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: Temperature Sensor Circuits & Connector Terminal ID (DA1)

1) Code P1116

Code P1116 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 Code P1116 is present, go to step 2). If Code P1116 is not present, service other codes as necessary.

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 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 .

Fig 2: TP Sensor Harness Connector Terminal ID (DA2)

3) Check Temperature Sensor Resistance

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 and a no-start condition, DO NOT service Code 116 at this time. Repair no start condition and repeat QUICK TEST.
- For diagnosing vehicles without a no-start condition, go to step 4).

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.

10) Code P0118 Or P0113: Induce Opposite Code (Code 117 Or 112)

Code 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, go to next 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.

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 pins 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.

20) Code P0117 or P0112

Code 117 (ECT) or 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.
- 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. 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.

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 .

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 and 51 (PWR GND). 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.

90) Continuous Memory Code 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.

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).

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.

100) Diagnostic Trouble Code P0125

This code indicates ECT sensor has not reached normal operating temperature. Possible causes for this fault are:
- Thermostat leaking or stuck open.
- Low coolant.
Repair cooling system as necessary. Clear PCM memory, and repeat QUICK TEST.