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 Circuit & Connector Terminal ID (DA1 - B2300 & B3000)

TEST PIN NO. 7 (ECT) WIRE COLOR IDENTIFICATION

Application	Wire Color
B2300 & B3000	Light Green/Red

TEST PIN NO. 25 (IAT) WIRE COLOR IDENTIFICATION

Application	Wire Color
B2300 & B3000	Gray

TEST PIN NO. 46 (SIG RTN) WIRE COLOR IDENTIFICATION

Application	Wire Color
B2300 & B3000	Gray/Red

1) Code 114 Or 116 Code 114 (IAT) or 116 (ECT) 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 114 or 116 is present, go to next step. If none of these codes are 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. See 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 CIRCUIT TEST C.

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 116 at this time. Go to CIRCUIT TEST AA for 3.0L, CIRCUIT TEST AB for 2.3L.
For all others, go to next step.

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: TP Sensor Wiring Harness Connector Terminal ID (DA2 - B2300 & B3000)

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.

10) Code 113 Or 118: Induce Opposite Code (Code 112 Or 117) Code 113 (IAT) or 118 (ECT) indicates corresponding sensor signal is greater than self-test maximum. Maximum signal voltage for ECT and IAT sensor is 4.6 volts. Following are possible causes for excess voltage signals.

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 signal terminal and SIG RTN terminal at sensor wiring harness connector. Repeat QUICK TEST. If Code 112 or 117 is displayed, replace suspect sensor and repeat QUICK TEST. If Codes 112 and 117 are not displayed, remove jumper wire and go to next step.

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 between test pin No. 7 (ECT sensor) or test pin No. 25 (IAT sensor) at breakout box and signal 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.

20) Code 112 Or 117: Induce Opposite Code (113 Or 118) Code 112 (IAT) or 117 (ECT) indicates sensor signal is less than self-test minimum. Minimum signal for IAT and ECT sensor is 0.2 volt. Following are possible causes for this fault.

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 113 or 118 is present, replace sensor and repeat QUICK TEST. If Codes 113 and 118 are not present, go to next step.

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 next step.

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 No. 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.

90) Continuous Memory Code 112, 113, 117 Or 118 A Continuous Memory Code 113 or 118 indicates sensor signal is greater than self-test maximum of 4.6 volts. Code is set during normal driving conditions. Continuous Memory Code 112 or 117 indicates sensor signal is less than self-test minimum of 0.2 volt. Code is set during normal driving conditions. Following are possible causes for these faults.

Faulty sensor
Open or grounded circuit in harness
Faulty PCM

SENSOR CODES

Sensor	Continuous Memory Code
IAT	112 Or 113
ECT	117 Or 118

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 next step. 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.

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 next step.

92) Inspect PCM & Wiring Harness Connectors Turn ignition off. Disconnect PCM 60-pin connector. Inspect connectors 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.

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) Continuous Memory Code 338 A Continuous Memory Code 338 indicates cooling system has not reached normal operating temperature. Following are possible causes for this fault.

Thermostat stuck open
Coolant outlet gasket leak
Water pump gasket leak

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