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 ACT and VAT sensors. 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 following components and circuits:

Air Charge Temperature (ACT) sensor.
Engine Charge Temperature (ECT) sensor.
Vehicle harness circuits (ACT, ECT and SIG RTN).
Electronic Control Assembly (ECA).

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

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

Fig 1: Temperature Sensor Circuit & Connector Terminal ID

TEST PIN NO. 7 (ECT) WIRE COLOR IDENTIFICATION

Application

Wire Color

Probe 3.0L

⁽¹⁾ Yellow/Red

1.9L

Blue/White

Except 1.9L & Probe 3.0L

Light Green/Red

⁽¹⁾	ECT wire may also be Yellow/Black.

TEST PIN NO. 25 (ACT) WIRE COLOR IDENTIFICATION

Application

Wire Color

1.9L

White/Green

2.3L

Gray

3.0L

Probe

⁽¹⁾ Yellow

Sable & Taurus (Except SHO)

Light Green/Purple

Taurus SHO, Tempo & Topaz

Gray

3.8L

Light Green/Purple

4.6L

Crown Victoria & Grand Marquis

Light Green/Purple

Town Car

Gray

5.0L

Cougar & Thunderbird

Light Green/Purple

Mark VII & Mustang

Gray

⁽¹⁾	ACT wire may also be White/Light Green.

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

Application

Wire Color

Probe 3.0L

⁽¹⁾ Light Green/Yellow

1.9L

Light Green/Black

Except 1.9L & Probe 3.0L

Gray/Red

⁽¹⁾	SIG RTN wire may also be Black/Blue.

1) Code 21/116 Or 24/114: Code 21/116 (ECT) or 24/114 (ACT) 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.
ACT 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, 24, 114 or 116 is present, go to step 2). If none of these codes are present, service other codes as necessary.

2) Check VREF Circuit Voltage At TPS Turn ignition off. Disconnect Throttle Position Sensor (TPS). With ignition on and engine off, measure voltage at TPS vehicle harness connector between VREF and SIG RTN. See Fig 2 . If voltage is 4-6 volts, reconnect TPS and go to step 3). If voltage is not 4-6 volts, go to CIRCUIT TEST C.

3) Check Temperature Sensor Resistance (KOEO) 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 Fig 3 . Reconnect vehicle 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 TFI, CIRCUIT TEST AB for DIS and CIRCUIT TEST AC for EDIS.
For other vehicles, go to step 4).

Fig 2: TPS Harness Connector Terminal ID

Fig 3: Temperature Sensors Resistance & Voltage Charts

4) Check Temperature Sensor Resistance (KOER) 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 Fig 3 . If resistance is within specification, replace ECA 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 51/118 Or 54/113: Induce Opposite Code (Code 61/117 Or 64/112) Code 51/118 (ECT) or 54/113 (ACT) indicate corresponding sensor signal is greater than self-test maximum. Maximum signal voltage for ECT and ACT sensor is 4.6 volts. Possible causes for excess voltage signals are:

Open circuit in vehicle harness (ACT or ECT).
Faulty connection.
Faulty sensor.
Faulty ECA.

Turn ignition off. Disconnect suspect temperature sensor. Connect a jumper wire between sensor SIG RTN terminal and SIG RTN terminal at temperature sensor vehicle harness connector. Repeat QUICK TEST . If Code 61, 64, 112 or 117 is displayed, replace suspect sensor and repeat QUICK TEST. If Code 61, 64, 112 or 117 is 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 ECA 60-pin connector. Check for damaged wiring, and repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance of sensor signal circuit between test pin No. 7 (ECT sensor) or test pin No. 25 (ACT sensor) at breakout box and sensor signal circuit terminal at sensor vehicle harness connector. Also measure resistance between test pin No. 46 and SIG RTN circuit at sensor vehicle harness connector. If both readings are less than 5 ohms, replace ECA. Remove breakout box, 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 61/117 or 64/112: Induce Opposite Code (51/118 or 54/113) Code 61/117 (ECT) or 64/112 (ACT) indicates sensor signal is less than self-test minimum. Minimum signal for ACT and ECT sensor is 0.2 volt. Possible causes for this fault are:

Circuit grounded in vehicle harness (ACT or ECT).
Faulty sensor.
Faulty ECA.
Faulty connection.

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

21) Check VREF Circuit Voltage At TPS Turn ignition off. Disconnect vehicle harness connector from suspect sensor. Disconnect TPS. Turn ignition on. Measure voltage between VREF and SIG RTN at TPS vehicle harness connector. If voltage is not 4-6 volts, go to CIRCUIT TEST C. If voltage is 4-6 volts, connect TPS and go to step 22).

22) Check Temperature Sensor Signal For Shorts To Ground Turn ignition off. Disconnect suspect sensor. Disconnect ECA 60-pin connector. Check for damaged wiring, and repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pin No. 7 (ECT) or 25 (ACT) and pins No. 40, 46 and 60. If any reading is less than 10,000 ohms, repair short circuit. Remove breakout box, and repeat QUICK TEST . If all readings are 10,000 ohms or more, replace ECA. Remove breakout box, 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 51/118, 54/113, 61/117 Or 64/112: Check Sensor 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 ECA.

SENSOR CODES

Sensor	Continuous Memory Code
ACT	54/113, 64/112
ECT	51/118, 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 indicated, disconnect and inspect connector and terminals. If connector and terminals are okay, replace sensor, clear continuous memory and repeat QUICK TEST . If fault is not indicated, go to step 91).

91) Check EEC-IV Vehicle 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 ECA. 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).

92) Inspect ECA & Vehicle Harness Connectors Turn ignition off. Disconnect ECA 60-pin connector. Inspect both connector and connector terminals for damage. If connectors and 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 INTERMITTENTS in TESTS W/O CODES article in the ENGINE PERFORMANCE Section.

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. 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 .

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 damaged or worn.

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