECT	51/118 Or 61/117

    Enter KOEO wiggle test mode. See CONTINUOUS MONITOR MODE (WIGGLE TEST)  under QUICK TEST. Observe analog voltmeter or scan tester for indication of fault while tapping sensor lightly and wiggling sensor connector. If fault is not indicated, go to step 91). If fault is indicated, disconnect and inspect connector and terminals. If connector and terminals are okay, replace sensor, clear continuous memory and repeat QUICK TEST.

11. 91) Check EEC-IV Wiring Harness  While in CONTINUOUS MONITOR MODE (WIGGLE TEST) , observe analog voltmeter or scan tester while wiggling and bending wiring harness, a small section at a time, from sensor to cowl. Also check harness from cowl to PCM. If fault is indicated, isolate fault and repair as necessary. Clear continuous memory, and repeat QUICK TEST. If no fault is found, go to step 92).
12. 92) Inspect PCM & Wiring Harness Connectors  Turn ignition off. Disconnect PCM 60-pin connector. Inspect both connector and connector terminals for damage. If connectors or terminals are damaged, repair as necessary and repeat QUICK TEST. If connectors and terminals are okay and fault cannot be duplicated at this time, see SUMMARY in this article.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 92) to step 100). No test procedures have been omitted.
13. 100) Continuous Memory Code 338  A Continuous Memory Code 338 indicates cooling system has not reached normal operating temperature. Possible causes for this fault are:
    • Thermostat stuck open.
    • Coolant outlet gasket leak.
    • Water pump gasket leak.

    Repair cooling system as necessary. Clear continuous memory, and repeat QUICK TEST.

14. 101) Continuous Memory Code 339  A Continuous Memory Code 339 indicates cooling system has overheated. Possible causes for this fault are:
    • Coolant level low.
    • Thermostat stuck closed.
    • Coolant system clogged.
    • Radiator fins clogged.
    • Water pump damaged or worn.
    • Radiator cap damaged or worn.
    • Cooling fan defective or worn.

    Repair cooling system as necessary. Clear continuous memory, and repeat QUICK TEST.