Engine Controls - Tests W/codes - 4.0L: Diagnosis Ford Aerostar I

DIAGNOSTIC FORMATS

There are 2 diagnostic formats used to test and service the EEC-IV system: QUICK TEST and CIRCUIT TESTS. QUICK TEST allows the technician to identify problems, and retrieve and record service codes. CIRCUIT TESTS check circuits, sensors and actuators.

If vehicle passes QUICK TEST, and there are no driveability symptoms or intermittent faults, the EEC-IV system is okay. Problem exists elsewhere.

Before starting any CIRCUIT TEST, follow all steps under QUICK TEST to find the correct CIRCUIT TEST.

KOEO & KOER SELF-TEST CODES

All service codes are 2 or 3-digit numbers. Codes are outputted, one digit at a time, by ECA. See appropriate chart under CODE-TO-TEST MENU(S) for definitions of codes. These codes indicate current faults in the system, and should be serviced in the order of appearance. Use appropriate chart under CODE-TO-TEST MENU(S) to find the correct CIRCUIT TEST. Codes are shown as voltage pulses (needle sweeps) on an analog Volt/Ohmmeter (VOM). see scheme 1

If using VOM, pay careful attention to the length of pauses in order to read codes correctly. There is a 1/2-second pause between number of sweeps in a digit, and a 2-second pause between the digits in a code. There is a 4-second pause between each code. KOEO codes are separated from Continuous Memory codes by a 6-second delay, a single 1/2-second sweep (Separator) and another 6-second delay. Record codes in the order received.

If using "Scan" Tool, it will count the pulses and display them as a digital code. The STAR Series Tester will add a zero (0) to single-digit Separator Code (10) and Dynamic Response Code (10). The Dynamic Response Code is displayed in KOER SELF-TEST. see scheme 1 If using "CHECK ENGINE" light, service codes are displayed as flashes.

DIAGNOSTIC AIDS

After all tests, servicing or repairs have been completed, repeat QUICK TEST procedure to ensure all EEC-IV systems work properly and service codes are no longer present.

KOEO SELF-TEST

Start engine and allow to idle until vehicle reaches operating temperature. If engine does not start or stalls after starting, continue KOEO SELF-TEST. DO NOT depress throttle on gasoline-engine vehicles. Turn ignition off and wait 10 seconds. Activate self-test procedure by using a jumper wire or appropriate test equipment. Turn ignition on, leaving engine off. Record all KOEO and Continuous Memory Codes.

If a Code 11 or 111 (pass code) is not received in the KOEO portion of test, service the KOEO codes. See appropriate chart under CODE-TO-TEST MENU(S). If the ECA will not output codes, go to TEST QA, step 1). If codes are received, check the following procedures

1. If "CHECK ENGINE" or "SERVICE ENGINE SOON" light is on when vehicle arrived for service, use recorded Continuous Memory Codes and appropriate chart under CODE-TO-TEST MENU(S) before addressing any other symptoms.
2. If engine runs or idles rough, go to TEST S step 2). On vehicles with DIS or EDIS, use recorded Continuous Memory Codes and appropriate chart under CODE-TO-TEST MENU(S).
3. Perform only the following. If Continuous Memory Codes 45, 46, 48, 215, 216, 217, 232 or 238 are received during KOEO SELF-TEST, see appropriate system test in the SYSTEM/COMPONENT TESTS article. If Codes 45, 46, 48, 215, 216, 217, 232 or 238 were not received, go to TEST S, step 2).
4. On all vehicles, except vehicles with EDIS, if vehicle has a no-start condition, go to TEST A, step 1). On vehicles with EDIS, go to TEST AA, step 1).
5. If vehicle displays a Code 11 or 111 (pass code) and does not have any of the symptoms described in previous steps, go to COMPUTED TIMING CHECK.

DO NOT enter this test sequence until a Code 11 or 111 (pass code) has been received in KOEO SELF-TEST. If system has not passed KOEO SELF-TEST, code recorded in KOER SELF-TEST may not be valid.

Deactivate self-test by removing and reconnecting jumper wire, or by procedure specified by test equipment in use. Start and run engine for 2 minutes at 2000 RPM to warm-up Heated Exhaust Gas Oxygen (HEGO) sensor. Turn engine off and wait 10 seconds. Activate KOER SELF-TEST using a jumper wire or appropriate procedure for test equipment used. Start engine. Record all service codes displayed. Check the following items

1. If engine starts and stalls, or stalls during self-test, go to TEST S, step 1).
2. If vehicle is equipped with a Brake On/Off (BOO) switch, brake pedal MUST be depressed and released AFTER the ID code portion of test.
3. On vehicles with Power Steering Pressure Switch (PSPS), turn steering wheel at least 1/2 turn and release within 1-2 seconds after the ID code portion of test.
4. On vehicles with E4OD transmissions, the Overdrive Cancel Switch (OCS) MUST be cycled after the ID code portion of the test.
5. When the Dynamic Response Code appears, perform a brief Wide Open Throttle (WOT). DO NOT perform WOT unless requested.
6. If Code 98 or 998 is displayed, it indicates EEC-IV system is operating in Failure Management Effects Mode (FMEM) and vehicle has not passed KOEO SELF-TEST. Vehicle cannot be diagnosed while in FMEM mode. See Code 98 or 998 in appropriate CONTINUOUS MEMORY CODE chart under CODE-TO-TEST MENU(S).
7. If a Code 11 or 111 (pass code) is received during KOER SELF-TEST, service Continuous Memory Codes received in KOEO SELF-TEST. See appropriate CONTINUOUS MEMORY CODE chart under CODE-TO-TEST MENU(S) in this article.
8. If a Code 11 or 111 (pass code) is received during the Continuous Memory Code portion of KOEO SELF-TEST (Code 11-1-11) or (11-1-111), and no driveability problem exists, EEC-IV testing is complete. If driveability problems are still present, go to TESTS W/O CODES article in this section.
9. If KOER codes are present, refer to appropriate KOER SELF-TEST CODES chart under CODE-TO-TEST MENU(S). If system will not output codes, go to TEST QA, step 1).

CONTINUOUS MONITOR MODE (WIGGLE TEST)

The Continuous Monitor Mode allows technician to attempt a recreation of intermittent fault while monitoring the system. This mode, also called the wiggle test, may be used in both KOEO SELF-TEST and KOER SELF-TEST. CIRCUIT TESTS specify the use of this procedure to identify intermittent faults in specific circuits or components.

KOEO Wiggle Test Procedure

Connect test equipment. see scheme 2 Turn ignition on and activate self-test with jumper lead or diagnostic tester. Wait 10 seconds, deactivate, and then reactivate self-test. Wiggle test mode is now activated. Tap, move and wiggle the suspected sensor and/or harness area. If a fault is detected, a service code may be stored in memory and indicated at the diagnostic tester or "Scan" tool. Record or retrieve code and perform test indicated by appropriate CONTINUOUS MEMORY CODES chart under CODE-TO-TEST MENU(S).

KOER Wiggle Test Procedure

Connect test equipment. see scheme 2 Turn ignition off and wait 10 seconds. Start engine. Activate self-test with jumper lead or diagnostic tester. Wait 10 seconds, deactivate, and then reactivate self-test. DO NOT turn engine off. KOER wiggle test mode is now activated. Tap, move and wiggle the suspected sensor and/or harness area. If a fault is detected, a service code may be stored in memory and indicated at the diagnostic tester or "Scan" tool. Record or retrieve code and perform test indicated in appropriate CONTINUOUS MEMORY CODES chart under CODE-TO-TEST MENU(S).

INTERMITTENT & DIAGNOSIS BY SYMPTOMS

See the TESTS W/O CODES article in this section.

Cylinder Balance Test

This test helps identify a weak or noncontributing cylinder in engines with sequential PFI fuel systems. The ECA shuts off fuel supply to each injector and measures RPM drop. It computes the variation between cylinders and identifies the weak ones. This test mode is entered from the KOER SELF-TEST, after all codes have been displayed. Within 2 minutes after codes have been displayed, lightly depress throttle (a 2-3 degree throttle angle is required, NOT a wide open throttle). After a brief stabilizing period, ECA will activate the test procedure. The test will be repeated if the throttle is depressed within 2 minutes of the final code output. During the 2nd and 3rd test sequence, the percentage of allowable variation between cylinders is reduced. Service codes displayed during this test identify the weak or non-contributing cylinder. See CYLINDER BALANCE TEST SERVICE CODES table to identify the cylinder number corresponding to the service code displayed. If Code 90 is displayed during this test, it indicates a passing result. If Code 77 is displayed, repeat cylinder balance test. If throttle is moved during this test, Code 77 will appear, indicating that test is not completed. Total test time is about 3 minutes.

CYLINDER BALANCE TEST SERVICE CODES

KOEO CODE-TO-TEST MENU

KOEO SELF-TEST - CIRCUIT TEST & STEP MENU

KOER CODE-TO-TEST MENU

KOER SELF-TEST - CIRCUIT TEST & STEP MENU

CONTINUOUS CODE-TO-TEST MENU

CONTINUOUS MEMORY - CIRCUIT TEST & STEP MENU

Fuel-contaminated engine oil may affect some codes. If this is suspected, remove PCV valve from valve cover and repeat QUICK TEST. If problem is corrected, change engine oil and filter.

On CIRCUIT TEST H and CIRCUIT TEST J (Fuel Control), vacuum leaks in non-EEC related areas may also cause Code 41 or 91 to be displayed. Check the following: unmetered air leaks between airflow meter and throttle body, vacuum motors, engine seals, EGR system, PCV system, Canister Purge (CANP) and HEGO sensor. Code 42 or 92 may be caused by fuel-contaminated engine oil, ignition misfire, EGR system or CANP problems.

Note. In the following tests, circuit diagrams and illustrations are courtesy of Ford Motor Co.

CIRCUIT TESTS are grouped as follows

1. AA-C - No Start & Voltage Tests
2. DA-DQ - Input Sensor Tests
3. FD-FF - Additional Input Component Tests
4. G-J Fuel - Control Systems
5. KC-TC - ECA (Processor) Output Tests

TEST AA - NO START (4.0L EDIS IGNITION SYSTEMS)

Enter this CIRCUIT TEST only when all steps under QUICK TEST have been successfully completed and the engine still does not start, or when directed here from another test or chart.

This test is intended to diagnose only the following EEC-IV ignition systems and circuits

1. Spark (ECA Controlled)
2. Wiring Harness Circuits (PIP, IGN GND & VPWR)
3. ECA

EDIS Module Circuits (4.0L). Scheme 47

4.0L SPFI-MA TEST PIN WIRE COLOR I.D.

4.0L SPFI-MA TEST PIN WIRE COLOR I.D. (RANGER & EXPLORER, NAVAJO)

To prevent replacement of good components, be aware that the following non-EEC related areas and components may be the cause of problem

1. Fuel Quality & Quantity
2. Ignition (General Condition)
3. Engine Mechanical Components
4. Starter & Battery Circuits
5. Variable Reluctance Sensor (VRS)
6. EDIS Module
7. Coil Packs

1) Starting System Ensure fuel pump inertia switch is closed (button pushed in). Try to start engine. If engine does not crank, check vehicle starting and charging systems. If engine cranks, go to next step.

2) Check VREF Signal At TPS Ensure fuel pump inertia switch is set (button pushed in). Turn ignition off and wait 10 seconds. Set DVOM on 20-volt scale and disconnect Throttle Position Sensor (TPS). Turn ignition on, leaving engine off. Measure voltage at TPS harness connector between VREF and SIG RTN. If reading is less than 4 volts or more than 6 volts, go to TEST C, step 1). If reading is between 4 and 6 volts, reconnect TPS and go to next step.

TPS Harness Connectors. Scheme 48

3) Check For Spark At Plugs Disconnect any spark plug wire. Connect spark tester between plug wire and engine ground. Crank engine and check for spark. If spark is present and consistent, connect spark plug wire and go to next step. If there is no spark, check ignition system. Refer to the I - SYS/COMP TESTS article in this section.

4) Check Ignition Ground Continuity Turn ignition off. Wait 10 seconds. Disconnect and inspect ECA 60-pin connector. Install breakout box, leaving ECA disconnected. Disconnect EDIS module. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 16 at breakout box and IGN GND circuit at EDIS module vehicle harness connector. If resistance is more than 5 ohms, repair open in circuit and repeat QUICK TEST. If reading is less than 5 ohms, proceed to next the step.

5) Check PIP For Short To Power Turn ignition off. Wait 10 seconds. With breakout box installed, disconnect ECA. Disconnect EDIS module. Set DVOM on 20-volt scale. Measure voltage between test pin No. 56 at breakout box and battery negative post. If voltage is greater than 7 volts, repair short to power. Remove breakout box and rerun QUICK TEST. If voltage is NOT greater than 7 volts, go to the next step.

6) Check PIP Circuit Continuity Turn ignition off and wait 10 seconds. With breakout box installed, disconnect ECA. Disconnect EDIS module. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 56 at breakout box and PIP circuit at EDIS module vehicle harness connector. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open circuit. Remove breakout box, reconnect all components and rerun QUICK TEST.

7) Check PIP Circuit For Shorts to Ground Turn ignition off and wait 10 seconds. With breakout box installed, reconnect ECA. Disconnect EDIS module. Set DVOM on 200-k/ohm scale. Measure resistance between test pin No. 56 (PIP) and test pins No. 16, 40, 46 and 60 for short to ground. If any reading is less than 10 k/ohms, repair short in harness and repeat QUICK TEST. If engine still does not start, go to next step. If all readings are 10 k/ohms or more, go to next step.

8) Isolate Shorts In ECA Turn ignition off and wait 10 seconds. With breakout box installed, connect ECA to breakout box. Disconnect EDIS module. Set DVOM on 200-k/ohm scale. Measure resistance between test pin No. 56 (PIP) and test pins No. 37 and 57 for short to power. Measure resistance between test pin No. 56 and test pins No. 40 and 60 for short to ground. If all readings are less than 20 k/ohms or greater than 150 k/ohms, problem is in EDIS system. Replace ECA and repeat QUICK TEST. If any reading is 20-150 k/ohms go to next step.

9) Check PIP Signal Turn ignition off and wait 10 seconds. With breakout box installed, disconnect ECA. Reconnect EDIS module. Set DVOM on 20-volt scale. Measure voltage between test pin No. 56 and test pin No. 16 at breakout box. Crank engine and record reading. If voltage is less than 3 volts or greater than 7 volts, remove breakout box and rerun QUICK TEST. If voltage is 3-7 volts, replace EDIS module and go to next step.

10) Fuel Pump Check Connect pressure gauge to vehicle. Note initial pressure reading. Pressurize fuel system by turning ignition on for one second and observe pressure gauge. Turn ignition off and wait 10 seconds. Repeat sequence 5 times. If pressure increases, go to TEST S, step 1). If pressure does not increase, check fuel pump and system for mechanical problems.

Enter this CIRCUIT TEST only when directed by TEST C, TEST J, TEST PA, TEST PB or TEST PC.

Power Relay Circuits. Scheme 49

4.0L SPFI-MA TEST PIN WIRE COLOR I.D.

4.0L SPFI-MA TEST PIN WIRE COLOR I.D. (RANGER & EXPLORER, NAVAJO)

To prevent replacement of good components, be aware that the following non-EEC related areas may be the cause of problem: battery cables and ground straps, voltage regulator, alternator or ignition switch. This test is intended to diagnose the ECA, power relay, battery voltage and the following harness circuits

1. Signal Return
2. STO
3. STI
4. PWR GND
5. VPWR
6. KAPWR
7. VREF
8. Ignition

1) Battery Voltage Check Turn ignition on, leaving engine off. Set DVOM on 20-volt scale and measure voltage across battery terminals. If reading is less than 10.5 volts, service or replace discharged battery. If reading is 10.5 volts or more, go to next step.

2) Check Continuity Of PWR GND Circuit Turn ignition off and wait 10 seconds. Inspect ECA connector and pins. Install breakout box, leaving ECA connected. Set DVOM on 200-ohm scale and measure resistance between test pins No. 40 and 60 at breakout box and battery negative post. If readings are greater than 5 ohms, repair open in PWR GND circuit. Remove breakout box, reconnect components and repeat QUICK TEST. If both readings are less than 5 ohms, go to next step.

3) Check For Open Between SIG RTN & PWR GND Circuits At ECA With breakout box installed and ECA connected, turn ignition off and wait 10 seconds. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 46 and test pins No. 40 and 60 at breakout box. If both readings are less than 5 ohms, go to next step. If readings are greater than 5 ohms, disconnect ECA connector and inspect for corrosion or damaged pins. Repair as necessary. If fault is still present, replace ECA and repeat QUICK TEST.

4) Check Continuity Of SIG RTN Circuit With breakout box installed and ECA connected, turn ignition off and wait 10 seconds. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 46 at breakout box and SIG RTN circuit at self-test connector. If resistance is greater than 5 ohms, repair open in SIG RTN circuit. Remove breakout box, reconnect components and repeat QUICK TEST. If reading is less than 5 ohms, remove breakout box, connect ECA and go to next step.

5) Check KAPWR Circuit Voltage At EEC Power Relay Turn ignition on, leaving engine off. With ECA connected, set DVOM on 20-volt scale. Measure voltage between battery negative post and KAPWR circuit at EEC power relay harness connector. If reading is less than 10.5 volts, check KAPWR circuit from EEC power relay to battery positive post for open circuit. If reading is 10.5 volts or more, go to next step.

6) Check Ignition Circuit Voltage At EEC Power Relay Turn ignition on, leaving engine off. Ensure ECA is connected. Set DVOM on 20-volt scale. Measure voltage between battery negative post and IGNITION circuit at EEC power relay vehicle harness connector. If reading is less than 10.5 volts, check for open in ignition switch circuits. Repair wiring and repeat QUICK TEST. If reading is 10.5 volts or more, go to next step.

7) Check PWR GND Circuit Continuity Turn ignition off and wait 10 seconds. With ECA connected and DVOM on 200-ohm scale, measure resistance between battery negative post and PWR GND circuit at EEC power relay vehicle harness connector. If resistance is 5 ohms or more, repair wiring in ground circuit. Repeat QUICK TEST. If reading is less than 5 ohms, go to next step.

8) Check VPWR Circuit At EEC Power Relay Turn ignition on, leaving engine off. With ECA connected and DVOM on 20-volt scale, measure voltage between battery negative post and VPWR circuit at EEC power relay vehicle harness connector. If reading is 10.5 volts or more, repair open or short to ground in VPWR circuit between ECA and EEC power relay. Reconnect components and repeat QUICK TEST. If reading is less than 10.5 volts, replace EEC power relay. Repeat QUICK TEST.

Perform this test when a check for VREF signal has failed in sensor input TEST DA-through-TEST DR, or when directed by TEST A or TEST QA.

This circuit test is intended to diagnose only the ECA, SIG RTN, VREF, TP, EVP, PFE, DPFE, MAP and BP circuits.

Reference Voltage Circuits. Scheme 50

4.0L SPFI-MA TEST PIN WIRE COLOR I.D.

4.0L SPFI-MA TEST PIN WIRE COLOR I.D. (RANGER & EXPLORER, NAVAJO)

1) Check Battery Power Circuit Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair as necessary. Install breakout box, leaving ECA connected. Turn ignition on, leaving engine off. Set DVOM on 20-volt scale and measure voltage between test pin No. 37 and SIG RTN/PWR GND circuit of self-test connector. Record reading. Measure voltage across battery terminals. Record reading. If both readings are less than 10.5 volts, or if they differ by more than one volt, reconnect sensor (if applicable). Go to step 1) of TEST B. If reading is 10.5 volts or more and does not differ from one another by more than one volt, go to next step.

2) Check VREF Voltage With breakout box installed and ECA connected, turn ignition on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between test pins No. 26 and 46 at breakout box. If reading is 6 volts or more, go to step 4). If 4 volts or less, go to step 5). If reading is 4-6 volts, go to next step.

3) Check VREF & SIG RTN Circuit Continuity With breakout box installed and ECA disconnected, turn ignition off. If directed here by a sensor test, ensure sensor is disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 26 and VREF circuit terminal at vehicle harness connector of applicable sensor. Measure resistance between test pin No. 46 and SIG RTN circuit terminal at vehicle harness connector of applicable sensor. If both readings are less than 5 ohms, VREF voltage is okay. Remove breakout box, reconnect components and sensor, and repeat QUICK TEST. If any reading is 5 ohms or more, repair open in VREF or SIG RTN circuit. Remove breakout box, reconnect components and repeat QUICK TEST.

4) Check For Excess VREF Circuit Voltage Turn ignition off and wait 10 seconds. With breakout box installed, disconnect ECA and "Scan" tool or STAR tester (if applicable). Turn ignition on, leaving engine off. Set DVOM on 20-volt scale and measure voltage between test pin No. 26 and battery ground. If reading is less than 0.5 volt, replace ECA, remove breakout box, reconnect components and repeat QUICK TEST. If reading is 0.5 volt or more, repair short to battery power in EEC vehicle harness. Remove breakout box, reconnect components and repeat QUICK TEST. Replace ECA if fault still occurs.

5) Check For Shorted TPS Sensor Turn ignition off and wait 10 seconds. With breakout box installed and ECA connected, disconnect Throttle Position Sensor (TPS) from vehicle harness. Turn ignition on, leaving engine off. Set DVOM on 20-volt scale and measure voltage between test pins No. 26 and 46. If reading is 4 volts or more, replace TPS, remove breakout box, reconnect components and repeat QUICK TEST. If voltage is less than 4 volts on vehicles with EVP/PFE sensor, go to next step. If reading is less than 4 volts on all other models, go to step 7).

6) Check For Shorted EVP/PFE/DPFE Sensor Turn ignition off and wait 10 seconds. With breakout box installed and ECA connected, disconnect EVP/PFE/DPFE sensor. Turn ignition on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between test pins No. 26 and 46. If reading is 4 volts or more, replace EVP/PFE/DPFE sensor and repeat QUICK TEST. If reading is less than 4 volts, reconnect EVP/PFE/DPFE sensor and go to next step.

7) Check For Shorted MAP/BP Sensor All vehicles not equipped with a MAP/BP sensor, go to step 9). Turn ignition off and wait 10 seconds. With breakout box installed and ECA connected, disconnect MAP/BP sensor. Set DVOM on 20-volt scale. With ignition on and engine off, measure voltage between test pins No. 26 and 46. If reading is 4 volts or more, replace MAP/BP sensor. Remove breakout box, reconnect components and repeat QUICK TEST. If reading is less than 4 volts, reconnect MAP/BP sensor. Go to step 9).

Note. There is a break in the step numbering sequence at this point, skipping from step 7) to step 9). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

9) Check VREF Circuit For Short To Ground With breakout box installed and ECA disconnected, turn ignition off and wait 10 seconds. Disconnect TPS, MAP/BP, EVP/PFE/DPFE and 4EAT module (if equipped). Set DVOM on 200-ohm scale. Measure resistance between test pin No. 26 and test pins No. 20, 40, 46 and 60. If any resistance is less than 5 ohms, repair short to ground. Remove breakout box, connect all sensors and repeat QUICK TEST. If original problem still exists, replace ECA and repeat QUICK TEST. If reading is 5 ohms or more, connect sensors, replace ECA and repeat QUICK TEST.

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. For test results to be valid, avoid performing test in unusually hot or cold conditions.

This circuit test is intended to diagnose the following components and circuits

1. ACT Sensor
2. ECT Sensor
3. Vehicle Harness Circuits (ACT, ECT & SIG RTN)
4. ECA

Temperature Sensor Circuits. Scheme 51

4.0L SPFI-MA TEST PIN WIRE COLOR I.D.

4.0L SPFI-MA TEST PIN WIRE COLOR I.D. (RANGER & EXPLORER, NAVAJO)

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

1. Coolant Level Low
2. Electro Drive Cooling Fan
3. Engine Oil Level Low
4. Thermostat
5. Air Cleaner Duct
6. Cooling System, Water Pump or Fan
7. Engine Operating Temperature Low
8. Heat Riser Duct Valve
9. Ambient Temperature Too Low

1) Code 21/116 Or 24/114: Check Installation & Operation Of Temperature Sensor Codes 21/116 (ECT) or 24/114 (ACT) indicates that the corresponding sensor is out of self-test range. Correct range for measurement is .3-3.7 volts. Check for the following possible causes

1. Low Ambient Temperature (Less Than 50°F)
2. Low Coolant Level
3. Faulty Harness Connector
4. Faulty Sensor
5. ACT sensor improperly mounted in air cleaner

If vehicle cannot be started, go to step 3). If vehicle stalls, or starts then dies, go to TEST S, step 1).

Note. There is a break in the step numbering sequence at this point, skipping from step 1) to step 3). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

3) Check Temperature Sensor Resistance With Engine Off Turn ignition off and wait 10 seconds. Disconnect suspected sensor. Set DVOM on 200-k/ohm scale. Measure resistance between sensor signal circuit and SIG RTN circuit at sensor. See ACT & ECT SENSOR SPECIFICATIONS table below for voltage/resistance specifications.

ACT & ECT SENSOR SPECIFICATIONS

If resistance is within specification, perform the following step as applicable.

1. For ECT sensor with a no-start condition, go to TEST A, step 1). DO NOT service code 21/116 at this time.
2. For all others, go to next step.

If resistance is not within specification, replace suspected sensor. Reconnect vehicle harness and rerun QUICK TEST.

4) Check Temperature Sensor Resistance With Engine Running If engine has cooled down, warm engine before measuring ECT sensor resistance. Check for an open thermostat. Turn ignition off and wait 10 seconds. Disconnect suspected sensor. Run engine at 2000 RPM for 2 minutes. Set DVOM on 200-k/ohm scale. Measure resistance between sensor signal circuit and SIG RTN circuit at temperature sensor. See the ACT & ECT SENSOR SPECIFICATIONS table in this test for voltage/ resistance specifications. If resistance is within specification, replace ECA; reconnect components and repeat QUICK TEST. If sensor is not within specification, replace ECT sensor. Reconnect components and repeat QUICK TEST.

Note. There is a break in the step numbering sequence at this point, skipping from step 4) to step 10). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

10) Code 51/118 Or 54/113: Induce Opposite Code (61/117 Or 64/112) Code 51/118 (ECT) or 54/113 (ACT) and 58 (VAT) indicate that the corresponding sensor signal is greater than the self-test maximum. Maximum signal voltage for ECT and ACT sensors is 4.6 volts. Maximum signal voltage for VAT sensors is 3.5 volts. Possible causes for excess voltage signals are as follows

1. Open circuit in vehicle harness (ACT or ECT)
2. Faulty connection
3. Faulty sensor
4. Faulty ECA

Turn ignition off and wait 10 seconds. Disconnect suspected temperature sensor. Connect a jumper wire between sensor signal circuit and SIG RTN circuit at temperature sensor vehicle harness connector. Perform KOEO SELF-TEST. See KEY ON ENGINE OF (KOEO) SELF-TEST under QUICK TEST. If Code 61, 64, 112 or 117 is displayed, replace suspected sensor. Remove jumper wire, reconnect vehicle harness 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 and wait 10 seconds. Ensure suspected temperature sensor is disconnected. Disconnect ECA 60-pin connector. Check for damaged wiring and repair as necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 7 (ECT sensor) or test pin No. 25 (ACT sensor) at breakout box and sensor signal circuit 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, reconnect components and rerun QUICK TEST. If either reading is 5 ohms or more, repair open circuits. Remove breakout box, reconnect components and rerun QUICK TEST.

Note. There is a break in the step numbering sequence at this point, skipping from step 11) to step 20). Break is due to previous chart references to these testing procedures. 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 that sensor signal is less than the self-test minimum. Minimum signal for ACT and ECT sensor is 0.2 volt. Minimum signal for VAT sensor is 0.35 volt. Possible causes for this fault are as follows

1. Circuit grounded in vehicle harness (ACT or ECT)
2. Faulty sensor
3. Faulty ECA
4. Faulty connection

Turn ignition off and wait 10 seconds. Disconnect vehicle harness connector from suspected 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 code 51, 54, 113 or 118 is not displayed, go to next step.

21) Check VREF Circuit Voltage at TPS Turn ignition off and wait 10 seconds. Set DVOM on 20-volt scale. Disconnect TPS. With ignition on and engine off, measure voltage between VREF and SIG RTN at TPS vehicle harness connector. If reading is less than 4 volts or more than 6 volts, go to TEST C, step 1). If reading is 4-6 volts, connect TPS and go to next step.

TPS Connectors. Scheme 52

22) Check Temperature Sensor Signal For Shorts to Ground Turn ignition off and wait 10 seconds. Disconnect suspected sensor. Disconnect ECA 60-pin connector. Check for damaged wiring and repair as necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 200-k/ohm scale. Measure resistance between test pin No. 7 (ECT) or test pin No. 25 (ACT) and test pins No. 40, 46, and 60. If any reading is less than 10 k/ohms, repair short circuit. Remove breakout box, reconnect components and repeat QUICK TEST. If all readings are 10 k/ohms or more, replace ECA. Remove breakout box and reconnect components. Repeat QUICK TEST.

Note. There is a break in the step numbering sequence at this point, skipping from step 22) to step 90). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

90) Continuous Memory Code 51/118, 54/113, 61/117 or 68/112: Check Sensor A Continuous Memory Code 51/118 and 54/113 indicates that sensor signal is greater than the self-test maximum of 4.6 volts. The code is set during normal driving conditions.

Continuous Memory Code 61/117 and 64/112 indicates that sensor signal is less than the self-test minimum of 0.2 volt. The code is set during normal driving conditions.

Possible causes for these faults are as follows

1. Faulty sensor
2. Faulty ECA
3. Open or grounded circuit in harness

SENSOR CODES

Sensor Circuit Fault. Scheme 53

Enter KOEO wiggle test mode. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. Observe VOM or diagnostic 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 next step.

91) Check EEC-IV Vehicle Harness While in CONTINUOUS MONITOR MODE (WIGGLE TEST), observe VOM or diagnostic tester while wiggling and bending EEC-IV harness from sensor to cowl, a small section at a time. 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 next step.

92) Inspecting ECA & Vehicle Harness Connectors Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connector and connector terminals for obvious 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, clear codes and repeat QUICK TEST. Refer to INTERMITTENTS in the TESTS W/O CODES article.

Perform this test when directed by QUICK TEST. This test procedure is intended to diagnose only the MAF, ECA and vehicle harness circuits (VPWR, PWR GND, MAF and MAF RTN).

To prevent replacement of good components, be aware that the following non-EEC related areas may be the cause of problem

1. Air cleaner element
2. Inlet air duct
3. Throttle body

Mass Airflow Sensor (MAF) Circuits. Scheme 54

4.0L SPFI-MA TEST PIN WIRE COLOR I.D.

4.0L SPFI-MA TEST PIN WIRE COLOR I.D. (RANGER & EXPLORER, NAVAJO)

MAF SIGNAL VOLTAGE

MAF signal voltage is typical for A/T vehicles at normal operating temperature. Voltage signal may vary due to engine load and temperature.

1) Code 26/159: Check VPWR Circuit Voltage Code 26/159 indicates MAF sensor voltage is out of self-test range. If code is received during KOEO SELF-TEST, it indicates voltage exceeded the .70-volt test range. If Code 26/159 is received during KOER SELF-TEST, it indicates voltage is not within .20-1.50 volt operating range. Possible causes for this fault are as follows: faulty MAF sensor or faulty ECA.

Code 26/159 may be caused by the use of a garage exhaust ventilation system. Ensure vehicle is vented to outside atmosphere before repeating QUICK TEST.

Turn ignition off and disconnect MAF sensor. Set DVOM on 20-volt scale. Turn ignition on, leaving engine off. Measure voltage between VPWR circuit at MAF sensor vehicle harness connector and battery negative post. If voltage is greater than 10.5 volts, go to next step. If voltage is not greater than 10.5 volts, repair open in VPWR circuit and rerun QUICK TEST.

2) Check MAF Sensor Ground With ignition on and engine off, and MAF sensor disconnected, set DVOM on 20-volt scale. Measure voltage between VPWR circuit and PWR GND circuit at MAF sensor connector. If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts repair open PWR GND circuit. Connect MAF sensor and rerun QUICK TEST.

Note. There is a break in the step numbering sequence at this point, skipping from step 2) to step 10). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

10) Code 66/157 Or 72/129: Check Continuity Of MAF Signal & VPWR Circuits Code 66/157 indicates that MAF signal was less than .40 volt sometime during last 80 warm-up cycles. Code 72/129 indicates insufficient MAF change during DYNAMIC RESPONSE TEST. Possible causes for this fault are as follows

1. Open MAF Circuit
2. Open VPWR Circuit To MAF Sensor
3. Open PWR GND Circuit To MAF Sensor
4. Open MAF RTN Circuit To MAF Sensor
5. MAF Circuit Shorted To Ground
6. Faulty ECA Or MAF Sensor
7. Air Leak Before Or After MAF Sensor
8. MAF Sensor Disconnected

Ensure ignition is off. Disconnect and inspect 60-pin connector at ECA. Service as necessary. Disconnect MAF sensor and install breakout box; leave ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between VPWR circuit at MAF sensor vehicle harness connector and test pins No. 37 and 57 at breakout box.

On 2.9L, 3.0L and 4.0L MA, measure resistance between MAF circuit at MAF sensor vehicle harness connector and test pin No. 14 at breakout box.

On all others, measure resistance between MAF circuit at MAF sensor vehicle harness connector and test pin No. 50 at breakout box. If both resistances are less than 5 ohms, go to next step. If either resistance is greater than 5 ohms, remove breakout box and repair open circuit. Reconnect all components and rerun QUICK TEST.

11) Check MAF Ckt For Shorts To Ground & MAF RTN Ckt With ignition off and MAF sensor disconnected, set DVOM on 200-k/ohm scale. Disconnect ECA 60-pin connector. Inspect connector and terminals. Install breakout box, leaving ECA disconnected.

Measure resistance between test pin No. 14 and test pins No. 15, 40, and 60 at breakout box. If all resistances are greater than 10 k/ohms, go to next step. If resistance in any circuit is less than 10 k/ohms, repair short circuit. Remove breakout box, reconnect components and repeat QUICK TEST.

12) Check Continuity Of PWR GND Circuit Ensure ignition is off. Disconnect MAF sensor. Set DVOM on 200-ohm scale. Measure resistance between PWR GND circuit at MAF sensor vehicle harness connector and battery negative post. If resistance is less than 10 ohms, go to next step. If resistance is greater than 10 ohms, repair open circuit. Reconnect all components and repeat QUICK TEST.

13) Check Continuity Of MAF RTN Circuit With ignition off and MAF sensor disconnected, set DVOM on 200-ohm scale. Disconnect ECA 60-pin connector and inspect pins. Install breakout box; leave ECA disconnected. Measure resistance between MAF RTN circuit at MAF sensor vehicle harness connector and test pin No. 15 at breakout box.

If resistance is less than 5 ohms, go to next step. If resistance is more than 5 ohms, repair open circuit. Remove breakout box, reconnect components and repeat QUICK TEST.

14) Check MAF Signal For Short To Ground With ignition off, breakout box installed and ECA connected, disconnect MAF sensor. Set DVOM on 200-k/ohm scale.

Measure resistance between test pin No. 14 and test pins No. 15, 40 and 60 at breakout box. If resistances are greater than 10 k/ohms, go to next step. If all resistances are less than 10 k/ohms, replace ECA. Remove breakout box, reconnect components and repeat QUICK TEST.

15) Check MAF Circuit Output With ignition off, install breakout box. Ensure ECA and MAF are connected. Set DVOM on 20-volt scale. Start engine.

Measure voltage between test pin No. 14 at breakout box and battery negative post. If voltage is .36-1.5 volts, replace ECA; remove breakout box, reconnect components and repeat QUICK TEST. If voltage is not .36-1.5 volts, replace MAF sensor; remove breakout box, reconnect components and repeat the QUICK TEST.

Note. There is a break in the step numbering sequence at this point, skipping from step 15) to step 20). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

20) Code 56/158: Repeat Self-Test With MAF Sensor Disconnected With ignition off, disconnect MAF sensor from vehicle harness. Start engine and allow to idle for one minute. Turn ignition off. Repeat KOEO SELF-TEST. See KEY ON ENGINE OFF (KOEO) SELF-TEST under QUICK TEST. If Code 66 or 157 is present, replace MAF sensor and rerun QUICK TEST. If Code 66 or 157 is not present, go to next step.

21) Check MAF Circuit For Short To VPWR With ignition off, disconnect MAF sensor and ECA. Disconnect ECA 60-pin connector and inspect for damaged or corroded terminals. Repair as necessary. Set DVOM on 200-k/ohm scale. Measure resistance between MAF and VPWR circuits at MAF sensor vehicle harness connector. If resistance is greater than 10 k/ohms, replace ECA; remove breakout box, reconnect components and repeat QUICK TEST. If resistance is less than 10 k/ohms, repair short circuit; remove breakout box, reconnect components and repeat QUICK TEST.

Perform this test when directed by QUICK TEST or TEST S. Barometric pressure sensor output is digital and must be measured with an oscilloscope or MAP/BP tester.

To prevent replacement of good components, be aware that the following non-EEC related areas may be the cause of problem

1. Unusually High Or Low Atmospheric Barometric Pressure
2. Kinked Or Blocked Vacuum Lines
3. Engine Mechanical Condition (Valves, Vacuum Leaks, Valve Timing, EGR Valve, etc.)

This test is intended to diagnose the following

1. MAP/BP Sensor
2. Vehicle Harness Circuits (VREF, MAP/BP SIG & SIG RTN)
3. MAP Vacuum Line
4. ECA

MAP/BP Circuits & Tester Hookup. Scheme 55

4.0L SPFI-MA TEST PIN WIRE COLOR I.D.

4.0L SPFI-MA TEST PIN WIRE COLOR I.D. (RANGER & EXPLORER, NAVAJO)

MAP SENSOR SPECIFICATIONS

MAP/BP SENSOR SPECIFICATIONS

1) Code 22/126: Check For Power to MAP/BP Sensor Code 22/126 indicates MAP/BP sensor is out of self-test voltage range (1.4-1.6 volts). The following are possible causes of this code

1. MAP/BP Signal Circuit Open Between Sensor And ECA
2. MAP/BP Signal Circuit Shorted To VREF, SIG RTN Or Ground
3. Faulty MAP/BP Sensor
4. Vacuum Trapped At MAP/BP Sensor
5. High Atmospheric Pressure
6. Faulty ECA
7. VREF Circuit Open At Sensor
8. SIG RTN Open At Sensor

Turn ignition off. Disconnect MAP/BP sensor from vehicle harness. Connect MAP/BP tester between wiring harness and MAP/BP sensor. Connect "banana plugs" of tester into DVOM, and set DVOM on 20-volt scale.

Turn ignition on. If Red light or no light is on, then VREF is either too high or too low. Go to next step. If Green light is on, VREF is okay. Go to step 3).

2) Check For Power At Sensor Vehicle Harness Connector With MAP/BP sensor and MAP/BP tester connected, turn ignition on. Disconnect MAP/BP sensor. If only Green light on tester is lit, VREF is correct; replace MAP/BP sensor and repeat QUICK TEST. If Green light is not on, remove MAP/BP tester; reconnect MAP/BP sensor and go to TEST C, step 1).

3) Check MAP/BP Sensor Output With MAP/BP tester connected and ignition on, measure sensor output voltage. If output voltage is within range, for altitude in which vehicle is being tested, remove MAP/BP tester and go to next step. If output reading is outside range, remove MAP/BP tester and go to step 5).

If possible, measure output voltage several known good MAP/BP sensors on available vehicles. The average voltage reading will be typical for your location on date of testing.

MAP SENSOR VOLTAGE OUTPUT

4) Check Continuity Of MAP/BP SIG Circuit Turn ignition off and wait 10 seconds. Disconnect MAP/BP sensor from vehicle harness. Disconnect ECA 60-pin connector. Inspect for damaged wiring and repair as necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between MAP/BP SIG circuit at sensor vehicle harness connector and test pin No. 45. If reading is less than 5 ohms, replace ECA. Reconnect components and repeat QUICK TEST. If reading is 5 ohms or higher, repair open circuit. Remove breakout box, reconnect components and repeat QUICK TEST.

5) Check MAP/BP SIG Circuit For Shorts To VREF, SIG RTN & Ground Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for damaged wiring and repair as necessary. Install breakout box, leaving ECA disconnected. Disconnect harness at MAP/BP sensor. Set DVOM on 200-k/ohm scale. Measure resistance between test pin No. 45 and test pins No. 26, 46, 40 and 60. If any reading is less than 10 k/ohms, repair short circuit. Remove breakout box and reconnect all components. Repeat QUICK TEST. If all readings are 10 k/ohms or more, replace MAP/BP sensor. Remove breakout box and connect all wiring. Repeat QUICK TEST.

Note. There is a break in the step numbering sequence at this point, skipping from step 5) to step 7). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

7) KOER Code 22/126: Check For EGR-Related Codes KOER Code 22/126 indicates MAP/BP signal is out of self-test range during KOER SELF-TEST. Check for Codes 31, 32, 33, 34, 35, 326, 327, 328, 332, 334, 336 or 337. If codes are present, go to appropriate KOER SELF-TEST CODES under CODE-TO-TEST MENU(S) to find the proper CIRCUIT TEST. If codes are not present, go to next step.

8) Check MAP Sensor Operation Turn ignition off and wait 10 seconds. Disconnect vacuum hose from MAP sensor. Connect vacuum pump to MAP sensor and apply 18 in. Hg to sensor. If sensor does not hold vacuum, replace sensor; connect vacuum line and repeat QUICK TEST. If MAP sensor holds vacuum, release vacuum and go to next step.

9) Attempt To Eliminate Code 22/126 Turn ignition off and wait 10 seconds. Plug vacuum hose going to MAP sensor. Start engine and run at 1400-1600 RPM. Slowly apply 15 in. Hg to MAP sensor. With engine operating under these conditions, perform KOER SELF-TEST. Check for Code 22/126; disregard any other codes at this time. If Code 22/126 is still present, replace MAP sensor. If Code 22/126 is no longer displayed, inspect vacuum hose going to MAP sensor. If hose is okay, service other codes at this time. If no other code is present, check engine mechanical condition for cause of low vacuum.

10) Code 72/129: Repeat Dynamic Response (Goose) Test Code 72/129 indicates MAP sensor output did not change enough during dynamic response (Goose) test. Possible causes for this code are as follows

1. System failed to detect partial Wide Open Throttle (WOT)
2. Incorrect MAP sensor vacuum line routing
3. Faulty MAP sensor

Repeat KOER SELF-TEST. Ensure complete WOT is performed during dynamic response portion of test. If KOER Code 72/129 is still present, go to next step. If code is not present, service other codes as necessary.

11) Code 81/128: Check Vacuum Hoses Continuous memory code 81/128 indicates MAP sensor vacuum has not changed more than 2 in. Hg during normal vehicle operation. Possible causes for this code are as follows

1. MAP sensor vacuum supply hose is improperly routed, blocked or is leaking.
2. MAP sensor is leaking. - With ignition off, check vacuum lines for correct routing. Refer to Vehicle Emission Control Identification (VECI) decal. Check for disconnections, kinks or blockage. Repair vacuum lines as necessary and repeat QUICK TEST. If vacuum lines are okay, go to next step.

12) Check MAP Sensor Operation Turn ignition off and wait 10 seconds. Disconnect vacuum supply hose from MAP sensor. Install vacuum pump to MAP sensor. Apply 18 in. Hg to MAP sensor. If MAP sensor holds vacuum, release vacuum and go to next step. If sensor does not hold vacuum, replace MAP sensor; reconnect components and repeat QUICK TEST.

13) Ensure Vacuum To MAP Sensor Decreases During Dynamic Response (Goose) Test Turn ignition off and wait 10 seconds. Use a "T" fitting to install a vacuum gauge in the intake manifold MAP sensor supply line. Perform KOER SELF-TEST while observing vacuum gauge. If vacuum decreases by more than 10 in. Hg during dynamic response (Goose) test, remove gauge and replace MAP sensor; rerun QUICK TEST. If vacuum does not decrease by 10 in. Hg or more, EEC-IV system is okay; repair engine mechanical components as necessary to increase engine vacuum.

Note. There is a break in the step numbering sequence at this point, skipping from step 13) to step 90). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

90) Continuous Memory Code 22/126: Operate MAP/BP Sensor Continuous Code 22/126 indicates MAP/BP sensor was out of self-test range (1.4-1.6 volts) during normal driving conditions. Possible causes for this code are as follows

1. Faulty MAP/BP Sensor
2. Faulty wiring harness or connectors
3. Unusually high or low barometric pressure

While in KOEO wiggle test (see CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST), observe test equipment while performing the following

1. Connect a vacuum pump to MAP/BP sensor.
2. Slowly apply 25 in. Hg to sensor.
3. Slowly bleed off vacuum from sensor.
4. Lightly tap on sensor (to simulate road shock).
5. Wiggle sensor connector.

If a fault is indicated, disconnect sensor and inspect connectors. Repair as necessary. If connectors are okay, replace MAP/BP sensor. Rerun QUICK TEST. If a fault is not indicated, go to next step.

91) Check EEC-IV Vehicle Harness Stay in KOEO wiggle test. Observe VOM or diagnostic tester for indication of fault while shaking, bending or wiggling small sections of harness from sensor connector to firewall. Check harness from firewall to ECA in same manner. If fault is indicated, isolate fault in harness and repair as necessary. Clear codes and repeat QUICK TEST. If no fault is indicated, go to next step.

92) Check ECA & Vehicle Harness Connectors Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connectors and terminals for obvious damage. If connectors and terminals are not okay, repair as necessary. Repeat QUICK TEST. If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous Memory Code 22/126 testing is complete. Refer to INTERMITTENTS in the TESTS W/O CODES article.

Perform this test only when directed by QUICK TEST.

TPS Circuits. Scheme 56

4.0L SPFI-MA TEST PIN WIRE COLOR I.D.

The normal range of throttle angle measurement for TPS is 0-85 degrees. To pass QUICK TEST procedure, the range of throttle rotation (in degrees) must be within 3% of specification.

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault

1. Idle Speed
2. Binding Throttle Shaft Or Linkage
3. Throttle Stop Adjustment
4. Cruise Control Linkage

1) Code 23/121: Check For Other Codes Code 23/121 indicates TPS rotational setting may be out of self-test range. See TPS SPECIFICATION CHARTS. Possible causes for this fault are as follows

1. Binding Throttle Linkage
2. TPS not seated correctly
3. Faulty TPS
4. Faulty ECA

If you are at this step to service a KOEO Code 23/121, check for Code 31/327 in KOER SELF-TEST. If any of these codes is present, return to appropriate KOEO SELF-TEST CODES or KOER SELF-TEST CODES chart under CODE-TO-TEST MENU(S); proceed as directed to Code 31/327. If these codes are not present, go to next step.

2) Code 23/121: Check For Stuck Throttle Plate Code 23/121 indicates Throttle Position Sensor (TPS) rotational setting may be out of self-test range. Possible causes for this fault are as follows

1. Binding Throttle Linkage
2. TPS not seated correctly
3. Faulty TPS
4. Faulty ECA

Inspect throttle body and linkage for binding or sticking. Ensure linkage is in throttle-closed position. If throttle plate or linkage is binding, check for binding throttle or cruise control linkage, vacuum line or harness interference, etc. Repair any problem and repeat QUICK TEST. If no mechanical problem is found, go to next step.

3) Code 53/112: Attempt to Generate Code 63/122 Code 53/112 indicates TPS signal is greater than self-test maximum value. Possible causes for this fault are as follows

1. TPS not seated properly
2. Faulty TPS Sensor
3. Faulty ECA
4. VREF circuit shorted in vehicle harness

Turn ignition off and wait 10 seconds. Disconnect TPS from vehicle harness at throttle body. Inspect and repair any damaged wiring or connector pins. Repeat KOEO SELF-TEST. Ignore all other codes at this time. If Code 63/122 is not displayed, go to step 6). If Code 63/122 is displayed, go to next step.

4) Check VREF Circuit Voltage Turn ignition off and wait 10 seconds. Set DVOM on 20-volt scale. Disconnect TPS and both 4EAT module vehicle harness connectors. With ignition on and engine off, measure voltage between VREF and SIG RTN at TPS vehicle harness connector. If reading is less than 4 volts or more than 6 volts, reconnect sensor and go to TEST C, step 1). If reading is between 4 and 6 volts, replace TPS and repeat QUICK TEST.

Note. There is a break in the step numbering sequence at this point, skipping from step 4) to step 6). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

6) Checking TP Circuit For Short To Power Turn ignition off and wait 10 seconds. Disconnect TPS from harness. Set DVOM on 200-k/ohm scale. Disconnect ECA 60-pin connector. Inspect and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Measure resistance between test pin No. 47 and test pins No. 26 and 57. If either reading is less than 10 k/ohms, repair short in harness; connect components and repeat QUICK TEST. If both readings are 10 k/ohms or more, replace ECA; reconnect components and repeat QUICK TEST.

Note. There is a break in the step numbering sequence at this point, skipping from step 6) to step 10). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

10) Code 63/122: Attempt To Generate Code 53/123 or 23/121 Code 63/122 indicates TP signal is less than minimum self-test value. Refer to TPS SPECIFICATION CHART at beginning of this circuit test. Possible causes for this fault are as follows

1. TPS not seated correctly
2. Faulty TPS
3. Faulty ECA
4. Open circuit in vehicle harness
5. Grounded circuit in vehicle harness

Turn ignition off and wait 10 seconds. Disconnect TPS from harness. Install a jumper wire between VREF and TP circuit at TPS vehicle harness connector. Perform KOEO SELF-TEST. If no codes are generated, immediately remove jumper wire and go to step 14). Check for Codes 53/123 or 23/121 (ignore all other codes at this time). If Codes 53/123 or 23/121 are not present, remove jumper wire, and go to next step. If either Code 53/123 or 23/121 is displayed, replace TPS; remove jumper and repeat QUICK TEST.

11) Check VREF Circuit Voltage Turn ignition off and wait 10 seconds. Disconnect TPS from vehicle harness. Inspect and repair any damaged wiring. Set DVOM on 20-volt scale. With ignition on and engine off, measure voltage between VREF and SIG RTN circuits at TPS vehicle harness connector. If reading is less than 4 volts or more than 6 volts, go to TEST C, step 1). If reading is between 4 and 6 volts, reconnect all components and go to next step.

12) Check TPS Circuit Continuity Turn ignition off and wait 10 seconds. Leave TPS disconnected. Set DVOM on 200-ohm scale and disconnect ECA 60-pin connector. Inspect and repair any damaged wiring. Install breakout box and connect ECA. Measure resistance between TP circuit at TPS vehicle harness connector and test pin No. 47. If reading is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components and repeat QUICK TEST. If reading is less than 5 ohms, go to step 14).

Note. There is a break in the step numbering sequence at this point, skipping from step 12) to step 14). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

14) Check TP Circuit For Shorts To Ground Turn ignition off and wait 10 seconds. Leave TPS disconnected. Disconnect ECA 60-pin connector. Inspect and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-k/ohm scale. Measure resistance between test pin No. 47 and test pins No. 40, 46 and 60. If any reading is less than 10 k/ohms, repair short circuit; reconnect all components and repeat QUICK TEST. If all readings are 10 k/ohms or more, replace ECA. Remove breakout box, reconnect all components and repeat QUICK TEST.

Note. There is a break in the step numbering sequence at this point, skipping from step 14) to step 20). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

20) KOER Code 73/167: Perform Correct Dynamic Response (Goose) Test At Wide Open Throttle (WOT) KOER Code 73/167 indicates TPS did not exceed 25% of its rotation during dynamic response check portion of KOER SELF-TEST. A complete WOT must be performed during dynamic response check portion.

Run KOER SELF-TEST. Ensure WOT is performed during dynamic response portion of test. If Code 73/167 is still present, go to next step. If code is not present, system is unable to duplicate Code 73/167 at this time. Service any other KOER codes at this time. If no other KOER code is present, testing is complete.

21) Check TPS Movement During Dynamic Response Test Turn ignition off and disconnect ECA 60-pin connector. Inspect and repair any damaged wiring. Install breakout box and connect ECA. Set DVOM on 20-volt scale. Connect DVOM between test pins No. 46 and 47. Perform KOER SELF-TEST and ensure a proper WOT is performed. Monitor DVOM reading during dynamic response check. If reading exceeds 3.5 volts, replace ECA; remove breakout box, reconnect all components and repeat QUICK TEST. If reading does not exceed 3.5 volts, ensure TPS is correctly installed and adjusted. If TPS is correctly installed and adjusted, replace TPS. Repeat QUICK TEST.

Note. There is a break in the step numbering sequence at this point, skipping from step 21) to step 90). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

90) Continuous Memory Code 53/123: Monitor TPS Circuit Under Simulated Road Shock Conditions Enter KOEO wiggle test (see CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST); observe DVOM or diagnostic tester for indication of fault while slowly opening throttle to WOT. Slowly bring throttle to closed position, and lightly tap TPS and wiggle harness connector. This test checks for open or short in TPS, connectors and vehicle harness. If no fault is indicated, go to step 92). If fault is indicated, go to next step.

91) Measure TP Circuit Voltage While Exercising TPS Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect and repair any damaged wiring. Install breakout box, leaving ECA connected. Stay in KOEO wiggle test (as in previous step). Connect DVOM between test pins No. 47 and 46. Set DVOM on 20-volt scale. With ignition on and engine off, observe DVOM and repeat step 90). If fault occurs at less than 4.25 volts, inspect TPS connectors and terminals. If connectors and terminals are okay, replace TPS; clear codes and repeat QUICK TEST. If fault does not occur at less than 4.25 volts, TPS over-travel may have caused Continuous Memory Code 53/123. TPS is okay, go to next step to check harness.

92) Check EEC-IV Vehicle Harness While in KOEO wiggle test (CONTINUOUS MONITOR MODE), shake, bend and wiggle small sections of EEC-IV harness from TPS vehicle harness connector to firewall, and from firewall to ECA. If fault is indicated, isolate fault in wiring and repair as necessary. Clear codes and repeat QUICK TEST. If no fault is indicated, go to next step.

93) Check ECA & Harness Connectors Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connectors and terminals for obvious damage. If connectors and terminals are damaged, repair as necessary; clear Continuous Memory Codes and repeat QUICK TEST. If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous Memory Code 53/123 testing is complete.

94) Continuous Memory Code 63/122: Monitor TP Circuit Under Simulated Road Shock Conditions Enter KOEO wiggle test. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. Observe VOM or diagnostic tester for indication of fault while performing the following

1. Slowly open throttle to WOT.
2. Slowly bring throttle to closed position.
3. Lightly tap TPS and wiggle connector.

This test checks for open or short in TPS, connectors and vehicle harness. If fault is indicated, disconnect TPS. Inspect connectors and terminals. If connectors and terminals are okay, replace TPS. Clear Continuous Memory Codes and repeat QUICK TEST. If no fault is indicated, go to next step.

95) Check EEC-IV Vehicle Harness While in KOEO wiggle test (CONTINUOUS MONITOR MODE), shake, bend and wiggle small sections of EEC-IV harness from TPS sensor vehicle harness connector to firewall, and from firewall to ECA. If fault is indicated, isolate fault in wiring and repair as necessary. Clear Continuous Memory Codes and repeat QUICK TEST. If no fault is indicated, go to next step.

96) Check ECA & Harness Connectors Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connectors and terminals for damage. If connectors and terminals are damaged, repair as necessary. Clear Continuous Memory Codes and repeat QUICK TEST. If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous Memory Code 63/122 testing is complete.

Perform this test when directed by QUICK TEST.

This CIRCUIT TEST is intended to diagnose the following

1. VSS harness circuits
2. ECA
3. Vehicle Speed Sensor (VSS)

Vehicle Speed Sensor Circuit. Scheme 57

4.0L SPFI-MA TEST PIN WIRE COLOR I.D.

Perform this test when directed by QUICK TEST.

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: brakelight bulb, brakelight switch or brakelight fuse. This test is intended to diagnose a faulty BOO circuit or ECA.

BOO Circuit. Scheme 58

4.0L SPFI-MA TEST PIN WIRE COLOR I.D.

4.0L SPFI-MA TEST PIN WIRE COLOR I.D. (RANGER & EXPLORER, NAVAJO)

1) Code 74/536: Verify Brake Pedal Was Depressed Code 74/536 indicates that when brake pedal is depressed during KOER SELF-TEST, BOO signal did not cycle high and low. Possible causes for this fault are as follows

1. Brake pedal not depressed during self-test
2. Open brakelight circuit (BATT + side of BOO splice)
3. Short to ground or power
4. Faulty ECA

If brake was NOT depressed during KOER SELF-TEST, repeat test; depress and release brake pedal ONLY once during test. Depress and release brake pedal AFTER dynamic response code, but BEFORE brief WOT. If pedal was depressed, go to next step.

2) Check Operation Of Brakelights With ignition on, check operation of brakelights. If brakelights operate normally, go to next step. If brakelights do not operate, go to step 4). If brakelights are always on, go to step 5).

3) Check For BOO Circuit Cycling Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, and loose wires. Install breakout box, leaving ECA disconnected. Set DVOM on 20-volt scale. Measure voltage between test pins No. 2 or 5 and 40 while applying and releasing brake. If voltage cycles, switch circuit is okay; replace ECA and repeat QUICK TEST. If voltage does not cycle, repair open circuit in BOO circuit between ECA and BOO connection to brakelight circuit.

4) Check For Power To Brake Switch Ensure related fuses and brakelight bulbs are in good condition. Turn ignition off and wait 10 seconds. Disconnect brakelight switch (located on brake pedal). Set DVOM on 20-volt scale. Measure voltage between BATT (+) input to brakelight switch and chassis ground. If voltage is greater than 10 volts, verify operation of brakelight switch; if brakelight switch is okay, repair open circuit between brakelight switch and brakelight ground. Reconnect components and rerun QUICK TEST. If voltage is less than 10 volts, repair open BATT (+) circuit to brakelight switch. Reconnect all components and rerun QUICK TEST.

5) Verify Brake Switch Is Not Always Closed With ignition off, disconnect brakelight switch (located on brake pedal). Turn ignition on, leaving engine off. If brakelights are still on, go to next step. If brakelights are not on, verify proper installation of brakelight switch. If installation is okay, replace brakelight switch. Reconnect all components and rerun QUICK TEST.

6) Check For Short To Power In ECA Turn ignition off. Reconnect BOO circuit harness connector. Disconnect ECA. With ignition on and engine off, check if brakelights are on. If brakelights are on, go to next step (Cougar and Thunderbird with floor shift A/T). On all other models, repair short to power between ECA and harness connector; repeat QUICK TEST. If brake lights are not on, replace ECA and repeat QUICK TEST.

7) Check For Short To Power In the Brake/Shift Interlock Solenoid Turn ignition off. Disconnect ECA and brakelight switch. Disconnect brake/shift interlock solenoid. Turn ignition on. If brake lights are still on, repair short to power on BOO/brakelight circuit. Reconnect all components and rerun QUICK TEST. If brake lights are not on, replace brake/shift interlock solenoid. Reconnect all components and rerun QUICK TEST.

Note. There is a break in the step numbering sequence at this point, skipping from step 7) to step 10). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

10) Code 75/531: Check For Operation Of Brake Lights Code 75/531 indicates that while brake pedal was released during KOER SELF-TEST, BOO signal was high. Possible causes for this fault are as follows

1. Brake pedal depressed during entire self-test.
2. Open BOO/brakelight circuit (between ECA and brakelight ground)
3. Short to POWER
4. Faulty ECA

Turn ignition on. Check brakelight operation. If brakelights operate normally, go to next step. If brakelights are always on, go back to step 5). If brakelights are never on, inspect brakelight bulbs. If bulb is okay, repair open circuit between BOO connection to brakelight circuit and brakelight ground.

11) Check Continuity Of BOO Circuit Turn ignition off. Install breakout box, leaving ECA disconnected. Set DVOM on 20O-ohm scale. Disconnect BOO circuit harness connector. Measure resistance between test pin No. 2 at breakout box and BOO circuit at harness connector. If resistance is less than 5 ohms, replace ECA; remover breakout box, reconnect all components and rerun QUICK TEST. If resistance is greater than 5 ohms, repair open circuit. Remove breakout box, reconnect all components and repeat KOER SELF-TEST.

Note. There is a break in the step numbering sequence at this point, skipping from step 11) to step 90). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

90) Continuous Memory Code 536: Check For Proper Brakelight Switch Installation Code 536 indicates a BOO circuit failure. If BOO input does not cycle after a predetermined number of transitions from 0MPH to a specific speed, BOO input is assumed to be damaged and code 536 is set. Possible causes for this code are as follows

1. Brakelight switch improperly installed
2. Open brakelight/BOO circuit
3. Damaged brakelight switch
4. Damaged brakelight ground connection

Inspect brakelight switch for proper installation (alignment with pedal), corrosion or damaged wiring. Repair any problems and rerun QUICK TEST. If all components are in good condition, go to next step.

91) Check Brakelight For Ground Check brakelight ground connection for corrosion or other damage. Check brakelight connector and wires for corrosion or other damage. If brakelight wires, connector and connection are okay, go to next step. If wires, connector and connection are not okay, repair as necessary; clear codes and rerun QUICK TEST.

92) Check Brakelight/BOO circuits For Short To Power Do not depress brake pedal during this test. Turn ignition on, leaving engine off. While watching brakelights, wiggle brakelight/BOO circuit wires and connectors. If brakelights do not flash, go to next step. If brakelights flash, isolate and repair short to power as necessary. Clear codes and rerun QUICK TEST.

93) Check Brakelight Circuit Continuity With ignition off; depress and hold brake pedal. Wiggle brakelight circuit wires and connectors while observing brakelights. Tap brakelight switch to simulate road shock while observing brakelights. If brakelights are on constantly and do not blink or go off, go to next step. If brakelights blink or go off, isolate and repair open in brakelight circuit. Clear codes and rerun QUICK TEST.

94) Check Continuity Of BOO Circuit Turn ignition off. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Install breakout box, leaving ECA disconnected. Set DVOM on 20O-ohm scale. Measure resistance between test pin No. 2 or No. 5 at breakout box and brakelight circuit at brakelight switch connector. While observing DVOM, wiggle BOO circuit wires and connectors. If resistance is ever greater than 5 ohms, isolate and repair open circuit in BOO circuit; remover breakout box, clear codes rerun QUICK TEST. If resistance is always less than 5 ohms, fault cannot be duplicated at this time. Clear codes and see INTERMITTENTS in the TESTS W/O CODES article in this section.

Perform this test when instructed during QUICK TEST, or when directed by other test procedures.

This test is intended to diagnose only the following

1. MAP/BP Sensor
2. Mass Airflow (MAF) Sensor
3. Fuel Injectors
4. Throttle Position Sensor (TPS)
5. Air Charge Temperature (ACT) Sensor

4.0L SPFI-MA TEST PIN WIRE COLOR I.D.

If possible, measure several known good MAP/BP sensors on available vehicles. Average voltage reading will be typical for your location on date of testing.

MAP SENSOR VOLTAGE OUTPUT

4) Check ACT Sensor Ensure ambient temperature is greater than 50°F before performing this test. Check and repair any air leaks in front of ACT sensor. Turn ignition off. Install breakout box and connect ECA to breakout box. Set DVOM to 20-volt scale. See TEST DF for schematic. Connect DVOM to test pins No. 25 and 46. Start engine and let idle. Observe voltage as engine warms up. If voltage does not decrease smoothly and stabilize after engine reaches operating conditions, replace ACT sensor; remove breakout box and rerun QUICK TEST. If voltage decreases smoothly and stabilizes when engine reaches operating conditions, system is operating properly at this time. Reconnect all components and rerun QUICK TEST.

5) Visual Inspection Of MAF Sensor Code 184 indicates MAF sensor value is higher than expected. Code 185 indicates MAF sensor value is lower than expected. Turn ignition off. Check for air leaks between ISC solenoid and MAF sensor. Inspect MAF sensor for oil contamination caused by excessive blow-by or malfunctioning PCV. If problems are found, repair as necessary; clear codes and rerun QUICK TEST. If all checks are okay, go to step 8).

6) Check MAF Sensor Turn ignition off. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Install breakout box and connect ECA. Set DVOM on 20-volt scale. Start engine and allow to idle until engine reaches normal operating temperature. Measure voltage between MAF signal and test pin 40/60 of breakout box.

If voltage is within acceptable range, system is operating normally at this time. See INTERMITTENTS in the TESTS W/O CODES article in this section. If voltage is not within acceptable range, replace MAF sensor. See MAF SENSOR DATA table for specification. Reconnect all components and rerun QUICK TEST.

MAF Sensor Graph. Scheme 59

MAF SENSOR DATA

7) Visual Vacuum Checks Code 186 indicates pulse width is longer than expected (rich). Code 187 indicates pulse width is shorter than expected (lean). Inspect air cleaner and air inlet duct; replace or repair an necessary. Check for unmetered air between MAF sensor and ISC bypass solenoid. Check all engine vacuum hoses for damage, leaks, blockage and proper routing. Make necessary repairs and rerun QUICK TEST. If all items are okay, go to next step.

8) Check Fuel Pressure Turn ignition off. Install fuel pressure gauge. Ensure fuel pressure regulator is connected to manifold vacuum (if applicable). Start engine and run at idle. If fuel pressure is within specifications, go to next step. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. If fuel pressure is not within specifications, repair fuel pump or fuel pressure regulator as necessary.

9) Check Systems Ability To Hold Fuel Pressure Turn ignition on, leaving engine off. If fuel pressure remains at specification for 60 seconds, go to next step (for SEFI), or go to TEST H, step 7) (for EFI). If fuel pressure does not remain at specification, repair fuel delivery system as necessary.

10) Cylinder Balance Test Run KOER SELF-TEST. After last repeated code, wait 5-10 seconds then "goose" throttle lightly (not wide-open throttle). This will activate cylinder balance test. If code 90 is present after test, go back to step 5). If code 90 is not present after test, go to TEST H, step 4).

TEST H - FUEL CONTROL

Note. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article.

Perform this test when instructed during QUICK TEST, or when directed by other test procedures.

See HOW TO USE CIRCUIT TESTS in this article before performing this test. Fuel contaminated engine oil may affect Codes 41/172, 91/136, 42/173 or 92/137. If this is suspected, remove PCV valve from valve cover and repeat QUICK TEST. If problem is corrected, change engine oil and filter. Use this test to diagnose only the following components

1. HEGO sensor
2. HEGO sensor connection
3. Vacuum systems
4. ECA
5. HEGO signal and ground circuit
6. Electrical circuits (HEGO GND, HEGO, INJ 1-8, VPWR and SIG RTN)
7. Fuel injector

To prevent replacement of good components, be aware that the following non-EEC areas may be the cause of driveability concerns

1. Ignition coil, distributor cap or rotor
2. Faulty or fouled spark plugs or wires
3. Faulty CANP system
4. Distributorless Ignition System (DIS)
5. EGR valve and gasket
6. Air filter
7. Fuel or engine oil contamination
8. Poor electrical ground
9. Faulty fuel pressure
10. Intake or exhaust system leaks
11. Engine below normal operating temperature

INDIVIDUAL INJECTOR RESISTANCE (1)

INJECTOR BANK RESISTANCE

Test H - Fuel Control System Schematic. Scheme 60

4.0L SPFI-MA TEST PIN WIRE COLOR I.D.

4.0L SPFI-MA TEST PIN WIRE COLOR

1) Check For Contaminated Engine Oil Turn ignition off. Remove PCV valve from valve cover. Inspect valve cover hole and PCV for damage, sludge build up, blockage and movement of valve plunger. Repair as necessary. Perform KOER SELF-TEST. If vehicle is a no start, KOER codes 41/172, 91/136, 42/173 or 92/137, or Continuous Memory Codes 176, 177, 144/41, 91/139, 171, 175, 174 or 178 are set, reinstall PCV valve and go to next step. If no code is set, change engine oil and filter; reinstall PCV valve. Drive vehicle for 5 miles at 55 MPH. Rerun QUICK TEST.

2) Check Fuel Pressure Turn ignition off and wait 10 seconds. Install fuel pressure gauge. Ensure manifold vacuum supply is connected to fuel pressure regulator (if equipped). Run engine at idle and check fuel pressure. If vehicle will not start, cycle ignition on and off several times. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article.If vehicle is a no start, cycle ignition on and off several times. If fuel pressure is within specification, go to next step. If pressure is not to specification, remove fuel pressure gauge. Repair electric fuel pump or fuel pressure regulator.

3) Check Systems Ability To Hold Fuel Pressure Turn ignition on, leaving engine off. If fuel pressure remains at specification for 60 seconds, go to next step (for no starts), go to step 5) (for EFI), or go to step 6) (for SEFI). If fuel pressure is not as described, repair fuel delivery system as necessary.

4) Fuel Delivery Test Ensure fuel is of good quality. With ignition off, install fuel pressure gauge and pressurize fuel system as in step 1). Disconnect inertia switch. Crank engine for 5 seconds. If fuel pressure drop is greater than 5 psi after 5 seconds of cranking, EEC-IV system is not the cause of no-start condition. Check additional no-start tests in the TESTS W/O CODES article in this section. If fuel pressure drop is less than 5 psi, remove fuel pressure gauge and reconnect inertia switch; go to step 7) (for EFI), or step 8) (for SEFI).

5) Cylinder Balance Test: EFI Engines Connect a tachometer to engine. Start engine and run at idle. Disconnect and reconnect injectors one at a time, noting RPM drop as each injector is disconnected. Note that ISC motor will attempt to re-establish RPM. If each injector does not produce a momentary drop in RPM, go to step 7). If each injector produces a momentary drop in RPM, go to step 13) (for symptoms or codes 41/172, 91/136 or 176), step 24) (for codes 42/173, 92/137 or 177), or step 14) (for all others).

6) Cylinder Balance Test: SEFI Engines ONLY Perform KOER SELF-TEST. After last code is displayed, wait 5-10 seconds. Enter CYLINDER BALANCE TEST by briefly opening throttle for one second (not WOT). Test time is approximately 2-3 minutes. A Code 77/538 indicates throttle is touched when the test is ran, and that test is not completed. To interpret codes received from test, refer to CYLINDER BALANCE TEST SERVICE CODES table. If a Cylinder Balance Test Code is displayed, go to step 8). If a Cylinder Balance Test Code is not displayed, fuel delivery is okay; fault is in an area common to all cylinders. For symptoms or code 41/172, 91/136 or 176, go to step 13). For code 42/173, 92/137 or 177, go to step 24). For all other codes, go to step 14.

Code 538 could also be outputted if Continuous Memory Code 214 (CID) is present. If Continuous Memory Code 214 is present, see appropriate chart under CODE-TO-TEST MENU(S) for instruction.

CYLINDER BALANCE TEST SERVICE CODES

7) Check Injector & Harness Resistance: EFI Engines Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect pins for damage. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance of injector banks between test pins No. 37 and 58 (injector bank No. 1) or 59 (injector bank No. 2) at breakout box. Record resistance. Refer to appropriate INJECTOR BANK RESISTANCE table in this circuit test. If each resistance is within specifications for appropriate engine, go to step 12). If resistance is not as specified, repair open circuit on VPWR circuit (for no start), or go to step 9 (for all other conditions).

8) Check Injector & Harness Resistance: SEFI Engines Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect pins for damage. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure and record resistance between suspected injector circuit test pin and test pin No. 37. For no starts, measure and record resistance between any injector circuit test pin and test pin No. 37. Refer to appropriate INJECTOR BANK RESISTANCE table in this circuit test. If each resistance is within specifications for appropriate engine, go to step 12). If resistance is not as specified, repair open circuit on VPWR circuit (for no start), or go to step 9 (for all other conditions).

9) Check Continuity Of Fuel Injector Harness Turn ignition off and wait 10 seconds. Install breakout box, leaving ECA disconnected. Disconnect injector vehicle harness connector at injectors. Set DVOM to 200-ohm scale. Measure resistance between test pin No. 37/57 at breakout box and VPWR pin at each injector vehicle harness connector. See the TEST H - FUEL CONTROL SYSTEM SCHEMATIC figure near the beginning of this circuit test. Measure resistance between injector test pin(s) at breakout box and the same injector circuit signal pin at each injector vehicle harness connector. If each resistance is less than 5 ohms, go to next step. If each resistance is greater than 5 ohms, repair open circuit. Remove breakout box, reconnect all components and drive vehicle for 5 miles at 55 MPH. Rerun QUICK TEST.

10) Check Injector Harness Circuit For Short To Power Or Ground Turn ignition off and wait for 10 seconds. With breakout box installed and ECA disconnected, disconnect fuel injector vehicle harness. See the TEST H - FUEL CONTROL SYSTEM SCHEMATIC figure near the beginning of this circuit test. Set DVOM to 200-k/ohm scale. Measure resistance between injector test pin(s) and test pins No. 37/57, 40, 46 and 60. Measure resistance between injector test pin(s) at breakout box and chassis ground. If each resistance is greater than 10 k/ohms, replace injector per cylinder balance test service code and rerun QUICK TEST (for SEFI), or go to next step (for EFI). If each resistance is less than 10 k/ohms, repair short. Remove breakout box, reconnect all components and drive vehicle for 5 miles at 55 MPH. Rerun QUICK TEST.

11) Isolate Faulty Injector Circuit Turn ignition off. Install breakout box and disconnect ECA. Disconnect all injectors on suspected bank. With DVOM set on 200-ohm scale, connect one injector and measure resistance between test pins No. 37 and 58 or 59. Disconnect injector and repeat process for all other injectors. See appropriate INDIVIDUAL INJECTOR RESISTANCE table for specifications. If all injectors are within specifications, go to step 12). If injectors are not as specified, remove breakout box. Reconnect ECA and injectors. Repair open or short in injector harness. If circuit is okay, replace injector. Drive vehicle for 5 miles at 55 MPH. Rerun QUICK TEST.

12) Check Injector Drive Signal With ignition off and breakout box installed, connect ECA to breakout box. Use a non-powered 12-volt test light and connect as follows

1. EFI Engines - Connect test light between test pins No. 37 and 58 at breakout box. Connect light between test pins No. 37 and 59 at breakout box.
2. Sequential PFI Engines (SEFI) - Connect test light between test pin No. 37 and the suspected injector(s) test pin at breakout box.

Crank or start engine. If test light glows dimly, system is operating properly. remove breakout box and reconnect ECA. Clean and test injectors. Drive vehicle for 5 miles at 55 MPH. Rerun QUICK TEST and CYLINDER BALANCE TEST.

If test light does not glow dimly (no light/bright light), check injector circuit for shorts to ground. If system is okay, remove breakout box and replace ECA. Remove breakout box and reconnect all components. Drive vehicle for 5 miles at 55 MPH. Rerun QUICK TEST.

13) Check Thermactor Operation If vehicle is equipped with Pulse-Air or does not have Thermactor System, ignore this step and go to next step. With dual HEGO, code 41/172 refers to right or rear HEGO, and code 91/136 or 176 refers to left or front HEGO. A HEGO that is always lean could be caused by Thermactor air being diverted upstream from HEGO sensor. Turn ignition off and wait 10 second. Disconnect Thermactor air hose(s) from Thermactor pump. Run KOER SELF-TEST. If codes 41/172, 91/136 or 176 are present, reconnect Thermactor air hose(s) and go to next step. If codes 41/172, 91/136 or 176 are not present, repair thermactor system as necessary.

14) Check HEGO Integrity A HEGO sensor that is always lean, slow to switch or does not switch could be caused by the following

1. Moisture inside HEGO sensor, or harness connector causing a short to ground
2. HEGO sensor coated with containments
3. HEGO circuit open
4. HEGO circuit shorted to ground

Turn ignition off and wait 10 seconds. Inspect HEGO harness for chaffing, burns or other indications of damage; repair or replace as necessary. Inspect HEGO sensor and connector for signs of water entry; repair or replace as necessary. Start engine and run at 2000 RPM for 2 minutes. Turn ignition off and wait 10 seconds. Run KOER SELF-TEST. If fault codes are present, go to next step (for MAP sensor-equipped vehicles), or step 16) (for MAF sensor-equipped vehicles). If no code is present, go to step 21).

15) Checking HEGO Sensor On Engines With MAP Sensors Turn ignition off and set DVOM on 20-volt scale. Disconnect appropriate HEGO sensor from vehicle harness. Connect DVOM to HEGO SIGNAL lead at sensor connector and battery negative terminal (3-wire HEGO). Connect DVOM to HEGO SIGNAL and HEGO GND leads at sensor connector (4-wire HEGO). Disconnect and plug vacuum line MAP sensor. Start engine and apply 10-14 in Hg to Manifold Absolute Pressure (MAP) sensor. Run engine at 2000 RPM for 2 minutes. If reading is greater than 0.5 volt within 2 minutes, go to step 17). If reading is less than 0.5 volt within 2 minutes, replace HEGO sensor; reconnect MAP and rerun QUICK TEST.

Vacuum or air leaks in non-EEC-IV related areas may cause Code 41 or 91. Check the following areas: leaking vacuum actuator (A/C control motor, etc.) engine seals, EGR system, PCV system and lead contamination of HEGO sensor.

Checking HEGO Sensor. Scheme 61

16) Check HEGO Sensor On Engines With MAF Sensor The purpose of this test is to verify HEGO sensor can generate a voltage signal of greater than 0.5 volt during KOER SELF-TEST. With ignition off and DVOM set on 20-volt scale, disconnect appropriate HEGO sensor from harness. Depending on type of sensor (3 wires or 4 wires), connect DVOM as follows

1. 4-Wire HEGO Sensors - Connect DVOM between HEGO SIGNAL and HEGO GND at HEGO sensor connector.
2. 3-Wire HEGO Sensors - Connect DVOM to HEGO SIGNAL at sensor and battery negative terminal.

Rerun KOER SELF-TEST and monitor HEGO sensor voltage. If voltage is greater than 0.5 volt, go to next step. If voltage is less than 0.5 volt, replace HEGO sensor and rerun QUICK TEST.

Vacuum or air leaks in non-EEC-IV related areas may cause Code 41 or 91. Check the following areas: leaking vacuum actuator (A/C control motor, etc.) engine seals, EGR system, PCV system and lead contamination of HEGO sensor.

17) Check Continuity Of HEGO SIGNAL & HEGO GROUND Circuits Turn ignition off. Install breakout box, leaving ECA disconnected. Disconnect suspected HEGO sensor from vehicle harness. Inspect both ends of connector for damage or pushed-out pins, moisture, corrosion, loose wires or other damage. Repair as necessary. Set DVOM on 200-ohm scale. Measure resistance between HEGO SIGNAL (test pin No. 29) at breakout box and HEGO SIGNAL at vehicle harness connector.

On 3-Wire HEGO sensors, measure resistance between HEGO GROUND test pin at breakout box and battery negative terminal.

On 4-Wire HEGO sensors, measure resistance between HEGO GROUND test pin at breakout box and HEGO GND at vehicle harness connector. Where applicable, measure resistance between HEGO GND and SIG RTN at breakout box.

If each resistance is less than 5 ohms, go to next step. If each resistance is greater than 5 ohms, repair open circuit. Remove breakout box and reconnect all components. Drive vehicle for 5 minutes at 55 MPH. Rerun QUICK TEST.

18) Check HEGO Circuit For Short To Ground Turn ignition off. Leave breakout box installed and ECA disconnected. Disconnect HEGO sensor and set DVOM on 200-k/ohm scale. Measure resistance between HEGO SIGNAL (test pin No. 29) and test pins No. 40, 46 and 49 at breakout box. If any reading is less than 10 k/ohms, repair short to ground; remove breakout box, reconnect all components and repeat QUICK TEST. If reading is 10 k/ohms or more, go to next step.

19) Check HEGO Sensor For Short To Ground With ignition off, breakout box installed and ECA disconnected, set DVOM to 200-k/ohm scale. Disconnect HEGO sensor. Measure resistance between PWR GND and HEGO SIGNAL at HEGO sensor connector. For trucks with 4-wire sensors, measure resistance between PWR GND, HEGO GND, SIG RTN and HEGO SIG at HEGO sensor connector. If resistance is less than 10 k/ohms, replace HEGO sensor and remove breakout box; reconnect all components, drive vehicle for 5 miles at 55 MPH and repeat QUICK TEST. If resistance is greater than 10 k/ohms, perform the following procedure as applicable.

1. For codes 144/41, 139/91, 171, 174, 175 or 178, go to step 90).
2. On engines with MAP sensor, go to step 20).
3. On engines with MAF sensor, remove breakout box. Reconnect HEGO sensor and replace ECA. Drive vehicle for 5 miles at 55 MPH. Rerun QUICK TEST.

20) Attempt To Eliminate Code 41/172, 91/136 Or 176: Engines With MAP Sensor Turn ignition off. Install breakout box; reconnect ECA and HEGO sensor. Ensure MAP sensor vacuum hose is disconnected and plugged. Apply 10-14 in. Hg to MAP sensor. Start and run engine at 2000 RPM for 2 minutes. Allow engine to return to idle. Perform KOER SELF-TEST. If you are here for Continuous Memory Codes, vehicle has to be driven 5 miles at 55 MPH. If Code 41/172, 91/136 or 176 is still present, remove breakout box. Reconnect ECA and MAP sensor vacuum line. If engine still runs rough, go to TEST S, step 2). If engine does not run rough, replace ECA; drive vehicle 5 miles at 55 MPH then repeat QUICK TEST.

If Code 41/172, 91/136 or 176 is not present, remove breakout box and reconnect ECA and MAP sensor vacuum hose. HEGO input circuit and fuel delivery are okay; fault is in area common to all areas. Service as necessary.

21) Check Resistance Of HEGO Heating Element Turn ignition off. Disconnect suspected HEGO sensor. Inspect both ends of connector for damaged or pushed-out pins, moisture, corrosion, loose wires or other damage. Repair as necessary. Set DVOM on 200-ohm scale. Measure resistance between KPWR circuit and PWR GND circuit at HEGO sensor connector. Hot to warm resistance should be 5.0-30.0 ohms. Room temperature resistance is 2.0-5.0 ohms. If resistance is within specification, go to next step. If resistance is not as specified, replace HEGO sensor and repeat QUICK TEST.

Checking HEGO Sensor. Scheme 62

22) Check For Power At HEGO Harness Connector With ignition on and engine off, and HEGO disconnected, set DVOM on 20-volt scale. Measure voltage between KEY POWER circuit and PWR GND circuit at HEGO vehicle harness connector. If voltage is greater than 10.5 volts, HEGO system and fuel delivery are okay; HEGO sensor may have cooled before KOER SELF-TEST. If driveability symptom persists, fault is in area common to all cylinders, such as air or vacuum leaks, fuel contamination, EGR, MAP, etc. If voltage is less than 10.5 volts, go to next step.

Identifying HEGO Sensor Harness Connector. Scheme 63

23) Check Continuity Of Power Ground Circuit Turn ignition off and wait 10 seconds. Disconnect HEGO sensor and set DVOM on 200-ohm scale. Measure resistance between PWR GND circuit at HEGO vehicle harness connector and battery negative post. If resistance is less than 5 ohms, repair open in KEY POWER circuit. Reconnect HEGO and rerun QUICK TEST. If resistance is more than 5 ohms, reconnect HEGO sensor and repair open in PWR GND circuit. Reconnect HEGO sensor and rerun QUICK TEST.

24) Check HEGO SIGNAL For Short To Power On dual HEGO systems, Code 42/173 refers to right (or rear) side HEGO, and Code 92/137 or 177 refers to left (or front) side HEGO. Turn ignition off and wait 10 seconds. Disconnect appropriate HEGO sensor. Set DVOM on 20-volt scale. With ignition on and engine off, measure voltage between HEGO SIG and PWR GND at HEGO vehicle harness connector. If reading is less than .5 volt, go to step 26). If reading is NOT less than 0.5 volt, go to next step.

25) Check For Short To Power Turn ignition off. Disconnect HEGO sensor. Inspect both ends of connector for damaged or pushed-out pins, moisture, corrosion, loose wires or other damage. Repair as necessary. Set DVOM on 200-k/ohm scale. Disconnect ECA 60-pin connector. Install breakout box, leaving ECA disconnected. Measure resistance between KEY POWER circuit and HEGO SIG circuit at breakout box.

If reading is greater than 10 k/ohms, replace ECA. Remove breakout box and reconnect all components. Drive vehicle for 5 miles at 55 MPH. Rerun QUICK TEST.

If reading is less than 10 k/ohms, repair short circuit. Remove breakout box and reconnect all components. Drive vehicle for 5 miles at 55 MPH. Rerun QUICK TEST.

26) Check HEGO Sensor For Short To Ignition Run Circuit Turn ignition off and wait 10 seconds. Disconnect HEGO. Set DVOM to 200-k/ohm scale. Measure resistance between KEY POWER circuit and HEGO SIG circuit at HEGO sensor connector.

If resistance is greater than 10 k/ohms, go to next step for codes 42/173, 92/137 or 177. For codes 171, 174, 175 or 178, go to step 28) (MAP sensor), or step 30) (MAF sensor).

If resistance is less than 10 k/ohms, replace HEGO sensor. Drive vehicle for 5 miles at 55 MPH and rerun QUICK TEST.

27) Attempt To Generate Code 41/172, 91/136 Or 176 The following non-EEC areas may cause these codes: fuel-contaminated engine oil, ignition misfire and faulty CANP system. Turn ignition off and wait 10 seconds. Disconnect appropriate HEGO sensor. Using jumper wire, connect HEGO SIG circuit at HEGO vehicle harness connector to battery negative terminal. Repeat KOER SELF-TEST.

If Code 41/172, 91/136 or 176 is present, remove jumper wire and go to next step for engines with MAP. For all other engines, go to step 30).

If Codes 41/172, 91/136 or 176 is not present, remove jumper wire. Disconnect ECA connector and inspect for damage. If connector is okay, replace ECA. Drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST.

Because MAP sensor has a large influence on fuel control, Code 42/172 or 91/136 may be caused by a faulty MAP sensor, even though Code 22/126 has not been set. The next 2 steps test the MAP vacuum circuit.

28) Check MAP Sensor For Vacuum Leaks Turn ignition off and wait 10 seconds. Disconnect vacuum hose from MAP sensor and connect vacuum pump to sensor. Apply 18 in Hg to MAP sensor. If sensor holds vacuum, release vacuum and go to next step. If sensor does not hold vacuum, replace MAP sensor. Remove vacuum pump. Connect vacuum hose and reconnect HEGO. Drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST.

29) Check For Loss Of Vacuum To MAP Sensor Using a vacuum "T", connect vacuum gauge in intake manifold vacuum hose at MAP sensor. Start engine and note vacuum reading at a stable idle. Turn ignition off and wait 10 seconds. Remove "T" and vacuum gauge. Reconnect hose to MAP sensor. Connect vacuum gauge at a different intake manifold location. Start engine and note vacuum reading. If readings do not differ by more than 1 in. Hg, go to next step. If readings differ by more than 1 in. Hg, inspect vacuum hoses for leaks, kinks, or blockage. Repair as necessary. Reconnect all components and drive vehicle for 5 miles at 55 MPH. Rerun QUICK TEST.

30) HEGO Sensor Check Turn ignition off and wait 10 seconds. Disconnect HEGO sensor. Set DVOM on 20-volt scale. For 4-Wire HEGO, connect DVOM to HEGO SIGNAL and HEGO GND at HEGO sensor connector. For 3-Wire HEGO, connect DVOM to HEGO SIGNAL at HEGO sensor connector and battery negative post. Remove a vacuum hose to create vacuum leak, which will cause HEGO sensor to go lean. Start engine and run at approximately 2000 RPM. DVOM should indicate less than 0.4 volt within 30 seconds. If voltage is not as specified, replace HEGO sensor. Reconnect vacuum hoses and drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST. If voltage is as specified, go to next step.

Note. There is a break in the step numbering sequence at this point, skipping from step 30) to step 90). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

90) Check Continuous Monitor Mode Turn ignition off and wait 10 seconds. Ensure engine is at normal operating temperature. Start engine and run at 2000 RPM for 2 minutes then return to idle. Enter KOER wiggle test. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. While observing DVOM or "Scan" Tool, wiggle, shake or bend small sections of EEC-IV wiring harness from HEGO sensor to ECA. Wiggle, shake or bend small sections of EEC-IV wiring harness from HEGO GND to ECA. If no fault is indicated, remain in CONTINUOUS MONITOR MODE and go to next step. If fault is indicated, isolate and repair fault as necessary. Clear codes, remove breakout box and reconnect all components. Rerun QUICK TEST.

91) Continuous Monitor Test Drive Check While still in KOER wiggle test, test drive vehicle for 5 miles at 55 MPH with minimum road load. Drive an additional 5 miles at 55 MPH over rough roads. If possible, drive vehicle through a pool of water to shower HEGO sensor and connector. If fault is indicated, isolate fault and repair as necessary. Clear codes and remove breakout box. Rerun QUICK TEST. If no codes are indicated, exit KOER wiggle test and go to next step.

92) Check HEGO Switching Turn ignition off and wait 10 seconds. Inspect EEC-IV wire harness for proper routing and insulation. Check for burnt, chaffed or intermittently shorted or open wires. Repair as necessary. Disconnect ECA 60-pin connector and inspect for damaged or pushed-out pins, corrosion, loose wires or other damage; repair as necessary. Install breakout box and connect ECA to breakout box. Connect analog voltmeter to suspected HEGO sensor test pin and HEGO GND at breakout box. Test drive vehicle for 5 miles at 55 MPH while observing voltmeter. HEGO should switch from .3 volt to .9 volt within 3 seconds. If HEGO does not switch as described, replace HEGO sensor. Remove breakout box, reconnect all components and rerun QUICK TEST. If HEGO switches as described, fault cannot be identified or duplicated at this time. See INTERMITTENTS in the TESTS W/O CODES article in this section.

TEST HA - ADAPTIVE FUEL

Note. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article.

Perform this test when directed by QUICK TEST.

The ECA uses Adaptive Fuel logic primarily to compensate for normal variability in fuel system components. If fuel system appears to be too rich or too lean, adaptive fuel will make a corresponding shift in fuel delivery calculations to compensate and remove bias.

MAP SENSOR VOLTAGE OUTPUT

If possible, measure several known good MAP/BP sensors on available vehicles. Average voltage reading will be typical for your location on date of testing.

1) Continuous Memory Codes 181, 183, 189 Or 192: Is Vehicle SEFI or EFI? This test identifies areas that could cause HEGO sensor to detect excessive oxygen, resulting in adaptive fuel enriching the system to compensate. Excessive oxygen will be detected with lean conditions and certain rich conditions.

For vehicles with dual HEGO sensors, a related fuel code from both HEGO sensors could indicate a problem that is common to all cylinders. If a code is present from only one HEGO, this may help isolate a problem or be an early indication of a common problem.

1. Code 183 - Indicates the single right or rear HEGO detected a problem, and adaptive fuel rich limit has been reached at idle.
2. Code 192 - Indicates the left or front HEGO detected a problem, and adaptive fuel rich limit has been reached at idle.
3. Code 181 - Indicates the single right or rear HEGO detected a problem, and adaptive fuel rich limit has been reached.
4. Code 189 - Indicates the left or front HEGO detected a problem, and adaptive fuel rich limit has been reached.

Ensure a pass code (111) is received during both KOEO SELF-TEST and KOER SELF-TEST. Whenever a repair is made, clear Keep-Alive Memory (KAM). If driveability symptoms are not present, be aware of other temporary conditions that may have set this code, such as vehicle is out of fuel or fuel is contaminated.

If vehicle is SEFI equipped, go to next step. If vehicle is not SEFI equipped, go to step 3).

2) Run Cylinder Balance Test Run KOER SELF-TEST. After last repeated code, wait 5-10 seconds then "goose" throttle lightly (not WOT). Cylinder balance test will be activated. If Code 90 is present, go to next step. If Code 90 is not present, go to step 35).

3) Check For Vacuum/Air Induction Leaks Check all vacuum hose and connections for leaks or damage. Check air induction system for leak or damage. If leak or damage is found, repair as necessary; clear KAM and rerun QUICK TEST. If leak or damage is not found, go to next step.

4) Check For Low Fuel Pressure Turn ignition off and wait 10 seconds. Install fuel pressure gauge. Cycle ignition from off to run 2 to 3 times. Observe KOEO fuel pressure. Start engine, observe and record KOER fuel pressure. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. If fuel pressure is within specifications, go to next step. If fuel pressure is not within specifications, repair fuel system as necessary. Clear KAM and rerun QUICK TEST.

5) Check Systems Ability To Hold Fuel Pressure With fuel pressure gauge installed, cycle ignition from off to on 2 to 3 times to pressurize fuel system (do not start engine). If fuel pressure remains at specifications for 60 seconds, go to next step (MAP/BP-equipped vehicles), or step 7) (all other vehicles). If fuel pressure does not remain at specifications for 60 seconds, visually inspect fuel system for leaks and repair as necessary. Clear KAM and rerun QUICK TEST.

6) Check MAP/BP Frequency Turn ignition off and wait 10 seconds. Connect MAP/BP tester to MAP/BP sensor. Turn ignition on. Refer to MAP SENSOR VOLTAGE OUTPUT table at beginning of this circuit test. If MAP/BP voltage is within specifications, go to next step. If voltage is not within specifications, check wiring to MAP/BP sensor for corrosion, high resistance or other damage; repair as necessary. Clear KAM and rerun QUICK TEST. If wiring is okay, replace MAP/BP sensor; clear KAM and rerun QUICK TEST.

7) Check For Proper Battery Voltage To Fuel Injectors Turn ignition on, leaving engine off. Set DVOM to 20-volt scale. Measure and record voltage across battery terminals. Disconnect any fuel injector harness connector. Measure and record voltage between VPWR circuit at fuel injector vehicle harness connector and battery negative terminal. If both voltage readings are within one volt of each other, go to next step. If voltage readings differ by more than one volt, fuel injectors are not getting proper battery voltage. Isolate and repair problem. Clear KAM and rerun QUICK TEST.

8) Ensure CANP Solenoid Is Not Stuck Closed Enter Output State Check. Disconnect hose to manifold vacuum at CANP solenoid. Check for blockage and repair or replace hose as necessary. With outputs off, apply 16 in. Hg. vacuum to manifold vacuum side of CANP. Depress throttle to cycle outputs on. If vacuum releases, reconnect vacuum hose to CANP and go to next step (thermactor-equipped vehicles), or step 26) (all other vehicles). If vacuum does not release, repeat this step to verify results. If vacuum will not release, check canister and vacuum hose to canister for blockage; repair as necessary. If canister and hose are okay, replace CANP solenoid; clear KAM and rerun QUICK TEST.

9) Check Thermactor System For Upstream Air Leak Check thermactor air control and vacuum control valves. See the I - SYS/COMP TESTS article. If air control valve is operating properly, go to step 25). If air control valve is not operating properly, repair or replace valve as necessary. Clear KAM and rerun QUICK TEST.

Note. There is a break in the step numbering sequence at this point, skipping from step 9) to step 15). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

15) Continuous Memory Codes 179, 182, 188 Or 191: Is Vehicle SEFI or EFI? This test identifies areas that could cause engine to run rich, resulting in adaptive fuel reducing the system to compensate.

For vehicles with dual HEGO sensors, a related fuel code from both HEGO sensors could indicate a problem that is common to all cylinders. If a code is present from only one HEGO, this may help isolate a problem or it may be an early indication of a common problem.

1. Code 182 - Indicates the single right or rear HEGO detected a problem, and adaptive fuel lean limit has been reached at idle.
2. Code 191 - Indicates the left or front HEGO detected a problem, and adaptive fuel lean limit has been reached at idle.
3. Code 179 - Indicates the single, right or rear HEGO detected a problem, and adaptive fuel lean limit has been reached.
4. Code 188 - Indicates the left or front HEGO detected a problem, and adaptive fuel lean limit has been reached.

Ensure a pass code (111) is received during both KOEO SELF-TEST and KOER SELF-TEST. Whenever a repair is made, clear Keep-Alive Memory (KAM). If vehicle is SEFI equipped, go to next step. If vehicle is not SEFI equipped, go to step 17).

16) Run Cylinder Balance Test Run KOER SELF-TEST. After last repeated code, wait 5-10 seconds then "goose" throttle lightly (not WOT). Cylinder balance test will be activated. If Code 90 is present, go to next step. If Code 90 is not present, go to step 35).

17) Check For Low Fuel Pressure Turn ignition off and wait 10 seconds. Install fuel pressure gauge. Cycle ignition from off to run 2 to 3 times. Observe KOEO fuel pressure. Start engine, observe and record KOER fuel pressure. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. If fuel pressure is within specifications, go to next step. If fuel pressure is not within specifications, check condition of fuel pressure regulator vacuum hose, fuel return line and fuel pressure regulator. Repair fuel system as necessary. Clear KAM and rerun QUICK TEST.

18) Check Systems Ability To Hold Fuel Pressure With fuel pressure gauge installed, cycle ignition from off to on 2 to 3 times to pressurize fuel system (do not start engine). If fuel pressure remains at specifications for 60 seconds, go to next step (MAP/BP-equipped vehicles), or step 20) (all other vehicles). If fuel pressure does not remain at specifications for 60 seconds, visually inspect fuel system for leaks and repair as necessary. Clear KAM and rerun QUICK TEST.

19) Check MAP/BP Frequency Turn ignition off and wait 10 seconds. Connect MAP/BP tester to MAP/BP sensor. Turn ignition on. Refer to MAP SENSOR VOLTAGE OUTPUT table in this circuit test. If MAP/BP voltage is within specifications, go to next step. If voltage is not within specifications, check wiring to MAP/BP sensor for corrosion, high resistance or other damage; repair as necessary. Clear KAM and rerun QUICK TEST. If wiring is okay, replace MAP/BP sensor; clear KAM and rerun QUICK TEST.

20) Check Throttle Body And Air Induction System Check throttle body and air induction system for contamination, obstruction, etc. Repair or clean as necessary. Clear KAM and rerun QUICK TEST. If throttle body and air induction system are okay, go to next step.

21) Ensure CANP Will Hold Vacuum Turn ignition off and wait 10 seconds. Disconnect vacuum hose to manifold vacuum at CANP solenoid. Apply 16 in. Hg vacuum to manifold side of CANP solenoid. If solenoid holds vacuum for 20 seconds, reconnect vacuum hose and go to next step. If solenoid does not hold vacuum for 20 seconds, replace CANP solenoid. Clear KAM and rerun QUICK TEST.

Note. There is a break in the step numbering sequence at this point, skipping from step 21) to step 25). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

25) Check PCV Valve Turn ignition off and wait 10 seconds. Remove PCV valve and shake. If PCV valve rattles freely when shaken, go to next step. If PCV valve does not rattle, replace PCV valve. Clear KAM and rerun QUICK TEST.

26) Check HEGO Heater Circuit Turn ignition off and wait 10 seconds. Disconnect HEGO sensor(s). Set DVOM to 200-ohm scale. measure resistance between KEY POWER circuit and PWR GND circuit at HEGO sensor connector(s). Resistance should be 2 ohms (room temperature), or 35 ohms (hot).

Turn ignition on, leaving engine off. Set DVOM to 20-volt scale. Measure voltage between KEY POWER circuit and PWR GND circuit at HEGO sensor connector(s). Voltage should be 10.5 volts. If HEGO circuits check okay, go to next step. If HEGO circuits are not okay, isolate problem and repair as necessary. Clear KAM and rerun QUICK TEST.

27) Inspect HEGO Sensor For Contamination Remove HEGO sensor(s) from exhaust manifold. Visually inspect for contamination or other damage. If HEGO sensor(s) appears okay, go to next step (vehicles with EGR), or step 30) (all other vehicles). If HEGO sensor(s) is not okay, replace HEGO sensor; clear KAM and rerun QUICK TEST.

28) Verify Excessive Vacuum Is Not At EGR Valve During Idle Disconnect vacuum line at EGR valve. Connect vacuum gauge to EGR vacuum line. Start engine and let idle. If vacuum reading is less than 2.5 in. Hg, go to next step. If vacuum reading is greater than 2.5 in. Hg, check EVR solenoid filter for obstructions and repair as necessary. If EVR filter is okay, replace EVR solenoid; reconnect all components, clear KAM and rerun QUICK TEST.

29) Verify EGR Valve Is Fully Seated Inspect EGR valve to ensure proper seating. If EGR valve is fully seated, reconnect vacuum line to EGR valve and go to next step. If EGR Valve is not fully seated, service or replace EGR valve as necessary; clear KAM and rerun QUICK TEST.

30) Check Cooling System Ensure cooling system is in good condition and all components are operating properly. If cooling system is okay, go to next step. If system is not okay, repair as necessary. Clear KAM and rerun QUICK TEST.

Note. There is a break in the step numbering sequence at this point, skipping from step 30) to step 35). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

35) Check Ignition System Ensure ignition system is operating properly. Scope check engine spark plug, coil, secondary wires, distributor cap, rotor, timing, etc. If ignition system is operating properly, go to next step. If system is not operating properly, make necessary repairs. Clear KAM and rerun QUICK TEST.

36) Flow Check Injectors Flow check fuel injectors. See FUEL CONTROL in the SYSTEM/COMPONENT TESTS article in this section. If injectors are okay, go to next step. If injectors are not okay, clean or replace injectors as necessary. Clear KAM and rerun QUICK TEST.

37) Check Cylinder Compression Check cylinder compression. See MECHANICAL INSPECTION in the BASIC TESTING article in this section. If cylinder compression is not within specifications, service or repair engine as necessary. After servicing engine, clear KAM and rerun QUICK TEST. If cylinder compression is within specifications, go to the next step.

Note. There is a break in the step numbering sequence at this point, skipping from step 37) to step 40). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

The following road test is a suggested optional procedure. Follow all applicable safety procedures and traffic laws. This road test requires another person to accompany the driver. The accompanying person can make measurements, observe changes and record notes. If for some reason this test is not performed, go to the TESTS W/O CODES article in this section for other possible causes.

40) Road Test Vehicle The purpose of this test is to identify areas of concern by monitoring certain controlled parameters, while trying to recreate a driveability or MIL light symptom. To prepare for road test, do the following

1. Install fuel pressure gauge.
2. Install MAP/BP tester.
3. Disconnect ECA 60-pin connector; install breakout box and reconnect ECA to breakout box.
4. Connect "T" vacuum gauge into manifold vacuum line.
5. Have DVOM, writing materials and appropriate schematics or pin voltage charts on hand.

With ignition on and negative lead of DVOM connected to battery negative terminal, ensure the following signals are correct

1. POWERS: KAPWR (pin No. 1) is greater than 10.5 volts, VPWR (pins No. 37/57) is greater than 10.5 volts and VREF (pin No. 26) is 4-6 volts.
2. GROUNDS: PWR GND (pins No. 40/60), SIG RTN (pin No. 46) and IGN GND (pin No. 16) are 0-.5 volt.
3. OPTIONAL GROUNDS: HEGO GND (pin No. 49), CSE GND (pin No. 20) and MAF RTN (pin No. 9 or 15).

Drive vehicle and attempt to induce symptom. Information provided by customer may help when trying to recreate symptom. When symptom occurs, the accompanying passenger should observe and record changes in EEC-IV signals. Information about the symptom, operating condition value of EEC-IV signal and any other information available should be recorded on paper for analysis. If unable to duplicate symptom during road test, it is still useful to verify that EEC-IV values are in expected range.

Once road test has been completed, analyze results to locate and repair exact fault causing symptom. If problem cannot be identified, go to the TESTS W/O CODES article in this section for other possible causes of symptom.

Perform this test when instructed by QUICK TEST, or when directed by other test procedures.

This test is intended to diagnose only the following

1. Fuel Pump Relay
2. Inertia Switch
3. Harness Circuits (BATT +, VPWR, FUEL PUMP, GND & POWER To PUMP)
4. ECA

Fuel Pump Circuit (Ranger, Explorer, Navajo & Aerostar). Scheme 64

4.0L SPFI-MA TEST PIN WIRE COLOR I.D.

Due to the internal circuitry of ECA, a left/front HEGO signal short to power could produce a code 95/542 or 96/543.

35) Check Left/Front HEGO Sensor For Short To Power Turn ignition off and wait 10 seconds. Set DVOM to 200-k/ohm scale. Disconnect left or front HEGO sensor. Measure resistance between HEGO signal pin and KEY POWER pin at HEGO sensor connector. Is resistance is greater than 10 k/ohms, go to next step. If resistance is less than 10 k/ohms, replace HEGO sensor and rerun QUICK TEST. Clear Keep-Alive Memory (KAM).

HEGO Sensor Connector. Scheme 65

36) Check HEGO Circuit For Short To Power Turn ignition off and wait 10 seconds. Set DVOM to 20-volt scale. Disconnect left or front HEGO. Disconnect ECA 60-pin connector and inspect for damaged or pushed-out pins, corrosion, loose wire ore other damage. Leave ECA disconnected. Turn ignition on and measure voltage between HEGO signal at HEGO vehicle harness connector and chassis ground. If voltage is less than 2 volts, replace ECA; reconnect HEGO sensor and rerun QUICK TEST. If voltage is greater than 2 volts, repair short circuit. Reconnect ECA and HEGO sensor. Rerun QUICK TEST and clear KAM.

HEGO Sensor Vehicle Harness Connector. Scheme 66

Note. There is a break in the step numbering sequence at this point, skipping from step 36) to step 90). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

90) Continuous Memory Code 95/542: Check EEC-IV Harness Code 95/542 indicates one of the following conditions has occurred intermittently

1. Open circuit in or between fuel pump and FPM circuit at ECA
2. Faulty ground circuit at fuel pump
3. FPM or POWER-to-PUMP circuit short to power
4. Fuel pump relay contacts stuck open
5. FUEL PUMP circuit is activated when ECA expects circuit to be off

Start engine and perform wiggle test on vehicle harness to fuel pump, and to pump ground circuit harness. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. Lightly tap inertia switch and pump to simulate road shock. Check for engine miss or stumble while performing test. With ignition off, check harness connectors for corrosion or damage. Isolate and repair any faults; clear Code 95/542 and rerun QUICK TEST. If no fault is found, go to next step.

91) Check FPM Circuit Turn ignition off. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Install breakout box and leave ECA disconnected. With Key On Engine Off (KOEO), connect a test light between test pin No. 8 and test pin No. 37 at breakout box. With test light lit, perform wiggle test on FPM circuit between pump and monitor. Light should go out if fault is found during wiggle test. Isolate and repair any found faults; remove test set-up and rerun QUICK TEST. If no fault is found, go to next step.

92) Check For Shorts To Power With KOEO, breakout box installed and ECA disconnected, connect a test light between test pin No. 8 and test pin No. 40. Observe test light; perform wiggle test on FPM circuit and POWER-to-PUMP circuit. Lightly tap fuel pump relay to simulate road shock. If light comes on, it indicates fault exists; isolate and repair as necessary. Remove test set-up and rerun QUICK TEST. If no fault is found, go to step 96) (dual HEGO-equipped vehicles), or step 99) (all others).

93) Continuous Memory Code 96/543: Check For Continuous Memory Code 87/556 If Code 87 or 556 is present, go to step 95). If code 87 or 556 is not displayed, go to next step.

94) Check EEC-IV Harness A Continuous Memory Code 96/543, without an accompanying Continuous Memory Code 87/556, indicates that during vehicle operation, one of the following conditions has occurred

1. An open in BATT (+) circuit between BATT (+) and fuel pump relay
2. Fuel pump relay contacts open
3. Open in POWER-to-PUMP circuit from fuel pump relay to FPM splice (if applicable)
4. Left/front HEGO circuit short to power (dual HEGO)

With engine running, attempt to cause a miss or stumble while performing wiggle test on pump harness and connectors. With ignition off, inspect all fuel pump connectors and BATT (+) for damage or corrosion. If fault is found, isolate and repair as necessary. Clear Continuous Memory Codes and rerun QUICK TEST. If no fault is found, under certain conditions, a Continuous Memory Code 95/543 may have been set without a Continuous Memory Code 87/556, even though a fault has occurred in fuel pump primary circuit. Go to next step.

95) Continuous Code 87/556: Check EEC-IV Harness A Continuous Memory Code 87 or 556 indicates primary fuel pump circuit has failed during vehicle operation. Possible causes for this fault are as follows

1. Open in VPWR circuit between EEC power relay and fuel pump relay
2. Open coil in fuel pump relay
3. Open in fuel pump circuit (pin 22)
4. Faulty inertia switch

With engine running, attempt to cause a miss or stumble while performing wiggle test on VPWR circuit between EEC power relay and fuel pump relay. Wiggle fuel pump circuit harness (test pin No. 22) between ECA and fuel pump relay. Lightly tap fuel pump relay to simulate road shock. With ignition off, inspect ECA 60-pin connector for damage or corrosion. If fault is found, isolate and repair as necessary. Rerun QUICK TEST. If no fault is found, go to next step (dual HEGO-equipped vehicles), or if fault may not be duplicated at this time (all others), go to step 99).

Diagnostic Aids - Due to internal circuitry of ECA, an intermittent left/front HEGO signal short to power could produce a Continuous Memory Code 95/542 or 96/543.

96) Check Left/Front HEGO Circuit For Short To Power Turn ignition off. Install breakout box and leave ECA disconnected. Connect test light between left/front HEGO test pin and pin No. 40 at breakout box. See schematic at beginning of TEST H for appropriate HEGO test pin No. Perform wiggle test on left/front HEGO circuit to ECA. Lightly tap HEGO sensor to simulate road shock. If light goes on, it indicates fault exists; isolate and repair as necessary. Remove test set-up, clear Keep-Alive Memory (KAM) and rerun QUICK TEST. If no fault is indicated, go to next step.

Note. There is a break in the step numbering sequence at this point, skipping from step 96) to step 99). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

This road test is a suggested optional procedure. Follow all applicable safety procedures and traffic laws. This road test requires another person to accompany the driver. The accompanying person can make measurements, observe changes and record notes. If for some reason this test is not performed, go to the TESTS W/O CODES article in this section for other possible causes.

99) Road Test Vehicle This test identifies areas of concern by monitoring certain controlled parameters while trying to recreate a driveability or MIL light symptom. To prepare for road test, do the following

1. Install fuel pressure gauge.
2. Install MAP/BP tester.
3. Disconnect ECA 60-pin connector; install breakout box and reconnect ECA to breakout box.
4. Connect "T" vacuum gauge into manifold vacuum line.
5. Have DVOM, writing materials and appropriate schematics or pin voltage charts on hand.

With ignition on and negative lead of DVOM connected to battery negative terminal, ensure the following signals are correct

1. POWERS: KAPWR (pin No. 1) is greater than 10.5 volts, VPWR (pins No. 37/57) is greater than 10.5 volts, and VREF (pin No. 26) is 4-6 volts.
2. GROUNDS: PWR GND (pins No. 40/60), SIG RTN (pin No. 46) and IGN GND (pin No. 16) are 0-.5 volt.
3. OPTIONAL GROUNDS: HEGO GND (pin No. 49), CSE GND (pin No. 20) and MAF RTN (pin No. 9 or 15).

Drive vehicle and attempt to induce symptom. Information provided by customer may help when trying to recreate symptom. When symptom occurs, the accompanying passenger should observe and record changes in EEC-IV signals. Information about the symptom, operating condition value of EEC-IV signal and any other information available should be recorded on paper for analysis. If unable to duplicate symptom during road test, it is still useful to verify that EEC-IV values are in expected range.

Once road test has been completed, analyze results to locate and repair fault causing the symptom. If problem cannot be identified, go to the TESTS W/O CODES article in this section for other possible causes of symptom.

Perform this test when instructed by QUICK TEST, or when directed by other test procedures. This test is intended to diagnose only the following

1. CANP solenoid
2. ECA
3. Harness circuits (CANP and VPWR)

Canister Purge (CANP) Circuit. Scheme 67

4.0L SPFI-MA TEST PIN WIRE COLOR I.D.

Perform this test when instructed by QUICK TEST, or when directed by other test procedures. If engine is running rough or has rough idle, correct these conditions before performing test. Causes may be in ignition system, fuel system or EGR system. This test is intended to diagnose only the following

1. RPM during Self-Test mode
2. ISC solenoid
3. Harness circuits (ISC and VPWR)
4. Faulty ECA

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault

1. Engine temperature not up to operating temperature
2. Engine over operating temperature
3. A/C input (electrical problem)
4. Incorrect idle speed or throttle stop adjustment
5. Faulty cruise control linkage

Idle Speed Control (Air By-Pass) Circuit. Scheme 68

4.0L SPFI-MA TEST PIN WIRE COLOR I.D.

Perform this test when diagnosing a symptom. To prevent replacing good components, check the following non-EEC components and systems

1. Refrigerant charge
2. Low ambient temperature (less than 45°F)

This test is intended to diagnose only the following

1. Harness circuits (WAC, VPWR, GND, POWER to CLUTCH, and ACD)
2. WAC relay
3. A/C fan controller
4. ECA

WOT A/C Cut-Out Circuits (All Models). Scheme 69

Before entering this test, ensure A/C selector is off (and shift selector is in PARK for AXODE and E4OD vehicles). If A/C was on, rerun QUICK TEST. If Code 67 or 79/539 is present, continue with this test.

40) Check A/C Input Code 79/539 indicates ACCS input to ECA was high during self-test. Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector; inspect for corroded or damaged connector pins and repair as necessary. Install breakout box, leaving ECA disconnected. Set DVOM to 20-volt scale. With KOEO, measure voltage between test pin No. 10 at breakout box and chassis ground. If voltage is greater than one volt, repair short to power in A/C circuit. Remove breakout box, reconnect all components and rerun QUICK TEST. If voltage is less than one volt, go to next step for trucks with 2-digit codes and E4OD trans; on all other vehicles, replace ECA, reconnect all components and rerun QUICK TEST.

41) Check For Short To Power In ECA Turn ignition off and wait 10 seconds. Install breakout box, leaving ECA disconnected. Disconnect A/C clutch connector. Set DVOM to 20-volt scale. With KOEO, measure voltage between test pins No. 10 and 40. If voltage is greater than one volt, replace ECA; reconnect A/C clutch and rerun QUICK TEST. If voltage is less than one volt, diagnose transmission.

Note. There is a break in the step numbering sequence at this point, skipping from step 41) to step 43). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

A low idle with A/C on may be caused by the ECA not receiving or recognizing A/C input from pin No. 10

43) Check A/C Input Circuit Turn A/C switch to A/C position. Perform KOEO SELF-TEST. If Code 67 or 79/539 is present, ECA is receiving and recognizing A/C input from pin No. 10. Check for other possible cause of low idle. If Code 67 or 79/539 is not present, go to next step.

44) Check A/C Input Circuit Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector. Install breakout box, leaving ECA disconnected. Set DVOM to 20-volt scale. Turn A/C on. With KOEO, measure voltage between test pins No. 10 and 40.

If voltage is greater than 10.5 volts, replace ECA. Remove breakout box, reconnect all components and rerun QUICK TEST.

If voltage is less than 10.5 volts, repair open A/C circuit. Remove breakout box, reconnect all components and rerun QUICK TEST.

Enter this test when directed by QUICK TEST. This test is intended to diagnose only the following systems or components

1. Harness circuits (SIG RTN and OCT ADJ)
2. Octane shorting bar connector

Octane Adjust Circuit. Scheme 70

Perform this test only when directed by QUICK TEST.

To prevent replacing good components, be aware that the following non-EEC related areas may be the cause of problem

1. Technician testing EEC system did not perform brief Wide Open Throttle (WOT) after Dynamic Response Code.
2. Faulty mechanical engine components
3. Engine did not go over 2000 RPM during WOT

This test is intended to diagnose only the following

1. Throttle movement (minimum 3/4 throttle)
2. RPM increase is greater than 2000 RPM

If throttle is snapped open briefly, it may not be sufficient to pass WOT test. Ensure throttle is depressed fully to WOT, and engine speed exceeds 2000 RPM.

Code 77/538 Displayed: System Failed To Recognize WOT Test - Rerun KOER SELF-TEST as follows

1. Start engine
2. Activate KOER SELF-TEST
3. Observe ID Code 2 (Code 0 with STAR tester)
4. Observe Dynamic Response Code 1 (Code 0 with STAR tester)
5. Perform brief WOT
6. Testing is complete, KOER code output begins

If Code 77/538 is still displayed, replace ECA and rerun QUICK TEST. If Code 77/538 is no longer present, vehicle has passed dynamic response test; service other codes as necessary.

Perform this test only when instructed by QUICK TEST, or when directed by TEST QA.

To prevent replacing good components, be aware that the following non-EEC related areas may be the cause of problem

1. Fuse, bulb or socket

This test is intended to diagnose only the following

1. STO/MIL circuit
2. ECA
3. Data Communications Link (DCL)

"CHECK ENGINE" Light Circuit. Scheme 71

Data Communication Link (DCL) Circuit. Scheme 72

4.0L SPFI-MA TEST PIN WIRE COLOR I.D.

4.0L SPFI-MA TEST PIN WIRE COLOR I.D. (RANGER & EXPLORER, NAVAJO)

1) Malfunction Indicator Light (MIL) Always On If vehicle will not start, go to TEST A, step 1). Service all other KOEO and Continuous Memory Codes before proceeding with this test. Turn ignition off. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Connect DVOM between test pins No. 17 and 40 at breakout box. If resistance is greater than 5 ohms, replace ECA; remove breakout box and rerun QUICK TEST. If reading is less than 5 ohms, repair short between test pin No. 17 and self-test connector or "CHECK ENGINE" light. Remove breakout box, reconnect all components and repeat QUICK TEST.

Note. There is a break in the step numbering sequence at this point, skipping from step 1) to step 4). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

4) Malfunction Indicator Light (MIL) Never On: Check Continuity Of STO/MIL Circuit If vehicle will not start, go to TEST A, step 1). Turn ignition on; leave engine off. Set DVOM on 20-volt scale. Measure voltage between battery negative terminal to ground side of MIL fuse. If voltage is greater than 10.5 volts, go to step 6). If voltage is less than 10.5 volts, go to next step.

5) Check For Voltage At Fuse Set DVOM on 20-volt scale. With Key On Engine Off (KOEO), measure voltage from battery negative post to hot side of MIL fuse. If voltage is greater than 10.5 volts, repair fuse or open circuit. Reconnect ECA and verify repair by turning ignition to RUN position. If voltage is not greater than 10.5 volts, repair MIL/VBAT circuit. Reconnect ECA and verify repair by turning ignition to RUN position.

6) Check Continuity Of VBAT Circuit Turn ignition off. Set DVOM to 200-k/ohm scale. Measure resistance between MIL fuse (at ground side) and MIL bulb socket (VBAT side). If resistance is greater than 10 k/ohms, repair open circuit in MIL circuit. Verify repair by turning ignition to RUN position. If resistance is less than 10 k/ohms, go to next step.

7) Check MIL Bulb Response To Grounding Turn ignition off. Attach one end of jumper wire to negative battery terminal or chassis ground. Attach other end of jumper wire to ground side of MIL bulb socket. Turn ignition to RUN position. If MIL light comes on, turn ignition off. Remove jumper wire and go to next step. If MIL light does not come on, turn ignition off and remove jumper wire. Replace MIL bulb socket. Turn ignition to RUN position to verify operation.

8) Check Continuity Of MIL Circuit Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Install breakout box and leave ECA disconnected. Set DVOM to 200-ohm scale. Measure resistance between test pin No. 17 at breakout box and MIL. If resistance is less than 5 ohms, replace ECA. Remove breakout box. Verify operation by turning ignition switch to RUN position. If resistance is greater than 5 ohms, repair open MIL circuit. Turn ignition switch to RUN position to verify operation.

Note. There is a break in the step numbering sequence at this point, skipping from step 8) to step 10). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

10) "CHECK ENGINE" Or "SERVICE ENGINE SOON" Light Intermittent, Check For Intermittent Short From STO To Ground If vehicle does not start, go to TEST A, step 1). The light comes on when a Continuous Memory Code is present. Service all Continuous Memory Codes before proceeding. If no codes are outputted, proceed with this test. Enter KOEO wiggle test. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. Observe DVOM for indication of fault while performing wiggle test on harness in the following areas

1. From self-test connector to dash panel
2. Dash panel to ECA
3. Dash panel to Malfunction Indicator Light (MIL).

If a fault is indicated, repair as necessary and rerun QUICK TEST. If a fault is not indicated, then fault cannot be duplicated at this time. Testing for this fault is complete.

Note. There is a break in the step numbering sequence at this point, skipping from step 10) to step 15). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

15) "CHECK ENGINE" Or "SERVICE ENGINE SOON" Light Flashes With Erratic Idle: Check STI Circuit For Short To Ground Vehicle symptoms indicate STI is grounded and ECA is performing self-test without tester installed. With ignition off, disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair as necessary. Set DVOM on 200-k/ohm scale. Measure resistance between STI connector and engine block ground. If resistance is less than 10 k/ohms, repair short circuit. Reconnect ECA and retest. If resistance is not less than 10 k/ohms, reconnect ECA. Verify symptom and test for other rough idle symptoms.

Note. There is a break in the step numbering sequence at this point, skipping from step 15) to step 20). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

20) "CHECK ENGINE" Message Displayed If vehicle will not start, go to TEST A, step 1). Perform KOEO SELF-TEST. If result is Code 11-10-11 (pass code), repair fault in electronic message center Data Communications Link (DCL). If pass code is not displayed, service codes as required in self-test procedures.

Note. There is a break in the step numbering sequence at this point, skipping from step 20) to step 25). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

25) Continuous Memory Code 529: "CHECK ENGINE" Or "CHECK DCL" Message Displayed Codes 529 and 533 indicate circuit failure has occurred on Data Communications Link (DCL). These codes can occur alone or in conjunction with another code. "CHECK ENGINE" or "CHECK DCL" message will be displayed under the following conditions

1. Code 529 indicates ECA or Data Communicator Link (DCL) circuit failure.
2. Code 533 indicates Data Communication Link to Electronic

Perform this test when directed by QUICK TEST. This test is intended to diagnose only the EEC-IV portion of ignition system. For additional information on ignition system and component testing, see the I - SYS/COMP TESTS article.

To prevent replacing good components, be aware that the following non-EEC related areas may be at fault

1. EDIS ignition module
2. EDIS coil packs
3. Spark plugs and/or high tension cables
4. Variable reluctance sensor
5. Secondary ignition component arcing

This test is intended to diagnose the following circuits and components

1. IDM and SAW Harness circuit
2. ECA assembly

IDM Circuit Schematic(4.0L MA EFI Truck). Scheme 73

4.0L SPFI-MA TEST PIN WIRE COLOR I.D.

4.0L SPFI-MA TEST PIN WIRE COLOR I.D. (RANGER & EXPLORER, NAVAJO)

1) Continuous Memory Code 14/211: Erratic Ignition Code 14/211 indicates 2 successive erratic Profile Ignition Pick-Up (PIP) pulses occurred, resulting in a possible engine miss or stall. Possible causes for this fault are as follows

1. Loose wires or connectors
2. Arcing secondary ignition components
3. On-board transmitter equipment (2-way radio)

Repair any problems in listed items as necessary; clear code and rerun QUICK TEST. If problem is not found in items listed, go to step 4).

2) Code 16/226: IDM Circuit Failure Code 16/226 indicates ECA did not receive IDM signal from EDIS module in KOEO SELF-TEST. Possible causes for this problem are as follows

1. Open or short in IDM or IGN GND circuit harness
2. Faulty EDIS module - If engine starts, go to next step. If engine does not start, diagnose EDIS system.

3) Continuous Memory Code 18/212: Check For Other Codes Code 18/212 indicates loss of IDM input signal to ECA. Possible causes for this fault are as follows

1. Open or shorted harness
2. Faulty EDIS module
3. Faulty ECA

If Continuous Memory Code 45, 46, 48, 215, 216 or 217 is present, see testing procedure for EDIS in the I - SYS/COMP TESTS article in this section. If Code 45, 46, 48, 215, 216 or 217 is not present, go to next step.

4) Continuous Memory Codes 18/212: Check IDM Circuit Continuity Turn ignition off and wait 10 seconds. Disconnect EDIS module. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair as necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 4 at breakout box and EDIS module harness connector pin No. 2. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open circuit. Remove breakout box and reconnect all components. Clear codes and rerun QUICK TEST.

5) Check IDM Circuit For Short To Ground Turn ignition off and wait 10 seconds. Disconnect EDIS module connector. Install breakout box and leave ECA disconnected. With DVOM on 200-k/ohm scale, measure resistance between test pin No. 4 and test pins No. 40, 46 and 60. If readings are 10 k/ohms or more, go to next step. If any reading is less than 10 k/ohms, remove breakout box and repair short to ground in IDM circuit. Reconnect all components and rerun QUICK TEST.

6) Check IDM Circuit For Shorts To Power (Except VREF Circuit) With ignition off, install breakout box. Disconnect ECA and EDIS module. Measure voltage between test pin No. 4 and test pins No. 40 and 60. To check for short to VBAT, turn ignition off. To check for short to VPWR, turn ignition on. If voltage is less than 10.5 volts, go to next step. If any reading is greater than 10.5 volts, repair short circuit. Remove breakout box and reconnect all components. Rerun QUICK TEST.

7) Check IDM Circuit For Short To VREF & PIP Turn ignition off. Install breakout box, leaving ECA disconnected. Disconnect EDIS module. Set DVOM to 200-k/ohm scale.

To check for shorts to VREF, measure resistance between test pins No. 36 and 26 at breakout box. To test for shorts to PIP, measure resistance between test pins No. 36 and 56 at breakout box.

If each resistance is greater than 10 k/ohms, go to next step. If resistance is not greater than 10 k/ohms, repair short circuit. Remove breakout box, reconnect all components and repeat QUICK TEST.

During this test, when 4-wire HEGO is connected to vehicle harness, a short to SIGRTN (pin No. 46) may be indicated along with an actual short to PWR GND.

8) Check ECA For Short To Ground Turn ignition off and wait 10 seconds. Disconnect EDIS module. Install breakout box and connect ECA. With DVOM on 200-k/ohm scale, measure resistance between test pin No. 4 and test pins No. 16, 20, 40, 46 and 60. If readings are 10 k/ohms or more, reconnect components and go to next step. If any reading is less than 10 k/ohms, replace ECA. Reconnect all components and rerun QUICK TEST.

9) Check EDIS Module Turn ignition off and wait 10 seconds. Enter KOER wiggle test. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. Observe VOM or diagnostic tester for indication of fault while lightly tapping on EDIS module to simulate road shock. Wiggle all EDIS harness connectors. If fault is indicated, go to next step. If fault is not indicated, disconnect and inspect EDIS harness connectors and terminals for damage. If connectors and terminals are okay, check ignition system. See the SYSTEM/COMPONENT TESTS article in this section. If ignition is okay, replace ECA.

10) Check EEC-IV Harness Remain in CONTINUOUS MONITOR MODE (WIGGLE TEST). Wiggle, shake or bend small sections of harness, working from EDIS connectors to firewall. Observe VOM or diagnostic tester for indication of fault. Repeat process from firewall to ECA. This test checks for the following circuit faults

1. PIP Open/Shorted To Ground (check at test pin No. 56)
2. SAW Shorted To Ground (check at test pin No. 36)
3. Ignition Ground Open (check at test pin No. 16)
4. IDM Open To Ground (check at test pin No. 4)
5. IDM Shorted To Power (check at test pin No. 4)

Perform CONTINUOUS MONITOR MODE (WIGGLE TEST) on these circuits, one at a time, to isolate fault. If fault is indicated, isolate fault and repair harness. Repeat QUICK TEST. If no fault is indicated, go to next step.

11) Check ECA & Harness Connectors Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion or loose wires. If connector is damaged, repair as necessary; clear codes and repeat QUICK TEST. If connector is okay, perform appropriate procedure listed as follows, based on the Continuous Memory Code displayed

1. Code 14/211 - Erratic ignition fault in EEC system cannot be duplicated. Remove breakout box and reconnect all components. Diagnose EDIS ignition system.
2. Code 18/212 - Replace ECA. Remove breakout box and reconnect all components. Start and run engine for about one minute, then rerun QUICK TEST.

Perform this test when checking computed timing, or when directed by QUICK TEST. This test is intended to diagnose the following

1. Harness circuit (SAW)
2. Base timing
3. Faulty ECA

To prevent replacing good components, be aware that the following non-EEC related areas may be at fault

1. Basic engine condition (valves, vacuum leaks, valve timing, EGR valve, etc.)
2. EDIS module
3. Distributor

IDM Circuit (4.0L MA EFI Truck). Scheme 74

During this test, when 4-wire HEGO is connected to vehicle harness, a short to SIG RTN (pin No. 46) may be indicated along with an actual short to PWR GND.

7) Check SAW Voltage at ECA With ignition off and breakout box installed, connect ECA to breakout box. Reconnect EDIS module. Ensure timing switch on breakout box is in DIST position. Set DVOM on 20-volt AC scale. With KOER, measure voltage between test pin No. 36 and battery negative post. If AC voltage is NOT .6-1.8 volts on 4.0L EFI, replace ECA; remove breakout box and repeat QUICK TEST. If AC voltage is .6-1.8 volts on 4.0L EFI, EEC-IV system is okay; remove breakout box, reconnect ECA. Check the ignition system. See the SYSTEM/COMPONENT TESTS article.

Perform this test when directed by QUICK TEST or other test procedures. This test is intended to diagnose only the following

1. ECA
2. EEC power relay
3. Harness circuits (SIG RTN, STO, STI, VPWR, VREF)

No Codes/Codes Not Listed Circuits. Scheme 75

4.0L SPFI-MA TEST PIN WIRE COLOR I.D.

4.0L SPFI-MA TEST PIN WIRE COLOR I.D. (RANGER & EXPLORER, NAVAJO)

After-market devices, such as alarm system, may cause self-test to abort if wiring is connected to certain EEC components. If a device is installed, disconnect it completely from EEC system. Before continuing with this circuit test, restore EEC circuits to original and rerun QUICK TEST.

1) Check VREF Voltage At Self-Test Connector Turn ignition off. Wait 10 seconds. Disconnect ECA 60-pin connector. Inspect it for damaged pins, corrosion, or loose wires. Repair as necessary. Install breakout box and connect ECA. Set DVOM on 20-volt scale. With Key On Engine Off (KOEO), measure voltage between test pin No. 26 and SIG RTN at self-test connector. If reading is NOT 4-6 volts, go to TEST C, step 1). If reading is 4-6 volts, go to next step.

2) Check STI Circuit Continuity Turn ignition off and wait 10 seconds. With breakout box installed and ECA disconnected, set DVOM on 200-ohm scale. Measure resistance between test pin No. 48 at breakout box and Self-Test Input (STI) at self-test connector pigtail. If reading is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in circuit; remove breakout box and reconnect ECA. Rerun QUICK TEST.

3) Check STO Circuit Continuity With breakout box installed and ECA disconnected, set DVOM on 200-ohm scale. Measure resistance between test pin No. 17 at breakout box and Self-Test Output (STO) at self-test connector. If reading is less than 5 ohms, go to next step. If reading is 5 ohms or more, repair open circuit; remove breakout box and reconnect ECA. Rerun QUICK TEST.

4) Check EGO Signal For Short To Power With breakout box installed, ECA disconnected and DVOM on 20-volt scale, measure voltage between HEGO SIGNAL test pin No. 29 or 44 and test pin No. 40 or 60 (refer to schematic at beginning of TEST H). If voltage is greater than 2 volts, go to next step. If voltage is less than 2 volts, go to step 6).

5) Isolate Short To Harness Or HEGO Sensor With breakout box installed and ECA disconnected, set DVOM to 20-volt scale. Disconnect HEGO (bank No. 1) sensor connector. With KOEO, measure voltage between HEGO SIGNAL test pin No. 20 or 44 and test pin No. 40 or 60 (refer to schematic at beginning of TEST H). If voltage is greater than 2 volts, repair short to power in HEGO SIGNAL circuit. Remove breakout box, reconnect all components and rerun QUICK TEST. If voltage is less than 2 volts, replace HEGO sensor (bank No. 1). Remove breakout box, reconnect all components and rerun QUICK TEST.

6) Check STO Circuit For Short To Ground With breakout box installed and ECA disconnected, set DVOM on 200-k/ohm scale. Measure resistance between STO at self-test connector and engine block ground. If reading is greater than 10k/ohms, go to next step. If resistance is less than 10 k/ohms, repair STO or MIL/SIL circuit for short to ground. Reconnect ECA and repeat QUICK TEST.

7) Check If Power Relay Always On With ignition off, install breakout box, leaving ECA disconnected. Set DVOM on 20-volt scale. Connect DVOM between test pin No. 37 or 57 and pin No. 40 or 60. Turn ignition on then off. Wait 10 seconds. If reading does not change from 10.5 volts (or more) to less than one volt, go to next step. If reading changes from 10.5 volts (or more) to less than one volt, go to step 8).

8) Check VPWR Circuit For Short To Power With ignition off, breakout box installed and EEC power relay or Integrated Relay Controller Module (IRCM) disconnected, set DVOM on 20-volt scale. Ensure ECA is disconnected. Connect DVOM to test pin No. 37 or 57 and test pin No. 40 or 46 at breakout box. If voltage is greater than one volt, repair short to VPWR circuit. Remove breakout box, reconnect ECA and rerun QUICK TEST. If voltage is less than one volt, replace EEC-IV power relay or IRCM. Remove breakout box, reconnect ECA and rerun QUICK TEST.

9) Check Malfunction Indicator Light (MIL) Function If MIL is always on, go to TEST ML, step 1). If MIL is always off, go to TEST ML, step 4). If MIL is working normally, replace ECA. Repeat QUICK TEST procedures.

Perform this test when directed by QUICK TEST. This test is intended to diagnose only the following components or systems

1. ECA
2. Harness circuits (KAPWR)

EEC Power Relay Circuit. Scheme 76

4.0L SPFI-MA TEST PIN WIRE COLOR I.D.

4.0L SPFI-MA TEST PIN WIRE COLOR I.D. (RANGER & EXPLORER, NAVAJO)

1) Continuous Memory Code 15/512 Displayed Code 15/512 indicates ECA is experiencing power interruption in its Keep-Alive Memory (KAM) circuit. Clear Continuous Memory Codes. See CLEARING CODES in this article. Wait 5 minutes to allow code to reset. Repeat KOEO SELF-TEST for Continuous Memory Code output. If Continuous Memory Code 15/512 is not displayed, Continuous Memory Code 15/512 testing is complete. Service other codes as necessary. If Continuous Memory Code 15/512 is displayed during retest, go to next step.

Continuous Memory Code 15/512 may be displayed when power to Keep-Alive Memory (KAM) test pin No. 1 at ECA is interrupted. This code may be set when installing a breakout box, and may be displayed the first time self-test is performed and power is restored to ECA. Repeat self-test to ensure correct diagnosis.

2) Inspect Engine Compartment Wire Routing Ensure EEC-IV components and wiring are not close to high-tension secondary voltage wires or ignition components. If EEC-IV wiring is close to high-tension wires, reroute EEC wiring. Clear codes and wait 5 minutes. Repeat KOEO SELF-TEST. If Continuous Memory Code 15/512 is no longer displayed, Continuous Memory Code 15/512 testing is complete; service other codes as necessary. If Continuous Memory Code 15/512 is still displayed, go to next step.

3) Code 15/511: Check KAPWR Circuit Voltage Code 15/511 indicates ECA memory (ROM) failed during KOEO SELF-TEST. Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector and inspect for damaged pins and loose wires. Service as necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 20-volt scale. Connect DVOM positive test lead to test pin No. 1 and negative test lead to pin No. 40 or 60 at breakout box. With KOEO, observe voltage reading while wiggling, bending and shaking small sections of EEC harness from EEC to dash. If reading is less than 10.5 volts, repair open circuit; reconnect ECA and repeat QUICK TEST. If reading is 10.5 volts or more, replace ECA; remove breakout box and repeat QUICK TEST.

Perform this circuit test when directed by other CIRCUIT TESTS. This test is intended to diagnose only the following

1. ECA
2. Throttle plate linkage

1) Check For Codes 23, 53, 63, 121, 122 Or 123 If vehicle is equipped with a speed control, speed control servo must be electrically disconnected. This prevents speed control system from affecting throttle plate movement during Output State Check. Rerun QUICK TEST or Output State Check.

Turn ignition off and wait 10 seconds. Perform KOEO SELF-TEST. If Codes 23, 53, 63, 121, 122 or 123 are displayed, go to appropriate KOEO SELF-TEST CODES chart under CODE-TO-TEST MENU(S) and service code(s) as necessary. If no code is displayed, go to TEST QA, step 1). If Code 11/111 (pass code) is displayed, go to next step.

2) Check Throttle Linkage Check throttle and linkage for sticking or binding. If throttle and linkage are okay, replace TPS and repeat QUICK TEST. If throttle and linkage are binding, repair as necessary and repeat QUICK TEST.

Perform this test only when directed by TEST A or TEST AA.

This test is intended to diagnose the following components or systems

1. ISC by-pass air system
2. MAP system
3. EGR system
4. MAF system

4.0L SPFI-MA TEST PIN WIRE COLOR I.D.

4.0L SPFI-MA TEST PIN WIRE COLOR I.D. (RANGER & EXPLORER, NAVAJO)

To prevent replacing good components, be aware that the following non-EEC-IV areas may be at fault

1. Faulty power or ground connections
2. Ignition system (distributor cap, rotor, wires, coil and plugs)
3. Basic mechanical engine components (cam timing, compression, etc.)

1) ISC-BPA Check Attempt to start engine at part throttle. If engine starts and runs smoothly at part throttle, go to TEST KE, step 4). If engine does not function as described, go to step 3).

2) Check For RPM Drop Turn ignition off. Connect a tachometer. Start engine and disconnect ISC solenoid. If RPM drops or engine stalls, reconnect ISC solenoid and go to next step. If RPM does not drop, go to step 4).

3) Power To MAP/BP Sensor If vehicle is not equipped with a MAP/BP sensor, go directly to step 8). Use Ford Motor Co. MAP/BP tester for this test. If Green light is on, VREF circuit voltage is okay. If Red light (or no light) is on, VREF circuit voltage is either too low or too high. Turn ignition off and disconnect MAP/BP sensor from vehicle harness. Connect MAP/BP tester between vehicle harness and MAP/BP sensor. Connect banana plugs of tester into DVOM, and set DVOM on 20-volt scale. With tester connected, turn ignition on. If Green light is on, go to next step. If light is not on, repair open in VREF circuit and remove MAP/BP tester. Reconnect components and retest symptom.

MAP/BP Tester & Circuit. Scheme 77

4) MAP/BP Tester Output Reading Measure several known good MAP/BP sensors to obtain average voltage for specific location and date of testing. With MAP/BP tester and DVOM connected, turn ignition on and measure MAP/BP SIG voltage at MAP sensor. If voltage is in within specification for the specific altitude, go to step 8) (vehicles with MA sensors), or go to next step (all others). See MAP VOLTAGE OUTPUT table. If voltage is not within specification for the specific altitude, replace MAP/BP sensor.

MAP VOLTAGE OUTPUT

5) Check Vacuum Lines Check vacuum lines for correct routing. Refer to VECI decal. Check MAP sensor vacuum line for leaks or blockage. If vacuum lines are okay, go to next step. If vacuum lines are not okay, repair as necessary. Rerun QUICK TEST.

6) Check MAP Sensor Turn ignition off and wait 10 seconds. Disconnect vacuum line from MAP sensor. Install vacuum pump to MAP sensor. Apply 18 in. Hg vacuum to MAP sensor. If MAP sensor holds vacuum, release vacuum and remove vacuum pump. Reconnect vacuum line to MAP sensor and go to next step. If MAP sensor does not hold vacuum, replace MAP sensor. Reconnect vacuum line and rerun QUICK TEST.

7) Check Vacuum Manifold Source Turn ignition off. Disconnect MAP sensor vacuum hose from manifold vacuum "T" fitting, and install vacuum gauge in its place. Start engine and observe vacuum gauge. If manifold vacuum is present, remove vacuum gauge; reconnect MAP sensor vacuum hose and go to next step. If vacuum is not present, remove obstruction; reconnect all components and rerun QUICK TEST.

8) Check EGR Vacuum If vehicle is not equipped with EGR system hardware, go directly to TEST H, step 2). Step 8) and step 9) attempt to determine if EGR system is the cause of driveability symptom or no-start condition. Disconnect and plug vacuum line at EGR valve. Attempt to start engine. If vehicle could not start previously and still does not start, or if vehicle driveability fault is still present, go to next step. If vehicle did not start previously but starts now, or if driveability symptoms are eliminated, go to TEST DN, step 42) (vehicles with EVP), or go to TEST DL, step 21) (all others).

9) Check EGR Valve Inspect EGR valve for leaks. If valve is fully closed, go to TEST H, step 2). If EGR valve is leaking or is not fully seated, replace or repair valve.

Perform this test only when directed by QUICK TEST. This test is intended to diagnose only the following circuits or systems

1. Clutch Engage/Interlock Switch
2. Neutral Drive/Gear Switch
3. ECA
4. Harness Circuits: CES, CIS, NDS, NGS and SIG RTN

4.0L SPFI-MA TEST PIN WIRE COLOR I.D.

4.0L SPFI-MA TEST PIN WIRE COLOR I.D. (RANGER & EXPLORER, NAVAJO)

1) Code 67/522, 525, 527, 528 Or 634 System Identification Code 67/522, 525, 527, 528 Or 634 is a result of voltage being high at either pin No. 10 (A/C input) or pin No. 30 (neutral drive) while cranking engine or during KOEO SELF-TEST. Possible causes for these faults are as follows

1. A/C circuit shorted to power
2. Clutch engage/interlock circuits open
3. Neutral drive/gear switch open
4. Faulty ECA
5. Starter relay disconnected during self-test

Neutral Gear/Clutch Input Circuit. Scheme 78

Checking Clutch Engage Switch. Scheme 79

Note. There is a break in the step numbering sequence at this point, skipping from step 1) to step 8). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

8) Check Neutral Drive Input Turn ignition off and wait 10 seconds. Ensure heater control is in OFF position (if equipped). Ensure transmission is in NEUTRAL or PARK position. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires; repair as necessary. Install breakout box and connect ECA to breakout box. Set DVOM to 20-volt scale. With KOEO, measure voltage between test pin No. 30 and chassis ground. If voltage is less than one volt, go to TEST KM, step 40) (vehicles with A/C), or replace ECA, remove breakout box and rerun QUICK TEST (all others). If voltage is greater than one volt, go to next step.

Checking Neutral Drive Switch. Scheme 80

9) Check Neutral Drive Switch Turn ignition off and wait 10 seconds. Install breakout box, leaving ECA disconnected. Set DVOM to 200-ohm scale. Disconnect vehicle harness from neutral drive switch and measure resistance across switch. If resistance is less than 5 ohms, repair open circuit in vehicle harness Neutral Drive circuit. Remove breakout box, reconnect all components and rerun QUICK TEST. If resistance is greater than 5 ohms, replace neutral drive switch. Remove breakout box, reconnect all components and rerun QUICK TEST.

10) Check Neutral Drive Input Turn ignition off and wait 10 seconds. Ensure transmission is in NEUTRAL or PARK position. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires; repair as necessary. Install breakout box and connect ECA to breakout box. Set DVOM to 20-volt scale. Disconnect 4EAT module 16-pin connector. With KOEO, measure voltage between test pin No. 30 and chassis ground. If voltage is less than one volt, replace ECA. Remove breakout box, reconnect all components and rerun QUICK TEST. If voltage is greater than one volt, go to next step.

Checking Neutral Drive Input. Scheme 81

11) Check NDS Circuit Continuity Between ECA And 4EAT Module Turn ignition off and wait 10 seconds. Install breakout box and leave ECA disconnected. Disconnect 4EAT 16-pin connector. Set DVOM to 200-ohm scale. Measure resistance between test pin No. 30 and NDS pin at 4EAT module vehicle harness connector. If resistance is less than 5 ohms, diagnose 4EAT system; remove breakout box, reconnect all components and rerun QUICK TEST. If resistance is greater than 5 ohms, repair open circuit; remove breakout box, reconnect all components and rerun QUICK TEST.

Checking NDS Continuity. Scheme 82

12) Check NDS Circuit For Short To Ground Or Closed Neutral Drive Switch Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires; repair as necessary. Install breakout box and leave ECA disconnected. Set DVOM to 200-k/ohm scale. Place transmission in DRIVE position. Measure resistance between test pins No. 30 and 40/60. If resistance is greater than 10 k/ohms, NDS circuit okay. Diagnose other possible causes. If resistance is less than 10 k/ohms, repair closed neutral drive switch or short circuit. Remove breakout box, reconnect all components and rerun QUICK TEST.

Perform this test only when directed by QUICK TEST. To prevent replacing good components, be aware that the following non-EEC areas may be at fault

1. Hydraulic or emergency brake system
2. Transmission linkage
3. Internal transmission components

This test is intended to diagnose only the following components or circuits

1. Harness circuits (CCO, SS 3/4-4/3 and VPWR)
2. CCO solenoid
3. Shift solenoid 3/4-4/3
4. ECA

A4LD Transmission Circuits. Scheme 83

4.0L SPFI-MA TEST PIN WIRE COLOR I.D.

4.0L SPFI-MA TEST PIN WIRE COLOR I.D. (RANGER & EXPLORER, NAVAJO)

1) Code 86/556 Or 89/639: Check Solenoid Resistance Code 86/556 indicates ECA did not detect a voltage drop when Shift Solenoid 3/4 (SS 3/4) was activated. Code 89/626 indicates ECA did not detect a voltage drop when CCO solenoid was activated. Possible causes for this fault are as follows

1. CCO/SS resistance out of limits
2. CCO/SS circuit open or grounded
3. Faulty ECA

Ensure codes match appropriate transmission solenoid circuit. Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair as necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 37/57 and test pins No. 53 (CCO) and 52 (SS 3/4). If resistance is 26-40 ohms, go to step 4). If resistance is NOT 26-40 ohms, go to next step.

2) Check Continuity Of Vehicle Harness Circuits With ignition off, install breakout box. Leave ECA and transmission bulkhead connector (A4LD solenoids) disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 37/ 57 at breakout box and VPWR circuit pin of vehicle harness connector at transmission. Measure resistance between appropriate ECA signal output pin (No. 52 or 53) at breakout box and same circuit at transmission vehicle harness connector. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open circuit. Remove breakout box, reconnect all components and rerun QUICK TEST.

3) Check Transmission Vehicle Harness Circuits With ignition off, install breakout box, leaving ECA disconnected. Disconnect transmission bulkhead connector. Set DVOM on 200-k/ohm scale. Measure resistance between appropriate test pin No. 53 (CCO) or 52 (SS 3/4) and test pins No. 37 and 57 at breakout box. Measure resistance between appropriate test pin No. 53 (CCO) or 52 (SS 3/4) and test pins No. 40, 60 and 46 at breakout box and at chassis ground. If all resistances are greater than 10 k/ohms, go to next step. If any resistance is less than 10 k/ohms, repair short circuit. Remove breakout box and reconnect components. Rerun QUICK TEST.

4) Check VPWR Voltage To Transmission Solenoids - With ignition off, breakout box installed and ECA connected, set DVOM on 20-volt scale. Disconnect transmission bulkhead connector. Turn ignition on, leaving engine off. Measure voltage between test pins No. 37/57 at bulkhead connector and chassis ground. If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts, replace ECA. Remove breakout box and reconnect all components. Rerun QUICK TEST.

5) Check Output Driver Signal Turn ignition off. Install breakout box, leaving ECA connected. Disconnect A4LD transmission bulkhead connector. Connect test light between test pin No. 37/57 and appropriate test pin No. 53 (CCO) or 52 (SS 3/4) at breakout box. Enter KOEO SELF-TEST. If test light flashes momentarily and then stays off, fault is internal in transmission. Repair internal electrical fault as necessary. If light does not flash momentarily and then stay off, replace ECA. Remove breakout box and reconnect all components. Repeat QUICK TEST.

TEST TC - E4OD AUTOMATIC TRANSMISSION

Note. You should perform this test when Codes 26, 47, 56, 66, 67, 91, 92, 93, 94, 97, 98 and 99 are displayed during KOEO SELF-TEST, Codes 26 and 65 are displayed during KOER SELF-TEST, or Codes 29, 49, 56, 59, 62, 66, 69 and 99 are displayed during CONTINUOUS MONITOR MODE testing or when directed here during DIAGNOSIS BY SYMPTOM tests. This circuit test is intended to diagnose only the following: harness circuits, CCC, CCS, 4WD LOW, EPC, CILY, OCS, SS1, SS2, SIGRTN, TOT, MLP, VPWR and ECA.

The Transmission Solenoid Assembly (7G391) and Manual Lever Position (MLP) sensor (7F293) are not diagnosed in this circuit test as they are not controlled by the ECA.

RPM Sensor Circuit. Scheme 84

4WD Low & Overdrive Cancel Harness Schematic. Scheme 85

1) Code 67: Check Resistance Through MLP Sensor Code 67 indicates that total resistance in the MLP sensor is out of Self-Test range when the selector lever is in "P" (correct range is 3770-4607 ohms). Possible causes for this fault are: faulty MLP sensor, open or shorted harness, faulty ECA.

Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector and inspect for corroded or damaged pins. Service or repair as necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 10 k/ohm scale. With KOEO, measure resistance between test pins No. 30 and 46 at the breakout box while moving the selector from "P" to "L" and back to "P". Record specifications and compare to specification table. If resistance is within specification, go to step 3). If resistance is not as specified, go to next step.

MLP RESISTANCE SPECIFICATIONS

2) Checking Continuity of MLP Harness Ensure key is off and MLP sensor is disconnected from harness. Use a mirror to inspect ends of transmission harness connector at MLP sensor for damage or corrosion. Repair as necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 30 at the breakout box and corresponding pin at the MLP sensor vehicle harness connector. Measure resistance between test pin No. 46 at the breakout box and corresponding pin at the MLP sensor vehicle harness connector. If both resistances are less than 5 ohms, go to next step. If resistances are not as specified, repair open circuit, remove breakout box, reconnect components and rerun QUICK TEST.

3) Check MLP Harness For Short To Power Or Ground Turn key off. Ensure MLP sensor harness is disconnected. Install breakout box leaving ECA disconnected. Set DVOM on 200-k/ohm scale. Measure resistance between test pin No. 30 and test pins No. 37 and 57 at the breakout box. Measure resistance between test pin No. 30 and test pins No. 40, 46 and 60 at the breakout box. Measure resistance between test pin No. 30 at the breakout box and chassis ground. If all resistances are greater than 10 k/ohms, go to next step. If resistances are less than 10 k/ohms, repair short circuits, remove breakout box, reconnect components and rerun QUICK TEST.

TEST PIN WIRE COLOR IDENTIFICATION

4) Checking ECA Output Voltage Ensure key is off. Disconnect MLP sensor from harness. Install breakout box and connect ECA. With KOEO, set DVOM on 20-volt scale. Measure voltage between test pins No. 30 and 46 at the breakout box. If voltage is 4.75-5.25 volts, service or adjust MLP sensor. If voltage is not as specified, replace ECA, reconnect components and rerun QUICK TEST.

5) Code 47, 65 or 97: Verify Self-Test Mode Code 47 indicates 4WD LOW selector lever is not in 2WD or 4WD High position during KOEO Self-Test. This condition may be accompanied by an early shift in the 4WD High range. Code 65 indicates that Overdrive Cancel Switch (OCS) is not cycled between the engine I.D. code and "Goose Test" in the KOER Self-Test. Code 97 indicates an Overdrive Cancel Light (OCL) fault during KOER Self-Test. Possible causes for this fault are: faulty 4WD LOW switch, faulty OCS switch, burned out bulb, open harness, shorted harness or faulty ECA. Rerun QUICK TEST. If none of the above codes are present, fault cannot be duplicated at this time, testing is complete. If Code 97 is present, go to step 7). If any other codes are present, go to next step.

6) Cycle 4WD LOW Or Overdrive Cancel Switch Circuit Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector and inspect for corroded or damaged pins. Service or repair as necessary. Install breakout box, leaving ECA disconnected. With KOEO, set DVOM on 20-volt scale.