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Home >> Mazda >> 1999 >> B2500 SX, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 4 (Engine Controls - Self-Diagnostics - EEC-V - 6.8L (99S E Series & 99S F350 To F550)) >> System Tests >> Test DA: Temperature Sensor Test (IAT & ECT) >> Diagnostic Aids

Diagnostic Aids

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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 Intake Air Temperature (IAT) sensor. Engine coolant temperature must be more than 50°F (10°C) to pass KOEO SELF-TEST and more 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 percent due to sensor and VREF variations.

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

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

NOTE: On some models, IAT sensor is part of Mass Airflow (MAF) sensor assembly. If all 6 terminals of MAF sensor connector are being used, IAT sensor is integral to MAF sensor. See WIRING DIAGRAMS article.

  1. 1) DTC P1116

    This DTC indicates sensor is out of self-test range. Correct range for measurement is .3-3.7 volts. Check for following possible causes:
    • Low coolant level.
    • Faulty harness connector.
    • Faulty sensor.

    Start engine and run until engine is at normal operating temperature. If vehicle cannot be started, go to step  3). Ensure upper radiator hose is hot and pressurized. Repeat KOER ON-DEMAND SELF-TEST . If DTC P1116 is present, go to next step. If DTC P1116 is not present, engine was not at closed loop operating conditions. Repair any other DTCs that are present.

  2. 2) Check VREF Circuit Voltage At TP Sensor

    Turn ignition off. Disconnect Throttle Position (TP) sensor. Turn ignition on. Measure voltage between VREF and SIG RTN terminals at TP sensor wiring harness connector. See Fig 1 or Fig 2 . If voltage is 4-6 volts, reconnect TP sensor and go to next step. If voltage is not 4-6 volts, go to TEST C .

  3. 3) Check Temperature Sensor Resistance (KOEO)

    Turn ignition off. Disconnect ECT sensor. Measure resistance between ECT signal circuit terminal and SIG RTN terminal at ECT sensor wiring harness connector. See IAT & ECT SENSOR SPECIFICATIONS  table. See Fig 3. If resistance is not as specified, replace ECT sensor. If resistance is as specified, perform following step as applicable:
    • For diagnosing vehicles with ECT sensor related fault and a no-start condition, DO NOT service DTC P1116 at this time. Repair no-start condition. See TROUBLE SHOOTING - NO CODES - EEC-V article.
    • For diagnosing vehicles with cooling fan concerns or engine cooling concerns, DO NOT service DTC P1116 at this time. Service next DTC. If no other DTCs are present, identify symptom and repair as necessary. See TROUBLE SHOOTING - NO CODES - EEC-V article.
    • For diagnosing vehicles without a no-start condition, cooling fan concern or engine cooling concern, go to next step.
    Fig 1: Identifying Throttle Position (TP) Sensor Connector Terminals (Contour 2.0L, Cougar 2.0L & Mystique 2.0L)
    G96I29122Courtesy of FORD MOTOR CO.
    Fig 2: Identifying Throttle Position (TP) Sensor Connector Terminals (All Other Models)
    G96J29123Courtesy of FORD MOTOR CO.
    Fig 3: Identifying Temperature Sensor Circuits & Connector Terminals (Except Pickup - F150 Lightning)
    G99I02649Courtesy of FORD MOTOR CO.
    Fig 4: Identifying Temperature Sensor Circuits & Connector Terminals (Pickup - F150 Lightning)
    G99I02593Courtesy of FORD MOTOR CO.

  4. 4) Check Temperature Sensor Resistance (KOER)

    Reconnect all connectors. Start engine and operate at 2000 RPM for 2 minutes. Turn ignition off. Disconnect ECT sensor. Measure resistance between ECT signal circuit terminal and SIG RTN terminal at ECT sensor wiring harness connector. See IAT & ECT SENSOR SPECIFICATIONS  table. If resistance is as specified, replace PCM. If resistance is not as specified, replace ECT sensor.
    IAT & ECT SENSOR SPECIFICATIONS (1)

    Temperature °F (°C) Volts 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) 1.02 5370
    176 (80) 0.78 3840
    194 (90) 0.60 2800
    212 (100) 0.46 2070
    (1) Values may vary by 15 percent.
    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) DTC P0118 Or P0113: Check For Short To VPWR Or VREF

    DTC P0118 (ECT) or P0113 (IAT) indicate corresponding sensor signal is more 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 sensor connector. Turn ignition on. Using scan tool, select ECT V or IAT V PID from PID/DATA monitor. If PID value is more than 4.8 volts, go to step  13). If PID value is 4.8 volts or less, go to next step.

  6. 11) Induce Opposite DTC (117 Or 112)

    Turn ignition off. Disconnect suspect temperature sensor. Connect a jumper wire between signal circuit (ECT or IAT) terminal and SIG RTN terminal at suspect sensor wiring harness connector. With scan tool installed, turn ignition on.
    NOTE: If communication link error is displayed, remove jumper wire and go to step  13).

    Using scan tool, select ECT V or IAT V PID from PID/DATA monitor. If PID value is less than .2 volt, replace suspect sensor. If PID value is .2 volt or more, remove jumper wire and go to next step.

  7. 12) Check Resistance Of Sensor Signal & SIG RTN Circuits

    Turn ignition off. Ensure suspect temperature sensor is disconnected. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure resistance between PCM connector pin No. 38 (ECT sensor) or No. 39 (IAT sensor) and SIG RTN terminal at suspect sensor wiring harness connector. Also measure resistance between PCM connector pin No. 91 (SIG RTN) and SIG RTN terminal at suspect sensor wiring harness connector. If both resistance readings are less than 5 ohms, replace PCM. If any resistance reading is 5 ohms or more, repair open circuit.

  8. 13) Check For Sensor Signal Short To VPWR Or VREF

    Turn ignition on. Measure voltage between ground and signal circuit (ECT or IAT) at suspect sensor wiring harness connector. If voltage is more than 4.8 volts, check for short to VPWR or VREF in wiring harness. If wiring harness is okay, replace PCM. If voltage is 4.8 volts or less, go to  TEST C, step 5).
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 13) to step 20). No test procedures have been omitted.

  9. 20) DTC P0117 Or P0112

    DTC P0117 (ECT) or P0112 (IAT) indicates sensor signal is less than self-test minimum. Minimum signal for IAT and ECT sensor is .2 volt. Possible causes for these faults are:
    • Circuit grounded in wiring harness.
    • Faulty sensor.
    • Faulty connection.
    • Faulty PCM.

    Turn ignition off. Disconnect suspect temperature sensor connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Turn ignition on. Using scan tool, select ECT V of IAT V PID from PID/DATA monitor menu. If PID value is less than 4.2 volts, go to next step. If PID value is 4.2 volts or more, replace sensor.

  10. 21) Check VREF Circuit Voltage At TP Sensor

    Turn ignition off. Disconnect TP sensor connector. Turn ignition on. Measure voltage between VREF and SIG RTN at TP sensor wiring harness connector. If voltage is 4-6 volts, connect TP sensor and go to next step. If voltage is not 4-6 volts, see TEST C .

  11. 22) Check Signal Circuit For Short To Ground

    Turn ignition off. Disconnect suspect sensor. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure resistance between PCM connector pin No. 91 and pin No. 38 (ECT) or No. 39 (IAT) . If any resistance reading is less than 10,000 ohms, repair short to ground. If all resistance readings are 10,000 ohms or more, replace PCM.
    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.

  12. 90) Continuous Memory DTC P0112, P1112, P0113, P0117, P1117 Or P0118: Check For Intermittent

    These DTCs indicate possible intermittent fault. Possible causes for these faults are:
    • Faulty sensor.
    • Faulty sensor connector.
    • Open or grounded circuit in harness.
    • Faulty PCM.

    Turn ignition on. Using scan tool, select ECT or IAT PID from PID/DATA monitor menu. While observing PID, tap on sensor to simulate road shock. Wiggle sensor connector. If no change in temperature reading occurs, go to next step. If any change in temperature occurs, turn ignition off. Inspect connectors for loose, damaged or corroded terminals. Repair as necessary. If connectors are okay, replace sensor. If Continuous Memory DTCs P1112 and P1117 are present, reconnect all components. Clear DTCs and perform COMPREHENSIVE COMPONENT MONITOR REPAIR VERIFICATION DRIVE CYCLE. See DRIVE CYCLES  under ADDITIONAL SYSTEM FUNCTIONS. After drive cycle is complete, repeat QUICK TEST  procedures to ensure all EEC-V systems are working properly and DTCs are no longer present.

  13. 91) Check EEC-V Wiring Harness

    While still observing PID, wiggle and bend small sections of wiring harness working toward PCM. If no fault is found, go to next step. If fault is indicated, isolate fault and repair as necessary. If Continuous Memory DTCs P1112 and P1117 are present, reconnect all components. Clear DTCs and perform COMPREHENSIVE COMPONENT MONITOR REPAIR VERIFICATION DRIVE CYCLE. See DRIVE CYCLES under ADDITIONAL SYSTEM FUNCTIONS. After drive cycle is complete, repeat QUICK TEST  procedures to ensure all EEC-V systems are working properly and DTCs are no longer present.

  14. 92) Inspect PCM & Wiring Harness Connectors

    Turn ignition off. Disconnect PCM 104-pin connector. Inspect connector for damaged pins, corrosion and loose terminals. If connectors and terminals are damaged, repair as necessary. If Continuous Memory DTCs P1112 and P1117 are present, reconnect all components. Clear DTCs and perform COMPREHENSIVE COMPONENT MONITOR REPAIR VERIFICATION DRIVE CYCLE. See DRIVE CYCLES  under ADDITIONAL SYSTEM FUNCTIONS. After drive cycle is complete, repeat QUICK TEST  procedures to ensure all EEC-V systems are working properly and DTCs are no longer present. If connectors and terminals are okay, fault cannot be identified at this time. Testing is complete. If Continuous Memory DTCs P1112 and P1117 are present, reconnect all components. Clear DTCs and perform COMPREHENSIVE COMPONENT MONITOR REPAIR VERIFICATION DRIVE CYCLE. See DRIVE CYCLES  under ADDITIONAL SYSTEM FUNCTIONS. After drive cycle is complete, repeat QUICK TEST  procedures to ensure all EEC-V systems are working properly and DTCs are no longer present.
    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.

  15. 100) DTC P0125

    This DTC indicates ECT sensor has not reached normal operating temperature. Possible causes for this fault are:
    • Insufficient engine warm-up time.
    • Thermostat leaking or stuck open.
    • Low coolant.

    Check and repair cooling system as necessary. Clear DTCs and repeat QUICK TEST .

  16. 110) DTC P1184: Check Operation Of Engine Oil Temperature (EOT) Sensor

    Connect scan tool. Run engine at 2000 RPM until engine oil temperature becomes stabilized. Check for KOER DTCs. If DTC P1184 is present, go to next step. If DTC P1184 is not present, engine oil temperature was not at operating temperature. Repair other DTCs as required.

  17. 111) DTC P0298, P1183 Or P1184: Check Temperature Signal

    Using scan tool, select EOT V PID from PID/DATA MONITOR & RECORD menu. If voltage is less than .3 volt, go to next step. If voltage is .3 volt or more go to step  115).

  18. 112) Induce Opposite EOT Signal To PCM

    While monitoring PID voltage, disconnect EOT sensor. If voltage is more than 4.2 volts, replace EOT sensor. If voltage is 4.2 volts or less, go to next step.

  19. 113) Check EOT Signal Circuit For Short To Ground

    Turn ignition switch to OFF position. Disconnect PCM connector(s). Measure resistance PCM connector terminal C39 (EOT) and terminal C17 (SIG RTN) circuits and between terminal C39 (EOT) and terminals A24, A25, A26 and A27 (PWR GND) circuits. If each resistance measurement is more than 10 k/ohms, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Program PCM. See FLASH VEHICLE IDENTIFICATION (VID) BLOCK PROCEDURE . If any resistance measurement is 10 k/ohms or less, repair short.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 113) to step 115). No test procedures have been omitted.

  20. 115) Check For High EOT Signal

    If voltage is more than 4.2 volts, go to next step. If voltage is 4.2 volts or less, go to step  120).

  21. 116) Induce Low Signal To PCM

    Disconnect EOT sensor. Connect jumper wire between EOT sensor harness connector terminals (EOT and SIG RTN). Turn ignition switch to ON position. Using scan tool, access EOTV PID from PID/DATA MONITOR & RECORD menu. If EOTV PID voltage is less than .3 volt, replace EOT sensor. If EOTV PID voltage is .3 volt or more, go to next step.

  22. 117) Check EOT Sensor Signal & SIG RTN Circuits For Open

    Turn ignition switch to OFF position. Disconnect PCM connector(s). Measure resistance of EOT circuit between PCM harness connector terminal C39 and EOT sensor. Measure resistance of SIG RTN circuit between PCM harness connector terminal C17 and EOT sensor. If each resistance measurement is less than 5 ohms, replace PCM. If any resistance measurement is 5 ohms or more, repair open circuit.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 117) to step 120). No test procedures have been omitted.

  23. 120) Intermittent EOT Sensor Check

    While observing PID, tap on sensor to simulate road shock. Wiggle sensor connector. If no large change in PID voltage occurs, go to next step. If any large change in PID voltage occurs, turn ignition switch to OFF position. Inspect connectors for loose, damaged or corroded terminals. Repair as necessary. If connectors are okay, replace EOT sensor.

  24. 121) Check EEC-V Wiring Harness

    While still observing PID, wiggle and bend small sections of wiring harness working toward PCM. If no fault is found, go to next step. If fault is indicated, isolate fault and repair as necessary. If Continuous Memory DTCs P0298, P1183 or P1184 are present, reconnect all components. Clear DTCs and perform COMPREHENSIVE COMPONENT MONITOR REPAIR VERIFICATION DRIVE CYCLE. See DRIVE CYCLES  under ADDITIONAL SYSTEM FUNCTIONS. After drive cycle is complete, repeat QUICK TEST  procedures to ensure all EEC-V systems are working properly and DTCs are no longer present.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 121) to step 130). No test procedures have been omitted.

  25. 130) DTC P0298: Engine Oil Over Temperature

    Check for engine overheating condition or mechanical problem. If concern is found, repair as necessary. If concern is not found, go to next step.

  26. 131) Check For EOT Sensor

    Engine oil temperature strategy can be activated in PCM without an EOT sensor. Ensure vehicle is equipped with an EOT sensor. If vehicle is equipped, go to step  111). If vehicle is not equipped, improper transmission gear selection or excessive RPM for extended period may have caused engine protection strategy in PCM.
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