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 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 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: Temp Sensor Circuits & Connector Terminals

1. Step 1) DTC P1116  This trouble code 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 QUICK TEST . If DTC P1116 is present, go to next step. If DTC P1116 is not present, fault is intermittent and cannot be duplicated at this time. testing is complete.

2. Step 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 terminal. See Figure. 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. Step 3) Check Temperature Sensor Resistance (KOEO)  Turn ignition off. Disconnect suspect sensor. Measure resistance between signal circuit (ECT or IAT) terminal and SIG RTN terminal at sensor wiring harness connector. See ACT & ECT SENSOR  SPECIFICATIONS table. If resistance is not within specification, replace suspected sensor and repeat QUICK TEST . If resistance is within specification, 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 and repeat QUICK TEST .
   • For diagnosing vehicles without a no-start condition, go to next step.
4. Step 4) Check Temperature Sensor Resistance (KOER)  Warm engine to normal operating temperature. Turn ignition off. Disconnect suspect sensor. Start engine and operate at 2000 RPM for 2 minutes. Measure resistance between signal circuit (ECT or IAT) terminal and SIG RTN terminal at sensor wiring harness connector. See ACT & ECT 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 .
   ACT & ECT 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)	1.02	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. Step 10) DTC P0118 Or P0113: Induce Opposite DTC (117 Or 112)  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 temperature sensor. Connect a jumper wire between signal circuit (ECT or IAT) terminal and SIG RTN terminal at sensor wiring harness connector. With scan tester installed, turn ignition on.

   NOTE: If communication link error is displayed, remove jumper wire and go to step 12).

   Access ECT or IAT PID. If the PID is less than 0.2 volt, replace sensor and repeat QUICK TEST . If PID is 0.2 volt or more, remove jumper wire and go to next step.

6. Step 11) Check Continuity Of Sensor Signal & SIG RTN Circuits  Turn ignition off. Ensure suspect temperature sensor is disconnected. Disconnect PCM 104-pin connector. Check for damaged wiring, and repair as necessary. Install Breakout Box (014-00950), leaving PCM disconnected. Measure resistance between test pin No. 38 (ECT sensor) or test pin No. 39 (IAT sensor) at breakout box and SIG RTN terminal at sensor wiring harness connector. Also, measure resistance between test pin No. 91 (SIG RTN) 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 and repeat QUICK TEST .
7. Step 12) Check For Sensor Signal Short To VREF  Turn ignition off. Ensure suspect temperature sensor is disconnected. Measure resistance between test pin No. 90 (VREF) and test pin No. 38 (ECT sensor) or test pin No. 39 (IAT sensor) at breakout box. If resistance is 10,000 ohms or more, replace PCM and repeat QUICK TEST . If either resistance is less than 10,000 ohms, repair short circuit to VREF and repeat QUICK TEST .
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 12) to step 20). No test procedures have been omitted.
8. Step 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 0.2 volt. Possible causes for this fault are:
   • Circuit grounded in wiring harness.
   • Faulty sensor.
   • Faulty connection.
   • Faulty PCM.

   Turn ignition off. Disconnect wiring harness connector from suspect sensor. Check for damaged wiring, and repair as necessary. With scan tester connected, turn ignition on. Using scan tester, access ECT of IAT PID. If PID is less than 4.2 volts, go to next step. If PID is 4.2 volts or more, replace sensor and repeat QUICK TEST .

9. Step 21) Check VREF Circuit Voltage At TP Sensor  Turn ignition off. Disconnect TP sensor wiring harness 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, go to CIRCUIT TEST C.
10. Step 22) Check Signal Circuit For Short To Ground  Turn ignition off. Disconnect suspect sensor. Disconnect PCM 104-pin connector. Check for damaged wiring, and repair as necessary. Install Breakout Box (014-00950), leaving PCM disconnected. Measure resistance between test pin No. 38 (ECT) or 39 (IAT) and test pins No. 24, 51 and 91. 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.
11. Step 90) Continuous Memory DTC P0112, P1112, P0113, P0117, P1117 Or P0118: Check Sensor  These trouble codes indicate possible intermittent fault. Possible causes for these faults are:
    • Faulty sensor.
    • Faulty sensor connector.
    • Open or grounded circuit in harness.
    • Faulty PCM.

    With scan tester connected, turn ignition on. Access ECT or IAT PID. 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, isolate fault and repair as necessary.

12. Step 91) Check EEC-V Wiring Harness  While in PID, wiggle and bend small sections of wiring harness working toward PCM. If fault is indicated, isolate fault and repair as necessary. Clear memory, and repeat QUICK TEST . If no fault is found, go to step 92).
13. Step 92) Inspect PCM & Wiring Harness Connectors  Turn ignition off. Disconnect PCM 104-pin connector. Inspect connector for damaged pins, corrosion and loose wires. If connectors and terminals are damaged, repair as necessary and repeat QUICK TEST . If connectors and terminals are okay, fault cannot be duplicated at this time and testing is complete.
    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.
14. Step 100) DTC P0125  These DTCs indicate 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.

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