Engine Controls - Tests W/codes - 4.0l Ford Explorer I

INTRODUCTION

Perform all steps in BASIC TESTING article in the ENGINE PERFORMANCE Section. If no fault is found while performing BASIC DIAGNOSTIC PROCEDURES, proceed with self-diagnostics. If no service code or only pass codes are found during self-diagnostics, proceed to TESTS W/O CODES article in the ENGINE PERFORMANCE Section for diagnosis by symptoms.

SELF-DIAGNOSTIC SYSTEM

DIAGNOSTIC FORMATS

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

Before starting any CIRCUIT TEST, follow all steps under QUICK TEST to find correct CIRCUIT TEST. If vehicle passes QUICK TEST and no driveability symptoms or intermittent faults exist, EEC-IV system is okay.

SERVICE CODES

During QUICK TEST, 3 types of service codes are retrieved: KOEO, KOER and Continuous Memory codes. See QUICK TEST for self-test procedures. Codes may be cleared from ECA memory after they have been recorded or repaired. See CLEARING CODES.

KOEO & KOER CODES (HARD FAULTS)

These codes indicate faults are present at time of testing. A hard fault may cause CHECK ENGINE or Malfunction Indicator Light (MIL) to glow and remain on until fault is repaired. If KOEO or KOER codes are retrieved during KOEO SELF-TEST or KOER SELF-TEST, use SERVICE CODE REFERENCE CHARTS to find correct testing and repair procedures.

CONTINUOUS MEMORY CODES (SOFT FAULTS)

These codes indicate a fault that may or may not be present at time of testing. These codes are used to diagnose intermittent problems. Continuous Memory Codes are retrieved during KOEO SELF-TEST. Some codes may turn on MIL or CHECK ENGINE light. Corresponding soft trouble code will be retained in ECA memory. If fault does not reoccur within 40 warm-up cycles (80 cycles on some models), ECA will automatically clear code.

Technician may clear service codes from memory. See CLEARING CODES. Intermittent faults may be caused by a sensor, connector or wiring-related problems. See INTERMITTENTS in TESTS W/O CODES article in the ENGINE PERFORMANCE Section.

RETRIEVING CODES

Service codes are retrieved from EEC-IV system through self-test connector. Various methods and test equipment may be used to access these codes

1. Analog Volt-Ohmmeter (VOM)
2. Scan Tester
3. In-Dash Malfunction Indicator Light (MIL) Or CHECK ENGINE Light

SELF-TEST CONNECTOR LOCATIONS

KOEO & KOER SELF-TEST CODES

All service codes are 2 or 3-digit numbers. ECA outputs codes one digit at a time. These codes indicate current faults in system and should be serviced in order of appearance. Use SERVICE CODE REFERENCE CHARTS to find correct CIRCUIT TEST.

Codes are shown as voltage pulses. If using CHECK ENGINE light, service codes are displayed as light pulses. If using Volt-Ohmmeter (VOM), service codes are displayed as needle sweeps. (Scheme 4)

Pay careful attention to length of pauses in order to read codes correctly. A 1/2-second pause occurs between number of sweeps in a digit and a 2-second pause occurs between digits in a code. A 4-second pause occurs 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 order received.

Scan tester, if used, will count pulses and display them as a digital code. STAR Series Tester will add a zero (0) to single-digit Separator Code (10) and Dynamic Response Code (10). Dynamic Response Code is displayed in KOER SELF-TEST. (Scheme 4)

SEPARATOR CODE

Single 1/2-second separator pulse is issued 6-9 seconds after last KOEO code. Continuous Memory Codes (soft faults) are then displayed 6-9 seconds after 1/2-second separator code. Some digital test equipment may display separator code as "10" instead of "1".

PASS CODES

Code 11 or 111 indicates system passes that portion of test. If Code 11 or 111 is not retrieved in KOEO SELF-TEST, codes retrieved during KOER SELF-TEST may not be valid. Code 11-1-11 or 111-1-111, output during KOEO SELF-TEST, indicates no KOEO code or Continuous Memory Code was recorded.

CONTINUOUS MEMORY CODES

Continuous Memory Codes are displayed after separator pulse code in KOEO SELF-TEST. These codes result from information stored by ECA during continuous self-test monitoring. These codes indicate faults recorded within last 40 engine starts (80 engine starts on some models). Fault may or may not be currently present. See SERVICE CODE REFERENCE CHARTS . Use these codes for diagnosis only when KOEO SELF-TEST and KOER SELF-TEST result in Code 11 or 111.

FAST CODES

At start of KOEO SELF-TEST and after Wide Open Throttle (WOT) request in KOER SELF-TEST, ECA outputs short bursts of information, known as FAST CODES, which were used by manufacturer during assembly. With most equipment, these code bursts are not visible; an entire code sequence lasts less than 1/2 second. If this fluctuation is visible on test equipment, ignore it.

Scheme 4

CLEARING CODES

To clear codes from ECA memory, start KOEO SELF-TEST. When service codes appear on test equipment or CHECK ENGINE light, disconnect jumper wire from Self-Test Input (STI) connector. If using STAR Series Tester, unlatch center button. This procedure erases Continuous Memory Codes from ECA memory. If problem has not been corrected or fault is still present, hard code will immediately be reset in ECA memory.

Note. To clear KAM, disconnect negative battery terminal for at least 5 minutes.

Description

Following procedures are functional tests of EEC-IV system. (Scheme 6) These 5 basic test steps must be carefully followed in sequence to avoid misdiagnosis or replacement of non-faulty components.

1. Visual Check & Vehicle Preparation
2. Equipment Hookup
3. KOEO (Key On Engine Off) SELF-TEST
4. Computed Timing Check
5. KOER (Key On Engine Running) SELF-TEST

Diagnostic Aids

After each service or repair procedure has been completed, repeat QUICK TEST to ensure all EEC-IV systems work properly and fault codes are no longer present.

VISUAL CHECK & EQUIPMENT HOOKUP

Complete all steps in BASIC TESTING article in the ENGINE PERFORMANCE Section before proceeding to self-diagnostic tests. Ensure vacuum hoses and EEC-IV wiring harnesses are properly connected.

Apply parking brake, and place shift lever in PARK (A/T) or NEUTRAL (M/T) position. Block drive wheels. Turn off all electrical loads. Connect appropriate test equipment to vehicle as follows

Analog Volt-Ohmmeter (VOM)

1. Turn ignition switch to OFF position. Set VOM at 0-15V DC range. Connect positive lead of VOM to positive battery terminal.
2. Connect negative VOM lead to Self-Test Output (STO) terminal of self-test connector. (Scheme 5) Connect jumper wire from Self-Test Input (STI) pigtail to signal return terminal of self-test connector. KOEO SELF-TEST will activate when ignition is turned on.

Scan Tester

Follow manufacturer instructions to hook up equipment and record service codes.

STAR Series Tester

Turn ignition switch to OFF position. Connect color-coded adapter cable leads to diagnostic tester. Connect 2service connectors of adapter cable to vehicle self-test connector and STI pigtail connector. Connect timing light. Go to KOEO SELF-TEST.

Scheme 5

Scheme 6

KOEO SELF-TEST

Ensure engine is warmed to normal operating temperature. If engine does not start (or stalls after starting), continue KOEO SELF-TEST. DO NOT depress throttle on gasoline vehicles. Turn ignition off. Wait 10 seconds. Ensure test equipment is properly attached. Turn ignition on (engine off). Record all KOEO and Continuous Memory Codes.

If a Code 11 or 111 (pass code) is not retrieved in KOEO portion of test, service KOEO codes. See SERVICE CODE REFERENCE CHARTS . If ECA will not output codes, go to CIRCUIT TEST QA . If service codes are retrieved

1. Service codes in order retrieved. See «SERVICE CODE REFERENCE CHARTS»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) .
2. On DIS and EDIS models, see IGNITION SYSTEM in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section if Continuous Memory Code 45, 46, 48, 215, 216, 217, 232 or 238 is retrieved during KOEO SELF-TEST.
3. If vehicle has a no-start condition, go to «CIRCUIT TEST AC (EDIS)»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l__circuit-test-ac-no-start) .
4. If vehicle displays a Code 11 or 111 (pass code) and does not have any of symptoms described in previous steps, go to COMPUTED TIMING CHECK.

COMPUTED TIMING CHECK

Turn ignition off. Connect timing light. Using jumper wire or test equipment, activate KOER SELF-TEST. If engine starts and stalls (or stalls during self-test), go to CIRCUIT TEST S . Start engine, and check for following

1. If Code 98 or 998 is displayed, EEC-IV system is operating in Failure Mode Effects Management (FMEM). Vehicle cannot be diagnosed in KOER SELF-TEST; rerun KOEO SELF-TEST.
2. Check computed timing after last service code has been displayed. Timing will remain fixed for 2 minutes after last code has been retrieved unless self-test is deactivated.
3. Computed timing, at crankshaft, should equal base timing (see vehicle emission decal) plus 20 degrees BTDC. This timing may vary 3 degrees (+/-). If computed timing is within specification, perform KOER SELF-TEST. If timing is not within specification, go to step 2 of CIRCUIT TEST PC - SPARK TIMING CHECK (EDIS VEHICLES).

DO NOT enter this test sequence until a Code 11 or 111 (pass code) has been retrieved in KOEO SELF-TEST. If system has not passed KOEO SELF-TEST, codes 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 engine, and run it for 2 minutes at 2000 RPM to warm 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 following items

1. If engine starts and stalls (or stalls during self-test), go to «CIRCUIT TEST S»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) .
2. If Code 98 or 998 is displayed, 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 «SERVICE CODE REFERENCE CHARTS»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) .
3. If vehicle is equipped with a Brake On-Off (BOO) switch, brake pedal must be depressed and released after ID code portion of test.
4. On vehicles with Power Steering Pressure Switch (PSPS), turn steering wheel at least 1/2 turn and release within 1-2 seconds after ID code portion of test.
5. On vehicles with E4OD transmissions, Overdrive Cancel Switch (OCS) must be cycled after ID code portion of test.
6. If Dynamic Response Code appears, perform a brief Wide Open Throttle (WOT). DO NOT perform WOT unless requested.
7. If a Code 11 or 111 (pass code) is retrieved during KOER SELF-TEST, service Continuous Memory Codes retrieved in KOEO SELF-TEST. See «SERVICE CODE REFERENCE CHARTS»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) .
8. If a Code 11 or 111 (pass code) is retrieved during Continuous Memory Code portion of KOEO SELF-TEST (Code 11-1-11 or Code 111-1-111) and no driveability problem exists, EEC-IV testing is complete. If driveability problems are still present, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section.
9. If KOER codes are present, see «SERVICE CODE REFERENCE CHARTS»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) . If system will not output codes, go to «CIRCUIT TEST QA»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) .

CONTINUOUS MONITOR MODE (WIGGLE TEST)

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

KOEO Wiggle Test

Connect test equipment. Turn ignition on, and activate self-test using jumper lead or diagnostic tester. Wait 10 seconds, and then deactivate and reactivate self-test. Wiggle test mode is now activated. Tap, move and wiggle suspect sensor and/or harness area. If a fault is detected, a service code may be stored in memory and indicated at diagnostic tester or scan tester. Retrieve code, and perform appropriate test. See SERVICE CODE REFERENCE CHARTS .

KOER Wiggle Test

Connect test equipment. Turn ignition off, and wait 10 seconds. Start engine. Activate self-test using jumper lead or diagnostic tester. Wait 10 seconds, and then deactivate and reactivate self-test. DO NOT turn engine off. KOER wiggle test mode is now activated. Tap, move and wiggle suspect sensor and/or harness area. If a fault is detected, a service code may be stored in memory and indicated at diagnostic tester or scan tester. Retrieve code, and perform appropriate test. See SERVICE CODE REFERENCE CHARTS .

ADDITIONAL SYSTEM FUNCTIONS

Additional diagnostic system features are available to help diagnose driveability problems and service EEC-IV systems.

Check Engine Light & Malfunction Indicator Light (MIL)

CHECK ENGINE light and MIL are intended to alert driver of certain malfunctions in EEC-IV system.

Light may also be used to retrieve service codes stored in ECA. When hooked up for KOEO SELF-TEST or KOER SELF-TEST, light will display all codes which turn on light during vehicle operation, not just Continuous Memory Codes.

If light comes on during vehicle operation, vehicle should be inspected as soon as possible. Immediately turning off engine is not necessary; vehicle can be driven with light on.

If light comes on and then goes off during vehicle operation, code causing light to glow will be stored in ECA memory as a Continuous Memory Code.

Light should come on when ignition is turned on and go out when engine is started. If light does not come on, see SYMPTOMS in TESTS W/O CODES article in the ENGINE PERFORMANCE Section. If hard fault codes are not present, ECA turns out light when it receives a Profile Ignition Pick-Up (PIP) signal.

Output State Check

Output state check is used as an aid for servicing EEC-IV system output actuators. It allows technicians to operate most output actuators on command. This mode is entered from KOEO SELF-TEST after all codes have been retrieved. Leave SELF-TEST activated, and depress throttle to initiate test sequence. Each time throttle is depressed and released, output actuators will change from on to off or off to on.

Failure Mode Effects Management (FMEM), Code 98 Or 998 -FMEM mode allows system operation when sensors fail or transmit signals that are out of normal operating range. During FMEM mode, ECA substitutes a mid-range signal for defective sensor while continuing to monitor sensor. If faulty sensor's signals return to normal operating range, ECA will use those signals. A Code 98 or 998 will be displayed when FMEM mode is in effect.

Hardware Limited Operational Strategy (HLOS)

If a number of system or sensor failures are present and ECA is not receiving enough information to operate, ECA will switch to HLOS mode. ECA will output fixed values to allow operation of vehicle. Driveability performance will be reduced.

Cylinder Balance Test

This test helps identify a weak or non-contributing cylinder in engines with sequential PFI fuel systems. ECA shuts off fuel supply to each injector and measures RPM drop. It computes variation between cylinders and identifies weak ones. This test mode is entered from 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 test procedure. Test will be repeated if throttle is depressed within 2 minutes of final code output. During second and third test sequences, percentage of allowable variation between cylinders is reduced. Service codes displayed during this test identify weak or non-contributing cylinder. See CYLINDER BALANCE TEST SERVICE CODES . If Code 90 is displayed during this test, system has passed test. If Code 77 is displayed, repeat cylinder balance test. If throttle is moved during this test, Code 77 will appear, indicating test is not completed. Total test time is about 3 minutes.

CYLINDER BALANCE TEST SERVICE CODES

SUMMARY

If no service code or Code 11-1-11 or 111-1-111 (pass code) is present, but driveability problem still exists, proceed to EEC-IV DIAGNOSIS BY SYMPTOM . If driveability problem still cannot be located, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section for diagnosis by symptoms or intermittent diagnostic procedures.

EEC-IV DIAGNOSIS BY SYMPTOM

Scheme 7

Scheme 8

Scheme 9

Scheme 10

Scheme 11

Scheme 12

DIAGNOSTIC TROUBLE CODE (DTC) DEFINITION (AEROSTAR, EXPLORER & RANGER 4.0L)

DIAGNOSTIC TROUBLE CODE (DTC) DEFINITION

CIRCUIT TESTS

Note. A breakout box, connected to vehicle harness at ECA, is necessary to perform most circuit tests. References to Test Pin No. found in CIRCUIT TEST steps refer to test terminals on manufacturer breakout box overlay. Circuit diagrams at beginning of each test identify circuit and wire colors.

HOW TO USE CIRCUIT TESTS

1. Ensure all non-EEC-IV related faults found while performing steps in BASIC TESTING article in the ENGINE PERFORMANCE Section have been corrected. DO NOT perform any CIRCUIT TEST unless instructed by a QUICK TEST procedure. Follow each test step in order until fault is found. When more than one code is retrieved, start with first code displayed.
2. CIRCUIT TESTS ensure electrical circuits are okay before sensors or other components are replaced. Always test circuits for continuity between sensor and ECA. Test all circuits for short to power, opens or short to ground. Voltage Reference (VREF) and Voltage Power (VPWR) circuits should be tested with ignition on unless otherwise specified in CIRCUIT TESTS.
3. DO NOT measure voltage or resistance at ECA. DO NOT connect any test light unless specified in testing procedure. All measurements are made by probing rear of connector. Isolate both ends of a circuit and turn ignition off when checking continuity, unless instructed otherwise.
4. Disconnect solenoids and switches from harness before measuring continuity and resistance or applying voltage. After each repair, check all component connections and repeat QUICK TEST.
5. An open circuit is defined as a resistance reading of greater than 5 ohms. This specification tolerance may be too high for some items in EEC-IV system. If resistance approaches 5 ohms, always clean suspect connector and coat it with protective dielectric silicone grease. A short is defined as a resistance reading of less than 10,000 ohms to ground, unless stated otherwise in CIRCUIT TEST.

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

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

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

CIRCUIT TESTS are grouped as follows.

1. A-C - No Start & Voltage Tests
2. DA-DS - Input Sensor Tests
3. FD-FF - Additional Input Component Tests
4. G-J - Fuel Control System Tests
5. KD-TG - ECA (Processor) Output Tests

CIRCUIT TEST INDEX

CIRCUIT TEST AC - NO START (EDIS IGNITION SYSTEMS)

Enter this CIRCUIT TEST only when all steps under QUICK TEST have been successfully completed and engine still does not start or if directed here from another test or chart. This test is only intended to diagnose

1. Spark (ECA-controlled).
2. Wiring harness circuits (PIP, IGN GND and VPWR).
3. ECA.

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

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

Scheme 13

CIRCUIT TEST AC TEST PIN WIRE COLOR ID

Scheme 14

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 Turn ignition off. Disconnect Throttle Position Sensor (TPS). Turn ignition on (engine off). Measure voltage between VREF and SIG RTN at TPS harness connector. (Scheme 14) If voltage is not 4-6 volts, go to «CIRCUIT TEST C»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l). If voltage is 4-6 volts, reconnect TPS and go to next step.
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, reconnect spark plug wire and go to step 4). If spark is not present, check ignition system. See EDIS SYSTEM in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
4. Check IGN GND Continuity Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for damage and repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Disconnect EDIS module. Measure resistance between test pin No. 16 at breakout box and IGN GND terminal at EDIS module wiring harness connector. If resistance is 5 ohms or more, repair open in IGN GND circuit and repeat QUICK TEST. If reading is less than 5 ohms, go to next step.
5. Check PIP For Short To Power Ensure ignition is turned off. Disconnect EDIS module. Measure voltage between test pin No. 56 at breakout box and negative battery terminal. If voltage is greater than 7 volts, repair PIP circuit short to power and repeat QUICK TEST. If voltage is not greater than 7 volts, go to next step.
6. Check PIP Circuit Continuity Ensure ignition is turned off. Measure resistance between test pin No. 56 at breakout box and PIP terminal at EDIS module wiring harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open PIP circuit and repeat QUICK TEST.
7. Check PIP Circuit For Shorts To Ground Ensure ignition is turned off. 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 10,000 ohms, repair short in PIP circuit and repeat QUICK TEST. If engine still does not start, go to next step. If all readings are 10,000 ohms or more, go to step next step.
8. Isolate Shorts In ECA Ensure ignition is turned off. With breakout box installed, connect ECA to breakout box. Disconnect EDIS module. 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 any resistance is not 20,000-150,000 ohms, replace ECA and repeat QUICK TEST. If all resistances are 20,000-150,000 ohms, go to next step.
9. Check PIP Signal Turn ignition off. Wait 10 seconds. With breakout box installed, disconnect ECA. Reconnect EDIS module. Measure voltage between test pin No. 56 and test pin No. 16 at breakout box while cranking engine. Record voltage. If voltage is 3-7 volts, go to next step. If voltage is not 3-7 volts, replace EDIS module and repeat QUICK TEST.
10. Fuel Pump Check Connect fuel pressure gauge to vehicle. Note initial pressure reading. Pressurize fuel system by turning ignition on for one second. Record system pressure. Turn ignition off, and wait 10 seconds. Repeat sequence 5 times. If pressure increases, go to «CIRCUIT TEST S»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l). If pressure does not increase, go to FUEL SYSTEM in SYSTEM & COMPONENT TESTING - EEC-IV.

Enter this CIRCUIT TEST only when directed by CIRCUIT TEST C, CIRCUIT TEST J, CIRCUIT TEST PA, CIRCUIT TEST PB or CIRCUIT TEST PC. To prevent replacement of good components, be aware following non-EEC related areas may be cause of problem: battery cables, ground straps, voltage regulator, alternator and ignition switch. This test is intended to diagnose ECA, power relay, battery voltage and following harness circuits.

1. Signal Return
2. PWR GND
3. VPWR
4. KAPWR
5. VREF
6. Ignition Switch

Scheme 15

CIRCUIT TEST B TEST PIN WIRE COLOR ID

1. Battery Voltage Check Turn ignition on (engine off). Measure battery voltage. If voltage is less than 10.5 volts, recharge or replace battery. If voltage is 10.5 volts or more, go to next step.
2. Check Continuity Of PWR GND Circuit Turn ignition off. Wait 10 seconds. Disconnect ECA. Inspect connector pins for damage and repair as necessary. Install Breakout Box (T83L-50-EEC-IV). Connect ECA to breakout box. Measure resistance between test pins No. 40 and 60 at breakout box and negative battery terminal. If resistance is 5 ohms or more, repair open in PWR GND circuit. Remove breakout box, and repeat QUICK TEST. If both resistances are less than 5 ohms, go to next step.
3. Check For Open Between SIG RTN & PWR GND Circuits At ECA Ensure ignition is turned off. With breakout box installed and ECA connected, set DVOM on 200-ohm scale. Measure resistance between test pin No. 46 and test pins No. 40 and 60 at breakout box. If readings are 5 ohms or more, disconnect ECA connector. Inspect connector pins for damage and repair as necessary. If fault is still present, replace ECA and repeat QUICK TEST. If readings are less than 5 ohms, go to next step.
4. Check Continuity Of SIG RTN Circuit Ensure ignition is turned off. Measure resistance between test pin No. 46 at breakout box and SIG RTN terminal at self-test connector. If resistance is 5 ohms or more, repair open in SIG RTN circuit. Remove breakout box, and repeat QUICK TEST. If reading is less than 5 ohms, go to next step.
5. Check KAPWR Circuit Voltage At EEC Power Relay Turn ignition off. Locate relay block in engine compartment. Disconnect EEC power relay from relay block. Turn ignition on. Measure voltage between negative battery terminal and KAPWR terminal at EEC power relay connector. If voltage is 10.5 volts or less, check KAPWR circuit between EEC power relay and battery power for open circuit. If voltage is 10.5 volts or more, go to next step.
6. Check Ignition Circuit Voltage At EEC Power Relay Ensure EEC power relay is disconnected. Turn ignition on. Measure voltage between negative battery terminal and IGNITION terminal at EEC power relay connector. If voltage is less than 10.5 volts, check for open in ignition switch circuits. Repair wiring, and repeat QUICK TEST. If voltage 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 to breakout box, measure resistance between negative battery terminal and PWR GND terminal at EEC power relay connector. If resistance is 10 ohms or more, repair open circuit in ground circuit. Repeat QUICK TEST. If reading is less than 10 ohms, go to next step.
8. Check VPWR Circuit Continuity Turn ignition off. Measure resistance between test pins No. 37 and 57 (VPWR) at breakout box and VPWR terminal of EEC power relay connector. If resistance is 5 ohms or more, repair VPWR open circuit between EEC power relay and ECA. Repeat QUICK TEST. If reading is less than 5 ohms, go to next step.
9. Check VPWR Circuit Voltage Turn ignition off. Install EEC power relay. Turn ignition on. With ECA connected, measure voltage between test pins No. 37 and 57 (VPWR) and test pins No. 40 and 60 (PWR GND) and 46 (SIG RTN) at breakout box. If voltage is 10.5 volts or more, repair circuit between ECA and EEC power relay. Repeat QUICK TEST. If voltage 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 CIRCUIT TEST DA and CIRCUIT TEST DS, or if directed by CIRCUIT TEST A or CIRCUIT TEST QA. SIG RTN is a dedicated ground used by most EEC-IV system sensors. VREF is a 5-volt reference voltage that is continuously output by ECA. This consistent voltage signal is used on all 3-wire sensors. This circuit test is only intended to diagnose SIG RTN, VREF, TP, EVP, PFE, DPFE, MAP and BP circuits.

Scheme 16

CIRCUIT TEST C TEST PIN WIRE COLOR ID

1. Check Battery Power Circuit Turn ignition off, and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for damage and repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving ECA connected. Turn ignition on. Measure and record voltage between breakout box test pin No. 37 and SIG RTN terminal of self-test connector. Measure and record voltage across battery terminals. If both readings are less than 10.5 volts, or if they differ by more than 1.0 volt, reconnect sensor (if applicable) and go to CIRCUIT TEST B. If voltages are 10.5 volts or more and do 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, set DVOM on 20-volt scale. Turn ignition on. Measure voltage between test pins No. 26 and 46 at breakout box. If voltage is 4-6 volts, go to step 3). If voltage is more than 6 volts, go to step 4). If voltage is less than 4 volts, go to next step.
3. Check VREF & SIG RTN Circuit Continuity Turn ignition off. If directed here by a sensor test, ensure sensor is disconnected. Measure resistance between test pin No. 26 and VREF terminal at wiring harness connector of applicable sensor. Measure resistance between test pin No. 46 and SIG RTN circuit terminal at wiring harness connector of applicable sensor. If both readings are less than 5 ohms, VREF circuit is okay. If either reading is 5 ohms or more, repair open in VREF or SIG RTN circuit and repeat QUICK TEST.
4. Check For Excess VREF Circuit Voltage Turn ignition off. With breakout box installed, disconnect ECA and scan tester or STAR tester (if applicable). Turn ignition on. Measure voltage between test pin No. 26 and battery ground. If voltage is less than 0.5 volt, replace ECA and repeat QUICK TEST. If voltage is 0.5 volt or more, repair short to battery power in wiring harness. Remove breakout box and repeat QUICK TEST. Replace ECA if fault still occurs.
5. Check For Shorted TPS Turn ignition off. Connect ECA to breakout box. Disconnect Throttle Position Sensor (TPS) from wiring harness. Turn ignition on. Measure voltage between test pins No. 26 and 46 at breakout box. If voltage is 4 volts or more, replace TPS and repeat QUICK TEST. If voltage is less than 4 volts on models with EVP, PFE or DPFE sensor, go to next step; if voltage is less than 4 volts on all other models, go to step 7 .
6. Check For Shorted EVP/PFE/DPFE Sensor Turn ignition off. Disconnect EVP/PFE/DPFE sensor. Turn ignition on. Measure voltage between test pins No. 26 and 46. If voltage is 4 volts or more, replace EVP/PFE/DPFE sensor and repeat QUICK TEST. If voltage is less than 4 volts, reconnect EVP/PFE/DPFE sensor and go to next step.
7. Check For Shorted MAP/BP Sensor On models not equipped with a MAP/BP sensor, go to next step; on all other vehicles, turn ignition off. Disconnect MAP/BP sensor. Turn ignition on. Measure voltage between test pins No. 26 and 46. If voltage is 4 volts or more, replace MAP/BP sensor. Remove breakout box, and repeat QUICK TEST. If voltage is less than 4 volts, reconnect MAP/BP sensor and go to next step.
8. Check VREF Circuit For Short To Ground Turn ignition off. Disconnect TPS, MAP/BP sensor and EVP/PFE/DPFE sensor (if equipped). 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, and repeat QUICK TEST. If original problem still exists, replace ECA and repeat QUICK TEST. If readings are 5 ohms or more, 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.

This circuit test is intended to diagnose following components and circuits

1. Air Charge Temperature (ACT) sensor.
2. Engine Charge Temperature (ECT) sensor.
3. Wiring harness circuits (ACT, ECT and SIG RTN).
4. Electronic Control Assembly (ECA).

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

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

Scheme 17

CIRCUIT TEST DA TEST PIN WIRE COLOR ID

1. 1) Code 21/116 Or 24/114 Code 21/116 (ECT) or 24/114 (ACT)indicates corresponding sensor is out of self-test range. Correct range for measurement is.3-3.7 volts. Check for following possible causes: Low ambient temperature (less than 50°F). Low coolant level. Faulty harness connector. Faulty sensor. ACT sensor improperly mounted in air cleaner. If vehicle cannot be started, go to step 3). If vehicle stalls, go to «CIRCUIT TEST S»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l). Ensure upper radiator hose is hot and pressurized. Repeat QUICK TEST. If Code 21, 24, 114 or 116 is present, go to next step. If none of these codes are present, service other codes as necessary.
2. 2) Check VREF Circuit Voltage At TPS Turn ignition off. Disconnect Throttle Position Sensor (TPS). Turn ignition on. Measure voltage at TPS wiring harness connector between VREF and SIG RTN. see scheme 15 If voltage is 4-6 volts, reconnect TPS and go to next step. If voltage is not 4-6 volts, go to «CIRCUIT TEST C»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l).
3. 3) Check Temperature Sensor Resistance Turn ignition off. Disconnect suspect sensor. Measure resistance between sensor signal circuit and SIG RTN circuit at sensor. If resistance is not within specification, replace suspected sensor. See «ACT & ECT SENSOR SPECIFICATIONS»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l). Reconnect wiring harness, and repeat QUICK TEST. If resistance is within specification, perform following step as applicable. For diagnosing vehicles with ECT sensor and a no-start condition, DO NOT service Code 21/116 at this time. Go to CIRCUIT TEST AC (EDIS). For other vehicles, go to step 4). ACT & ECT SENSOR SPECIFICATIONS Temperature °F (°C) Voltage Ohms 50 (10) 3.5 58,750 68 (20) 3.1 37,300 86 (30) 2.6 24,270 104 (40) 2.1 16,150 122 (50) 1.7 10,970 140 (60) 1.3 7700 158 (70) 1.0 5370 176 (80).8 384 194 (90).6 280 212 (100).5 207 230 (110).4 155
4. 4) Warm engine to normal operating temperature. Turn ignition off. Disconnect suspect sensor. Run engine at 2000 RPM for 2 minutes. Measure resistance between sensor signal circuit and SIG RTN circuit at temperature sensor. See «ACT & ECT SENSOR SPECIFICATIONS»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l). If resistance is within specification, replace ECA and repeat QUICK TEST. If sensor is not within specification, replace sensor and repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 4) to step 10). No test procedures have been omitted.
5. 10) Code 51/118 Or 54/113: Induce Opposite Code (Code 61/117 Or 64/112) Code 51/118 (ECT) or 54/113 (ACT) indicate corresponding sensor signal is greater than self-test maximum. Maximum signal voltage for ECT and ACT sensor is 4.6 volts. Possible causes for excess voltage signals are: Open circuit in wiring harness (ACT or ECT). Faulty connection. Faulty sensor. Faulty ECA. Turn ignition off. Disconnect suspect temperature sensor. Connect a jumper wire between sensor SIG RTN terminal and SIG RTN terminal at temperature sensor wiring harness connector. Repeat QUICK TEST. If Code 61, 64, 112 or 117 is displayed, replace suspect sensor and repeat QUICK TEST. If Code 61, 64, 112 or 117 is not displayed, remove jumper wire and go to next step.
6. 11) Check Continuity Of Sensor Signal & SIG RTN Circuits Turn ignition off. Ensure suspect temperature sensor is disconnected. Disconnect ECA 60-pin connector. Check for damaged wiring, and repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance of sensor signal circuit between test pin No. 7 (ECT sensor) or test pin No. 25 (ACT sensor) at breakout box and sensor signal circuit terminal at sensor wiring harness connector. Also measure resistance between test pin No. 46 and SIG RTN circuit at sensor wiring harness connector. If both readings are less than 5 ohms, replace ECA and repeat QUICK TEST. If either reading is 5 ohms or more, repair open circuit. Remove breakout box and repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 11) to step 20). No test procedures have been omitted.
7. 20) Code 61/117 or 64/112: Induce Opposite Code (51/118 or 54/113) Code 61/117 (ECT) or 64/112 (ACT) indicates sensor signal is less than self-test minimum. Minimum signal for ACT and ECT sensor is 0.2 volt. Possible causes for this fault are: Circuit grounded in wiring harness (ACT or ECT). Faulty sensor. Faulty ECA. Faulty connection. Turn ignition off. Disconnect wiring harness connector from suspect sensor. Check for damaged wiring, and repair as necessary. Repeat KOEO SELF-TEST. If Code 51, 54, 113 or 118 is displayed, replace sensor repeat QUICK TEST. If Codes 51, 54, 113 and 118 is not displayed, go to next step.
8. 21) Check VREF Circuit Voltage At TPS Turn ignition off. Disconnect wiring harness connector from suspect sensor. Disconnect TPS. Turn ignition on. Measure voltage between VREF and SIG RTN at TPS wiring harness connector.If voltage is not 4-6 volts, go to «CIRCUIT TEST C»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l). If voltage is 4-6 volts, connect TPS and go to next step.
9. 22) Check Temperature Sensor Signal For Shorts To Ground Turn ignition off. Disconnect suspect sensor. Disconnect ECA 60-pin connector. Inspect for damage and repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pin No. 7 (ECT) or 25 (ACT) and pins No. 40, 46 and 60. If any reading is less than 10,000 ohms, repair short circuit and repeat QUICK TEST. If all readings are 10,000 ohms or more, replace ECA and repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 22) to step 90). No test procedures have been omitted.
10. 90) Continuous Memory Code 51/118, 54/113, 61/117 Or 64/112 A Continuous Memory Code 51/118 or 54/113 indicates sensor signal is greater than self-test maximum of 4.6 volts. Code is set during normal driving conditions. Continuous Memory Code 61/117 or 64/112 indicates sensor signal is less than self-test minimum of 0.2 volt. Code is set during normal driving conditions. Possible causes for these faults are: Faulty sensor. Open or grounded circuit in harness. Faulty ECA. SENSOR CODES Sensor Continuous Memory Code ACT 54/113, 64/112 ECT 51/118, 61/117 Enter KOEO wiggle test mode. See «CONTINUOUS MONITOR MODE (WIGGLE TEST)»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l__continuous-monitor-mode-wiggle-test) under QUICK TEST. Observe analog voltmeter or scan tester for indication of fault while tapping sensor lightly and wiggling sensor connector. If fault is indicated, disconnect and inspect connector and terminals. If connector and terminals are okay, replace sensor, clear continuous memory and repeat QUICK TEST. If fault is not indicated, go to next step.
11. 91) Check EEC-IV Wiring Harness While in CONTINUOUS MONITOR MODE (WIGGLE TEST), observe analog voltmeter or scan tester while wiggling and bending wiring harness, a small section at a time, from sensor to cowl. Also check harness from cowl to 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.
12. 92) Inspect ECA & Wiring Harness Connectors Turn ignition off. Disconnect ECA 60-pin connector. Inspect both connector and connector terminals for damage. If connectors and terminals are damaged, repair as necessary and repeat QUICK TEST. If connectors and terminals are okay and fault cannot be duplicated at this time, see INTERMITTENTS in TESTS W/O CODES article in the ENGINE PERFORMANCE Section. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 92) to step 100). No test procedures have been omitted.
13. 100) Continuous Memory Code 338 A Continuous Memory Code 338 indicates cooling system has not reached normal operating temperature. Possible causes for this fault are: Thermostat stuck open. Coolant outlet gasket leak. Water pump gasket leak. Repair cooling system as necessary. Clear continuous memory, and repeat QUICK TEST.
14. 101) Continuous Memory Code 339 A Continuous Memory Code 339 indicates cooling system has overheated. Possible causes for this fault are: Coolant level low. Thermostat stuck closed. Coolant system clogged. Radiator fins clogged. Water pump damaged or worn. Radiator cap damaged or worn. Cooling fan damaged or worn. Repair cooling system as necessary. Clear continuous memory, and repeat QUICK TEST.

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

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

1. Air Cleaner Element
2. Inlet Air Duct
3. Throttle Body

Code 26/159, retrieved during KOEO SELF-TEST, indicates voltage exceeded .7-volt test range. Code 26/159, retrieved during KOER SELF-TEST, indicates voltage is not within .2-1.5 volts operating range. Possible causes are faulty MAF sensor or ECA.

Scheme 18

CIRCUIT TEST DC TEST PIN WIRE COLOR ID

MAF SIGNAL VOLTAGE (1)

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

1. 1) Code 26/159: Check VPWR Circuit Voltage Turn ignition off. Disconnect MAF sensor connector. Set DVOM on 20-volt scale. Turn ignition on. Measure voltage between VPWR terminal at MAF sensor wiring harness connector and negative battery terminal. If voltage is less than 10.5 volts, repair open in VPWR circuit and repeat QUICK TEST. If voltage is 10.5 volts or more, go to next step.
2. 2) Check MAF Sensor Ground Turn ignition on. Disconnect MAF sensor. Measure voltage between VPWR terminal and PWR GND terminal at MAF sensor connector. If voltage is less than 10.5 volts, repair open PWR GND circuit. Connect MAF sensor, and repeat QUICK TEST. If voltage is 10.5 volts or more, go to next step. NOTE: A break in step numbering sequence occurs at this point.Procedure skips from step 2) to step 10). No test procedures have been omitted.
3. 10) Code 66/157 Or 72/129: Check Continuity Of MAF & VPWR Circuits Continuous Memory Code 66/157 indicates MAF signal was less than 0.4 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: Open MAF circuit. Open VPWR circuit to MAF sensor. Open PWR GND circuit to MAF sensor. Open MAF RTN circuit to MAF sensor. MAF circuit shorted to ground. Faulty ECA or MAF sensor. Air leak before or after MAF sensor. MAF sensor disconnected. Turn ignition off. Disconnect MAF sensor. Disconnect ECA 60-pin connector. Inspect for damage and repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between VPWR terminal at MAF sensor wiring harness connector and test pins No. 37 and 57 at breakout box. Measure resistance between MAF terminal at MAF sensor wiring harness connector and test pin No. 14 at breakout box. If all resistances are less than 5 ohms, go to next step. If any resistance is 5 ohms or more, repair open MAF circuit and repeat QUICK TEST.
4. 11) Check MAF & MAF RTN Circuit Measure resistance between test pin No. 14 and test pins No. 15, 40 and 60 at breakout box. If resistance in any circuit is less than 10,000 ohms, repair short circuit and repeat QUICK TEST. If all circuit resistances are 10,000 ohms or more, go to next step.
5. 12) Check Continuity Of PWR GND Circuit Turn ignition off. Set DVOM on 200-ohm scale. Measure resistance between PWR GND terminal at MAF sensor wiring harness connector and negative battery terminal. If resistance is 10 ohms or more, repair open PWR GND circuit and repeat QUICK TEST. If resistance is less than 10 ohms, go to next step.
6. 13) Check Continuity Of MAF RTN Circuit Measure resistance between MAF RTN terminal at MAF sensor wiring harness connector and test pin No. 15 at breakout box. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open MAF RTN circuit and repeat QUICK TEST.
7. 14) Check MAF Signal For Short To Ground Turn ignition off. Disconnect MAF sensor. Connect ECA to breakout box. Measure resistance between test pin No. 14 and pins No. 15, 40 and 60 at breakout box. If any circuit resistance is less than 10,000 ohms, replace ECA and repeat QUICK TEST. If each circuit resistance is 10,000 ohms or more, go to next step.
8. 15) Check MAF Circuit Output Turn ignition off. Connect MAF sensor wiring harness connector. Set DVOM on 20-volt scale. Start engine. Measure voltage between test pin No. 14 at breakout box and negative battery terminal. If voltage is 0.4-1.5 volts, go to next step. If voltage is not 0.4-1.5 volts, replace MAF sensor. Repeat QUICK TEST.
9. 16) Start engine. Measure voltage between test pins No. 14 and 15 at breakout box. If voltage is 0.4-1.5 volts, replace ECA and repeat QUICK TEST. If voltage is not 0.4-1.5 volts, replace MAF sensor and repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 16) to step 20). No test procedures have been omitted.
10. 20) Code 56/158 Turn ignition off. Disconnect MAF sensor wiring harness connector. Start engine, and allow it to idle for one minute. Turn ignition off. Repeat KOEO SELF-TEST. If Code 66 or 157 is present, replace MAF sensor and repeat QUICK TEST. If Code 66 or 157 is not present, go to next step.
11. 21) Check MAF Circuit For Short To VPWR Turn ignition off. Disconnect ECA 60-pin connector, and inspect it for damaged or corroded terminals. Service if necessary. Measure resistance between MAF and VPWR terminals at MAF sensor wiring harness connector. If resistance is 10,000 ohms or more, replace ECA and repeat QUICK TEST. If resistance is less than 10,000 ohms, repair short circuit and repeat QUICK TEST.

Perform this test when directed by QUICK TEST or CIRCUIT TEST S. Barometric pressure sensor output is digital and must be measured using an oscilloscope or MAP/BP tester. To prevent replacement of good components, be aware following non-EEC related areas may be 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 following

1. MAP/BP sensor.
2. Wiring harness circuits (VREF, MAP/BP SIG and SIG RTN).
3. MAP vacuum line.
4. ECA.

Scheme 19

CIRCUIT TEST DF TEST PIN WIRE COLOR ID

MAP SENSOR SPECIFICATIONS

MAP/BP SENSOR SPECIFICATIONS

1. 1) Code 22/126: Check Power To MAP/BP Sensor Code 22/126 indicates MAP/BP sensor is out of self-test voltage range (1.4-1.6 volts). Following are possible causes of this code: Vacuum trapped at MAP/BP sensor. High atmospheric pressure. MAP/BP signal circuit open between sensor and ECA. MAP/BP signal circuit shorted to VREF, SIG RTN or ground. VREF circuit open at sensor. SIG RTN circuit open at sensor. Faulty MAP/BP sensor. Faulty ECA. Turn ignition off. Disconnect MAP/BP sensor from wiring harness.Connect MAP/BP tester between wiring harness and MAP/BP sensor. Connect banana plugs of tester into DVOM. Set DVOM on 20-volt scale. Turn ignition on. If Red light or no light is on, VREF is out of range. Go to next step. If Green light is on, VREF is okay. Go to step 3) .
2. 2) Check Power At Sensor Wiring Harness Connector Disconnect MAP/BP sensor. Turn ignition on. If Green light on tester is lit, replace MAP/BP sensor and repeat QUICK TEST. If Green light is not on, remove MAP/BP tester. Connect MAP/BP sensor, and go to «CIRCUIT TEST C»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) .
3. 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 not within range, remove MAP/BP tester and go to step 5) . Diagnostic Aids If possible, measure output voltage of several known good MAP/BP sensors on available vehicles. Average voltage reading will be typical for location and time of testing. MAP SENSOR VOLTAGE OUTPUT Elevation (Feet) Volts 0 1.55-1.63 1000 1.52-1.60 2000 1.49-1.57 3000 1.46-1.54 4000 1.43-1.51 5000 1.40-1.48 6000 1.37-1.45 7000 1.35-1.43
4. 4) Check MAP/BP SIG Circuit Continuity Turn ignition off. Disconnect MAP/BP sensor wiring harness connector. Disconnect ECA 60-pin connector. Inspect for damage and repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between MAP/BP SIG terminal at sensor wiring harness connector and test pin No. 45. If reading is less than 5 ohms, replace ECA and repeat QUICK TEST. If reading is 5 ohms or more, repair open MAP/BP SIG circuit and repeat QUICK TEST.
5. 5) Check MAP/BP SIG Circuit For Shorts To VREF, SIG RTN & Ground Turn ignition off, and wait 10 seconds. Disconnect ECA60-pin connector. Inspect for damage and repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Disconnect wiring harness at MAP/BP sensor. Measure resistance between test pin No. 45 and test pins No. 26, 40, 46 and 60. If any resistance is less than 10,000 ohms, repair short circuit. Repeat QUICK TEST. If all readings are 10,000 ohms or more, replace MAP/BP sensor. Repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 5) to step 7). No test procedures have been omitted.
6. 7) KOER Code 22/126: Check For EGR-Related Codes Code 22/126 indicates MAP/BP signal is out of self-test range during KOER SELF-TEST. If Code 31, 32, 33, 34, 35, 326, 327, 328, 332, 334, 336 or 337 is present, perform applicable CIRCUIT TEST. See «SERVICE CODE REFERENCE CHARTS»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) . If codes are not present, go to next step.
7. 8) Check MAP Sensor Operation Turn ignition off. Disconnect vacuum hose from MAP sensor. Connect vacuum pump to MAP sensor, and apply 18 in. Hg. If vacuum is not held, replace sensor and repeat QUICK TEST. If MAP sensor holds vacuum, release vacuum and go to next step.
8. 9) Attempt To Eliminate Code 22/126 Plug MAP sensor vacuum supply hose. Start engine, and run it at 1400-1600 RPM. Slowly apply 15 in. Hg to MAP sensor. Perform KOER SELF-TEST. Check for Code 22/126, disregarding any other codes at this time. If Code 22/126 is still present, replace MAP sensor. If Code 22/126 is not present, inspect MAP sensor vacuum supply hose. 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.
9. 10) Code 72/129: Repeat Dynamic Response Test Code 72/129 indicates MAP sensor output did not change enough during dynamic response test. Possible causes for this code are: System failed to detect Wide Open Throttle (WOT). Incorrect MAP sensor vacuum hose routing. Faulty MAP sensor. Repeat KOER SELF-TEST. Ensure complete WOT is performed during dynamic response portion of test. If Code 72/129 is still present, go to step next step. If code is not present, service any other codes as necessary.
10. 11) Code 81/128 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: MAP sensor vacuum hose is improperly routed, blocked or is leaking. MAP sensor is leaking. Check vacuum lines for correct routing. Refer to Vehicle Emission Control Identification (VECI) decal. Check for loose connections, kinks and blockage. Repair vacuum lines as necessary. If vacuum lines are okay, go to next step.
11. 12) Check MAP Sensor Operation Turn ignition off. Disconnect vacuum supply hose from MAP sensor. Attach 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 and repeat QUICK TEST.
12. 13) Verify Vacuum To MAP Sensor Decreases During Dynamic Response Test Turn ignition off. Use a "T" fitting to install a vacuum gauge in MAP sensor vacuum hose. Perform KOER SELF-TEST while observing vacuum gauge. If vacuum decreases by more than 10 in. Hg during dynamic response test, replace MAP sensor and repeat QUICK TEST. If vacuum does not decrease by more than 10 in. Hg, EEC-IV system is okay. Check for engine mechanical problems affecting engine vacuum. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 13) to step 90). No test procedures have been omitted.
13. 90) Code 22/126 Continuous Memory 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: Faulty MAP/BP sensor. Faulty wiring harness or connectors. Unusually high or low barometric pressure. Enter «CONTINUOUS MONITOR MODE (WIGGLE TEST)»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l__continuous-monitor-mode-wiggle-test) . Observe test equipment while performing following: Connect a vacuum pump to MAP/BP sensor. Slowly apply 25 in. Hg to sensor. Slowly bleed off vacuum from sensor. Lightly tap on sensor (to simulate road shock). Wiggle sensor connector. If a fault is indicated, disconnect sensor and inspect connectors. Repair if necessary. If connectors are okay, replace MAP/BP sensor. Repeat QUICK TEST. If a fault is not indicated, go to next step.
14. 91) Check EEC-IV Wiring Harness Stay in wiggle test. Observe analog VOM or scan tester for indication of fault while bending or wiggling small sections of harness from sensor connector to firewall and from firewall to ECA. If fault is indicated, isolate fault in harness and repair as necessary. Repeat QUICK TEST. If no fault is indicated, go to next step.
15. 92) Check ECA & Wiring Harness Connectors Turn ignition off, and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connectors and terminals for damage. Repair if necessary. If connectors and terminals are okay, fault cannot be duplicated at this time. Testing is complete. Refer to INTERMITTENTS in TESTS W/O CODES article in the ENGINE PERFORMANCE Section.

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

1. Throttle Position Sensor (TPS).
2. Wiring harness circuits (TP, SIG RTN and VREF).
3. ECA.

Normal range of throttle angle measurement for TPS is 0-85 degrees. To pass QUICK TEST procedure, range of throttle rotation (in degrees) must be within 3 percent of specification. (Scheme 21) To prevent replacement of good components, be aware following non-EEC related areas may be at fault

1. Idle speed.
2. Binding throttle shaft or linkage.
3. Throttle stop adjustment.
4. Throttle Position Sensor (TPS) not seated.

Scheme 20

CIRCUIT TEST DH TEST PIN WIRE COLOR ID

Scheme 21

1. 1) Code 23/121: Check For Other Codes Code 23/121 indicates TPS rotational setting may be out of self-test range. Possible causes for this fault are: Binding throttle linkage. TPS not seated correctly. Faulty TPS. Faulty ECA. Perform KOER SELF-TEST. Check for Code 31/327. If either of these codes are present with Code 23/121, service Code 31/327 and repeat QUICK TEST. If these codes are not present, go to Idle speed. Binding throttle shaft or linkage. Throttle stop adjustment. Throttle Position Sensor (TPS) not seated. .
2. 2) Code 23/121: Check For Binding Throttle Plate Inspect throttle body and linkage for binding. If throttle plate is binding, check for binding throttle or cruise control linkage, vacuum line or harness interference, etc. Repair as necessary, and repeat QUICK TEST. If no mechanical problem is found, go to next step.
3. 3) Code 53/123: Attempt To Generate Code 63/122 Code 53/123 indicates TPS signal is greater than self-test maximum value. Possible causes for this fault are: TPS not seated properly. Faulty TPS. VREF circuit shorted in wiring harness. Faulty ECA. Turn ignition off. Disconnect TPS wiring harness connector. Inspect and repair connector pins if damaged. Repeat KOEO SELF-TEST. Ignore all other codes at this time. If Code 63/122 is not displayed, go to step 5) . If Code 63/122 is displayed, go to next step.
4. 4) Check VREF Circuit Voltage Turn ignition on. Measure voltage between VREF and SIG RTN terminals at TPS wiring harness connector. If reading is 4-6 volts, replace TPS and repeat QUICK TEST. If reading is not 4-6 volts, reconnect sensor and go to «CIRCUIT TEST C»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) .
5. 5) Check TP Circuit For Short To Power Turn ignition off. Disconnect TPS from wiring harness. Disconnect ECA 60-pin connector. Inspect for damage and repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pin No. 47 and test pins No. 26 and 57. If either resistance is less than 10,000 ohms, repair short circuit in wiring harness and repeat QUICK TEST. If both resistances are 10,000 ohms or more, replace ECA and repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point.Procedure skips from step 5) to step 10). No test procedures have been omitted.
6. 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. Possible causes for this fault are: TPS not seated correctly. Faulty TPS. Open circuit in wiring harness. Grounded circuit in wiring harness. Faulty ECA. Turn ignition off, and wait 10 seconds. Disconnect TPS from harness. Install a jumper wire between VREF and TP terminals at TPS wiring harness connector. Perform KOEO SELF-TEST. If either Code 53/123 or 23/121 is present, replace TPS and repeat QUICK TEST. If Codes 53/123 and 23/121 are not present, remove jumper wire and go to next step. If any other codes are present, ignore at this time. If no codes are present, remove jumper wire and go to step 13) .
7. 11) Check VREF Circuit Voltage Turn ignition on. Measure voltage between VREF and SIG RTN terminals at TPS wiring harness connector. If voltage is not 4-6 volts, reconnect all components and go to «CIRCUIT TEST C»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) . If voltage is 4-6 volts, go to next step.
8. 12) Check TPS Circuit Continuity Turn ignition off. Leave TPS disconnected. Disconnect ECA 60-pin connector. Inspect for damage and repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between TP terminal at TPS wiring harness connector and test pin No. 47. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST. If resistance is less than 5 ohms, go to next step.
9. 13) Check TP Circuit For Shorts To Ground Turn ignition off. Leave TPS disconnected. Disconnect ECA 60-pin connector. Inspect for damage and repair as necessary. Measure resistance between test pin No. 47 and test pins No. 40, 46 and 60. If any reading is less than 10,000 ohms, repair short circuit and repeat QUICK TEST. If all readings are 10,000 ohms or more, replace ECA and repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point.Procedure skips from step 13) to step 20). No test procedures have been omitted.
10. 20) KOER Code 73/167: Repeat Dynamic Response Test KOER Code 73/167 indicates TPS did not exceed 25% rotation during dynamic response portion of KOER SELF-TEST. A complete Wide Open Throttle (WOT) must be performed during dynamic response portion of test.Perform KOER SELF-TEST. Ensure WOT is obtained 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. If no other service codes are present, testing is complete.
11. 21) Check TPS Movement During Dynamic Response Test Turn ignition off. Disconnect ECA 60-pin connector. Inspect for damage and repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA connected. Connect DVOM between test pins No. 46 and 47 at breakout box. Perform KOER SELF-TEST. Ensure a WOT is obtained during dynamic response portion of test. If DVOM reading exceeds 3.5 volts, replace ECA 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: A break in step numbering sequence occurs at this point.Procedure skips from step 21) to step 90). No test procedures have been omitted.
12. 90) Continuous Memory Code 53/123 This test monitors TPS under simulated road conditions. Enter wiggle test. See «CONTINUOUS MONITOR MODE (WIGGLE TEST)»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l__continuous-monitor-mode-wiggle-test) under QUICK TEST. Fully open throttle while observing DVOM or diagnostic tester for indication of fault. Slowly bring throttle to closed position. Lightly tap TPS and wiggle harness connector. If no fault is indicated, go to step 92) . If fault is indicated, go to next step.
13. 91) Measure TP Circuit Voltage While Exercising TPS Turn ignition off, and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect it for damaged wiring, and repair if necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA connected. Stay in wiggle test (as in previous step). Connect DVOM between test pins No. 47 and 46. Set DVOM on 20-volt scale. Turn ignition on. 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 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 wiring harness.
14. 92) Check EEC-IV Wiring Harness While in wiggle test, bend and shake small sections of EEC-IV harness from TPS connector to firewall and from firewall to ECA while observing analog voltmeter or scan tester. 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.
15. 93) Check ECA & Harness Connectors Turn ignition off, and wait 10 seconds. Disconnect ECA 60-pin connector from breakout box and inspect for damage. If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous Memory Code 53/123 testing is complete. If connector or terminals are damaged, repair as necessary. Clear codes from ECA memory, and repeat QUICK TEST.
16. 94) Continuous Memory Code 63/122 This test checks for open or short circuit in TPS and wiring harness under simulated road conditions. Enter wiggle test. See «CONTINUOUS MONITOR MODE (WIGGLE TEST)»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l__continuous-monitor-mode-wiggle-test) under QUICK TEST. Observe VOM or diagnostic tester for indication of fault while performing following: Fully open throttle to WOT. Slowly bring throttle to closed position. Lightly tap TPS and wiggle connector. If fault is indicated, disconnect TPS. Inspect connectors and terminals. If connectors and terminals are okay, replace TPS. Clear codes from ECA memory, and repeat QUICK TEST. If no fault is indicated, go to next step.
17. 95) Check EEC-IV Wiring Harness Stay in wiggle test (as in previous step). Bend, wiggle and shake small sections of EEC-IV harness from TPS wiring harness connector to firewall and from firewall to ECA while observing analog voltmeter or scan tester. If fault is indicated, isolate fault in wiring and repair as necessary and repeat QUICK TEST. If no fault is indicated, go to next step.
18. 96) Check ECA & Harness Connectors Turn ignition off, and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connectors and terminals for damage. If connectors and terminals are damaged, repair as necessary and repeat QUICK TEST. If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous Memory Code 63/122 testing is complete.

Perform this test when directed by QUICK TEST. This CIRCUIT TEST is intended to diagnose

1. Vehicle Speed Sensor (VSS)
2. VSS Wiring Harness Circuits
3. ECA

Scheme 22

CIRCUIT TEST DP TEST PIN WIRE COLOR ID

Preliminary Instructions (A/T)

Record and clear continuous memory codes. Warm engine to normal operating temperature. In Low gear, accelerate hard to 35 MPH and coast down to a stop. Shut off engine. Perform KOEO SELF-TEST. Go to step 1 .

Preliminary Instructions (M/T)

Record and clear continuous memory codes. Warm engine to normal operating temperature. Accelerate moderately to 40 MPH. Start in first gear, shifting no higher than second gear. Coast down to idle, and stop. Shut engine off. Perform KOEO SELF-TEST, and record continuous memory codes. Go to step 1 .

1. Continuous Memory Code 29/452 Code 29/452 indicates ECA detected incorrect output from VSS sometime during vehicle operation. Possible causes for this code are: Faulty VSS Open Or Shorted Circuit Faulty ECA Perform appropriate drive cycle procedure. See «PRELIMINARY INSTRUCTIONS (A/T)»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l__preliminary-instructions-at) or «PRELIMINARY INSTRUCTIONS (M/T)»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l__preliminary-instructions-mt) . Ensure driveability complaint can be verified. If Code 29/452 is still present or driveability complaint can be verified, go to step 2). If code is not present or complaint cannot be verified, fault cannot be duplicated at this time. Clear codes, and see SYMPTOMS in TESTS W/O CODES article in the ENGINE PERFORMANCE Section.
2. Check VSS Circuit Continuity Turn ignition off. Disconnect VSS sensor. Remove ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV) leaving ECA disconnected. Measure resistance between VSS DIF (+) terminal at VSS wiring harness connector and test pin No. 3 at breakout box. Measure resistance between VSS DIF (-) terminal at VSS wiring harness connector and test pin No. 6 at breakout box. If any resistance reading is more than 5 ohms, service open circuit in VSS wiring harness and repeat step 1). If both resistance readings are 5 ohms or less, go to next step.
3. Check VSS Circuits For Shorts To Power Or Ground Turn ignition off. Ensure ECA and VSS are disconnected. Measure resistance between test pin No. 3 and test pins No. 6, 37 and 40 at breakout box. If any reading is less than 500 ohms, repair shorts in VSS wiring harness and repeat step 1). If all readings are greater than 500 ohms, go to next step.
4. Check VSS Resistance Turn ignition off, and wait 10 seconds. Disconnect VSS wiring harness connector. Measure resistance across VSS terminals. If reading is 190-250 ohms, replace ECA and repeat step 1). If reading is not 190-250 ohms, replace VSS and repeat step 1).

Perform this test when directed by QUICK TEST. This CIRCUIT TEST is intended to diagnose

1. PSOM output to ECA.
2. PSOM (+) and PSOM (-) wiring harness circuits.
3. ECA.

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

1. Cruise control system.
2. Rear anti-lock brake system.
3. Instrumentation system.

Scheme 23

Scheme 24

CIRCUIT TEST DS TEST PIN WIRE COLOR ID

1. 1) Continuous Memory Code 29/452 Code 29/452 indicates ECA detected incorrect output from VSS sometime during vehicle operation. Following are possible causes of code. PSOM Output To ECA PSOM (+) And PSOM (-) Wiring Harness Circuits ECA Turn ignition off. Remove ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pins No. 3and 6 at breakout box. If reading is 21,000-55,000 ohms, go to step 4) . If resistance is not 21,000-55,000 ohms, go to next step.
2. 2) Check PSOM Circuit Continuity Ensure ignition is off. Disconnect PSOM wiring harness connector. Measure resistance between test pin No. 3 at breakout box and PSOM + circuit at PSOM wiring harness connector. If resistance is less than 5 ohms, repair open circuit and repeat QUICK TEST. If resistance is more than 5 ohms, go to next step.
3. 3) Check PSOM Circuit For Open Ensure ignition is off. Measure resistance between test pin No. 3 and test pins No. 6, 37 and 40 at breakout box. If resistance is 10,000 ohms or less, repair open circuit and repeat QUICK TEST. If resistance is more than 10,000 ohms, go to next step.
4. 4) Turn ignition off. Connect ECA to breakout box. Connect wiring harness connector to PSOM. Set DVOM on 20-volt AC scale. Start engine, and warm it to normal operating temperature. Measure voltage between test pins No. 3 and 6 while gradually increasing vehicle speed to 50 MPH. If maximum voltage is less than 4.5 volts, fault is in instrument cluster. If maximum voltage received is more than 4.5 volts, replace ECA.

Perform this test when directed by QUICK TEST. This test is intended to diagnose a faulty BOO switch circuit or ECA. To prevent replacement of good components, be aware following non-EEC related areas may be at fault

1. Brakelight bulb.
2. Brakelight switch or brakelight fuse.

Scheme 25

TEST PIN 2 (BOO) WIRE COLOR ID

1. 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: Brake pedal not depressed during self-test. Brake pedal pressed during entire self-test. Open brakelight circuit. Short to ground or power. Faulty ECA. If brake was not depressed during KOER SELF-TEST, repeat test. Depress and release brake pedal only once during test. If pedal was depressed, go to next step.
2. 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. 3) Check For BOO Switch Circuit Cycling Turn ignition off. Wait 10 seconds. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Set DVOM on 20-volt scale. Measure voltage between test pins No. 2 and 40 while applying and releasing brake. If voltage cycles, replace ECA and repeat QUICK TEST. If voltage does not cycle, repair open circuit in BOO switch circuit between ECA and BOO switch connection to brakelight circuit. Repeat QUICK TEST.
4. 4) Check For Power To Brake Switch Ensure related fuses and brakelight bulbs are in good condition. Turn ignition off. Disconnect brakelight switch (located on brake pedal). Measure voltage between BATT (+) input to brakelight switch and ground. If voltage is greater than 10 volts, check condition of brakelight switch. If brakelight switch is okay, repair open circuit between brakelight switch and brakelight ground. Repeat QUICK TEST. If voltage is less than 10 volts, repair open BATT (+) circuit to brakelight switch and repeat QUICK TEST.
5. 5) Verify Brake Switch Is Not Always Closed Turn ignition off. Disconnect brakelight switch (located on brake pedal). Turn ignition on. If brakelights are still on, go to next step. If brakelights are not on, verify correct installation of brakelight switch. If installation is okay, replace brakelight switch and repeat QUICK TEST.
6. 6) Check For Short To Power In ECA Turn ignition off. Disconnect ECA. Turn ignition on, and check brakelights. If brakelights are on, repair short to power between ECA and harness connector and repeat QUICK TEST. If brakelights are not on, replace ECA and repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point.Procedure skips from step 6) to step 10). No test procedures have been omitted.
7. 10) Code 75/531 Code 75/531 indicates that while brake pedal was released during KOER SELF-TEST, BOO switch signal was high. Possible causes for this fault are: Brake pedal depressed during entire self-test. Open BOO switch/brakelight circuit (between ECA and brakelight ground). Short to POWER. Faulty brakelight switch. Faulty ECA. Turn ignition on. Check brakelight operation. If brakelights operate normally, go to next step. If brakelights are always on, go to step 5) . If brakelights are off, inspect brakelight bulbs. If bulb is okay, repair open circuit between BOO switch connection to brakelight circuit and brakelight ground.
8. 11) Check Continuity Of BOO Switch Circuit Turn ignition off. Disconnect brakelight switch (located on brake pedal). Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pin No. 2 at breakout box and BOO switch terminal at switch wiring harness connector. If resistance is less than 5 ohms, replace ECA and repeat QUICK TEST. If resistance is 5 ohms or more, repair open circuit between ECA and BOO switch connection to brakelight circuit and repeat KOER SELF-TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 11) to step 90). No test procedures have been omitted.
9. 90) Continuous Memory Code 536 Code 536 indicates a BOO switch circuit failure. If BOO switch input does not cycle after a predetermined number of transitions from zero MPH to a specific speed, BOO switch input failure is presumed and Code 536 is set. Possible causes for this code are: Brakelight switch improperly installed. Open brakelight/BOO switch circuit. Damaged brakelight switch. Poor brakelight ground connection. Inspect brakelight switch for incorrect installation, poor alignment with pedal and damaged wiring. Repair if necessary, and repeat QUICK TEST. If all components are in good condition, go to next step.
10. 91) Check Brakelight For Ground Check brakelight connector and wires for corrosion and damage. If connector or wires are corroded or damaged, repair as necessary, and repeat QUICK TEST. If brakelight connector and wires are okay, go to next step.
11. 92) Check BOO Switch Circuits For Short To Power DO NOT depress brake pedal during this test. Turn ignition on. While watching brakelights, wiggle brakelight/BOO switch circuit wires and connectors. If brakelights flash, isolate and repair short to power. Repeat QUICK TEST. If brakelights do not flash, go to next step.
12. 93) Check Brakelight Circuit Continuity Turn ignition off. Depress and hold brake pedal. Observe brakelights. Tap brakelight switch to simulate road shock. Wiggle brakelight circuit wires and connectors. If brakelights blink or go off, isolate and repair open in brakelight circuit. Clear codes, and repeat QUICK TEST. If brakelights are on constantly and do not blink or go off, go to next step.
13. 94) Check Continuity Of BOO Switch Circuit Turn ignition off. Disconnect ECA 60-pin connector. Inspect and repair any damaged terminals. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 2 at breakout box and brakelight circuit at brakelight switch connector. While observing DVOM, wiggle BOO switch circuit wires and connectors. If resistance is 5 ohms or more, isolate and repair open circuit in BOO switch circuit. Repeat QUICK TEST. If resistance is less than 5 ohms, fault cannot be duplicated at this time. See SYMPTOMS in TESTS W/O CODES article in the ENGINE PERFORMANCE Section.

Perform this test when directed by QUICK TEST or CIRCUIT TEST S. This CIRCUIT TEST is intended to diagnose

1. Blower motor input circuit.
2. Daytime Running Lights (DRL) input circuit.
3. Headlight input circuit.
4. Rear window defrost input circuit.
5. ECA.

Electrical load inputs are used for idle speed control strategy so correct idle can be maintained regardless of electrical demands on engine. ECA uses 4 accessories to determine electrical load status: blower motor, headlights, rear window defroster, and daytime running lights (if equipped).

Scheme 26

1. 1) Isolate Faulty System If idle speed fault occurs when blower motor is on, go to step 10). If idle speed fault occurs when daytime running lights are on, go to step 20) . If idle speed fault occurs when headlights are on, go to step 30) . If idle speed fault occurs when rear window defroster is on, go to step 40) . NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 1) to step 10). No test procedures have been omitted.
2. 10) Check Blower Motor Switch (Low Speed) Turn ignition and all accessories off. Remove ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Turn ignition on. Turn climate control motor switch to low-speed position "1" or "2". Measure voltage between test pin No. 14 at breakout box and chassis ground. If voltage is not 10-17 volts, go to step 13) . If voltage is 10-17 volts, go to next step.
3. 11) Check Blower Motor Switch (High Speed) Turn ignition and all accessories off. Turn climate control motor switch to high-speed position "3" or "4". Turn ignition on. Measure voltage between test pin No. 14 at breakout box and chassis ground. If voltage is less than 1.5 volts, replace ECA and confirm idle speed fault has been corrected. If voltage is 1.5 volts or more, go to next step.
4. 12) Check Blower Circuit For Short To Power Turn ignition off. Disconnect blower motor relay. Measure resistance between test pin No. 14 and pins No. 37 and 57 at breakout box. If resistance is more than 10,000 ohms, check for damaged blower motor or relay. If resistance is 10,000 ohms or less, repair short circuit.
5. 13) Check Blower Circuit Continuity Turn ignition off. Disconnect blower motor relay. Measure resistance between BLR terminal at power distributor box and test pin No. 14 at breakout box. If resistance is 5 ohms or more, repair open circuit. If resistance is less than 5 ohms, go to next step.
6. 14) Check Blower Circuit For Short To Power Turn ignition off. Disconnect blower motor relay. Measure resistance between test pin No. 14 and test pins No. 40, 46 and 60 at breakout box. If resistance is more than 10,000 ohms, check for damaged blower motor or relay. If resistance is 10,000 ohms or less, repair short circuit. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 14) to step 20). No test procedures have been omitted.
7. 20) Check DRL Circuit Voltage (Headlights On) Turn ignition and all accessories off. Remove ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Apply parking brake. Turn ignition on. Turn headlights on. Measure voltage between test pin No. 42 at breakout box and chassis ground. If voltage is not 10-17 volts, go to step 23) . If voltage is 10-17 volts, go to next step.
8. 21) Check DRL Circuit Voltage (Headlights Off) Turn headlights off. Release parking brake. Turn ignition on. Measure voltage between test pin No. 42 at breakout box and chassis ground. If voltage is less than 1.5 volts, replace ECA and confirm idle speed fault has been corrected. If voltage is 1.5 volts or more, go to next step.
9. 22) Check DRL Circuit For Short To Power Turn ignition off. Disconnect DRL relay. Measure resistance between test pin No. 42 and pins No. 37 and 57 at breakout box. If resistance is more than 10,000 ohms, check daytime running lights module for malfunction. If resistance is 10,000 ohms or less, repair short circuit and confirm idle speed fault has been corrected.
10. 23) Check DRL Circuit Continuity Turn ignition off. Disconnect daytime running lights relay. Measure resistance between DRL relay connector and test pin No. 42 at breakout box. If resistance is 5 ohms or more, repair open circuit and confirm idle speed fault has been corrected. If resistance is less than 5 ohms, go to next step.
11. 24) Check DRL Circuit For Short To Power Turn ignition off. Disconnect daytime running lights relay. Measure resistance between test pin No. 42 and test pins No. 40, 46 and 60 at breakout box. If resistance is more than 10,000 ohms, check daytime running lights module for malfunction. If resistance is 10,000 ohms or less, repair short circuit and confirm idle speed fault has been corrected. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 24) to step 30). No test procedures have been omitted.
12. 30) Check Headlight Circuit Voltage (Headlights Off) Turn ignition and all accessories off. Remove ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Turn ignition on. Measure voltage between test pin No. 45 at breakout box and chassis ground. If voltage is 1.5 volts or more, go to step 34) . If voltage is less than 1.5 volts, go to next step.
13. 31) Check Headlight Circuit Voltage (Headlights On) Turn all accessories off. Turn ignition on. Turn headlights on. Measure voltage between test pin No. 45 at breakout box and chassis ground. If voltage is 10-17 volts, replace ECA and confirm idle speed fault has been corrected. If voltage is not 10-17 volts, go to next step.
14. 32) Check HDL Circuit Continuity Turn ignition off. Disconnect headlight relay. Measure resistance between HDL terminal at power distribution box and test pin No. 45 at breakout box. If resistance is 5 ohms or more, repair open circuit and confirm idle speed fault has been corrected. If resistance is less than 5 ohms, go to next step.
15. 33) Check HDL Circuit For Short To Ground Turn ignition off. Disconnect headlight relay. Measure resistance between test pin No. 45 and test pins No. 40, 46 and 60 at breakout box. If each resistance is more than 10,000 ohms, check headlight switch for malfunction. If any circuit resistance is 10,000 ohms or less, repair short circuit and confirm idle speed fault has been corrected.
16. 34) Check HDL Circuit For Short To Power Turn ignition off. Disconnect headlight relay. Measure resistance between test pin No. 45 and pins No. 37 and 57 at breakout box. If resistance is more than 10,000 ohms, check headlight switch for malfunction. If resistance is 10,000 ohms or less, repair short circuit and confirm idle speed fault has been corrected. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 34) to step 40). No test procedures have been omitted.
17. 40) Check DEF Circuit Voltage (Defrost Off) Turn ignition off. Turn all accessories off. Remove ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Turn ignition on. Measure voltage between test pin No. 15 at breakout box and chassis ground. If voltage is 10-17 volts, go to next step. If voltage is not 10-17 volts, go to step 43) .
18. 41) Check DEF Circuit Voltage (Defrost On) Turn ignition on. Turn rear window defroster on. Measure voltage between test pin No. 15 at breakout box and chassis ground. If voltage is less than 3 volts, replace ECA and confirm idle speed fault has been corrected. If voltage is 3 volts or more, go to next step.
19. 42) Check DEF Circuit For Short To Power Turn ignition off. Disconnect rear window defroster relay. Measure resistance between test pin No. 15 and test pins No. 37 and 57 at breakout box. If resistance is more than 10,000 ohms, check DEF switch or relay for malfunction. If resistance is 10,000 ohms or less, repair short circuit and confirm idle speed fault has been corrected.
20. 43) Check DEF Circuit Continuity Turn ignition off. Disconnect rear window defroster switch. Measure resistance between DEF terminal at power distribution box and test pin No. 15 at breakout box. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit and confirm idle speed fault has been corrected.
21. 44) Check DEF Circuit For Short To Ground Turn ignition off. Disconnect rear window defroster relay. Measure resistance between test pin No. 15 and test pins No. 40, 46 and 60 at breakout box. If each circuit resistance is more than 10,000 ohms, check DEF switch and relay circuit for malfunction. If any circuit resistance is 10,000 ohms or less, repair short circuit and confirm idle speed fault has been corrected.

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

1. PCV malfunction.
2. Excessive blow-by.
3. PCV malfunction.
4. Vacuum leaks.
5. Incorrect fuel pressure.
6. Throttle binding.

Perform this test when instructed during QUICK TEST or if directed by other test procedures. This test is only intended to diagnose

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

Scheme 27

1. 1) Throttle Position Sensor (TPS) Integrity Code 121 indicates TPS is inconsistent with MAF value. Code 124 indicates TPS value is higher than expected. Code 125 indicates TPS value is lower than expected. Turn ignition off. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect ECA to breakout box. Set DVOM on 20-volt scale. Connect DVOM to test pins No. 46 and 47. Slowly apply throttle to wide open position and release to closed position. See «CIRCUIT TEST DH»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) for schematic and specific TPS values. If voltage varies suddenly, ensure TPS is properly installed on throttle body. If TPS is properly installed, replace TPS and repeat QUICK TEST. If voltage does not vary suddenly, go to step 6) for Continuous Memory Code 121 or next step for all other codes.
2. 2) Check Throttle Body Check throttle and/or cruise control linkage for binding or rough operation. Inspect throttle body for sludge build-up. Check engine vacuum hoses. Refer to Vehicle Emission Control Information (VECI) decal for proper vacuum hose routing. Check for air leak between ISC solenoid and MAF sensor. Repair as necessary and repeat QUICK TEST. If no problems are found, go to next step.
3. 3) Check MAP/BP Sensor Output Refer to «CIRCUIT TEST DF»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) for MAP/BP sensor output check. (Scheme 19)for connector terminal identification and MAP/BP tester hookup. With tester connected and ignition on, measure sensor output voltage. If output voltage is within range for specified altitude, remove MAP/BP tester and go to next step. See «MAP SENSOR VOLTAGE OUTPUT»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) for specification. If output voltage is not within range, replace MAP/BP sensor and repeat QUICK TEST. Diagnostic Aids If possible, measure several known good MAP/BP sensors. Average voltage reading will be typical for location and day of testing. MAP SENSOR VOLTAGE OUTPUT Elevation (Feet) Volts 0 1.55-1.63 1000 1.52-1.60 2000 1.49-1.57 3000 1.46-1.54 4000 1.43-1.51 5000 1.40-1.48 6000 1.37-1.45 7000 1.35-1.43
4. 4) Check ACT Sensor Ensure ambient temperature is more than 50°F (10°C) before performing this test. Check and repair any air leaks in front of ACT sensor. Turn ignition off. Connect ECA to breakout box. Connect DVOM to breakout box test pins No. 25 and 46. Start engine, and let it idle. Monitor voltage as engine warms up. See «CIRCUIT TEST DA»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) for voltage specifications. If voltage does not decrease smoothly and stabilize after engine reaches operating temperature, replace ACT sensor and repeat QUICK TEST. If voltage decreases smoothly and stabilizes when engine reaches operating conditions, system is operating properly at this time. Reconnect all components, and repeat QUICK TEST.
5. 5) Code 184 Or 185: Visually Inspect MAF Sensor Code 184 indicates MAF sensor signal is higher than expected. Code 185 indicates MAF sensor signal 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 repeat QUICK TEST. If all checks are okay, go to step 8).
6. 6) Check MAF Sensor Turn ignition off. Disconnect ECA 60-pin connector. Inspect and repair any damaged terminals. Connect ECA to breakout box. Set DVOM on 20-volt scale. Start engine, and warm it to normal operating temperature. Measure voltage between test pins No. 40 and 60 and MAF test pin at breakout box. See «MAF TEST PIN NO. IDENTIFICATION»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l). If voltage is not within specification, replace MAF sensor and repeat QUICK TEST. See «MAF SENSOR DATA»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l). (Scheme 27) If voltage is within acceptable range, system is operating normally at this time. See SYMPTOMS in TESTS W/O CODES article in the ENGINE PERFORMANCE Section. MAF TEST PIN NO. ID Application Test Pin No. All Models 14 MAF SENSOR DATA Engine Condition (1) Voltage Idle 0.8 20 MPH 1.0 40 MPH 1.7 60 MPH 2.1 (1) With engine at normal operating temperature.
7. 7) Visual Vacuum Checks Code 186 indicates fuel injector pulse width is longer than expected (rich). Code 187 indicates fuel injector pulse width is shorter than expected (lean). Inspect air cleaner and air inlet duct. Replace or repair an necessary. Check for unmetered air leaks between MAF sensor and ISC by-pass solenoid. Check all engine vacuum hoses for damage, blockage and improper routing. Make necessary repairs, and repeat QUICK TEST. If all checks are okay, go to next step.
8. 8) Check Fuel Pressure Turn ignition off. Install fuel pressure gauge. Ensure fuel pressure regulator vacuum hose is connected (if applicable). Start engine, and allow it to 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 as necessary. See FUEL SYSTEM in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
9. 9) Verify Fuel Pressure Retention Ability Turn ignition on. If fuel pressure remains at specification for 60 seconds, go to next step (SEFI) or go to «CIRCUIT TEST H - FUEL CONTROL»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l__circuit-test-h-fuel-control), step 7) (except SEFI). If fuel pressure does not remain at specification, repair fuel delivery system as necessary. See FUEL SYSTEM in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
10. 10) Cylinder Balance Test Perform KOER SELF-TEST. After last code, wait 5-10 seconds, and 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 «CIRCUIT TEST H - FUEL CONTROL»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l__circuit-test-h-fuel-control), step 4).

CIRCUIT TEST H - FUEL CONTROL

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

Perform this test when instructed during QUICK TEST or if directed by other test procedures. Fuel-contaminated engine oil may affect Codes 41/172, 91/136, 42/173 and 92/137. If fuel-contaminated engine oil is suspected, remove PCV valve from valve cover and repeat QUICK TEST. If problem is corrected, change engine oil and filter. Only use this test to diagnose

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

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

1. Ignition system.
2. Faulty evaporative emission system.
3. EGR system.
4. Air intake system.
5. Engine oil contamination.
6. Fuel system.
7. Intake or exhaust system leaks.
8. Engine cooling system.

INDIVIDUAL INJECTOR RESISTANCE (1)

INJECTOR BANK RESISTANCE

Scheme 28

1. 1) Check For Contaminated Engine Oil Turn ignition off. Remove PCV valve from valve cover. Inspect PCV system for damage. Inspect valve for blockage and movement of valve plunger. Repair as necessary. Perform KOER SELF-TEST. If vehicle is a no-start, KOER Code 41/172, 42/173, 91/136 or 92/137 or Continuous Memory Code 41/144, 91/139, or 172 is present, install PCV valve and go to step 2). If no codes are set, change engine oil and filter. Install PCV valve, and drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST.
2. 2) Check Fuel Pressure Turn ignition off. 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. Check fuel pressure. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. If fuel pressure is within specification, go to next step. If pressure is not within specification, go to FUEL SYSTEM in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
3. 3) Check System Ability To Hold Fuel Pressure Turn ignition on. If fuel pressure remains at specification for 60 seconds, go to next step (no-starts), step 5) (non-SEFI) or step 6) (SEFI). If fuel pressure is not as described, repair fuel delivery system as necessary.
4. 4) Fuel Delivery Test Release fuel system pressure. Install fuel pressure gauge, and pressurize fuel system as in step 1). Disconnect inertia switch. Crank engine 5 seconds. If fuel pressure drop is greater than 5 psi after 5 seconds of cranking, EEC-IV system is not causing no-start condition. Check additional no-start tests in TESTS W/O CODES article in the ENGINE PERFORMANCE Section. If fuel pressure drop is less than 5 psi, remove fuel pressure gauge. Connect inertia switch. Go to step 7) for non-SEFI or step 8) for SEFI.
5. 5) Cylinder Balance Test (Non-SEFI) Connect a tachometer to engine. Start engine, and run it at idle. Disconnect and reconnect injectors individually, noting RPM drop as each injector is disconnected. 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 Codes 41/172, 91/136 or 176. For Codes 42/173, 92/137 or 177, go to step 24) . Go to step 14) for all other codes.
6. 6) Cylinder Balance Test (SEFI) Perform KOER SELF-TEST. After last code is displayed, wait 5-10 seconds. Enter CYLINDER BALANCE TEST by lightly goosing throttle (not WOT). Test time is about 2-3 minutes. To interpret codes retrieved from test, refer to «CYLINDER BALANCE TEST SERVICE CODES»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) . If cylinder balance fault code is present, go to step 8). If a cylinder balance fault code is not present, fuel delivery is okay; fault is in area common to all cylinders. Code 77/538 indicates throttle was touched when test was ran and test is not completed. Code 538 could also be output if Continuous Memory Code 214 (CID) is present. If Continuous Memory Code 214 is present, see appropriate chart under «SERVICE CODE REFERENCE CHARTS»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) for instruction. 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 ). CYLINDER BALANCE TEST SERVICE CODES Service Code Application 90 Pass 10 Cylinder No. 1 20 Cylinder No. 2 30 Cylinder No. 3 40 Cylinder No. 4 50 Cylinder No. 5 60 Cylinder No. 6 70 Cylinder No. 7 80 Cylinder No. 8 77/538 Retest
7. 7) Check Injector & Harness Resistance (Non-SEFI) Turn ignition off. Wait 10 seconds. Disconnect ECA 60-pin connector. Inspect pins for damage and repair if necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance of injector banks between test pins No. 37 and 58 at breakout box. Measure resistance of injector banks between test pins No. 37 and 59 at breakout box. Record resistances. Refer to «INJECTOR BANK RESISTANCE»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) in this circuit test. If each resistance is within specifications, 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. 8) Check Injector & Harness Resistance (SEFI) Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector. Install EEC-IV Breakout Box (T83L-50-EEC-IV), 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 «INJECTOR BANK RESISTANCE»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) table in this circuit test. If each resistance is within specification, 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. 9) Check Continuity Of Fuel Injector Harness Turn ignition off. Disconnect injector wiring harness connector at injectors. Set DVOM to 200-ohm scale. Measure resistance between test pins No. 37 and 57 at breakout box and each injector VPWR terminal at wiring harness connector. Measure resistance between injector test pin(s) at breakout box and same injector circuit terminal at each injector wiring harness connector. If each resistance is less than 5 ohms, go to step 10). If each resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components and drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST.
10. 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 wiring harness. Set DVOM to 200-k/ohm scale. Measure resistance between injector test pin(s) and test pins No. 37, 40, 46, 57 and 60. Measure resistance between injector test pin(s) at breakout box and chassis ground. If each resistance is 10,000 ohms or more, replace injector per cylinder balance test service code and repeat QUICK TEST (SEFI) or go to next step (non-SEFI). If each resistance is less than 10,000 ohms, repair short. Remove breakout box, reconnect all components and drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST.
11. 11) Isolate Faulty Injector Circuit Turn ignition off. Install breakout box, and disconnect ECA. Disconnect all injectors on suspect bank. With DVOM set on 200-ohm scale, connect one injector and measure resistance between test pins No. 37 and 58 (injector bank No. 1) or 59 (injector bank No. 2). Disconnect injector, and repeat process for all other injectors. See «INDIVIDUAL INJECTOR RESISTANCE»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) . If all injectors are within specification, go to next step. If injectors are not as specified, replace injector. Remove breakout box, and reconnect components. Drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST.
12. 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: Non-SEFI 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. SEFI Connect test light between test pin No. 37 and suspect injector test pin at breakout box.
13. Crank or start engine. If test light glows dimly, system is operating correctly. Clean injectors, and drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST and CYLINDER BALANCE TEST. If test light does not glow dimly (no light/bright light), replace ECA. Reconnect all components, and drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST.
14. 13) Check Thermactor Operation If vehicle is equipped with pulse-air or does not have thermactor system, go to next next step. A HEGO which is always lean could be caused by thermactor air being diverted upstream from HEGO sensor. With dual HEGO, Code 41/172 applies to right or rear HEGO and Code 91/136 or 176 applies to left or front HEGO. Turn ignition off. Disconnect thermactor air hose(s) from thermactor pump. Run KOER SELF-TEST. If Code 41/172, 91/136 or 176 is present, reconnect thermactor air hoses and go to step 90) . If no codes are present, repair thermactor system as necessary.
15. 14) Check HEGO Integrity A HEGO sensor which is always lean, slow to switch or does not switch could be caused by: Moisture inside HEGO sensor or connector causing a short to ground. HEGO sensor coated with contaminants. HEGO circuit open. HEGO circuit shorted to ground. Turn ignition off. Inspect HEGO wiring harness for damage. Inspect HEGO sensor and connector for signs of fluid entry. Repair or replace as necessary. Start engine, and run it at 2000 RPM for 2 minutes. Turn ignition off. Run KOER SELF-TEST. If fault codes are present, go to next step (MAP sensor-equipped models) or step 16) (MAF sensor-equipped models). If no code is present, go to step 21) .
16. 15) Check HEGO Sensor (Engines With MAP Sensors) Vacuum or air leaks in non-EEC-IV areas could cause Code 41, 91, 136, 172 or 176. Check following possibilities before continuing: Leaking vacuum actuated motor. Leaking intake gasket. EGR system. PCV system. Lead-contaminated HEGO sensor. Turn ignition off. Ensure MAP sensor output voltage is correct. See «CIRCUIT TEST DF»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) , step 3). Disconnect appropriate HEGO sensor from wiring harness. Connect DVOM to HEGO SIGNAL lead at sensor from wiring harness. On 3-wire HEGO, connect DVOM to HEGO SIGNAL lead at sensor connector and battery negative terminal. On 4-wire HEGO, connect DVOM to HEGO SIGNAL and HEGO GND leads at sensor connector. On all models, disconnect and plug vacuum line at MAP sensor. Start engine, and apply 10-14 in. Hg to MAP sensor. Run engine at 2000 RPM for 2 minutes. If reading is 0.5 volt or more, go to step 17). If reading is less than 0.5 volt, replace HEGO sensor and repeat QUICK TEST.
17. 16) Check HEGO Sensor (Engines With MAF Sensor) 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. On 4-wire HEGO, connect DVOM between HEGO SIGNAL and HEGO GND at HEGO sensor connector. On 3-wire HEGO, connect DVOM to HEGO SIGNAL at sensor and battery negative terminal. On all models, run engine at 2000 RPM for 2 minutes. Repeat KOER SELF-TEST and monitor HEGO sensor voltage. If voltage is 0.5 volt or more at end of self-test, go to next step. If voltage is less than 0.5 volt, replace HEGO sensor and repeat QUICK TEST.
18. 17) Check Continuity Of HEGO Circuits Turn ignition off. Install breakout box, leaving ECA disconnected. Disconnect suspect HEGO sensor from wiring harness. Inspect both ends of connector for damage, moisture and corrosion. 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 wiring harness connector. On 3-wire HEGO, measure resistance between HEGO GROUND test pin at breakout box and battery negative terminal. On 4-wire HEGO, measure resistance between HEGO GROUND test pin at breakout box and HEGO GND at wiring harness connector. Where applicable, measure resistance between HEGO GND and SIG RTN at breakout box. On all models, go to next step if each resistance is less than 5 ohms. If any resistance is 5 ohms or more, repair open circuit. Remove breakout box, and reconnect all components. Drive vehicle for 5 minutes at 55 MPH. Repeat QUICK Test.
19. 18) Check HEGO Circuit For Short To Ground Turn ignition off. Leave breakout box installed and ECA disconnected. Disconnect HEGO sensor. Measure resistance between HEGO SIGNAL and test pins No. 40, 46 and 49 at breakout box. If any reading is less than 10,000 ohms, repair short to ground. Reconnect all components, and repeat QUICK TEST. If reading is 10,000 ohms or more, go to next step.
20. 19) Check HEGO Sensor For Short To Ground Disconnect HEGO sensor. On 4-wire HEGO, measure resistance between PWR GND, HEGO GND, SIG RTN and HEGO SIG at HEGO sensor connector. On all HEGO sensors, measure resistance between PWR GND and HEGO SIGNAL at HEGO sensor connector. If resistance is less than 10,000 ohms, replace HEGO sensor. Connect all components, and drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST. If resistance is 10,000 ohms or more, perform following procedure as applicable. For Codes 144/41, 139/91, 171, 174, 175 and 178, go to step 90) . For all other codes, go to next step if engine is equipped with MAP sensor. If engine is equipped with MAF sensor, replace ECA. Drive vehicle for 5 miles at 55 MPH, and repeat QUICK TEST.
21. 20) Attempt To Eliminate Code 41/172, 91/136 Or 176 (Engines With MAP Sensor) Turn ignition off. Connect ECA to breakout box. Connect HEGO sensor. Disconnect and plug MAP sensor vacuum hose. 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 diagnosing continuous memory codes, drive vehicle 5 miles at 55 MPH. If Code 41/172, 91/136 or 176 is still present, remove breakout box. Connect all components. If engine runs rough, go to step 2) of CIRCUIT TEST S. If engine does not run rough, replace ECA, drive vehicle 5 miles at 55 MPH and repeat QUICK TEST. If code is not present, remove breakout box and connect all components. HEGO input circuit and fuel delivery are okay; fault is in area common to all systems. See TESTS W/O CODES article in the ENGINE PERFORMANCE Section.
22. 21) Check Resistance Of HEGO Heating Element Turn ignition off. Disconnect suspect HEGO sensor. Inspect both ends of connector for damage, moisture and corrosion. Repair if necessary. Set DVOM on 200-ohm scale. Measure resistance between IGNITION RUN circuit and PWR GND circuit at HEGO sensor connector. Hot to warm engine resistance should be 5-30 ohms. Cold engine resistance is 2-5 ohms. If resistance is within specification, go to next step. If resistance is not as specified, replace HEGO sensor and repeat QUICK TEST.
23. 22) Check For Power At HEGO Harness Connector Disconnect HEGO sensor. Turn ignition on. Measure voltage between IGNITION RUN and PWR GND circuits at HEGO wiring harness connector. If voltage is 10.5 volts or more, HEGO system and fuel delivery are okay. HEGO sensor may have cooled before KOER SELF-TEST. If driveability symptom continues, fault is in area common to all cylinders. See TESTS W/O CODES article in the ENGINE PERFORMANCE Section. If voltage is less than 10.5 volts, go to next step.
24. 23) Check Continuity Of Power Ground Circuit Turn ignition off. Measure resistance between PWR GND circuit at HEGO wiring harness connector and negative battery terminal. If resistance is less than 5 ohms, repair open in IGNITION RUN circuit and repeat QUICK TEST. If resistance is 5 ohms or more, repair open in PWR GND circuit and repeat QUICK TEST.
25. 24) Check HEGO SIGNAL For Short To Power On dual HEGO systems, Code 42/173 applies to right or rear HEGO. Codes 92/137 and 177 applies to left or front HEGO. Turn ignition off. Disconnect appropriate HEGO sensor. Turn ignition on. Measure voltage between HEGO SIG and PWR GND at HEGO wiring harness connector. If reading is less than 0.5 volt, go to step 26) . If reading is 0.5 volt or more, go to next step.
26. 25) Check For Short To Power Turn ignition off. Disconnect HEGO sensor. Inspect both ends of connector for damage, moisture and corrosion. Repair if necessary. Drive vehicle 5 miles at 55 MPH and repeat QUICK TEST. If connector is okay, go to next step.
27. 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 IGNITION RUN circuit and HEGO SIG circuit at HEGO sensor connector. If resistance is 10,000 ohms or more, go to next step for Codes 42/173, 92/137 and 177; for codes 171, 174, 175 and 178, go to step 28) (MAP sensor) or 30) (MAF sensor). If resistance is less than 10,000 ohms, replace HEGO sensor. Drive vehicle for 5 miles at 55 MPH, and repeat QUICK TEST.
28. 27) Attempt To Generate Code 41/172, 91/136 Or 176 Turn ignition off. Disconnect appropriate HEGO sensor. Using jumper wire, connect HEGO SIG circuit at HEGO wiring harness connector to negative battery 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 sensor or step 30) for engines with MAF sensor. If Codes 41/172, 91/136 and 176 are not present, remove jumper wire. Disconnect ECA connector, and inspect it for damage. If connector is okay, replace ECA. Drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST. Diagnostic Aids Because MAP sensor greatly influences fuel control, MAP sensor may malfunction without setting Code 22/126. Next 2 steps test MAP vacuum circuit.
29. 28) Check MAP Sensor For Vacuum Leaks Turn ignition off. Disconnect vacuum hose from MAP sensor. Connect vacuum pump to sensor. Apply 18 in. Hg to MAP sensor. If sensor does not hold vacuum, replace MAP sensor. Drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST. If sensor holds vacuum, release vacuum and go to step 29).
30. Check For Loss Of Vacuum To MAP Sensor Using vacuum "T", connect vacuum gauge in MAP sensor vacuum hose. Start engine. Note vacuum reading at idle stabilizes. Turn ignition off. Remove "T" and vacuum gauge. Reconnect hose to MAP sensor. Connect vacuum gauge at a different manifold vacuum 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 and blockage. Repair as necessary. Connect all components, and drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST.
31. 30) HEGO Sensor Check Turn ignition off. Disconnect HEGO sensor. For 4-wire HEGO sensor, connect DVOM to HEGO and HEGO GND or SIG RTN at HEGO sensor connector. For 3-wire HEGO sensor, connect DVOM to HEGO SIGNAL at HEGO sensor connector and negative battery terminal. On all models, remove PCV valve from hose. Start engine, and run it at about 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: A break in step numbering sequence occurs at this point. Procedure skips from step 30) to step 90). No test procedures have been omitted.
32. 90) Check Continuous Monitor Mode Start engine, and warm it to normal operating temperature. Raise engine speed to 2000 RPM for 2 minutes and then return to idle. Enter KOER wiggle test. See «CONTINUOUS MONITOR MODE (WIGGLE TEST)»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l__continuous-monitor-mode-wiggle-test) under QUICK TEST. While observing DVOM or scan tester, shake or bend small sections of wiring harness from HEGO sensor to ECA. Wiggle, shake or bend small sections of 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. Repeat QUICK TEST.
33. 91) Continuous Monitor Test Drive Check While still in KOER wiggle test, drive vehicle for 5 miles at 55 MPH over smooth roads. Drive an additional 5 miles at 55 MPH over rough roads. If possible, drive vehicle through a pool of water to wet HEGO sensor and connector. If fault is indicated, isolate fault and repair as necessary. Clear codes, and remove breakout box. Repeat QUICK TEST. If no codes are indicated, exit KOER wiggle test and go to next step.
34. 92) Check HEGO Switching Turn ignition off. Inspect wire harness for proper routing. Check for burnt, chaffed or open wires. Repair if necessary. Disconnect ECA 60-pin connector. Inspect it for damaged or pushed-out pins and repair as necessary. Install breakout box. Connect ECA to breakout box. Connect analog voltmeter to suspect 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 fluctuate between .3 and .9 volt in 3 second cycles. If HEGO does not switch as described, replace HEGO sensor. Connect all components, and repeat QUICK TEST. If HEGO switches as described, fault cannot be identified at this time. See INTERMITTENTS in TESTS W/O CODES article in the ENGINE PERFORMANCE Section.

CIRCUIT TEST HA - ADAPTIVE FUEL

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

Perform this test when directed by QUICK TEST. ECA uses adaptive fuel logic to compensate for normal variances in fuel system components. If fuel system appears to be too rich or too lean, adaptive fuel will make appropriate shift in fuel delivery calculations to compensate.

If possible, measure several known good MAP/BP sensors. Average voltage reading will be typical for location and day of testing.

MAP SENSOR VOLTAGE OUTPUT

CIRCUIT TEST HA ACRONYMS

1. 1) Continuous Memory Codes 181, 183, 189 & 192 This test identifies areas which could cause HEGO sensor to detect excessive oxygen, resulting in adaptive fuel enriching system to compensate. Excessive oxygen will be detected with lean conditions and certain rich conditions. For models with dual HEGO sensors, a related fuel code from both HEGO sensors could indicate a problem 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. Code 183 Indicates single right or rear HEGO detected a problem and adaptive fuel rich limit has been reached at idle. Code 192 Indicates left or front HEGO detected a problem and adaptive fuel rich limit has been reached at idle. Code 181 Indicates single right or rear HEGO detected a problem and adaptive fuel rich limit has been reached. Code 189 Indicates left or front HEGO detected a problem and adaptive fuel rich limit has been reached. Ensure a pass Code (111) is retrieved during both KOEO SELF-TEST and KOER SELF-TEST. Whenever a repair is made, clear KAM. If driveability symptoms are not present, be aware of other temporary conditions which may have set this code, such as fuel contamination or vehicle is out of fuel. For SEFI models, go to next step. For non-SEFI models, go to step 3).
2. 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. 3) Check For Vacuum/Air Induction Leaks Check vacuum hoses, air induction system and EGR tube for leaks and damage. Repair if necessary. Clear KAM, and repeat QUICK TEST. If leak or damage is not found, go to go to next step.
4. 4) Check For Low Fuel Pressure Turn ignition off. Release fuel system pressure. Install fuel pressure gauge. Cycle ignition from OFF to RUN position twice. 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 specification, go to next step. If fuel pressure is not within specification, repair fuel system. Clear KAM, and repeat QUICK TEST.
5. 5) Check System Ability To Hold Fuel Pressure With fuel pressure gauge installed, cycle ignition from OFF to ON position twice to pressurize fuel system (DO NOT start engine). If fuel pressure remains at specification for 60 seconds, go to next step (MAP/BP equipped vehicles) or step 7) (all other vehicles). If fuel pressure does not remain at specification for 60 seconds, repair fuel system as necessary. Clear KAM, and repeat QUICK TEST.
6. 6) Check MAP/BP Frequency Turn ignition off. Connect MAP/BP tester to MAP/BP sensor. (Scheme 19)in CIRCUIT TEST DF. Turn ignition on. If MAP/BP voltage is within specification, go to next step. See «MAP SENSOR VOLTAGE OUTPUT»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l). If voltage is not within specification, check wiring to MAP/BP sensor for corrosion and other damage. Repair as necessary. Clear KAM, and repeat QUICK TEST. If wiring is okay, replace MAP/BP sensor. Clear KAM, and repeat QUICK TEST.
7. 7) Check For Proper Battery Voltage To Fuel Injectors Turn ignition on. Measure and record voltage across battery terminals. Disconnect any fuel injector harness connector. Measure and record voltage between VPWR circuit at fuel injector wiring 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 correct voltage. Repair as necessary. Clear KAM, and repeat QUICK TEST.
8. 8) Verify CANP Solenoid Is Not Stuck Closed Enter OUTPUT STATE CHECK. See ADDITIONAL SYSTEM FUNCTIONS. Disconnect hose to manifold vacuum at CANP solenoid. Check for blockage. Repair or replace hose as necessary. With outputs off, apply 16 in. Hg vacuum to manifold vacuum side of CANP. Apply throttle to cycle outputs on. If vacuum releases, reconnect vacuum hose to CANP and go to next step (thermactor-equipped vehicles) or step 25) (all other vehicles). If vacuum does not release, repeat this step to verify results. If vacuum now releases, go to next step (thermactor-equipped vehicles). If vacuum will not release, replace CANP solenoid. Clear KAM, and repeat QUICK TEST.
9. 9) Check Thermactor System For Upstream Air Leak Check thermactor air control and vacuum control valves. See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. 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 repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 9) to step 15). No test procedures have been omitted.
10. 15) Continuous Memory Codes 179, 182, 188 & 191 This test identifies areas which could cause engine to run rich, resulting in adaptive fuel reducing system to compensate. For vehicles with dual HEGO sensors, a related fuel code from both HEGO sensors could indicate a problem 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. Code 179 Indicates single right or rear HEGO detected a problem and adaptive fuel lean limit has been reached. Code 182 Indicates single right or rear HEGO detected a problem and adaptive fuel lean limit has been reached at idle. Code 188 Indicates left or front HEGO detected a problem and adaptive fuel lean limit has been reached. Code 191 Indicates left or front HEGO detected a problem and adaptive fuel lean limit has been reached at idle. Ensure a pass Code (111) is received during both KOEO SELF-TEST and KOER SELF-TEST. Whenever a repair is made, clear KAM. For SEFI vehicles, go to step 16). For non-SEFI vehicles, go to step 17).
11. 16) Run Cylinder Balance Test Run KOER SELF-TEST. After last repeated code, wait 5-10 seconds and 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).
12. 17) Check For Low Fuel Pressure Turn ignition off. Release fuel system pressure. Install fuel pressure gauge. Cycle ignition from OFF to RUN position twice. 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 specification, go to next step. If fuel pressure is not within specification, repair fuel system as necessary. Clear KAM, and repeat QUICK TEST.
13. 18) Check System Ability To Hold Fuel Pressure With fuel pressure gauge installed, cycle ignition from OFF to ON position twice to pressurize fuel system (do not start engine). If fuel pressure remains at specification for 60 seconds, go to next step (MAP/BP-equipped vehicles) or step 20) (all other vehicles). If fuel pressure does not remain at specification for 60 seconds, repair fuel system as necessary. Clear KAM, and repeat QUICK TEST.
14. 19) Check MAP/BP Frequency Turn ignition off. Connect MAP/BP tester to MAP/BP sensor. Turn ignition on. Refer to «MAP SENSOR VOLTAGE OUTPUT»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l). If voltage is not within specification, check wiring to MAP/BP sensor for corrosion or other damage. Repair if necessary. Clear KAM, and repeat QUICK TEST. If wiring is okay, replace MAP/BP sensor. Clear KAM, and repeat QUICK TEST. If MAP/BP voltage is within specification, go to next step.
15. 20) Check Throttle Body & Air Induction System Check throttle body and air induction system for contamination and obstruction. Repair if necessary. Clear KAM, and repeat QUICK TEST. If throttle body and air induction system are okay, go to next step.
16. 21) Check PCV Valve Turn ignition off. Remove and shake PCV valve. If PCV valve rattles freely when shaken, go to next step. Replace PCV valve if it does not rattle. Clear KAM, and repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 21) to step 26). No test procedures have been omitted.
17. 26) Check HEGO Heater Circuit Turn ignition off. Disconnect HEGO sensor(s). Measure resistance between IGNITION RUN circuit and PWR GND circuit at HEGO sensor connectors. Resistance should be 2 ohms (cold) or 35 ohms (hot). Set DVOM to 20-volt scale. Turn ignition on. Measure voltage between IGNITION RUN circuit and PWR GND circuit at HEGO sensor connectors. Voltage should be 10.5 volts. If HEGO circuit checks are within specification, go to next step. If HEGO circuit check are not within specification, isolate problem and repair as necessary. Clear KAM, and repeat QUICK TEST.
18. 27) Inspect HEGO Sensor For Contamination Remove HEGO sensor(s) from exhaust manifold. Visually inspect for contamination and other damage. If HEGO sensors appear okay, go to next step (models with EGR) or step 30) (models without EGR). If HEGO sensors are contaminated or damaged, replace HEGO sensor. Clear KAM, and repeat QUICK TEST.
19. 28) Check EGR Vacuum Supply At Idle Disconnect vacuum line at EGR valve. Connect vacuum gauge to EGR vacuum line. Start engine, and let it idle. If vacuum reading is less than 2.5 in. Hg, go to next step. If vacuum reading is 2.5 in. Hg or more, check EVR solenoid filter for obstructions. Repair as necessary. If EVR filter is okay, replace EVR solenoid. Connect all components, clear KAM, and repeat QUICK TEST.
20. 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 repeat QUICK TEST.
21. 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 cooling system requires service, repair or replace as necessary. Clear KAM, and repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 30) to step 35). No test procedures have been omitted.
22. 35) Check Ignition System Ensure ignition system is operating properly. Scope check engine to verify no abnormal primary or secondary ignition firing lines exist. If ignition system is operating properly, go to next step. If system is not operating properly, make necessary repairs. See IGNITION SYSTEMS in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. Clear KAM, and repeat QUICK TEST.
23. 36) Injector Flow Check Check fuel injector flow using Fuel Injector Tester (Rotunda 113-00001). If injector flow is okay, go to next step. If injectors are restricted, clean or replace injectors as necessary. Clear KAM, and repeat QUICK TEST.
24. 37) Check Cylinder Compression Check cylinder compression. See MECHANICAL INSPECTION in BASIC TESTING article in the ENGINE PERFORMANCE Section. If cylinder compression is not within specifications, repair or replace engine as necessary. Clear KAM, and repeat QUICK TEST. If cylinder compression is within specification, go to next step. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 37) to step 40). No test procedures have been omitted. WARNING: Following road test is an optional procedure. Follow all applicable safety procedures and traffic laws. This road test requires a driver and an assistant. Assistant should make measurements, observe changes and record notes. If this test is not performed, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section for other possible causes.
25. 40) Road Test Vehicle Purpose of this test is to identify faults by monitoring certain controlled parameters while trying to recreate a driveability fault or symptom. To prepare for road test: Install fuel pressure gauge. Install MAP/BP tester. Disconnect ECA 60-pin connector, install breakout box and reconnect ECA to breakout box. Connect "T" vacuum gauge into manifold vacuum line. Have DVOM, writing materials, appropriate schematics and pin voltage charts available. With ignition on and negative lead of DVOM connected to battery negative terminal, ensure following signals are correct: POWERS: KAPWR (pin No. 1) is more than 10.5 volts, VPWR (pins No. 37 and 57) is more than 10.5 volts and VREF (pin No. 26) is 4-6 volts. GROUNDS: PWR GND (pins No. 40 and 60), SIG RTN (pin No. 46) and IGN GND (pin No. 16) are 0-.5 volt. OPTIONAL GROUNDS: HEGO GND (pin No. 49), CSE GND (pin No. 20) and MAF RTN (pin No. 9 or 15) are 0-.5 volt. Drive vehicle and attempt to induce symptom. Information provided by vehicle operator may help when trying to recreate symptom. When symptom occurs, assistant should observe and record changes in voltage signals. Information about symptom, operating condition value of voltage signal and any other information available should be recorded for analysis. If unable to duplicate symptom during road test, verify EEC-IV values are within acceptable range. After road test is completed, analyze results to locate and repair fault causing symptom. If problem cannot be identified, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section for other possible causes of symptom.

Perform this test when instructed by QUICK TEST. This test is only intended to diagnose

1. Fuel pump relay.
2. Inertia switch.
3. Wiring harness circuits (BATT +, VPWR, FUEL PUMP, GND and POWER-TO-PUMP).
4. ECA.

Scheme 29

CIRCUIT TEST J TEST PIN WIRE COLOR ID

Scheme 30

Scheme 31

Scheme 32

1. 1) No Fuel System Pressure: Check Fuel Pump Operation Turn ignition switch from OFF to RUN position several times (DO NOT turn to START position). If fuel pump runs briefly each time ignition is turned to RUN position, fuel pump circuit is okay. If fuel pump does not run, go to next step.
2. 2) Check For VPWR To ECA Turn ignition off. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect ECA to breakout box. Turn ignition on. Measure voltage between test pins No. 37 and 40 at breakout box. Measure voltage between test pins No. 57 and 60 at breakout box. If both voltage readings are more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, go to «CIRCUIT TEST B - CHECKING VEHICLE BATTERY»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l), step 1).
3. 3) Check Voltage To POWER-TO-PUMP Circuit With ignition on, measure voltage between chassis ground and POWER-TO-PUMP circuit at fuel pump relay while cranking engine. If reading is less than 8 volts, go to step 4). If reading is 8 volts or more, check fuse to fuel pump relay. If fuse is okay, repair open in BATT+ circuit between fuel pump relay and battery positive terminal. Remove breakout box, and repeat QUICK TEST.
4. 4) Checking BATT (+) Circuit To Fuel Pump Relay Turn ignition on. Leave breakout box installed and ECA connected. Locate fuel pump relay. Measure voltage between chassis ground and BATT (+) circuit at fuel pump relay. If voltage is less than 10.5 volts, repair open in BATT (+) circuit between fuel pump relay and positive battery terminal. Repeat QUICK TEST. If reading is 10.5 volts or more, go to next step.
5. 5) Check Voltage At POWER-TO-PUMP Circuit Turn ignition off. Connect jumper wire from test pin No. 22 to test pin No. 40 or 60 at breakout box. Turn ignition on. Measure voltage between chassis ground and POWER-TO-PUMP circuit at fuel pump relay. If voltage is 10.5 volts or more, replace ECA and repeat QUICK TEST. If voltage is less than 10.5 volts, replace fuel pump relay, and repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 5) to step 7). No test procedures have been omitted.
6. 7) Code 87/556: Check VPWR To Fuel Pump Relay Code 87/556 indicates a fuel pump primary circuit failure. Possible causes for this fault are: Inertia switch not reset or circuit open. Open or shorted circuit. Faulty fuel pump relay. Faulty ECA. Disconnect fuel pump relay. Turn ignition on. Measure voltage between chassis ground and VPWR circuit at fuel pump relay wiring harness connector. If reading is 10.5 volts or more, go to next step. If reading is less than 10.5 volts, verify inertia switch is in ON position. If switch is okay, repair open in VPWR circuit between EEC power relay and fuel pump relay. Connect fuel pump relay and repeat QUICK TEST.
7. 8) Check Fuel Pump Relay Turn ignition off. Disconnect fuel pump relay. (Scheme 30) Set DVOM on 200-ohm scale. On Bronco, Pickup and Van relays, measure resistance between terminals No. 85 and 86. On all other relays, measure resistance between VPWR pin and FUEL PUMP circuit pin at fuel pump relay. Both resistances should be 40-85 ohms. Set DVOM to 20-k/ohm scale. On Bronco, Pickup and Van relays, measure resistance between terminal No. 85 and terminals No. 30 and 87. On all other relays, measure resistance between FUEL PUMP circuit pin and both POWER-TO-PUMP and BATT (+) pins at fuel pump relay. All resistances should be greater than 10,000 ohms. If resistances are as specified, go to next step. If resistances are not as specified, replace fuel pump relay and repeat QUICK TEST.
8. 9) Check For Short To Power Turn ignition off. Disconnect fuel pump relay. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Turn ignition on. Measure voltage between test pin No. 22 and negative battery terminal. If voltage is less than 1.0 volt, go to next step. If voltage is 1.0 volt or more, repair short circuit. Reconnect ECA, and attempt to start vehicle. If vehicle fails to start, replace ECA. Repeat QUICK TEST.
9. 10) Check For Shorts To Ground Turn ignition off. Leave fuel pump relay disconnected. Measure resistance between test pin No. 22 and test pins No. 40 and 60. If resistance is less than 10,000 ohms, repair short in FUEL PUMP circuit. Remove breakout box, and repeat QUICK TEST. If resistance is 10,000 ohms or more, go to next step.
10. 11) Check Fuel Pump Circuit Continuity Turn ignition off. Leave fuel pump relay disconnected. Measure resistance between FUEL PUMP circuit at fuel pump relay wiring harness connector and test pin No. 22 at breakout box. If resistance is less than 5 ohms, replace ECA and repeat QUICK TEST. If resistance is 5 ohms or more, repair open circuit. Reconnect all components, and repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 11) to step 20). No test procedures have been omitted.
11. 20) Code 95/542 A KOEO Code 95/542 indicates one of following conditions: Engine Starts: Fuel pump secondary circuit shorted to power. Fuel pump relay contacts always closed. Open in Fuel Pump Monitor (FPM) circuit between ECA and connection to POWER-TO-PUMP circuit. HEGO short to power (dual HEGO applications). Faulty ECA. No Start: Inertia switch not reset or electrically open. Open circuit in or between ECA and fuel pump. Faulty ground connection at fuel pump. If engine starts, go to step 21). If engine does not start, go to step 24).
12. 21) Check Fuel Pump Operation Turn ignition on. Wait 5 seconds. Listen for fuel pump operation. If fuel pump is off, go to step 23). If fuel pump is on, go to next step.
13. 22) Check For Fuel Pump Relay Always Closed Turn ignition off. Disconnect fuel pump relay. Turn ignition on. If fuel pump is off with relay disconnected, replace fuel pump relay and repeat QUICK TEST. If fuel pump is on with relay disconnected, repair short to power in POWER-TO-PUMP/FPM circuit. (For models with relay block, also check fuel pump prime plug circuit). Repeat QUICK TEST.
14. 23) Check Continuity Of Fuel Pump Monitor (FPM) Circuit Turn ignition off. Disconnect ECA 60-pin connector. Inspect and repair any damaged terminals. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Disconnect fuel pump relay. Measure resistance between test pin No. 8 at breakout box and POWER-TO-PUMP circuit at fuel pump relay wiring harness connector. If resistance is less than 5 ohms, go to step 35) (dual HEGO) or replace ECA and repeat QUICK TEST (single HEGO). If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST.
15. 24) Check Inertia Switch Turn ignition off. Disconnect fuel pump inertia switch. Ensure switch is reset. Measure resistance of inertia switch. If resistance is less than 5 ohms, reconnect switch and check for open in POWER-TO-PUMP circuit, poor fuel pump ground or open in fuel pump. If resistance is 5 ohms or more, reset or replace inertia switch. Repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 24) to step 30). No test procedures have been omitted.
16. 30) Code 96/543 Code 96/543 indicates fuel pump secondary circuit failure between BATT (+) supply and FPM connection to POWER-TO-PUMP circuit. Following are possible causes: No Start: Open circuit between BATT (+) supply and FPM connection to POWER-TO-PUMP circuit. Fuel pump relay contacts are always open. Engine Starts: HEGO short to power (dual HEGO models). Faulty ECA. If engine starts, go to step 35) (dual HEGO) or replace ECA and repeat QUICK TEST (single HEGO). If engine does not start, go to step 31).
17. 31) Check For BATT (+) To Fuel Pump Relay Turn ignition off. Disconnect fuel pump relay. Connect DVOM between BATT (+) terminal at fuel pump relay wiring harness connector and negative battery terminal. If voltage is 10.5 volts or more, go to next step. If voltage is less than 10.5 volts, check fuse/fusible link for BATT (+) supply to fuel pump relay. If fuse/fusible link is okay, repair open circuit in BATT (+) circuit. Repeat QUICK TEST.
18. 32) Check POWER-TO-PUMP Circuit Continuity Turn ignition off. With fuel pump relay disconnected, measure resistance between POWER-TO-PUMP terminal at fuel pump relay wiring harness connector and negative battery terminal. If resistance is less than 10 ohms, replace fuel pump relay. Reconnect relay and repeat QUICK TEST. If resistance is 10 ohms or more, repair open circuit in POWER-TO-PUMP circuit between FPM splice and fuel pump relay. Repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 32) to step 35). No test procedures have been omitted. Diagnostic Aids Due to internal circuitry of ECA, a left/front HEGO signal short to power could produce a Code 95/542 or 96/543.
19. 35) Check Left/Front HEGO Sensor For Short To Power Turn ignition off. Disconnect left or front HEGO sensor. (Scheme 31) Measure resistance between HEGO SIGNAL terminal and KEY POWER terminal at HEGO sensor wiring harness connector. (Scheme 32) If resistance is 10,000 ohms or more, go to step 36). If resistance is less than 10,000 ohms, replace HEGO sensor. Clear KAM, and repeat QUICK TEST.
20. 36) Check HEGO Circuit For Short To Power Turn ignition off. Disconnect ECA. Inspect and repair any damaged terminals. Turn ignition on. With left or front HEGO sensor disconnected, measure voltage between HEGO SIGNAL at HEGO wiring harness connector and chassis ground. If voltage is less than 2 volts, replace ECA and repeat QUICK TEST. If voltage is 2 volts or more, repair short circuit. Reconnect ECA and HEGO sensor. Clear KAM, and repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 36) to step 90). No test procedures have been omitted.
21. 90) Continuous Memory Code 95/542 Code 95/542 indicates one of following conditions: Faulty ground circuit at fuel pump. FPM or POWER-TO-PUMP circuit short to power. Fuel pump relay contacts stuck closed. Open circuit in or between fuel pump and FPM circuit at ECA. Left or front HEGO circuit short to power (dual HEGO system). FUEL PUMP circuit is activated at a time that is not programmed into ECA strategy. Start engine, and enter wiggle test. See «CONTINUOUS MONITOR MODE (WIGGLE TEST)»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l__continuous-monitor-mode-wiggle-test) under QUICK TEST. Check for engine miss or intermittent fuel pump deactivation while performing following: Shake and bend POWER-TO-PUMP circuit wiring harness connector between fuel pump relay and fuel pump. Shake and bend fuel pump ground circuit between fuel pump and ground. Lightly tap fuel pump to simulate road shock. Lightly tap inertia switch to simulate road shock. With ignition off, check harness connectors for corrosion and damage. Isolate and repair any faults. Clear continuous memory, and repeat QUICK TEST. If no faults are found, go to next step.
22. 91) Check FPM Circuit Turn ignition off. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Connect test light between test pin No. 8 and test pin No. 37 at breakout box. With test light on, perform wiggle test on FPM circuit between fuel pump and ECA. Light will go out if fault is found, indicating an open circuit. If a fault is found, repair as necessary and repeat QUICK TEST. If no fault is found, go to next step.
23. 92) Check For Shorts To Power Connect a test light between breakout box test pin No. 8 and test pin No. 40. Test light should be off. Observe test light while bending and shaking FPM circuit and POWER-TO-PUMP circuit. Lightly tap fuel pump relay to simulate road shock. Fault is indicated if test light comes on. Isolate and repair fault as necessary, and repeat QUICK TEST. If no fault is found, go to step 96) (dual HEGO) or step 99) (single HEGO).
24. 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 Codes 87 and 556 are not displayed, go to next step.
25. 94) Check EEC-IV Harness A Continuous Memory Code 96/543, without an accompanying Continuous Memory Code 87/556, indicates one of following conditions has occurred during vehicle operation: An open in BATT (+) circuit between BATT (+) and fuel pump relay. Fuel pump relay contacts open. Open in POWER-TO-PUMP circuit between fuel pump relay to FPM splice (if applicable). Left/front HEGO circuit short to power (dual HEGO). Start engine. Check for engine miss or intermittent fuel pump deactivation while performing following: Shake and bend BATT (+) circuit wiring harness between power source and fuel pump relay. Shake and bend POWER-TO-PUMP circuit wiring harness connector between fuel pump relay and FPM splice (if applicable). Lightly tap fuel pump relay to simulate road shock. Turn ignition off. Inspect all fuel pump relay and BATT (+) connectors for damage and corrosion. If fault is found, repair as necessary. Clear and repeat QUICK TEST. If no fault is found, a Continuous Memory Code 95/543 may have been set without a Continuous Memory Code 87/556 under certain conditions, even though a fault has occurred in fuel pump primary circuit. Go to next step for fuel pump primary circuit check.
26. 95) Continuous Memory 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: Open in VPWR circuit between EEC power relay and fuel pump relay. Open coil in fuel pump relay. Open in fuel pump circuit (pin No. 22). Faulty inertia switch. Start engine. Check for engine miss or intermittent fuel pump deactivation while performing following: Shake and bend VPWR circuit wiring harness between EEC and fuel pump relay. Shake and bend FP circuit wiring harness connector between fuel pump relay and ECA. Lightly tap fuel pump relay to simulate road shock. Lightly tap inertia switch to simulate road shock (if equipped). Turn ignition off. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. If fault is found, isolate and repair as necessary. Repeat QUICK TEST. If no faults are found but Code 96/543 is present, go to next step (dual HEGO). If fault can not be duplicated at this time, 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.
27. 96) Check Left/Front HEGO Circuit For Short To Power Turn ignition off. Breakout box should be installed with ECA disconnected. Connect test light between left/front HEGO test pin and pin No. 40 at breakout box. Test light should be off. Observe test light while bending and shaking left/front HEGO circuit from HEGO sensor to ECA. Lightly tap HEGO SENSOR to simulate road shock. Fault is indicated if test light comes on. Isolate and repair as necessary. Clear Keep-Alive Memory (KAM), and repeat QUICK TEST. If no fault is indicated, go to next step. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 96) to step 99). No test procedures have been omitted. WARNING: Following road test is an optional procedure. Follow all applicable safety procedures and traffic laws. This road test requires a driver and an assistant. Assistant should make measurements, observe changes and record notes. If this test is not performed, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section for other possible causes.
28. 99) Road Test Vehicle Purpose of this test is to identify faults by monitoring certain controlled parameters while trying to recreate a driveability or MIL light symptom. To prepare for road test: Install fuel pressure gauge. Install MAP/BP tester. Disconnect ECA 60-pin connector, install breakout box and reconnect ECA to breakout box. Connect "T" vacuum gauge into manifold vacuum line. Have DVOM, writing materials and appropriate schematics and pin voltage charts available. With ignition on and negative lead of DVOM connected to negative battery terminal, ensure following signals are correct: POWERS: KAPWR (pin No. 1) is greater than 10.5 volts, VPWR (pins No. 37 and 57) is greater than 10.5 volts and VREF (pin No. 26) is 4-6 volts. GROUNDS: PWR GND (pins No. 40 and 60), SIG RTN (pin No. 46) and IGN GND (pin No. 16) are 0.0-0.5 volt. OPTIONAL GROUNDS: HEGO GND (pin No. 49), CSE GND (pin No. Step 20) and MAF RTN (pin No. 9 or 15) are 0.0-0.5 volt.

Test lights and DVOM are useful during diagnosis. For example: with Continuous Memory Code 87/556 (fuel pump primary circuit failure) and a surge or stall symptom, connect a test light to fuel pump relay between VPWR and ground. Connect DVOM between FP circuit at fuel pump relay and breakout box test pin No. 1. Under normal driving conditions, test light will be on and DVOM will read battery voltage. If vehicle stalls, ECA will open FP circuit and DVOM voltage will be low. If fault is in fuel pump circuit, test light and DVOM status will change as fault occurs. If test light at VPWR circuit goes out, fault is in VPWR circuit to fuel pump relay. If test light and DVOM status do not change and Continuous Memory Code 87/556 is set again, replace fuel pump relay. If only FP voltage goes low, fault is in FP circuit or ECA. To diagnose FP circuit and ECA, connect DVOM between breakout box test pin No. 1 and 22. If voltage goes low as symptom occurs, replace ECA. If voltage stays high as symptom occurs, fault is in FP circuit. For fuel pump secondary circuit Codes 95/542 and 96/543, circuits BATT (+), POWER-TO-PUMP and FPM can be diagnosed using same procedure. Drive vehicle and attempt to induce symptom. Information provided by vehicle operator may help when trying to recreate symptom. When symptom occurs, assistant should observe and record changes in voltage signals. Information about symptom and operating condition value of voltage signal and any other information available should be recorded for analysis. If unable to duplicate symptom during road test, verify EEC-IV values are within acceptable range. After test is completed, analyze results to locate and repair fault causing symptom. If problem cannot be identified, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section for other possible causes of symptom.

Perform this test when instructed by QUICK TEST. To prevent replacement of good components, be aware following non-EEC related areas may be at fault

1. Damaged vacuum hoses.
2. Damaged Backpressure Transducer (BPT).
3. EGR valve.
4. EVP sensor.

This test is only intended to diagnose

1. EVR solenoid.
2. ECA.
3. EVR and VPWR harness circuits.

EVR solenoid regulate vacuum to EGR valve by way of Backpressure Transducer (BPT). When energized, EVR opens a port between manifold vacuum and EGR valve. When not energized, EVR closes port to EGR and vacuum is vented to atmosphere.

Scheme 33

1. Code 558 Code 558 indicates failure in EVR solenoid circuit. Possible causes for this fault are: Faulty EVR solenoid. Faulty vacuum hoses. Open or ground circuit in wiring harness. Faulty ECA. Turn ignition off. Remove scan tester (if applicable). Disconnect cruise control servo wiring harness connector. Connect DVOM negative lead to STO terminal at Self-Test connector. Connect positive lead to positive battery terminal. Install a jumper wire between STI terminal and SIG RTN terminal at Self-Test connector. (Scheme 15)in CIRCUIT TEST B. Perform KOEO SELF-TEST until continuous memory test is complete. DVOM will read less than 1.0 volt when test is complete to indicate ECA has entered OUTPUT STATE CHECK. Depress and release throttle. If voltage does not increase, fully apply throttle and release. If STO voltage remains low, go to «CIRCUIT TEST QC»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l). If voltage increases, remain in OUTPUT STATE CHECK and go to next step.
2. Check EVR Solenoid Electrical Turn ignition off. Disconnect EVR solenoid wiring harness connector. Connect DVOM positive lead to VPWR terminal and negative test lead to EVR terminal at EVR solenoid wiring harness connector. Depress and release throttle 3-5 times to cycle solenoid output. If EVR solenoid voltage output change is 0.5 volt or more, go to next step. If EVR solenoid voltage output change is less than 0.5 volt, go to step 5).
3. Check EVR Solenoid Vacuum Turn ignition on. Disconnect EVR solenoid vacuum hoses. Install vacuum pump on EVR solenoid vacuum source port. Install vacuum gauge on solenoid output port. Apply 6 in. Hg, and hold. Depress and release throttle 3-5 times to cycle solenoid output. Turn ignition off. If vacuum gauge shows vacuum cycling at output port, go to next step. If vacuum gauge does not show vacuum cycling at output port, replace EVR solenoid and repeat QUICK TEST.
4. Check EVR Vacuum Hoses Remove jumper wire, vacuum pump and gauge. Remove vacuum hoses individually. Plug one end of hose. Connect vacuum pump at opposite end. Apply vacuum and observe gauge. If vacuum is not held, replace hose and repeat QUICK TEST. If vacuum is held, ensure vacuum port between BPT and EGR is not restricted. If vacuum port is clear, go to next step.
5. Check EVR Solenoid VPWR Turn ignition off. Disconnect EVR solenoid wiring harness connector. Turn ignition on. Measure voltage between VPWR at EVR solenoid wiring harness connector and negative battery terminal. If voltage is 10.5 volts or more, go to next step. If voltage is less than 10.5 volts, repair open VPWR circuit and repeat QUICK TEST.
6. Check EVR Solenoid Circuit Continuity Turn ignition off. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between EVR terminal at EVR solenoid wiring harness connector and test pin No. 31. If reading is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST.
7. Check EVR Solenoid Circuit For Short Turn ignition off. Measure resistance between test pin No. 31 and test pins No. 37 and 57 at breakout box. If each resistance is 10,000 ohms or more, replace ECA and repeat QUICK TEST. If reading is less than 10,000 ohms, repair short circuit and repeat QUICK TEST.

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

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

Scheme 34

CIRCUIT TEST KD TEST PIN WIRE COLOR ID

1. Check System Function Use only VOM or DVOM for this step. DO NOT use scan tester. Turn ignition off. Disconnect cruise control servo wiring harness connector. Connect DVOM negative lead to STO terminal at self-test connector. Connect positive lead to positive battery terminal. Install a jumper wire between STI terminal and SIG RTN terminal at self-test connector. (Scheme 15)in CIRCUIT TEST B. Perform KOEO SELF-TEST until continuous memory test is complete. DVOM will read less than one volt when test is complete to indicate ECA has entered OUTPUT STATE CHECK. Depress and release throttle. If voltage increases, remain in OUTPUT STATE CHECK and go to next step. If voltage does not increase, apply full throttle and release. If STO voltage does not increase, leave test equipment hooked up and go to «CIRCUIT TEST QC»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l).
2. Check CANP Solenoid Electrical Function Turn ignition on. Disconnect CANP solenoid. Connect DVOM positive test lead to VPWR terminal and negative test lead to CANP terminal at solenoid wiring harness connector. While observing DVOM, depress and release throttle several times to cycle output on and off. If CANP circuit voltage does not cycle 0.5 volt or more, remove jumper wire and go to step 6. If CANP circuit voltage cycles, remain in OUTPUT STATE CHECK and go to next step.
3. Check Solenoid For Vacuum Leaks Turn ignition on. Leave CANP solenoid disconnected. Disconnect vacuum hose at CANP solenoid from manifold vacuum side of solenoid. Apply 16 in. Hg vacuum to manifold vacuum side of CANP solenoid. If CANP solenoid does not hold vacuum for 20 seconds, replace solenoid and repeat QUICK TEST. If fault is still present, service fuel evaporation canister or hoses. If CANP holds vacuum for 20 seconds, remain in OUTPUT STATE CHECK, leave vacuum pump attached and go to next step.
4. Check Solenoid Mechanical Operation Connect CANP solenoid connector. Apply 16 in. Hg vacuum to manifold vacuum side of CANP solenoid. Depress and release throttle. If vacuum is released, check hose from CANP solenoid to canister for leaks and cracks. If hose is okay, remove jumper wire from STI to SIG RTN and go to next step. If vacuum is not released, check hose from CANP solenoid to canister for leaks and cracks. If hose is okay, replace CANP solenoid and repeat QUICK TEST.
5. Check Vacuum Supply To CANP Solenoid Disconnect vacuum hose from CANP solenoid on manifold vacuum (PCV) side. Start engine. If vacuum is present at vacuum hose, EEC system is okay. Check evaporative canister. If vacuum is not present at hose, check vacuum hose for improper routing, kinks and blockage. If hose is okay, check engine for cause of low vacuum.
6. Code 85/565 Or 569: Check CANP Solenoid Resistance Code85/565 or 569 indicates fault in CANP solenoid circuit. For vehicles with dual CANP systems, Code 565 refers to CANP 1; Code 569 refers to CANP 2. Possible causes for this fault are: Faulty CANP solenoid. Open in wiring harness circuit. Shorted wiring harness circuit. Faulty ECA. Turn ignition off. Set DVOM on 200-ohm scale. Disconnect CANP solenoid connector. Measure CANP solenoid resistance. If resistance is 40-90 ohms, go to next step. If resistance is not 40-90 ohms, replace CANP solenoid and repeat QUICK TEST.
7. Check Voltage Of VPWR Circuit With CANP solenoid disconnected, turn ignition on. Measure voltage between VPWR terminal at CANP solenoid harness connector and negative battery terminal. If resistance is 10.5 volts or more, go to next step. If resistance is less than 10.5 volts, repair open circuit and repeat QUICK TEST.
8. Check Continuity Of CANP Circuit Turn ignition off. Disconnect CANP solenoid. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pin No. 31 and CANP terminal at solenoid wiring harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST.
9. Check CANP Circuit For Short To Ground Turn ignition off. With CANP solenoid disconnected, measure resistance between test pin No. 31 and pins No. 40, 46 and 60 at breakout box. If all resistances are 10,000 ohms or more, go to next step. If any resistance is less than 10,000 ohms, repair short to ground and repeat QUICK TEST.
10. Check CANP Circuit For Short To Power Turn ignition off. With CANP solenoid disconnected, measure resistance between test pin No. 31 and test pins No. 37 and 57 at breakout box. If all resistances are 10,000 ohms or more, replace ECA and repeat QUICK TEST. If any resistance is less than 10,000 ohms, repair circuit short to power and repeat QUICK TEST. If code is repeated, replace ECA and repeat QUICK TEST.

Perform this test when instructed by QUICK TEST or if 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 terminals intended to diagnose

1. RPM during SELF-TEST mode.
2. ISC solenoid.
3. Wiring harness circuits (ISC and VPWR).
4. ECA.

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

1. Engine temperature under or over correct operating range.
2. A/C input (electrical problem).
3. Incorrect idle speed or throttle stop adjustment.
4. Faulty cruise control linkage.

Scheme 35

CIRCUIT TEST KE TEST PIN WIRE COLOR ID

Scheme 36

1. 1) Code 12/412 Or 16 Code 12/412 indicates engine RPM could not be controlled within upper RPM limit during KOER SELF-TEST. Code 16 indicates engine RPM was too low to perform HEGO test during KOER SELF-TEST. Possible causes for this fault are: Open or shorted circuit. Sticking or binding throttle linkage. Incorrect idle airflow setting. Throttle body or ISC solenoid contaminated. Faulty ISC solenoid. Faulty ECA. Mechanical faults unrelated to EEC-IV which could affect RPM. Turn ignition off. Connect tachometer to engine. Start engine. Disconnect Idle Speed Control (ISC) harness. If RPM drops or engine stalls, go to next step. If RPM does not drop or engine does not stall, go to step 3).
2. 2) Check For EGR Codes If EGR service Code 31/327, 32/326/328, 33/332, 34/336/334 or 213 is displayed, reconnect ISC solenoid. Go to appropriate KOER SELF-TEST. See «SERVICE CODE REFERENCE CHARTS»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l). If these codes are not displayed, go to next step.
3. 3) Check For Other EEC-IV Codes If Code 22/126, 41/172, 42/173, 91/136 or 92/137 is displayed, reconnect ISC solenoid. Go to appropriate KOER SELF-TEST. See «SERVICE CODE REFERENCE CHARTS»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l). If these codes are not displayed, go to next step.
4. 4) Measure ISC Solenoid Resistance Turn ignition off. Disconnect ISC solenoid. Connect DVOM positive lead to VPWR terminal and negative lead to ISC terminal. (Scheme 36) Measure resistance of ISC solenoid. If resistance is not 6-13 ohms, replace ISC solenoid and repeat QUICK TEST. If resistance is 6-13 ohms, go to next step.
5. 5) Check For Internal Short To ISC Solenoid Case Turn ignition off. With ISC solenoid disconnected, measure resistance from either ISC terminal pin to ISC solenoid housing. If resistance is more than 10,000 ohms, go to next step. If resistance is 10,000 ohms or less, replace ISC solenoid. Repeat QUICK TEST.
6. 6) Check VPWR Circuit Voltage Leave ISC harness disconnected. Turn ignition on. Measure voltage between VPWR terminal at ISC harness connector and battery ground terminal. If voltage is 10.5 volts or more, go to next step. If voltage is less than 10.5 volts, repair open in circuit and repeat QUICK TEST.
7. 7) Check ISC Circuit Continuity Turn ignition off. Leave ISC solenoid disconnected. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pin No. 21 and ISC terminal at ISC wiring harness connector. If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, repair open circuit and repeat QUICK TEST.
8. 8) Check ISC Circuit For Short To Ground Turn ignition off. Leave ISC solenoid disconnected. Measure resistance between test pin No. 21 and test pins No. 40, 46 and 60. If any resistance is less than 10,000 ohms, repair short to ground and repeat QUICK TEST. If all resistances are 10,000 ohms or more, go to next step.
9. 9) Check ISC Circuit For Short To Power Turn ignition on. Measure voltage between breakout box test pin No. 21 and chassis ground. If voltage is more than 1.0 volt, repair short circuit. Reconnect all components, and repeat QUICK TEST. If code or symptom is still present, replace ECA. If voltage is 1.0 volt or less, go to next step.
10. 10) Check ISC Signal From ECA Turn ignition off. Reconnect ISC solenoid. Connect ECA to breakout box. Set DVOM on 20-volt scale. Connect DVOM between test pins No. 21 and 40 at breakout box. Start engine. Observe DVOM while slowly increasing engine speed to 3000 RPM. If DVOM voltage reading is 3.0-11.5 volts, go to next step. If DVOM voltage reading is not 3.0-11.5 volts, remove ISC solenoid to confirm that it is not open. If ISC is okay, replace ECA and repeat QUICK TEST.
11. 11) Check Base Idle Verify base idle speed is correct. See ADJUSTMENTS article in the ENGINE PERFORMANCE Section. If base idle speed is within specification, remove ISC solenoid and inspect for contamination. Repair or replace as necessary. Repeat QUICK TEST. If code or symptom is still present, replace ISC solenoid. If base idle speed is not correct, reset idle speed to specification. Repeat QUICK TEST. If unable to set idle to specification, go to step 12).
12. 12) Check For Faults Affecting Idle Speed Check following mechanical items for faults: Throttle linkage and/or cruise control linkage (sticking or binding). Throttle body (contamination). Vacuum hoses. Check Vehicle Emission Control Information (VECI). Check for leaks around ISC solenoid (gaskets, etc.). If all of these items are okay, remove ISC solenoid and inspect for contamination. Repair or replace as necessary. Repeat QUICK TEST. If code or symptom is still present, replace ISC solenoid. If any of these items are faulty, service as necessary. Remove breakout box. Reconnect components, and repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 12) to step 15). No test procedures have been omitted.
13. 15) Code 13/411 Code 13/411 indicates engine RPM could not be controlled within lower RPM limit during KOER SELF-TEST. Possible causes for this fault are: Incorrect idle airflow setting. Vacuum leaks. Sticking or binding throttle linkage. Throttle plates open. Incorrect ignition timing (TFI ignition only). Throttle body or ISC solenoid contamination. ISC circuit shorted to ground. Faulty ISC solenoid. If above items are okay and idle is set to specification, remove ISC solenoid and inspect for contamination. Repair or replace as necessary. Repeat QUICK TEST. If code or symptom is present, replace ISC solenoid. If idle speed is not set to specification, reset and repeat QUICK TEST. If idle speed cannot be set to specification, go to next step.
14. 16) Check For Conditions Affecting Idle Speed Check following mechanical components: Vacuum hoses. Check Vehicle Emission Control Information (VECI). Throttle linkage and/or cruise control linkage (sticking or binding). Induction system (vacuum leaks). Throttle body (contamination). Ensure throttle plates are fully closed. Ensure CANP solenoid is not stuck open. Ensure base ignition timing is to specification on emission decal (TFI vehicles only). If above items are okay, go to next step. If fault is found, service as necessary and repeat QUICK TEST.
15. 17) Check For Internal Short To ISC Solenoid Case With ignition off and ISC solenoid disconnected, set DVOM on 200-k/ohm scale. Measure resistance from either ISC terminal pin to ISC solenoid housing. If resistance is more than 10,000 ohms, go to next step. If resistance is 10,000 ohms or less, replace ISC solenoid. Repeat QUICK TEST.
16. 18) Check ISC Circuit For Short To Ground Turn ignition off. Leave ISC solenoid disconnected. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box(T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pin No. 21 and test pins No. 40, 46 and 60. If any resistance is less than 10,000 ohms, repair short to ground. Reconnect components, and repeat QUICK TEST. If all resistances are 10,000 ohms or more, go to next step.
17. 19) Check ISC Signal From ECA Turn ignition off. Connect ECA to breakout box. Reconnect ISC solenoid. Set DVOM on 20-volt scale. Connect DVOM between test pins No. 21 and 40. Start engine. Observe DVOM while slowly increasing and decreasing engine RPM. If voltage is 3.0-11.5 volts, remove ISC solenoid and inspect for contamination. Repair or replace as necessary, and repeat QUICK TEST. If code or symptom is still present, replace ISC solenoid. If voltage is not 3.0-11.5 volts, replace ECA and repeat QUICK TEST.

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

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

This test is only intended to diagnose

1. Wiring harness circuits (WAC, VPWR, GND, POWER-TO-CLUTCH and ACD).
2. WAC relay.
3. A/C fan controller.
4. ECA.

Scheme 37

CIRCUIT TEST KM TEST PIN WIRE COLOR ID

1. 1) No A/C: Check For Voltage At A/C Clutch Check all A/C-related fuses in fuse panel before proceeding with this test. Turn ignition off. Disconnect A/C clutch wiring harness connector. Turn A/C switch to A/C position. Start engine, and wait 10 seconds. Measure voltage between power side of A/C clutch wiring harness connector and negative battery terminal. If voltage is 10.5 volts or more, EEC-IV system is okay. Check A/C system. If voltage is less than 10.5 volts, go to next step.
2. 2) Check Continuity Of POWER-TO-CLUTCH Circuit Turn ignition off. Disconnect A/C clutch and WAC relay wiring harness connectors. Measure resistance between power side of A/C clutch wiring harness connector and POWER-TO-CLUTCH terminal at WAC relay wiring harness connector. If resistance is 5 ohms or less, reconnect A/C clutch and go to next step. If resistance is more than 5 ohms, repair open circuit and retest system.
3. 3) Check For Power On A/C Demand Circuit Turn ignition on. Turn A/C switch on. Set DVOM to 20-volt scale. Measure voltage between A/C demand input terminal at WAC relay wiring harness connector and chassis ground. If voltage is 10.5 volts or more, go to step 5). If voltage is less than 10.5 volts, verify operation of A/C clutch cycling pressure switch and A/C demand switch. If components are okay, repair open circuit and reconnect all components. Recheck system.
4. 4) Check Continuity Between WAC Relay & A/C Relay Turn ignition off. Disconnect WAC and A/C relays. Set DVOM on 200-ohm scale.Measure resistance between A/C relay output to WAC relay circuit at A/C relay wiring harness connector and A/C relay input at WAC relay wiring harness connector. If resistance is less than 5 ohms, reconnect WAC relay and check A/C system. If resistance is 5 ohms or more, repair open circuit. Connect relays, and check system operation.
5. 5) Check WAC Circuit For Short To Ground Turn ignition off. Disconnect 60-pin ECA connector. Disconnect WAC relay. Inspect wiring, and repair if damaged. Measure resistance between WAC terminal at WAC relay and chassis ground. If resistance is less than 10,000 ohms, repair short and recheck system operation. If resistance is 10,000 ohms or more, go to next step.
6. 6) Check For Voltage At ACCS Input To ECA Turn ignition off. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Set A/C switch to A/C position. Turn ignition on. Measure voltage between test pins No. 10 and 40 at breakout box. If voltage is 10.5 volts or less, repair open circuit. Connect all components, and check system operation. If voltage is more than 10.5 volts, go to next step.
7. 7) Check WAC Relay Turn ignition off. Connect WAC relay, leaving A/C clutch disconnected. Turn ignition on. Set A/C switch to A/C position. Measure voltage between power side of A/C clutch wiring harness connector and negative battery terminal. If voltage is 10.5 volts or more, replace ECA. If voltage is less than 10.5 volts, replace WAC relay. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 7) to step 15). No test procedures have been omitted.
8. 15) No A/C Output At WOT: Enter Output State Check Use only VOM or DVOM for this step. DO NOT use scan tester. Turn ignition off. Disconnect cruise control servo wiring harness connector. Connect DVOM negative lead to STO terminal at self-test connector. Connect positive lead to positive battery terminal. Install a jumper wire between STI terminal and SIG RTN terminal at self-test connector. (Scheme 43)in CIRCUIT TEST QA. Perform KOEO SELF-TEST until continuous memory test is complete. DVOM will read less than 1.0 volt when test is complete to indicate ECA has entered OUTPUT STATE CHECK. Depress and release throttle. If voltage increases to 10.5 volts or more, remain in OUTPUT STATE CHECK and go to next step. If voltage does not increase to 10.5 volts, depress throttle to WOT and release. If STO voltage does not go high, leave test equipment connected and go to «CIRCUIT TEST QC»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l), step 2).
9. 16) Check For VPWR To Relay With vehicle in OUTPUT STATE CHECK, disconnect wiring harness from WAC relay. Measure voltage between VPWR circuit at WAC relay wiring harness connector and chassis ground. If voltage is less than 10.5 volts, repair open in VPWR circuit between EEC power relay and WAC relay. Remove test equipment, and retest system. If voltage is 10.5 volts or more, go to next step.
10. 17) Check WAC System For Cycling Leave vehicle in OUTPUT STATE CHECK. Disconnect WAC relay wiring harness connector. Connect DVOM positive test lead to VPWR circuit and connect negative test lead to WAC circuit at WAC relay wiring harness connector. Check DVOM while depressing and releasing throttle several times to cycle output on and off. If voltage cycles from high to low, replace WAC relay. If voltage does not cycle, remove test leads. Reconnect speed control servo, and go to next step.
11. 18) Check Continuity Of WAC Circuit Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pin No. 54 and WAC terminal at WAC relay wiring harness connector. If resistance is 5 ohms or more, repair open circuit. Reconnect all components, and retest system. If resistance is less than 5 ohms, go to next step.
12. 19) Check WAC Circuit For Short To Power Turn ignition off. Leave ECA and WAC relay disconnected. Turn ignition on. Measure voltage between test pin No. 54 and chassis ground. If voltage is 1.0 volt or less, replace ECA and retest system. If voltage is more than 1.0 volt, repair short circuit. If symptom is still present, replace ECA. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 19) to step 30). No test procedures have been omitted.
13. 30) Cycle A/C Demand Switch Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Connect DVOM negative test lead to test pin No. 40 and positive test lead to test pin No. 43. Turn ignition on. Cycle A/C switch. If voltage goes high and low as switch is cycled, go to step 43). If voltage does not cycle, go to next step.
14. 31) Check Continuity Of A/C Demand (ACD) Circuit Turn ignition off. Measure resistance between test pin No. 43 at breakout box and A/C Demand switch. If resistance is more than 5 ohms, repair open in ACD circuit and repeat QUICK TEST. If resistance is 5 ohms or less, EEC-IV system is okay. Remove breakout box, and reconnect components. Fault is in A/C system. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 31) to step 35). No test procedures have been omitted.
15. 35) Check A/C Demand Circuit For Short To Power Turn ignition off. Disconnect WAC relay. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. With A/C Demand switch in OFF position, turn ignition on. Measure voltage between chassis ground and test pin No. 43 at breakout box. If voltage is 1.0 volt or less, EEC-IV system is okay. Fault is in A/C system. If voltage is more than 1.0 volt, check operation of A/C Demand switch. If switch operation is okay, repair short circuit and retest system. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 35) to step 40). No test procedures have been omitted. Diagnostic Aids Before entering this test, ensure A/C selector is in OFF position and shift selector is in PARK position (AXOD-E and E4OD vehicles). If A/C was on, repeat QUICK TEST. If Code 67 or 79/539 is present, continue with this test.
16. 40) Check A/C Input Code 79/539 indicates ACCS input to ECA was high during SELF-TEST. Code 67 indicates Neutral Drive Switch (NDS) or ACCS circuit voltage was high during SELF-TEST. Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Set DVOM to 20-volt scale. Turn ignition on. Measure voltage between test pin No. 10 at breakout box and chassis ground. If voltage is 1.0 volt or more, repair short to power in A/C circuit and repeat QUICK TEST. If voltage is less than 1.0 volt, go to next step for vehicles with 2-digit codes and E4OD transmission. On all other vehicles, replace ECA and repeat QUICK TEST.
17. 41) Check For Short To Power In ECA Turn ignition off. Disconnect A/C clutch connector. Set DVOM to 20-volt scale. Turn ignition on. Measure voltage between test pins No. 10 and 40 at breakout box. If voltage is 5 volts or more, replace ECA and repeat QUICK TEST. If voltage is less than 5 volts, go to «CIRCUIT TEST TD»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l). Diagnostic Aids A low idle with A/C on may be caused by ECA not receiving or recognizing A/C input from pin No. 10
18. 42) 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 causes of low idle. If Codes 67 and 79/539 are not present, go to next step.
19. 43) Check A/C Input Circuit Turn ignition off. Install breakout box, leaving ECA disconnected. Set DVOM to 20-volt scale. Turn A/C on. Turn ignition on. Measure voltage between test pins No. 10 and 40. If voltage is 10.5 volts or more, replace ECA and repeat QUICK TEST. If voltage is less than 10.5 volts, repair open A/C circuit. Remove breakout box, reconnect all components and repeat QUICK TEST.

Enter this test when directed by QUICK TEST. This test is only intended to diagnose

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

Purpose of Octane Adjust Shorting Bar is to provide optimum spark advance for fuel used. If engine detonates (spark knock), remove Octane Shorting Bar. This retards spark advance about 3-4 degrees. If engine continues to detonate, use fuel with a higher octane rating.

Scheme 38

CIRCUIT TEST KP TEST PIN WIRE COLOR ID

1. Code 57/341 Code 57/431 indicates Octane Adjust Shorting Bar is not in place or OCT ADJ circuit is open. Turn ignition off. Inspect Octane Adjust in-line connector. If shorting bar has been removed, go to next step. If shorting bar is in place, go to step 4 .
2. Check For Modification Decal If vehicle has modification decal indicating OCT ADJ shorting bar was removed as a factory authorized procedure, testing is complete. If engine is detonating, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section. If vehicle does not have modification decal, go to next step.
3. Check For Code 57/341 Replace OCT ADJ shorting bar. Perform KOEO SELF-TEST. If Code 57/341 is present, go to next step. If code is not present, testing is complete. If driveability faults are present, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section.
4. Check Octane Adjust Circuit Continuity Continuity should exist from OCT ADJ circuit, through in-line connector and shorting bar, to SIG RTN circuit. Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pin No. 46 and OCT ADJ test pin at breakout box. If resistance is more than 5 ohms, repair open OCT ADJ circuit, shorting bar or SIG RTN circuit. Repeat QUICK TEST. If resistance is 5 ohms or less, replace ECA and repeat QUICK TEST.
5. Check For Code 11 Start engine. Warm it to normal operating temperature. Turn ignition off. Perform KOEO SELF-TEST. If Code 11 or 111 is present, go to next step. If Code 11 or 111 is not present, use higher octane fuel or check for other possible causes for Code 57/341. For all other codes, return to QUICK TEST.
6. Verify In-Line Shorting Bar Is Installed Turn ignition off. Inspect Octane Adjust in-line connector. If shorting bar is installed, go to step 8 . If shorting bar is not installed, go to next step.
7. Check For Modification Decal If vehicle has modification decal indicating OCT ADJ shorting bar was removed as a factory authorized procedure, testing is complete. If engine is detonating, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section. If vehicle does not have modification decal, go to step 10 .
8. Check For Technical Service Bulletin (TSB) If a TSB authorizing removal of OCT ADJ shorting bar exists, go to next step. If a TSB authorizing removal of OCT ADJ shorting bar does not exist, testing is complete. If driveability faults are present, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section.
9. Verify Drive Concern Turn ignition off. Locate and remove shorting bar. Test drive vehicle to verify complaint. If detonation is present, go to next step. If detonation is not present, EEC-IV is okay; testing is complete.
10. Check Octane Adjust Circuit For Short To Ground Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between OCT ADJ circuit at in-line connector and test pins No. 40 and 60 at breakout box. If resistance is 10,000 ohms or less, repair short circuit and repeat QUICK TEST. If each resistance is more than 10,000 ohms, go to next step.
11. Check ECA Turn ignition off. Disconnect OCT ADJ shorting bar. Turn ignition on. Measure voltage between breakout box OCT ADJ test pin terminal and test pins No. 40 and 60. If voltage is less than 4 volts, replace ECA. If engine still detonates, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section. If voltage is 4 volts or more, remove breakout box and go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section.

Perform this test only when directed by QUICK TEST. To prevent replacing good components, be aware following non-EEC related areas may be cause of problem

1. Technician 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 only intended to diagnose

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

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

1. Code 77/538 Displayed: System Failed To Recognize WOT Test Repeat KOER SELF-TEST as follows: Activate SELF-TEST. Start engine. Observe ID Code start of test. Observe Dynamic Response Code 1 (Code 0 with STAR tester). Perform brief WOT. Testing is complete; service code output begins. Ensure vehicle speed reached 2000 RPM during WOT. If Code 77/538 is present, replace ECA. If Code 77/538 is not present, vehicle has passed dynamic response test. Service other codes if necessary.

Perform this test only when instructed by QUICK TEST or if directed by CIRCUIT TEST QA. This circuit test does not apply to vehicles with electronic instrument cluster. To prevent replacing good components, be aware that fuse, bulb or bulb socket may be cause of problem. This test is only intended to diagnose

1. STO/MIL circuit.
2. ECA.

Scheme 39

CIRCUIT TEST ML TEST PIN WIRE COLOR ID

1. 1) Malfunction Indicator Light (MIL) Always On If vehicle will not start, go to «CIRCUIT TEST AC»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l__circuit-test-ac-no-start) Service all KOEO and Continuous Memory Codes before proceeding with this test. Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pins No. 17 and 40 at breakout box. If resistance is more than 5 ohms, replace ECA and repeat QUICK TEST. If resistance is 5 ohms or less, repair short between test pin No. 17 and self-test connector or between test pin No. 17 and MIL light. Reconnect all components, and repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 1) to step 4). No test procedures have been omitted.
2. 4) Malfunction Indicator Light (MIL) Does Not Light If vehicle will not start, go to step 1) . Turn ignition on. Measure voltage between negative battery terminal to ground side of MIL fuse. If voltage is more than 10.5 volts, go to step 6) . If voltage is 10.5 volts or less, go to next step.
3. 5) Check For Voltage At Fuse Turn ignition on. Measure voltage from negative battery terminal to power side of MIL fuse. If voltage is more than 10.5 volts, replace fuse. Verify repair by turning ignition switch to RUN position. If voltage is 10.5 volts or less, repair open MIL/VBAT circuit. Verify repair by turning ignition switch to RUN position.
4. 6) Check Voltage At VBAT Circuit Turn ignition on. Measure voltage between VBAT side of MIL bulb and negative battery terminal. If voltage is 10.5 volts or less, repair open in MIL circuit between fuse and bulb. Verify repair by turning ignition switch to RUN position. If voltage is more than 10.5 volts, go to next step.
5. 7) Check MIL Bulb Response To Grounding Turn ignition off. Attach jumper wire between ground side of MIL bulb socket and chassis ground. Turn ignition on. 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 on to verify correct MIL operation.
6. 8) Check Continuity Of MIL Circuit Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pin No. 17 at breakout box and MIL terminal at wiring harness connector. If resistance is less than 5 ohms, replace ECA. If resistance is 5 ohms or more, repair open MIL circuit. Turn ignition on to verify correct MIL operation. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 8) to step 10). No test procedures have been omitted.
7. 10) MIL On Intermittently, Check For Intermittent Short From STO To Ground If vehicle does not start, go to step 1) . Light comes on when a fault code is present. Service all fault codes before proceeding. If no codes are output, proceed with this test. Enter KOEO wiggle test. See «CONTINUOUS MONITOR MODE (WIGGLE TEST)»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l__continuous-monitor-mode-wiggle-test) under QUICK TEST. Check DVOM for indication of fault while performing wiggle test on harness in following areas: From self-test connector to dash panel. Dash panel to ECA. Dash panel to Malfunction Indicator Light (MIL). If a fault is indicated, repair as necessary and repeat QUICK TEST. If a fault is not indicated, fault cannot be duplicated at this time. Testing is complete. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 10) to step 15). No test procedures have been omitted.
8. 15) MIL Flashes With Erratic Idle Symptoms indicate STI is grounded and ECA is performing self-test without tester installed. Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between STI connector and engine block ground. If resistance is 10,000 ohms or less, repair short circuit. Reconnect ECA, and turn ignition on to verify correct MIL operation. If resistance is more than 10,000 ohms, MIL circuit is okay. Verify symptom, and test for other rough idle symptoms. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 15) to step 20). No test procedures have been omitted.
9. 20) CHECK ENGINE Message Displayed If vehicle will not start, go to step 1) . Perform KOEO SELF-TEST. If result is Code 11-10-11 or Code 111-10-111 (pass code), fault is in instrument cluster. If pass code is not displayed, service codes as necessary. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 20) to step 25). No test procedures have been omitted.
10. 25) Continuous Memory Code 529 Or 533: CHECK ENGINE Or CHECK DCL Message Displayed Codes 529 and 533 indicate circuit fault has occurred on Data Communications Link (DCL). These codes can occur alone or with another code. Fault will occur under following conditions: Code 529 indicates ECA or Data Communicator Link (DCL) circuit failure. Code 533 indicates Data Communication Link to Electronic Instrument Cluster circuit failure. If vehicle does not start, go to step 1). If vehicle starts, clear continuous memory codes. Wait 5 minutes, and repeat KOEO SELF-TEST. If result is pass code (Code 11-10-11 or 111-10-111), fault is in instrument cluster. If pass code is not displayed, service codes as necessary.

Perform this test when directed by QUICK TEST. This test is only intended to diagnose EEC-IV portion of ignition system. For additional information on ignition system and component testing, see I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. To prevent replacing good components, be aware following non-EEC related areas may be at fault

1. EDIS ignition module.
2. EDIS coil packs.
3. Spark plugs and/or wires.
4. Variable reluctance sensor.
5. Secondary ignition short to ground.

This test is intended to diagnose

1. IDM and SAW harness circuits.
2. ECA assembly.

Scheme 40

1. Continuous Memory Code 211: Erratic Ignition Code 211 indicates 2 successive erratic Profile Ignition Pick-Up (PIP) pulses occurred. Possible causes for this fault are: Loose wires or connectors. Secondary ignition short to ground. On-board transmitter equipment (2-way radio). Repair any problems found as necessary. Clear codes, and repeat QUICK TEST. If problem is not found, go to step 4).
2. Code 226: IDM Circuit Failure Code 226 indicates ECA did not receive IDM signal from EDIS module in KOEO SELF-TEST. Possible causes for this problem are: Open or short in IDM or IGN GND circuit wiring harness. Faulty EDIS module. If engine does not start, go to IGNITION SYSTEMS in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. If engine starts, go to step 4 .
3. Continuous Memory Code 212: Check For Other Codes Code 212 indicates loss of IDM input signal to ECA. Possible causes for this fault are: Open or short circuit in wiring harness. Faulty EDIS module. Faulty ECA. If Continuous Memory Code 215, 216 or 217 is also present, go to IGNITION SYSTEMS in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. If Code 215, 216 or 217 is not also present, go to next step.
4. Continuous Memory Code 212: Check IDM Circuit Continuity Turn ignition off. Disconnect EDIS module. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pin No. 4 at breakout box and pin No. 2 at EDIS module wiring harness connector. If resistance is 5 ohms or more, repair open circuit. Clear codes, and repeat QUICK TEST. If resistance is less than 5 ohms, go to next step.
5. Check IDM Circuit For Short To Power (Except VREF) Turn ignition off. Ensure ECA and EDIS module are disconnected. Monitor circuit voltage by connecting DVOM between test pin No. 4 and test pins No. 40 and 60. To check VBAT circuit, turn ignition off. To check VPWR circuit, turn ignition on. If either voltage reading is more than 10.5 volts, repair short circuit and repeat QUICK TEST. If voltage is 10.5 volts or less, go to next step.
6. Check IDM Circuit For Short To VREF & PIP Turn ignition off. Ensure ECA and EDIS module are disconnected. To check for shorts to VREF, use DVOM to measure resistance between test pins No. 4 and 26 at breakout box. To test for shorts to PIP, measure resistance between test pins No. 4 and 56 at breakout box. If either resistance is 10,000 ohms or less, repair short circuit and repeat QUICK TEST. If each resistance is more than 10,000 ohms, go to next step. Diagnostic Aids 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 IDM Circuit For Short To Ground Turn ignition off. Ensure ECA and EDIS module are disconnected. Measure resistance between test pin No. 4 and test pins No. 40, 46 and 60 at breakout box. If any resistance is less than 10,000 ohms, repair short to ground in IDM circuit and repeat QUICK TEST. If all resistances are 10,000 ohms or more, go to next step.
8. Check EDIS Module Turn ignition off. Connect EDIS module to wiring harness connector. Connect ECA to breakout box. Start engine, and allow it to idle. Connect positive lead of DVOM to test pin No. 4 and negative lead to test pin No. 16. Observe DVOM for voltage surge (fault) while lightly tapping on ignition components to simulate road shock. Wiggle all EDIS harness connectors. If fault is not indicated, disconnect and inspect EDIS wiring harness connectors and terminals for damage. If connectors and terminals are okay, check ignition system. See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. If fault is indicated, leave DVOM connected to breakout box and go to next step.
9. Check EEC-IV Harness Ensure engine is idling at correct RPM. Wiggle, shake or bend small sections of harness, working from DIS connectors to firewall. Observe DVOM for indication of fault. Repeat process from firewall to ECA. If fault is indicated, isolate fault and repair wiring harness. Repeat QUICK TEST. If no fault is indicated, go to next step.
10. Check ECA & Harness Connectors Turn ignition off. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. If connector is damaged, repair as necessary and repeat QUICK TEST. If connector is okay, go to next step.
11. Check ECA For Short To Ground Turn ignition off. Disconnect EDIS module connector. Connect ECA to breakout box. Measure resistance between test pin No. 4 and test pins No. 16, 20, 40, 46 and 60. If each resistance is more than 10,000 ohms, check ignition system. See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. If any resistance is 10,000 ohms or less, replace ECA and repeat QUICK TEST.

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

1. SAW wiring harness circuit.
2. Base timing.
3. Faulty ECA.

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

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

Scheme 41

TEST PIN NO. 36 (SAW) WIRE COLOR ID

Scheme 42

1. Check For Power To ECA Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Turn ignition on. Measure voltage between test pins No. 37 and 40 at breakout box. Measure voltage between test pins No. 57 and 60 at breakout box. If both readings are 10.5 volts or more, go to next step. If either reading is less than 10.5 volts, go to «CIRCUIT TEST B»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l).
2. Check SAW Circuit For Continuity Turn ignition off. Disconnect EDIS module. Measure resistance between test pin No. 36 at breakout box and SAW terminal at EDIS module wiring harness connector. (Scheme 42) If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, repair open circuit. Reconnect all components, and check ignition timing.
3. Check SAW Circuit For Shorts To Power (Except VREF) Turn ignition off. Leave ECA and EDIS module disconnected. Measure voltage between test pin No. 36 and test pin No. 40 or 60 at breakout box. To check for short to VBAT, turn ignition off. To check for short to VPWR, turn ignition on. If any reading is more than 10.5 volts, repair short circuit and repeat QUICK TEST. If voltage is 10.5 volts or less, go to next step.
4. Check SAW Circuit For Shorts To VREF, Ground & PIP Turn ignition off. Leave ECA and EDIS module disconnected. To check for shorts to ground, measure resistance between test pin No. 36 and test pins No. 16, 20, 40, 46 and 60. To check for shorts to VREF, measure resistance between test pins No. 26 and 36. To check for shorts to PIP circuit, measure resistance between test pins No. 36 and 56. If each resistance is more than 10,000 ohms, go to next step. If resistance is 10,000 ohms or less, repair short circuit and repeat QUICK TEST. Diagnostic Aids During this test, a short to SIG RTN (pin No. 46) may be indicated along with an actual short to PWR GND when 4-wire HEGO is connected to vehicle wiring harness.
5. Check SAW Voltage At ECA Turn ignition off. Connect ECA to breakout box. Reconnect EDIS module. Place timing switch on breakout box in DIST position. Set DVOM on 20-volt AC scale. Start engine. Measure voltage between test pin No. 36 and negative battery terminal. If AC voltage is not 0.1-1.9 volts, replace ECA and repeat QUICK TEST. If AC voltage within specification, EEC-IV system is okay. Remove breakout box, reconnect ECA and check ignition system. See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.

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

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

Aftermarket 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 state and repeat QUICK TEST.

Scheme 43

CIRCUIT TEST QA TEST PIN WIRE COLOR ID

1. Check VREF Voltage At Self-Test Connector Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect ECA to breakout box. Set DVOM on 20-volt scale. Turn ignition on. Measure voltage between test pin No. 26 at breakout box and SIG RTN terminal at self-test connector. If reading is 4-6 volts, go to step 3). If reading is not 4-6 volts, go to next step.
2. Check SIG RTN Circuit Continuity Turn ignition off. Disconnect ECA from breakout box. Measure resistance between test pin No. 46 at breakout box and SIG RTN terminal at self-test connector. If resistance is less than 5 ohms, go to «CIRCUIT TEST C»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l). If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST.
3. Check STI Circuit Continuity Turn ignition off. Disconnect ECA from breakout box. Measure resistance between test pin No. 48 at breakout box and Self-Test Input (STI) terminal at pigtail connector. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST. If resistance is less than 5 ohms, go to next step.
4. Check STO Circuit Continuity Turn ignition off. Leave ECA disconnected from breakout box. Measure resistance between test pin No. 17 at breakout box and STO terminal at self-test connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST.
5. Check EGO Signal For Short To Power Turn ignition off. Leave ECA disconnected from breakout box. Measure voltage between test pin No. 40 or 60 and HEGO SIGNAL test pin No. 29 or 44 at breakout box. For HEGO circuit schematics (Scheme 28)in CIRCUIT TEST H. If voltage is more than 2 volts, go to next step. If voltage is 2 volts or less, go to step 7).
6. Isolate Short To Harness Or HEGO Sensor Turn ignition off. Leave ECA disconnected from breakout box. Disconnect right/rear HEGO sensor connector. Turn ignition on. Measure voltage between HEGO SIGNAL test pin No. 29 or 44 and test pin No. 40 or 60 at breakout box. If voltage is 2 volts or more, repair short to power in HEGO SIGNAL circuit. Reconnect all components, and repeat QUICK TEST. If voltage is less than 2 volts, replace right/rear HEGO sensor. Reconnect all components, and repeat QUICK TEST.
7. Check STO Circuit For Short To Ground Turn ignition off. Leave ECA disconnected from breakout box. Measure resistance between STO terminal at self-test connector and engine ground. If resistance is more than 5 ohms, go to next step. If resistance is 5 ohms or less, repair STO or MIL circuit for short to ground and repeat QUICK TEST.
8. Check If Power Relay Is Always On Turn ignition off. Leave ECA disconnected from breakout box. Connect DVOM between test pin No. 37 or 57 and pin No. 40 or 60 at breakout box. Turn ignition on and then off. Wait 10 seconds. If voltage does not change from 10.5 volts (or more) to less than 1.0 volt, go to next step. If voltage changes from 10.5 volts (or more) to less than 1.0 volt, go to step 10).
9. Check VPWR Circuit For Short To Power Turn ignition off. Leave ECA disconnected from breakout box. Disconnect EEC power relay. Connect DVOM to test pin No. 37 or 57 and test pin No. 40 or 46 at breakout box. If voltage is more than 1.0 volt, repair VPWR circuit short to power. Reconnect ECA, and repeat QUICK TEST. If voltage is 1.0 volt or less, replace EEC-IV power relay. Reconnect ECA, and repeat QUICK TEST.
10. Check Malfunction Indicator Light (MIL) Function If MIL is always on, go to «CIRCUIT TEST ML»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l), step 1). If MIL is always off, go to «CIRCUIT TEST ML»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l), step 4). If MIL is working normally, replace ECA and repeat QUICK TEST.

Perform this test when directed by QUICK TEST. This test is intended to diagnose

1. ECA.
2. KAPWR wiring harness circuits.

Scheme 44

TEST PIN NO. 1 (KAPWR) WIRE COLOR ID

1. Check KAPWR Circuit Voltage Code 15/512 indicates ECA power interruption in Keep-Alive Memory (KAM). Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure voltage between test pin No. 1 and pin No. 40 or 60 at breakout box. Observe voltage reading while wiggling, bending and shaking small sections of EEC-IV wiring harness from ECA to dash. If reading is less than 10.5 volts, repair open circuit and repeat QUICK TEST. If reading is 10.5 volts or more, go to next step. Diagnostic Aids Continuous Memory Code 15/512 may be displayed when power between ECA and KAPWR is interrupted. This code may be set when a breakout box is installed or battery is disconnected.
2. Inspect Engine Compartment Wire Routing Ensure EEC-IV wiring is not routed close to ignition components or secondary ignition wires. If necessary, 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. If Continuous Memory Code 15/512 is still present, replace ECA and repeat QUICK TEST.

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

1. ECA.
2. Throttle plate linkage.

1. Check For Codes 23, 53, 63, 121, 122 & 123 Disconnect cruise control servo wiring harness connector. Perform KOEO SELF-TEST. If Code 23, 53, 63, 121, 122 or 123 is present, go to appropriate CIRCUIT TEST. See «SERVICE CODE REFERENCE CHARTS»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) . Service code(s) as necessary. If pass code (11/111) is displayed, go to step 2). If no code is displayed, go to «CIRCUIT TEST QA»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) .
2. Check Throttle Linkage Check throttle and linkage for sticking and binding. If throttle and linkage are okay, replace Throttle Position Sensor (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 CIRCUIT TEST AC. This test is intended to diagnose

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

To prevent replacing good components, be aware 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. Engine mechanical components (cam timing, valves, etc.).

Scheme 45

1. ISC-BPA Check Try to start engine at part throttle. If engine starts and runs smoothly at part throttle, go to «CIRCUIT TEST KE»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l), step 4). If engine does not run as described, go to next step.
2. Check For RPM Drop Turn ignition off. Connect a tachometer to engine. Start engine. Disconnect ISC solenoid. If RPM drops or engine stalls, reconnect ISC solenoid and go to step 3). 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 to step 8. Test MAP/BP using Ford Motor Co. MAP/BP tester. Disconnect MAP/BP sensor. Turn ignition off. Connect MAP/BP tester between wiring harness and MAP/BP sensor. (Scheme 45) Connect banana plugs of tester into DVOM. 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.
4. MAP/BP Tester Output Reading Measure several known good MAP/BP sensors to obtain average voltage for location and date of testing. With MAP/BP tester and DVOM connected, turn ignition on. Measure MAP/BP voltage at MAP sensor. If voltage is in within specification for specific altitude, go to next step. See «MAP VOLTAGE OUTPUT»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l). If voltage is not within specification for specific altitude, replace MAP/BP sensor. MAP VOLTAGE OUTPUT Approximate Elevation (Ft.) Voltage Output (Volts) 0 1.59 1000 1.56 2000 1.53 3000 1.50 4000 1.47 5000 1.44 6000 1.41 7000 1.39
5. Check Vacuum Lines Check vacuum lines for correct routing.Refer to VECI decal. Check MAP sensor vacuum line for leaks and blockage. If vacuum lines are okay, go to next step. If vacuum lines are not okay, repair as necessary. Repeat QUICK TEST.
6. Check MAP Sensor Turn ignition off. Disconnect vacuum hose from manifold vacuum source. Install vacuum pump to MAP sensor hose. Apply 18 in. Hg vacuum to MAP sensor. If MAP sensor holds vacuum, release vacuum and remove vacuum pump. Reconnect vacuum hose to MAP sensor, and go to next step. If MAP sensor does not hold vacuum, replace MAP sensor or hose and repeat QUICK TEST.
7. Check Vacuum Manifold Source Turn ignition off. Disconnect MAP sensor vacuum hose from manifold vacuum source. Install vacuum gauge at manifold vacuum source. 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 repeat QUICK TEST.
8. Check EGR Vacuum If vehicle is not equipped with EGR system, go to «CIRCUIT TEST H»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l__circuit-test-h-fuel-control), step 2).
9. Check EGR Valve Inspect EGR valve for leaks. If valve is fully closed, go to «CIRCUIT TEST H»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l__circuit-test-h-fuel-control), step 2). If EGR valve is leaking or is not fully seated, repair or replace valve as necessary.

Perform this test only when directed by QUICK TEST. This test is intended to diagnose

1. Clutch Engage/Interlock Switch.
2. Neutral Drive/Gear Switch.
3. ECA.
4. Wiring harness circuits CES, CIS, NDS, NGS and SIG RTN.

Scheme 46

Scheme 47

CIRCUIT TEST TA TEST PIN WIRE COLOR ID

Scheme 48

1. 1) Code 67/522, 525, 527, 528 Or 634 System Identification Code67/522, 525, 527 or 528 is a result of voltage being high at either pin No. 10 (A/C input) or 30 (neutral drive) while cranking engine or during KOEO SELF-TEST. Possible causes for these faults are: A/C circuit shorted to power. Clutch engage/interlock circuits open. Neutral drive/gear switch open. Faulty ECA. Starter relay disconnected during self-test. On all A/T models, go to step 8). On M/T models, go to step 2).
2. 2) Check Neutral Gear/Clutch Input Turn ignition off. Turn A/C off (if equipped). Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pins No. 30 and 46 with transmission in Neutral and clutch pedal up. Measure resistance between test pins No. 30 and 46 with transmission in gear and clutch pedal down. If each resistance is less than 5 ohms, go to step 3). If resistance is 5 ohms or more, go to step 5).
3. 3) Check Neutral Gear/Clutch Input Integrity Turn ignition off. Leave ECA disconnected from breakout box. Measure resistance between test pins No. 30 and 46 with transmission in any gear and clutch pedal up. (Scheme 48) If resistance is less than 5 ohms, go to «CIRCUIT TEST KM»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l), step 40) (models with A/C) or replace ECA and repeat QUICK TEST (all others). If resistance is 5 ohms or more, go to next step.
4. 4) Check For Short To Ground Turn ignition off. Leave ECA disconnected from breakout box. Disconnect clutch engage switch. Measure resistance between test pins No. 30 and 46. If resistance is 10,000 ohms or more, go to «CIRCUIT TEST KM»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l), step 40) (models with A/C) or replace ECA and repeat QUICK TEST (all others). If resistance is less than 10,000 ohms, repair short circuit. Reconnect all components, and repeat QUICK TEST.
5. 5) Check Neutral Gear/Clutch Engage Switch Turn ignition off. Leave ECA disconnected from breakout box. Locate neutral gear switch (on transmission) and clutch engage switch (at clutch pedal linkage). Disconnect wiring harness at both switches, and inspect connectors for pushed-back pins. Measure resistance across neutral gear switch terminals with transmission in Neutral. Measure resistance across clutch engage switch with clutch pedal down. If each resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, replace open switch. Reconnect all components, and repeat QUICK TEST.
6. 6) Check Neutral Gear/Clutch Harness Turn ignition off. Leave ECA disconnected from breakout box. Disconnect neutral gear and clutch switches. Measure resistance between test pin No. 30 and neutral gear switch wiring harness connector. Measure resistance between test pin No. 30 and clutch engage switch harness connector. Measure resistance between test pin No. 46 and neutral gear switch wiring harness connector. Measure resistance between test pin No. 46 and clutch engage switch wiring harness connector. If any resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components and repeat QUICK TEST. If each resistance is less than 5 ohms, go to «CIRCUIT TEST KM»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l), step 40) (models with A/C) or replace ECA and repeat QUICK TEST (all others).
7. 7) Check Clutch Engage Switch (4.9L) Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Hold clutch pedal down and measure resistance between test pins No. 30 at breakout box and starter relay. If resistance is less than 5 ohms, go to «CIRCUIT TEST KM»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l), step 40) (models with A/C) or replace ECA and repeat QUICK TEST (all others). If each resistance is 5 ohms or more, repair open circuit. Reconnect all components, and repeat QUICK TEST.
8. 8) Check Neutral Drive Input Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Ensure A/C is off (if equipped). Ensure transmission is in Neutral or Park. Turn ignition on. Measure voltage between test pin No. 30 and chassis ground. If voltage is less than 1.0 volt, go to «CIRCUIT TEST KM»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l), step 40) (models with A/C) or replace ECA and repeat QUICK TEST (all others). If voltage is 1.0 volt or more, go to step next step.
9. 9) Check Neutral Drive Switch Resistance Turn ignition off. Leave ECA disconnected from breakout box. Disconnect wiring harness from neutral drive switch. Measure resistance across switch terminals. If resistance is less than 5 ohms, repair open in NDS circuit. Reconnect all components, and repeat QUICK TEST. If resistance is 5 ohms or more, replace neutral drive switch. Reconnect all components, and repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 9) to step 12). No test procedures have been omitted.
10. 12) Check NDS Circuit For Short To Ground Or Closed Neutral Drive Switch Turn ignition off. Leave ECA disconnected from breakout box. Place transmission in Drive. Measure resistance between test pin No. 30 and test pins No. 40 and 60 at breakout box. If resistance is 10,000 ohms or more, NDS circuit is okay. Diagnose other possible causes. If resistance is less than 10,000 ohms, repair closed neutral drive switch or short circuit. Reconnect all components, and repeat QUICK TEST.

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

1. Engine base condition (cam timing, valves, rings, etc.).
2. Brakes.
3. Transmission fluid, friction elements and cooling.
4. Transfer case linkage or internal condition.

This test is only intended to diagnose

1. Harness circuits 4x4 LOW/ OCIL and OCS.
2. Faulty ECA.

Scheme 49

Scheme 50

Scheme 51

1. Code 47/633, 65/632 Or 97/631 Code 47/633 indicates 4x4 Low selector lever is not in 4x2 or 4x4 HIGH position during KOEO SELF-TEST. Code 65/632 indicates Overdrive Cancel Switch (OCS) is not cycled between engine ID code and WOT check during KOER SELF-TEST. Code 97/631 indicates OCS circuit fault during KOEO SELF-TEST. Possible causes for these faults are: Faulty 4x4 Low switch or 4x4 selector lever position. Faulty OCS switch or switch not cycled. OCS bulb burned out. OCS circuit open or grounded. Faulty ECA. Perform QUICK TEST. If no codes are present, fault is intermittent and cannot be duplicated at this time. If Code 47/633 or 65/632 is present, go to step 2). If Code 97/631 is present, go to step 3).
2. Cycle 4x4 Or Overdrive Cancel Switch Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Turn ignition on. To check 4x4 LOW circuit, measure voltage between test pin No. 12 and test pins No. 40 and 60 at breakout box. To check OCS circuit, measure voltage between test pin No. 41 and test pins No. 40 and 60 at breakout box while cycling overdrive cancel switch. If voltage cycles, replace ECA and repeat QUICK TEST. If voltage does not cycle, go to step 3).
3. Check Circuits For Short To Ground Turn ignition off. Leave ECA disconnected from breakout box. Disconnect switch. To check 4x4 LOW circuit, measure resistance between test pin No. 12 and test pins No. 40 and 60 at breakout box. To check OCS circuit, measure resistance between test pin No. 41 and pins No. 40 and 60 at breakout box. If resistance is more than 10,000 ohms, go to step 4) (Code 97/631) or step 6) (Code 47/633 or 65/632). If resistance is 10,000 ohms or less, repair short circuit. Repeat QUICK TEST. If code is still present, go to step 5).
4. Check Power Through OCIL Circuit Turn ignition off. Leave ECA disconnected from breakout box. Measure voltage between test pin No. 32 and test pins No. 40 and 60 at breakout box. If voltage is more than 10.5 volts, replace ECA and repeat QUICK TEST. If voltage is 10.5 volts or less, go to step 5).
5. Check Output Driver Voltage Signal Turn ignition off. Leave ECA disconnected from breakout box. Disconnect switch. To check 4x4 LOW circuit, connect DVOM positive lead on KEY POWER terminal of fuse panel and negative lead on test pin No. 12 at breakout box. (Scheme 51) To check OCS circuit, connect DVOM positive lead on KEY POWER terminal of fuse panel and negative lead on test pin No. 32 at breakout box. If either voltage reading is less than 2 volts, check bulb and fuse. If bulb and fuse are okay, repair open circuit and repeat QUICK TEST. If both voltage readings are 2 volts or more, go to step 6).
6. Check Circuit Continuity Turn ignition off. Leave ECA disconnected from breakout box. Disconnect switch. To check 4x4 LOW circuit, connect DVOM positive lead on KEY POWER terminal of fuse panel and negative lead on test pin No. 12 at breakout box. To check OCS circuit, connect DVOM positive lead on KEY POWER terminal of fuse panel and negative lead on power side of OCS wiring harness connector. Connect DVOM positive lead on test pin No. 41 at breakout box and negative lead on power side of OCS wiring harness connector. If either resistance reading is 5 ohms or more, repair open circuit and repeat QUICK TEST. If both resistance readings are less than 5 ohms, go to step 7).
7. Check Circuits For Short To Power Turn ignition off. Leave ECA disconnected from breakout box. Disconnect switch. To check 4x4 LOW circuit, measure resistance between test pin No. 12 and test pins No. 37 and 57 at breakout box. To check OCS circuit, measure resistance between test pin No. 32 and test pins No. 37 and 57 at breakout box. Measure resistance between test pin No. 41 and test pins No. 37 and 57 at breakout box. If resistances are more than 10,000 ohms, replace switch and repeat QUICK TEST. If any resistance is 10,000 ohms or less, repair short circuit and repeat QUICK TEST.

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

1. Engine base condition (cam timing, valves rings, etc.).
2. Brakes.
3. Transmission fluid, friction elements and cooling.

This test is not intended to diagnose transmission. This test is intended to diagnose

1. Wiring harness circuits M/CCC, CCO, CCS, EPC, SS3/4, SS1, SS2, SS3, SIG RTN, EPC PWR and VPWR.
2. Faulty ECA.

CIRCUIT TEST TC ACRONYMS

Scheme 52

A4LD SERVICE CODE IDENTIFICATION

1. 1) OUTPUT STATE CHECK Code 91/621, 92/622, 93/626, 94/627, 629, 641 or 652 indicates shift solenoid did not respond to ECA command. Possible causes for these faults are: Faulty Manual Lever Position (MLP) sensor. Circuit open or grounded. Faulty ECA. To enter OUTPUT STATE CHECK, use only VOM or DVOM. DO NOT use scan tester. Turn ignition off. Disconnect cruise control servo wiring harness connector. Connect DVOM negative lead to STO terminal at self-test connector. Connect positive lead to positive battery terminal. Install a jumper wire between SIG RTN terminal at self-test connector and STI terminal. (Scheme 43)in CIRCUIT TEST QA. Perform KOEO SELF-TEST until continuous memory test is complete. DVOM will read less than 1.0 volt when test is complete to indicate ECA has entered OUTPUT STATE CHECK. Depress and release throttle. If voltage increases, remain in OUTPUT STATE CHECK and go to next step. If voltage does not increase, depress throttle to WOT and release. If STO voltage goes high, go to next step. If STO voltage does not go high, leave test equipment connected and go to «CIRCUIT TEST QC»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l), step 2).
2. 2) Check Solenoid Electrical Condition Turn ignition off. Disconnect transmission wiring harness connector. Inspect terminals, and repair if damaged. Connect VOM or DVOM positive test lead to solenoid VPWR connector. Connect negative test lead to appropriate solenoid terminal at transmission wiring harness connector. Cycle solenoid output on and off by depressing and releasing throttle 3-5 times. If voltage output changes 0.5 volt or more, fault is in transmission. If voltage output does not change 0.5 volt or more, go to next step.
3. 3) Check Continuity Between Solenoid & VPWR Circuits Turn ignition off. Leave transmission wiring harness disconnected. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between ECA output signal terminal at ECA wiring harness connector and output signal terminal at transmission wiring harness connector. Measure resistance between breakout box test pins No. 37 and 57 and VPWR terminal at transmission wiring harness connector. If either resistance is less than 5 ohms, repair open circuit and repeat QUICK TEST. If both resistances are 5 ohms or more, go to next step.
4. 4) Check Solenoid Circuit For Short To Power Or Ground Turn ignition off. Leave ECA disconnected from breakout box. Leave transmission wiring harness disconnected. Measure resistance between ECA output signal test pin and test pins No. 37 and 57 at breakout box. Measure resistance between ECA output signal test pin and pins No. 40, 46 and 60 at breakout box. Measure resistance between ECA output signal test pin and chassis ground. If either resistance is less than 10,000 ohms, repair short circuit and repeat QUICK TEST. If all resistances are 10,000 ohms or more, replace ECA and repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 4) to step 10). No test procedures have been omitted.
5. 10) Check VPWR To Solenoid Code 86/566 or 89/629 indicates shift solenoid did not respond to ECA command. Code 99/624 indicates failure of EPC circuit. Code 98/625 indicates EPC driver failure. Possible causes for these faults are: Faulty solenoid. Circuit open or grounded. Faulty ECA. Turn ignition off. Disconnect transmission wiring harness connector. Turn ignition on. Measure resistance between VPWR and EPC PWR terminal at transmission wiring harness connector and chassis ground. If voltage is less than 10.5 volts, repair open circuit and repeat QUICK TEST. If voltage is 10.5 volts or more, go to next step.
6. 11) Check Solenoid Resistance Turn ignition off. Leave transmission wiring harness connector disconnected. Measure resistance between VPWR and EPC PWR terminal and suspect component terminal at transmission wiring harness connector. If resistance is not 26-40 ohms (A4LD) or 3-7 ohms (except A4LD), fault is in transmission. If resistance is 26-40 ohms (A4LD) or 3-7 ohms (except A4LD), go to next step.
7. 12) Check Solenoid Signal & VPWR Circuit Continuity Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between breakout box test pins No. 37 and 57 and VPWR/EPC PWR terminal at transmission wiring harness connector. On A4LD models, measure resistance between CCO or SS3/4 test pin at breakout box and solenoid terminal at transmission wiring harness connector; on all models except A4LD, measure resistance between test pin No. 32 at breakout box and EPC solenoid terminal at transmission wiring harness connector. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST. If resistance is more than 5 ohms, go to next step.
8. 13) Check Circuit For Short To Power Or Ground Turn ignition off. Leave ECA disconnected from breakout box. Leave transmission wiring harness connector disconnected. On A4LD models, measure resistance between test pin No. 52 or 53 and pins No. 37 and 57 at breakout box. Measure resistance between test pin No. 52 or 53 and pins No. 40, 46 and 60 at breakout box. On all models except A4LD, measure resistance between test pin No. 38 and test pins No. 37 and 57 at breakout box. Measure resistance between test pin No. 38 and test pins No. 40, 46 and 60 at breakout box. If either resistance is less than 10,000 ohms, repair short circuit and repeat QUICK TEST. If all resistances are 10,000 ohms or more, replace ECA and repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 13) to step 20). No test procedures have been omitted.
9. 20) Check Solenoid Resistance KOEO Code 621 (SS1), 622 (SS2), 641 (SS3) or 643 (CCC) indicates failure in shift solenoid circuit. Possible causes for these faults are: Faulty shift solenoid. Circuit open or grounded. Faulty ECA. Turn ignition off. Disconnect transmission wiring harness connector. Measure resistance between suspect shift solenoid at transmission wiring harness connector and chassis ground. If resistance is 13-17 ohms, go to next step. If resistance is not 13-17 ohms, go to step 22).
10. 21) Check Shift Solenoid For Short To Power Turn ignition off. Disconnect transmission wiring harness connector. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Turn ignition on. Measure voltage between suspect shift solenoid at transmission wiring harness connector and chassis ground. If voltage is more than 0.5 volt, repair short to power and repeat QUICK TEST. If voltage is 0.5 volt or less, go to next step.
11. 22) Check Shift Solenoid For Short To Ground Turn ignition off. Leave transmission wiring harness connector disconnected. Measure resistance between suspect shift solenoid at transmission wiring harness connector and chassis ground. Measure resistance between suspect shift solenoid and other circuits at transmission wiring harness connector. If either resistance is less than 10,000 ohms, repair short circuit and repeat QUICK TEST. If all resistances are 10,000 ohms or more, go to next step.
12. 23) Check Shift Solenoid Circuit Continuity Turn ignition off. Leave transmission wiring harness connector disconnected. Install EEC-IV Breakout Box (T83L-50-EEC-IV) or 4EAT tester, leaving ECA disconnected. Measure resistance between suspect shift solenoid at breakout box and suspect shift solenoid terminal at transmission wiring harness connector. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST. If resistance is less than 5 ohms, go to next step.
13. 24) Check Shift Solenoid For Short To Power In Transmission Turn ignition off. Leave ECA disconnected from breakout box. Reconnect transmission wiring harness connector. Measure voltage between test pin No. 60 and suspect shift solenoid terminal at breakout box. If voltage is 0.5 volt or more, replace or repair solenoid short to power. If voltage is less than 0.5 volt, replace ECA and repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 24) to step 30). No test procedures have been omitted.
14. 30) Continuous Memory Codes 621, 622, 641 & 643 Continuous Memory Code 621 (SS1), 622 (SS2), 641 (SS3) or 643 (CCC) indicates a failure was detected in shift solenoid circuit during last 80 warm-up cycles. Possible causes for these faults are: Faulty shift solenoid. Circuit open or grounded. Turn ignition off. Check shift solenoid circuit between ECA and transmission. Repair or replace as necessary. If circuits are okay, go to next step.
15. 31) Check For Intermittent Short Or Open Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Turn ignition on. Connect test light between test pin No. 37 and suspect shift solenoid terminal at breakout box. Test light should be at partial brightness. Observe test light while wiggling and bending shift solenoid circuit between transmission and ECA. An open or short to power will be indicated by light going off. A short to ground will be indicated by light getting bright. Repeat procedure for all solenoids. If fault is indicated, isolate and repair as necessary. If no fault is indicated, go to next step. SHIFT SOLENOID TEST CIRCUITS ID Shift Solenoid Test Pin No. SS1 11 SS2 51 SS3 52 CCC 55
16. 32) Check For Intermittent Short To Ground Turn ignition off. Leave ECA disconnected from breakout box. Disconnect transmission wiring harness connector. Turn ignition on. Connect test light between test pin No. 37 and suspect shift solenoid terminal at breakout box. Test light should be off. Observe test light while wiggling and bending shift solenoid circuit between transmission and ECA. A short to ground will be indicated by light turning on. Repeat procedure for all solenoids. If fault is indicated, isolate and repair as necessary. If no fault is indicated, problem is intermittent and cannot be duplicated at this time.

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

1. Engine base condition (cam timing, valves rings, etc.).
2. Electrical (alternator, battery, add-on devices, etc.).
3. Transmission shift linkage.

This test is not intended to diagnose transmission. This test is intended to diagnose

1. Wiring harness circuits MLP, TSR, TSL, TSD, TSOD and SIG RTN.
2. ECA.

Scheme 53

1. 1) KOEO Codes 67/634, 522 & 654 KOEO Codes 67/634 522 and 654 indicate MLP sensor is out of self-test range (3770-4607 ohms) when gear selector is in PARK position. Possible causes for these faults are: Linkage not adjusted correctly. Faulty Manual Lever Position (MLP) sensor. Circuit open or grounded. Faulty ECA. Turn ignition off. Apply parking brake. Place transmission gear selector in NEUTRAL position. Place Manual Lever Position Sensor Gauge (T89T-70010-J) in sensor slot. If gauge does not fit, loosen MLP mounting bolts and adjust sensor as necessary. If gauge fits, go to next step.
2. 2) Check MLP Sensor Circuit Continuity Turn ignition off. Disconnect MLP sensor wiring harness connector. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between MLP terminal at MLP sensor wiring harness connector and test pin No. 30 at breakout box. Measure resistance between SIG RTN terminal at MLP sensor wiring harness connector and test pin No. 46 at breakout box. If either resistance is more than 5 ohms, repair open circuit and repeat QUICK TEST. If both resistances are 5 ohms or less, go to next step.
3. 3) Check MLP Sensor For Short To Power & Ground Turn ignition off. Leave ECA and MLP sensor disconnected. Measure resistance between test pin No. 30 and test pins No. 40, 46 and 60 at breakout box. Measure resistance between test pin No. 30 and chassis ground. If resistance is less than 10,000 ohms, repair short circuit and repeat QUICK TEST. If resistance is 10,000 ohms or more, go to next step.
4. 4) Check MLP Sensor Resistance Turn ignition off. Connect MLP sensor. Leave ECA disconnected from breakout box. Measure resistance between test pins No. 30 and 46 at breakout box while cycling gear selector. See «MLP SENSOR RESISTANCE»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l) . If resistance is within specification, replace ECA and repeat QUICK TEST. If resistance is not within specification, replace MLP sensor and repeat QUICK TEST. MLP SENSOR RESISTANCE Gear Selected Ohms Park 3770-4607 Reverse 1304-1593 Neutral 660-807 Overdrive 361-442 Drive 190-232 First 190-232 NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 4) to step 7). No test procedures have been omitted.
5. 7) Incorrect Shift/No Shift Turn ignition off. Check transmission fluid. Add or replace if necessary. Test drive vehicle to determine transmission shift patterns. If transmission always remains in 3rd gear when vehicle is operated with shift lever in Drive or Overdrive position, go to next step. If transmission does not operate as described, go to step 9) .
6. 8) Visual Inspection Visually check select switch and solenoid wiring harness between ECA and transmission. Repair or replace wiring harness if necessary and repeat QUICK TEST. If wiring harness is okay, go to next step.
7. 9) Diagnose Transmission Shift Patterns If transmission upshifts and downshifts correctly, EEC-IV system is okay. Fault is in transmission. If transmission does not shift correctly, turn ignition off. Inspect transmission switches and harness connectors for corrosion and damaged pins. Inspect wiring harness for incorrect routing. If any faults are found, repair or replace as necessary. If no faults are found, problem is intermittent and cannot be found at this time.

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

1. Transmission fluid level.
2. Transmission fluid temperature.
3. Ambient temperature.

This test is intended to diagnose

1. TOT sensor.
2. Wiring harness circuits TOT and SIG RTN.
3. Faulty ECA.

TOT SENSOR (AXOD-E) SPECIFICATIONS

1. 1) KOEO Code 26/636 KOEO Code 26/636 indicate TOT sensor is out of self-test range. Possible causes for these faults are: Transmission fluid incorrect temperature. Incorrect sensor resistance. Faulty ECA. Ensure transmission fluid temperature is more than 50°F (10°C). Repeat QUICK TEST. If Code 26/636 is present, go to next step. If Code 26/636 is not present, test is complete.
2. 2) Check VREF At Throttle Position Sensor (TPS) Turn ignition off. Disconnect TPS sensor wiring harness connector. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect ECA to breakout box. Turn ignition on. Measure voltage between VREF and SIG RTN terminals at TPS wiring harness connector. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, go to «CIRCUIT TEST C»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l).
3. 3) Check TOT Sensor Resistance Turn ignition off. Disconnect ECA from breakout box. Allow transmission to cool. Turn ignition on. Measure and record voltage between test pin No. 46 and TOT test pin at breakout box. Start engine, and warm transmission to normal operating temperature. Disconnect ECA from breakout box. Measure voltage between test pin No. 46 and TOT test pin at breakout box. If voltage is within specification, replace ECA and repeat QUICK TEST. If voltage is not within specification, replace TOT sensor and repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 3) to step 10). No test procedures have been omitted.
4. 10) KOEO Code 56 Or 637 KOEO Code 56 and 637 indicate TOT sensor output exceeds self-test maximum voltage. Possible causes for these faults are: Transmission fluid temperature incorrect. Open wiring harness circuit. Faulty ECA. Turn ignition off. Disconnect TOT wiring harness connector. Inspect terminals, and repair if damaged. Connect jumper wire between TOT and SIG RTN terminals. Perform KOER SELF-TEST. If Code 66/638 is present, replace TOT sensor and repeat QUICK TEST. If Code 66/638 is not present, go to next step.
5. 11) Check TOT & SIG RTN Circuit Continuity Turn ignition off. Leave TOT sensor disconnected. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box(T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between TOT circuit at TOT wiring harness connector and TOT test pin at breakout box. Measure resistance between SIG RTN circuit at TOT wiring harness connector and TOT test pin at breakout box. If either resistance is more than 5 ohms, repair open circuit and repeat QUICK TEST. If each resistance is 5 ohms or less, go to next step.
6. 12) Check TOT Sensor For Short To VPWR Turn ignition off. Leave ECA and TOT sensor disconnected. Measure resistance between TOT test pin and test pins No. 37 and 57 at breakout box. If resistance is more than 10,000 ohms, replace ECA and repeat QUICK TEST. If resistance is 10,000 ohms or less, repair short circuit and repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 12) to step 20). No test procedures have been omitted.
7. 20) KOEO Code 66 Or 638 KOEO Code 66 and 638 indicate TOT sensor output is lower than self-test minimum voltage. Possible causes for these faults are: Damaged TOT sensor. Shorted wiring harness circuit. Faulty ECA. Turn ignition off. Disconnect transmission wiring harness connector. Inspect terminals, and repair if damaged. Perform KOEO SELF-TEST. If Code 56 or 637 is present, replace TOT sensor and repeat QUICK TEST. If Code 66/638 is not present, go to next step.
8. 21) Check VREF At Throttle Position Sensor (TPS) Turn ignition off. Disconnect TPS sensor wiring harness connector. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect ECA to breakout box. Turn ignition on. Measure voltage between VREF and SIG RTN terminals at TPS wiring harness connector. see scheme 52 If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, go to «CIRCUIT TEST C»(/ford/explorer/i-1990-1994/remont/testing-diagnostics/#engine-controls-tests-wcodes-40l).
9. 22) Check TOT Sensor Resistance Turn ignition off. Disconnect ECA from breakout box. Measure resistance between TOT test pin at breakout box and test pins No. 40, 46 and 60. If resistance is more than 10,000 ohms, replace ECA and repeat QUICK TEST. If resistance is 10,000 ohms or less, repair short circuit and repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 22) to step 25). No test procedures have been omitted.
10. 25) Check Transmission Wiring Harness Turn ignition off. Check transmission internal and external wiring and connectors for damage and corrosion. Repair or replace if necessary. If wiring is okay, replace TOT sensor and repeat QUICK TEST. NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 25) to step 90). No test procedures have been omitted.
11. 90) Continuous Memory Code 637/638 Continuous Memory Code 637/638 indicates that a fault has been detected in TOT circuit at one or more times during previous 80 warm-up cycles. Possible causes for these faults are: Intermittent fault in TOT sensor. Intermittent short or open in wiring harness. Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect ECA to breakout box. Connect DVOM between test pins No. 2 and 46 at breakout box. Turn ignition on. Shake and bend TOT and SIG RTN wires between transmission and ECA. Voltage should remain stable or change gradually. If voltage drops or surges abruptly, fault in circuit is indicated. If fault is indicated, isolate and repair as necessary. If no faults are found, problem cannot be located at this time.

See also:
• SERVICE CODE REFERENCE CHARTS
• CIRCUIT TEST AC (EDIS)
• H - Step 1)
• HA
• CONTINUOUS MONITOR MODE (WIGGLE TEST)
• PRELIMINARY INSTRUCTIONS (A/T)
• PRELIMINARY INSTRUCTIONS (M/T)