Engine Controls - Tests W/codes - Eec-Iv: Diagnosis Ford Bronco V

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.

KOEO & KOER SELF-TEST Codes

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

Codes are shown as voltage pulses. If using MIL/CHECK ENGINE light, service codes are displayed as light pulses. If using Volt-Ohmmeter (VOM), service codes are displayed as needle sweeps. see scheme 1

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. see scheme 1

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.

KOEO SELF-TEST

Ensure engine is at normal operating temperature. If engine does not start (or stalls after starting), continue KOEO SELF-TEST.

Perform the following step(s) as applicable

1. On gasoline vehicles, DO NOT depress throttle.
2. On vehicles with Brake On/Off circuit, apply and release brake pedal after vehicle ID code is given.
3. On vehicles with Power Steering Pressure (PSP) switch, turn steering wheel 1/2 turn and release after vehicle ID code is given.
4. On vehicles with Transmission Control Switch (TCS), cycle TCS switch after vehicle ID code is given.

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, service KOEO codes. See SERVICE CODE REFERENCE CHARTS. If PCM 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.
2. If vehicle has a no-start condition, see CIRCUIT TEST AA.
3. If vehicle displays a Code 11 or 111 (pass code), go to KOER SELF-TEST.

KOER SELF-TEST

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 received from KOER SELF-TEST may not be valid.

Deactivate self-test by removing and reconnecting jumper wire or by procedure specified by manufacturer of test equipment in use. Start engine, and run it for 2 minutes at 2000 RPM to warm Heated Oxygen Sensor (HO2S). 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 Code 98 or 998 is displayed, EEC-IV system is operating in Failure Management Effects Mode (FMEM). PCM has detected an out-of-range sensor and has substituted a fixed value to enable vehicle to continue operation.
2. If vehicle is equipped with a Brake On-Off (BOO) switch, brake pedal must be depressed and released after ID code portion of test.
3. On vehicles with Power Steering Pressure (PSP) Switch, turn steering wheel at least 1/2 turn and release within 1-2 seconds after ID code portion of test.
4. On vehicles with Transmission Control Switch (TCS), cycle TCS switch after vehicle ID code is given.
5. If Dynamic Response Code appears, perform a brief Wide Open Throttle (WOT). DO NOT perform WOT unless requested.
6. 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.
7. If a Code 11 or 111 (pass code) is retrieved during Continuous Memory Code portion of KOEO SELF-TEST and no driveability problem exists, EEC-IV testing is complete. If driveability problems are still present, proceed to «TESTS W/O CODES»(ref-22970) article in the ENGINE PERFORMANCE section.
8. If KOER codes are present, see SERVICE CODE REFERENCE CHARTS. If system will not output codes, go to CIRCUIT TEST QA.

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

1) 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.

2) If a fault is detected, scan tester should indicate a tone or light and VOM will perform needle sweep and/or MIL will come on. A service code may be stored in continuous memory. Retrieve code, and perform appropriate test. See SERVICE CODE REFERENCE CHARTS.

KOER Wiggle Test

1) Turn ignition off. Connect test equipment. 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.

2) Tap, move and wiggle suspect sensor and/or harness area. If a fault is detected, scan tester should indicate a tone or light and VOM will perform needle sweep and/or MIL will come on. A service code may be stored in continuous memory. Retrieve code, and perform appropriate test. See SERVICE CODE REFERENCE CHARTS.

Cylinder Balance Test

1) This test helps identify a weak or non-contributing cylinder in engines with SFI fuel systems. PCM shuts off fuel supply to each injector and measures RPM drop. It computes variation between cylinders and identifies weak ones. Total test time is about 3 minutes.

2) This test mode is entered from KOER SELF-TEST after all codes have been displayed. Within 2 minutes after codes have been displayed, apply and release throttle). After a brief stabilizing period, PCM will activate test procedure.

3) 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. If a weak cylinder is indicated, repeat test. See CYLINDER BALANCE TEST SERVICE CODES table.

4) Test will be repeated if throttle is applied and released within 2 minutes of final code output. When repeating test sequence, percentage of allowable variation between cylinders is reduced. If Code 90 is displayed, cylinder identified in previous first test is considered weak. If code 90 cannot be obtained, cylinder is considered non-contributing.

CYLINDER BALANCE TEST SERVICE CODES

EEC-IV DIAGNOSIS BY SYMPTOM

2-DIGIT SERVICE CODE REFERENCE CHART. Scheme 1

3-DIGIT SERVICE CODE REFERENCE CHART (CODE 111 - 188). Scheme 2

3-DIGIT SERVICE CODE REFERENCE CHART (CODE 189 - 337). Scheme 3

3-DIGIT SERVICE CODE REFERENCE CHART (CODE 338 - 621). Scheme 4

3-DIGIT SERVICE CODE REFERENCE CHART (CODE 622 - 998). Scheme 5

CIRCUIT TEST AA - NO START (DISTRIBUTOR IGNITION SYSTEMS)

Enter this CIRCUIT TEST only when steps in QUICK TEST have been successfully completed but engine still does not start or if directed here from another test or chart.

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

1. Powertrain Control Module (PCM).
2. Spark (PCM-controlled).
3. Wiring harness circuits (PIP, SPOUT, IGN GND and VPWR).

TEST PIN NO. 16 (IGN GND) WIRE COLOR ID

TEST PIN NO. 36 (SPOUT) WIRE COLOR ID

TEST PIN NO. 56 (PIP) WIRE COLOR ID

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

1. Fuel quality and quantity.
2. Ignition (general system condition).
3. Engine mechanical components.
4. Starter and battery circuits.
5. Distributor.
6. Camshaft Position (CMP) sensor.
7. Ignition Control Module (ICM).
8. Ignition coil.

1) Starting System Try to start engine. If engine does not crank, check vehicle starting and charging systems. If engine cranks, verify Inertia Fuel Shutoff (IFS) switch button is pushed in. If IFS switch button is pushed in, go to next step.

2) Check VREF Signal At TP Sensor Turn ignition off. Disconnect Throttle Position (TP) sensor. Turn ignition on (engine off). Measure voltage at TP sensor harness connector between VREF and SIG RTN. (Scheme 6) If voltage is 4-6 volts, reconnect TP sensor and go to step 3). If voltage is not 4-6 volts, go to CIRCUIT TEST C.

TP Sensor Wiring Harness Connector Terminal ID (Bronco). Scheme 6

3) Check For Spark At Plugs Disconnect any spark plug wire. Connect spark tester between spark plug wire and ground. Crank engine and check for spark. If spark is present and consistent, connect spark plug wire and go to step 13). If spark does not exist, connect spark plug wire and go to next step.

4) Check For Spark At Coil Remove high-tension coil wire from distributor. Install spark tester. Check for spark while cranking engine. If spark exists, connect coil wire, and service ignition secondary system. If no spark exists, connect coil wire and go to next step.

5) Check Ignition Circuit Ground Continuity Turn ignition off. Wait 10 seconds. Disconnect and inspect PCM 60-pin connector. Install Break-out Box (T83L-50-EEC-IV), leaving PCM disconnected. On vehicles with distributor mounted ICM, disconnect connector. On all other vehicles, disconnect Camshaft Position (CMP) sensor. Measure resistance between test pin No. 16 at breakout box and IGN GND circuit of CMP or ICM sensor wiring harness connector. If reading is more than 5 ohms, repair open in IGN GND circuit and repeat QUICK TEST . If reading is 5 ohms or less, go to next step.

6) Isolate SPOUT Circuit Fault Connect ICM or CMP sensor, as applicable. Connect PCM to breakout box. Set breakout box timing switch to DIST position. Try to start vehicle. If vehicle starts, go to step 11). If vehicle does not start, go to next step.

7) Check SPOUT Signal Turn ignition off. Move breakout box timing switch to DIST position. Measure voltage between test pin No. 36 at breakout box and negative battery terminal while cranking engine. If voltage is 3-6 volts, EEC-IV system is not at fault. Diagnose ignition system. See IGNITION SYSTEM in SYSTEM/COMPONENT TESTS article in this section. If voltage is not 3-6 volts, go to next step.

8) Check SPOUT & PIP Circuits For Short Circuit Turn ignition off. With breakout box installed, move timing switch to COMPUTED position. Disconnect PCM from breakout box. On vehicles with distributor mounted ICM, disconnect connector. On all other vehicles, disconnect Camshaft Position (CMP) sensor. On all vehicle, turn ignition on. Measure voltage between test pin No. 36 (SPOUT) and negative battery terminal. Measure voltage between test pin No. 56 (PIP) and negative battery terminal. If either voltage is more than 10.5 volts, repair circuit for a short to power and repeat QUICK TEST . If engine still does not start or if all voltages are 10.5 volts or less, go to next step.

9) Turn ignition off. Measure resistance between test pin No. 36 (SPOUT) and test pins No. 16, 20, 40, 46 and 60 for short to ground. Measure resistance between test pin No. 36 and test pin No. 56 for short to PIP. Measure resistance between test pin No. 56 (PIP) and test pins No. 16, 20, 40, 46 and 60. If all readings are 10,000 ohms or more, go to next step. If any reading is less than 10,000 ohms, repair short in harness and repeat QUICK TEST . If engine still does not start, go to next step.

10) Isolate Shorts In PCM Turn ignition off. With breakout box installed, reconnect PCM. Measure resistance between test pin No. 36 (SPOUT) and test pins No. 37, 40, 57 and 60. Measure resistance between test pin No. 56 (PIP) and test pins No. 37, 40, 57 and 60. If any reading is less than 500 ohms, replace PCM and repeat QUICK TEST . If all readings are 500 ohms or more, ensure all components are connected and go to next step.

11) Check PIP Signal Turn ignition off. Set DVOM on 20-volt scale. With breakout box installed, move timing switch to COMPUTED position. While cranking engine, measure voltage between test pin No. 56 (PIP) and test pins No. 40 and 60. If voltage is 3-7 volts, replace PCM. Repeat QUICK TEST. If voltage is not 3-7 volts, go to next step.

12) Check Continuity Of PIP Circuit Turn ignition off. Disconnect PCM from breakout box. Disconnect distributor connector. Measure resistance between test pin No. 56 and PIP terminal of CMP or ICM wiring harness connector. If resistance is 5 ohms or more, repair open PIP circuit and repeat QUICK TEST. If resistance is less than 5 ohms, remove breakout box and diagnose ignition system. See IGNITION SYSTEM in appropriate SYSTEM/COMPONENT TESTS article in this section.

13) Verify SPOUT Signal If spark was present in step 3), turn ignition off. Disconnect PCM 60-pin connector. Inspect for damaged pins and repair as necessary. Install Breakout Box (T83L-50-EEC-IV). Connect PCM to breakout box. Ensure breakout box timing switch is in COMPUTED position. Set DVOM on 20-volt scale. Measure voltage between test pin No. 36 and pins No. 40 and 60 while cranking engine. If voltage is 3-6 volts, go to step 20). If voltage is not 3-6 volts, return to step 8).

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 13) to step 21). No test procedures have been omitted.

21) Fuel Pump Check Connect pressure gauge to vehicle. Note initial pressure reading. Pressurize fuel system by turning ignition on for one second, and observe pressure gauge. Turn ignition off, and wait 10 seconds. Repeat sequence 5 times. If pressure increases, go to CIRCUIT TEST S. If pressure does not increase, repair fuel system as necessary. See FUEL SYSTEM in BASIC TESTING article in this section.

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.

25) VPWR Circuit Check Turn ignition off. Disconnect CMP sensor. Turn ignition on. Measure voltage between VPWR circuit of CMP sensor wiring harness connector and negative battery terminal. If voltage is greater than 10.5 volts, go to step 4). If voltage is 10.5 volts or less, go to next step.

26) VPWR Continuity Check Turn ignition off. Disconnect PCM 60-pin connector, and inspect for damaged pins, corrosion and loose wires. Repair as necessary. Install breakout box, leaving PCM disconnected. Measure resistance between VPWR circuit of CMP sensor connector and test pins No. 37 and 57 at breakout box. If resistance is less than 5 ohms, go to CIRCUIT TEST B. If resistance is 5 ohms or more, repair open in VPWR circuit.

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

This test is only intended to diagnose

1. Power Control Module (PCM).
2. EEC power relay.
3. Ignition switch.
4. Wiring harness circuits (SIG RTN, PWR GND, VPWR, KAPWR and VREF).

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

1. Battery cables and ground straps.
2. Voltage regulator.
3. Alternator.
4. Ignition switch.

Power Relay Circuit ID (Bronco). Scheme 7

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 PCM. Inspect connector pins and repair if necessary. Install Breakout Box (T83L-50-EEC-IV), leaving PCM connected. 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, and repeat QUICK TEST . If both readings are less than 5 ohms, go to next step.

3) Check For Open Between SIG RTN & PWR GND Circuits At PCM With breakout box installed and PCM connected, measure resistance between test pin No. 46 and test pins No. 40 and 60 at breakout box. If readings are 5 ohms or more, replace PCM and repeat QUICK TEST . If resistance 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 of Data Link Connector (DLC). If resistance is 5 ohms or more, repair open in SIG RTN circuit and repeat QUICK TEST . If resistance 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 KAPWR terminal at EEC power relay connector and negative battery terminal. Measure voltage between test pin No. 1 at breakout box and negative battery terminal. If either voltage is 10.5 volts or less, open circuit between KAPWR circuit between EEC power relay and positive battery terminal. If voltage is 10.5 volts or more, go to next step.

Note. Vehicles equipped with Power Distribution Boxes use a diode to provide electrical surge protection for the ignition switch and Ignition Control Module (ICM). If a no-start/no-code condition exists, ensure diode continuity is present in one direction only before going to step 6).

6) Check Ignition Circuit Voltage At EEC Power Relay Ensure PCM is connected to breakout box and 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, repair open in ignition switch circuit 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 PCM 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 and 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 PCM. 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 PCM 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 PCM 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 if a check for VREF signal failed during sensor input test for CIRCUIT TEST DA and CIRCUIT TEST DS, or if directed here either by CIRCUIT TEST AA, 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 PCM. 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.

Reference Voltage Circuits & Connector Terminal ID (Bronco). Scheme 8

TEST PIN NO. 26 (VREF) WIRE COLOR ID

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

1) Check Battery Power Circuit Turn ignition off, and wait 10 seconds. Disconnect PCM 60-pin connector. Inspect for damage and repair as necessary. Install Breakout Box (T83L-50-EEC-IV). Connect PCM to breakout box. Turn ignition on. Measure and record voltage between breakout box test pin No. 37 and SIG RTN terminal of Data Link Connector (DLC). Measure and record voltage across battery terminals. If both readings are less than 10.5 volts, or if they differ by more than one 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 PCM connected, turn ignition on. Measure voltage between test pins No. 26 and 46 at breakout box. If voltage is 4-6 volts, go to next step. If voltage is more than 6 volts, go to step 4). If voltage is less than 4 volts, go to step 5).

3) Check VREF & SIG RTN Circuit Continuity Turn ignition off. If directed here by a sensor test, ensure sensor is disconnected. Disconnect PCM from breakout box. 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 PCM 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 PCM 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 PCM if fault still occurs.

5) Check For Shorted TP Sensor Turn ignition off. Connect PCM to breakout box. Disconnect Throttle Position (TP) sensor 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 TP sensor 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/BARO Sensor On models not equipped with a MAP/BARO sensor, go to next step. On all other models, turn ignition off. Disconnect MAP/BARO sensor. Turn ignition on. Measure voltage between test pins No. 26 and 46. If voltage is 4 volts or more, replace MAP/BARO sensor. Remove breakout box, and repeat QUICK TEST . If voltage is less than 4 volts, reconnect MAP/BARO sensor and go to step 8).

8) Check VREF Circuit For Short To Ground Turn ignition off. Disconnect PCM, TP sensor, MAP/BARO 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 1000 ohms, repair short to ground. Remove breakout box, and repeat QUICK TEST. If original problem still exists, replace PCM and repeat QUICK TEST . If readings are 1000 ohms or more, replace PCM 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 IAT sensor. Engine coolant temperature must be greater than 50°F (10°C) to pass KOEO SELF-TEST and greater than 180°F (82°C) to pass KOER SELF-TEST. Voltage values in this test are based on a 5-volt VREF signal. Values may vary up to 15% due to sensor and VREF variations.

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

1. Intake Air Temperature (IAT) sensor.
2. Engine Coolant Temperature (ECT) sensor.
3. Wiring harness circuits (IAT, ECT and SIG RTN).
4. Powertrain Control Module (PCM).

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

1. Coolant level low.
2. Cooling system, water pump or fan.
3. Engine operating temperature.
4. Engine oil level low.
5. Thermostat.
6. Air cleaner duct.
7. Ambient temperature.

Temperature Sensor Circuits & Connector Terminal ID (Bronco). Scheme 9

TEST PIN NO. 7 (ECT) WIRE COLOR ID

TEST PIN NO. 25 (IAT) WIRE COLOR ID

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

1) Code 114 Or 116 Code 114 (IAT) or 116 (ECT) indicates corresponding sensor is out of self-test range. Correct range for measurement is .3-3.7 volts.

Check for following possible causes

1. Low ambient temperature (less than 50°F).
2. Low coolant level.
3. Faulty harness connector.
4. Faulty sensor.
5. IAT sensor improperly mounted in air cleaner.

If vehicle cannot be started, go to step 3). If vehicle stalls, go to CIRCUIT TEST S. Ensure upper radiator hose is hot and pressurized. Repeat QUICK TEST . If Code 114 or 116 is present, go to next step. If none of these codes are present, service other codes as necessary.

2) Check VREF Circuit Voltage At TP sensor Turn ignition off. Disconnect Throttle Position (TP) sensor. Turn ignition on. Measure voltage at TP sensor wiring harness connector between VREF and SIG RTN. see scheme 13 If voltage is 4-6 volts, reconnect TP sensor and go to next step. If voltage is not 4-6 volts, go to CIRCUIT TEST C.

3) Check Temperature Sensor Resistance Turn ignition off. Disconnect suspect sensor. Measure resistance between sensor signal circuit and SIG RTN circuit at sensor. If resistance is not within specification, replace suspected sensor. See ECT & IAT SENSOR SPECIFICATIONS table. Reconnect wiring harness, and repeat QUICK TEST . If resistance is within specification, perform following step as applicable.

1. For diagnosing vehicles with ECT sensor and a no-start condition, DO NOT service Code 116 at this time. Go to CIRCUIT TEST AA for models with distributors.
2. For all others, go to next step.

ECT & IAT SENSOR SPECIFICATIONS

4) Warm engine to normal operating temperature. Turn ignition off. Disconnect suspect sensor. Run engine at 2000 RPM for 2 minutes. Measure resistance between sensor signal circuit and SIG RTN circuit at temperature sensor. See ECT & IAT SENSOR SPECIFICATIONS table above. If resistance is within specification, replace PCM and repeat the QUICK TEST . If sensor is not within specification, replace sensor and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 4) to step 10). No test procedures have been omitted.

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

1. Open circuit in wiring harness (IAT or ECT).
2. Faulty connection.
3. Faulty sensor.
4. Faulty PCM.

Turn ignition off. Disconnect suspect temperature sensor. Connect a jumper wire between sensor signal terminal and SIG RTN terminal at sensor wiring harness connector. Repeat QUICK TEST . If Code 112 or 117 is displayed, replace suspect sensor and repeat QUICK TEST. If Code 112 or 117 is not displayed, remove jumper wire and go to next step.

11) Check Continuity Of Sensor Signal & SIG RTN Circuits Turn ignition off. Ensure suspect temperature sensor is disconnected. Disconnect PCM 60-pin connector. Check for damaged wiring, and repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 7 (ECT sensor) or test pin No. 25 (IAT sensor) at breakout box and signal terminal at sensor wiring harness connector. Also measure resistance between test pin No. 46 and SIG RTN circuit at sensor wiring harness connector. If both readings are less than 5 ohms, replace PCM and repeat QUICK TEST . If either reading is 5 ohms or more, repair open circuit. Remove breakout box and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 11) to step 20). No test procedures have been omitted.

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

1. Circuit grounded in wiring harness (IAT or ECT).
2. Faulty sensor.
3. Faulty PCM.
4. Faulty connection.

Turn ignition off. Disconnect wiring harness connector from suspect sensor. Check for damaged wiring, and repair as necessary. Repeat KOEO SELF-TEST. If Code 113 or 118 is present, replace sensor and repeat QUICK TEST . If Code 113 or 118 is not present, go to next step.

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

22) Check Temperature Sensor Signal For Shorts To Ground Turn ignition off. Disconnect suspect sensor. Disconnect PCM 60-pin connector. Inspect for damage and repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 7 (ECT) or 25 (IAT) and pins No. 40, 46 and 60. If any reading is less than 10,000 ohms, repair short circuit and repeat QUICK TEST . If all readings are 10,000 ohms or more, replace PCM and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 22) to step 90). No test procedures have been omitted.

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

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

SENSOR CODES

Enter KOEO wiggle test mode. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. Observe analog voltmeter or scan tester for indication of fault while tapping sensor lightly and wiggling sensor connector. If fault is not indicated, go to next step. If fault is indicated, disconnect and inspect connector and terminals. If connector and terminals are okay, replace sensor, clear continuous memory and repeat QUICK TEST.

91) Check EEC-IV Wiring Harness While in CONTINUOUS MONITOR MODE (WIGGLE TEST), observe analog voltmeter or scan tester while wiggling and bending wiring harness, a small section at a time, from sensor to cowl. Also check harness from cowl to PCM. If fault is indicated, isolate fault and repair as necessary. Clear continuous memory, and repeat QUICK TEST. If no fault is found, go to next step.

92) Inspect PCM & Wiring Harness Connectors Turn ignition off. Disconnect PCM 60-pin connector. Inspect both connector and connector terminals for damage. If connectors or terminals are damaged, repair as necessary and repeat QUICK TEST. If connectors and terminals are okay and fault cannot be duplicated at this time, see SUMMARY in this article.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 92) to step 100). No test procedures have been omitted.

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

1. Thermostat stuck open.
2. Coolant outlet gasket leak.
3. Water pump gasket leak.

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

101) Continuous Memory Code 339 A Continuous Memory Code 339 indicates cooling system has overheated. Possible causes for this fault are

1. Coolant level low.
2. Thermostat stuck closed.
3. Coolant system clogged.
4. Radiator fins clogged.
5. Water pump damaged or worn.
6. Radiator cap damaged or worn.
7. Cooling fan defective or worn.

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

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

1. MAF sensor.
2. Wiring harness circuits (VPWR, PWR GND, MAF and MAF RTN).
3. Powertrain Control Module (PCM).

To prevent replacement of good components, be aware the 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 PCM.

MAF Sensor Ckt. & Conn. Terminal ID (Bronco - Black Conn.). Scheme 10

MAF Sensor Ckt. & Connector Terminal ID (Bronco - Gray Connector). Scheme 11

MAF WIRE COLOR & TEST PIN IDENTIFICATION

MAF RTN WIRE COLOR & TEST PIN IDENTIFICATION

TEST PINS NO. 37 & 57 (VPWR) WIRE COLOR ID

TEST PINS NO. 40 & 60 (PWR GND) WIRE COLOR ID

MAF SIGNAL VOLTAGE (1)

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

1) Code 159: Check VPWR Circuit Voltage Code 159 indicates that MAF sensor was out of range during KOEO or KOER SELF-TEST. Possible causes for this fault are

1. Air leak before or after MAF sensor.
2. Faulty MAF sensor.
3. Faulty IAC solenoid.
4. Open or grounded wiring harness.
5. Faulty PCM.

Repeat QUICK TEST procedures. If Code 412 is displayed, proceed to CIRCUIT TEST KE, step 1). If Code 411 is displayed, proceed to CIRCUIT TEST KE, step 15). If Code 411 or 412 is not present, go to next step.

2) VPWR Circuit Voltage Check 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.

3) Check MAF Sensor Ground Turn ignition on. With MAF sensor disconnected, 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 step 13).

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.

10) Continuous Memory Code 157: Check For Intermittent Sensor Failure Continuous Memory Code 157 indicates MAF signal was less than 0.4 volt sometime during last 80 warm-up cycles. Possible causes for this fault are

1. Open MAF circuit.
2. MAF circuit shorted to ground.
3. Faulty MAF sensor.
4. MAF sensor disconnected.

Start engine and allow to idle for 5-10 minutes. Perform KOEO SELF-TEST. If Code 157 is present, go to step 13). If Code 157 is not present, go to step 11).

11) Turn ignition off. Disconnect and inspect 60-pin connector at PCM. Service if necessary. Install Breakout Box (T83L-50-EEC-IV), leaving PCM connected. Connect DVOM between MAF test pin and MAF RTN test pin. See appropriate table at beginning of this CIRCUIT TEST. DVOM should read about 0.4 volt. Start engine and allow to idle. Lightly tap on MAF sensor and wiggle wiring harness to simulate road conditions. If sudden change in DVOM reading occurs, fault is indicated. If fault is indicated, replace MAF sensor and repeat QUICK TEST. If no fault is indicated, leave DVOM connected and go to next step.

12) Check Wiring Harness For Open Or Short Circuit Turn ignition on. Shake and bend small sections of wiring harness starting at MAF sensor and working toward dash panel. Shake and bend small sections of wiring harness starting at dash panel and working toward PCM. If fault is indicated, isolate and repair as necessary. If fault is not indicated, problem is intermittent and cannot be duplicated at this time.

13) Code 129 Or 157: Check For Air Leak At MAF Sensor Check for broken or loose air outlet tube clamps at throttle body and air cleaner assembly. Repair or replace as necessary. If no faults are found, go to next step.

14) Check Continuity Of MAF & VPWR Circuit Turn ignition off. Disconnect MAF sensor and PCM wiring harness connector. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between MAF terminal of MAF sensor wiring harness connector and test pins No. 37 and 57. Measure resistance between MAF terminal of MAF sensor wiring harness connector and MAF test pin at breakout box. If resistances are more than 5 ohms, repair open circuit and repeat QUICK TEST . If resistances are 5 ohms or less, go to step 15).

15) Check MAF Signal For Short To Ground Turn ignition off. Ensure MAF sensor and PCM wiring harness are disconnected. Measure resistance between MAF test pin and test pins No. 40, 60 and MAF RTN test pin. 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.

16) Turn ignition off. Ensure MAF sensor and PCM wiring harness connector are disconnected. 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 step 17).

17) Check Continuity Of MAF RTN Circuit Ensure ignition is turned off. Measure resistance between MAF RTN terminal of MAF sensor wiring harness connector and MAF RTN test pin at breakout box. If resistance is more than 5 ohms, repair open circuit and repeat QUICK TEST. If resistance is 5 ohms or less, go to next step.

18) Check MAF Circuit For Short To Ground Turn ignition off. Ensure MAF sensor is disconnected. Connect PCM to breakout box. Measure resistance between MAF test pin and test pins No. 40, 60 and MAF RTN test pin. If resistance is less than 10,000 ohms, replace PCM and repeat QUICK TEST . If resistance is 10,000 ohms or more, go to next step.

19) Check MAF Circuit Output Turn ignition off. Connect MAF sensor wiring harness connector. Start engine. Measure resistance between MAF test pin and negative battery terminal. If voltage is .36-1.50 volts, go to next step. If voltage is not .36-1.50 volts, replace MAF sensor and repeat QUICK TEST.

20) With engine running, measure resistance between MAF test pin and MAF RTN test pin at breakout box. If voltage is .36-1.50 volts, replace PCM and repeat QUICK TEST . If voltage is not .36-1.50 volts, replace MAF sensor and repeat QUICK TEST.

21) Code 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 157 is present, replace MAF sensor and repeat QUICK TEST. If Code 157 is not present, go to next step.

22) Check MAF Circuit For Short To VPWR Turn ignition off. Disconnect PCM 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 PCM 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/BARO tester. To prevent replacement of good components, be aware the 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 (compression, timing, etc.). This test is intended to diagnose the following
4. MAP/BARO sensor.
5. Wiring harness circuits (VREF, MAP/BARO SIG and SIG RTN).
6. MAP vacuum line.
7. Powertrain Control Module (PCM).

MAP/BARO Sensor Ckt., Conn. Terminal & Tester Hookup ID (Bronco). Scheme 12

TEST PIN NO. 26 (VREF) WIRE COLOR ID

TEST PIN NO. 45 (MAP/BARO SIG) WIRE COLOR ID

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

MAP SENSOR SPECIFICATIONS

MAP/BARO SENSOR SPECIFICATIONS

1) Code 22/126: Check Power To MAP/BARO Sensor Code 22/126 indicates MAP/BARO sensor is out of self-test voltage range (1.4-1.6 volts). Following are possible causes of this code

1. Vacuum trapped at MAP/BARO sensor.
2. High atmospheric pressure.
3. MAP/BARO signal circuit open between sensor and PCM.
4. MAP/BARO signal circuit shorted to VREF, SIG RTN or GND.
5. VREF circuit open at sensor.
6. SIG RTN circuit open at sensor.
7. Faulty MAP/BARO sensor.
8. Faulty PCM.

Turn ignition off. Disconnect MAP/BARO sensor from wiring harness.Connect MAP/BARO tester between wiring harness and MAP/BARO 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) Check Power At Sensor Wiring Harness Connector Disconnect MAP/BARO sensor. Turn ignition on. If Green light on tester is lit, replace MAP/BARO sensor and repeat QUICK TEST . If Green light is not on, remove MAP/BARO tester. Connect MAP/BARO sensor, and go to CIRCUIT TEST C.

3) Check MAP/BARO Sensor Output With MAP/BARO tester connected and ignition on, measure sensor output voltage. See MAP SENSOR VOLTAGE OUTPUT table. If output voltage is within range for altitude in which vehicle is being tested, remove MAP/BARO tester and go to next step. If output reading is not within range, remove MAP/BARO tester and go to step 5).

If possible, measure output voltage of several known good MAP/BARO sensors on available vehicles. Average voltage reading will be typical for location and time of testing.

MAP SENSOR VOLTAGE OUTPUT

4) Check MAP/BARO SIG Circuit Continuity Turn ignition off. Disconnect MAP/BARO sensor wiring harness connector. Disconnect PCM 60-pin connector. Inspect it for damaged wiring, and repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between MAP/BARO SIG terminal at sensor wiring harness connector and test pin No. 45. If reading is less than 5 ohms, replace PCM and repeat QUICK TEST . If reading is 5 ohms or more, repair open MAP/BARO SIG circuit and repeat QUICK TEST.

5) Check MAP/BARO SIG Circuit For Short To VREF, SIG RTN & Ground Turn ignition off, and wait 10 seconds. Disconnect PCM 60-pin connector. Inspect it for damaged wiring, and repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Disconnect wiring harness at MAP/BARO 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/BARO 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.

7) KOER Code 22/126: Check For EGR-Related Codes Code 22/126 indicates MAP/BARO signal is out of self-test range during KOER SELF-TEST. Possible causes for this code are

1. Excess EGR flow.
2. Damaged or mis-routed MAP/BARO sensor vacuum hose.
3. Faulty MAP/BARO sensor.

On Bronco, if Code 326, 327, 328, 332, 334, 336 or 337 is present, perform applicable CIRCUIT TEST. See SERVICE CODE REFERENCE CHARTS. If codes are not present, go to next step.

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.

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.

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

1. System failed to detect Wide Open Throttle (WOT).
2. Damaged or mis-routed MAP/BARO sensor vacuum hose.
3. Faulty MAP sensor.

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

11) Continuous Memory 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

1. MAP sensor vacuum hose is improperly routed, blocked or is leaking.
2. 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.

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.

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.

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

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

Enter CONTINUOUS MONITOR MODE (WIGGLE TEST). Observe test equipment while performing following

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

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

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 PCM. If fault is indicated, isolate fault in harness and repair as necessary. Repeat QUICK TEST . If no fault is indicated, go to next step.

92) Check PCM & Wiring Harness Connectors Turn ignition off, and wait 10 seconds. Disconnect PCM 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 this section.

Perform this test when during QUICK TEST procedure or if directed by other diagnostic tests. This test is intended to diagnose

1. Knock sensor.
2. Wiring harness circuits (KS and SIG RTN).
3. Powertrain Control Module (PCM).

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

1. Poor fuel quality.
2. Engine mechanical condition.
3. Ignition timing.

Knock Sensor Circuit & Connector Terminal ID (Bronco). Scheme 13

TEST PIN NO. 23 (KS) WIRE COLOR ID

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

1) Code 225: Generate Knock Signal Manually Code 225 indicates Knock Sensor (KS) signal was not received by PCM during dynamic response (goose) check in KOER SELF-TEST.

Possible causes for this fault are

1. Faulty Knock Sensor (KS).
2. Open or shorted harness.
3. Faulty PCM.

Disconnect PCM 60-pin connector. Inspect connector terminals for damage and repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving PCM connected. Turn ignition on. Measure DC voltage between test pins No. 23 and No. 46 at breakout box. If DC voltage is 2.4-2.6 volts, go to next step. If DC voltage is less than 2.4 volts, go to step 4). If DC voltage is more than 2.6 volts, go to step 5).

2) Check KS Voltage Increase Start engine. Leave DVOM test leads connected to test pins No. 23 and No. 46. Monitor AC voltage at idle and at 3000 RPM. If AC voltage increases, replace PCM and repeat QUICK TEST . If AC voltage does not increase, go to next step.

3) Check Continuity Of KS & SIG RTN Circuits Turn ignition off. Disconnect knock sensor wiring harness connector. Measure resistance between SIG RTN terminal at KS wiring harness connector and test pin No. 46 at breakout box. Measure resistance between KS terminal at wiring harness connector and test pin No. 23 at breakout box. If either reading is 5 ohms or more, repair open circuit and repeat QUICK TEST . If both readings are less than 5 ohms, go to next step.

4) Check KS Circuit For Short To Ground Turn ignition off. Measure resistance between test pin No. 23 and test pins No. 40, 46 and 60 at breakout box. If all readings are 10,000 ohms or more, replace knock sensor and repeat QUICK TEST. If Code 225 is still present, replace PCM. If any reading is less than 10,000 ohms, repair short circuit and repeat QUICK TEST.

5) Check KS Circuit For Short To Voltage Ensure PCM and KS are disconnected. Turn ignition on. Measure DC voltage between test pins No. 23 and 40. If reading is 0.5 volt or more, repair short circuit in wiring harness and repeat QUICK TEST . If reading is less than 0.5 volt, replace PCM and repeat QUICK TEST.

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

1. TP sensor.
2. Wiring harness circuits (TP, SIG RTN and VREF).
3. Powertrain Control Module (PCM).

Normal range of throttle angle measurement for TP sensor is 0-85 degrees. To pass QUICK TEST procedure, range of throttle rotation (in degrees) must be within 3 percent of specification. (Scheme 15)

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

1. Idle speed.
2. Binding throttle shaft or linkage.
3. Choke cam adjustment (if equipped).
4. TP sensor not seated.

TP Sensor Circuit & Connector Terminal ID (Bronco). Scheme 14

TEST PIN NO. 26 (VREF) WIRE COLOR ID

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

TEST PIN NO. 47 (TP) WIRE COLOR ID

TP Sensor Specification Chart (Bronco). Scheme 15

1) KOER Code 121: Check For Other Codes KOER Code 121 indicates TP sensor rotational setting may be out of self-test range. Possible causes for this fault are

1. Binding throttle linkage.
2. TP sensor not seated correctly.
3. Faulty TP sensor.
4. Faulty Powertrain Control Module (PCM).

Perform KOER SELF-TEST. Check for Code 327. If Code 327 is present with Code 121, service Code 327 and repeat QUICK TEST . If Code 327 is not present, go to next step.

2) KOEO Code 121: Check For Binding Throttle Plate Inspect throttle body for binding. If throttle body 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) Code 123: Attempt To Generate Code 122 Code 123 indicates TP sensor signal is greater than self-test maximum value. Possible causes for this fault are

1. TP sensor not seated properly.
2. Faulty TP sensor.
3. Short circuit to power.
4. Faulty PCM.

Turn ignition off. Disconnect TP sensor wiring harness connector. Inspect and repair connector pins if damaged. Repeat KOEO SELF-TEST. Ignore all other codes at this time. If Code 122 is not displayed, go to step 5). If Code 122 is displayed, go to next step.

4) Check VREF Circuit Voltage Turn ignition on. Measure voltage between VREF and SIG RTN terminals at TP sensor wiring harness connector. If reading is 4-6 volts, replace TP sensor and repeat QUICK TEST . If reading is not 4-6 volts, reconnect sensor and go to CIRCUIT TEST C.

5) Check TP Circuit For Short To Power Turn ignition off. Leave TP sensor disconnected. Disconnect PCM 60-pin connector. Inspect it for damage and repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving PCM 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 PCM 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.

10) Code 122: Attempt To Generate Code 121 Or 123 Code 122 indicates TP signal is less than minimum self-test value. (Scheme 15) Possible causes for this fault are

1. TP sensor not seated correctly.
2. Faulty TP sensor.
3. Open circuit in wiring harness.
4. Grounded circuit in wiring harness.
5. Faulty PCM.

Turn ignition off, and wait 10 seconds. Disconnect TP sensor from harness. Install a jumper wire between VREF and TP terminals at TP sensor wiring harness connector. Perform KOEO SELF-TEST. If no codes are generated, remove jumper wire and go to step 13). If Codes 121 and 123 are not present, remove jumper wire and go to next step. If either Code 121 or 123 is displayed, replace TP sensor and repeat QUICK TEST .

11) Check VREF Circuit Voltage Turn ignition on. Measure voltage between VREF and SIG RTN terminals at TP sensor wiring harness connector. If voltage is not 4-6 volts, reconnect all components and go to CIRCUIT TEST C. If voltage is 4-6 volts, go to next step.

12) Check TP Sensor Circuit Continuity Turn ignition off. Leave TP sensor disconnected. Disconnect PCM 60-pin connector. Inspect connector and repair if necessary. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between TP terminal at TP sensor 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.

13) Check TP Circuit For Shorts To Ground Turn ignition off. Leave TP sensor disconnected. Disconnect PCM 60-pin connector. Inspect wiring, and repair as necessary. With breakout box installed, 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 PCM 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.

20) Code 167: Repeat Dynamic Response Test KOER Code 167 indicates TP sensor did not exceed 25 percent 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 completed during dynamic response portion of test. If Code 167 is still present, go to next step. If code is not present, system is unable to duplicate Code 167 at this time. Service any other KOER codes. If no other service codes are present, testing is complete.

21) Check TP Sensor Movement During Dynamic Response Test -Turn ignition off. Disconnect PCM 60-pin connector. Inspect wiring, and repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM connected. Set DVOM on 20-volt scale. Connect DVOM between test pins No. 46 and 47 at breakout box. Perform KOER SELF-TEST and ensure proper WOT is completed during dynamic response test. If DVOM reading exceeds 3.5 volts during dynamic response test, replace PCM and repeat QUICK TEST . If reading does not exceed 3.5 volts, ensure TP sensor is correctly installed and adjusted. If TP sensor is correctly installed and adjusted, replace TP sensor. 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.

90) Continuous Memory Code 123 This test monitors TP sensor under simulated road conditions. Enter wiggle test. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. Connect DVOM or diagnostic tester to STO terminal of Data Link Connector (DLC). While slowly opening throttle to WOT, observe DVOM or diagnostic tester for indication of fault. Slowly bring throttle to closed position. Lightly tap TP sensor and wiggle harness connector. This test checks for open or short in TP sensor and wiring harness. If no fault is indicated, go to step 92). If fault is indicated, go to next step.

91) Measure TP Circuit Voltage While Exercising TP Sensor Turn ignition off, and wait 10 seconds. Disconnect PCM 60-pin connector. Inspect for damage and repair if necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM connected. Stay in wiggle test (as in previous step). Connect DVOM between test pins No. 47 and 46. Set DVOM on 20-volt scale. With ignition on and engine off, observe DVOM and repeat step 90). If fault occurs at less than 4.25 volts, inspect TP sensor connectors and terminals. If connectors and terminals are okay, replace TP sensor, clear codes and repeat QUICK TEST. If fault does not occur at less than 4.25 volts, TP sensor over-travel may have caused Continuous Memory Code 123. TP sensor is okay; go to next step to check wiring harness.

92) Check EEC-IV Wiring Harness While in wiggle test, bend and shake small sections of wiring harness from TP sensor wiring harness connector to firewall and from firewall to PCM 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.

93) Check PCM & Harness Connectors Turn ignition off, and wait 10 seconds. Disconnect PCM 60-pin connector from breakout box. Inspect connectors and terminals for damage, and repair as necessary. Clear codes from PCM memory, and repeat QUICK TEST . If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous Memory Code 123 testing is complete.

94) Continuous Memory Code 122 Enter wiggle test. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. Connect DVOM or diagnostic tester to STO terminal of Data Link Connector (DLC). Observe DVOM or diagnostic tester for indication of fault while performing the following

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

If fault is indicated, disconnect TP sensor. Inspect connectors and terminals. If connectors and terminals are okay, replace TP sensor. Clear codes from PCM memory, and repeat QUICK TEST . If no fault is indicated, go to next step.

95) Check EEC-IV Wiring Harness Stay in wiggle test (as in previous step). Bend, wiggle and shake small sections of wiring harness from TP sensor wiring harness connector to firewall and from firewall to PCM while observing analog voltmeter or scan tester. If fault is indicated, isolate fault in wiring and repair as necessary. Clear codes from PCM memory, and repeat QUICK TEST. If no fault is indicated, go to next step.

96) Check PCM & Harness Connectors Turn ignition off. Inspect PCM 60-pin connector and terminals for damage. Repair connector terminals if necessary. Clear codes from PCM memory, and repeat QUICK TEST . If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous Memory Code 122 testing is complete.

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

1. VREF, DPFE, SIG RTN, EVR and VPWR harness circuits.
2. DPFE sensor.
3. EVR solenoid.
4. EGR valve assembly.
5. Vacuum hoses.
6. Powertrain Control Module (PCM).

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

1. Faulty or damaged EGR valve.
2. Restricted exhaust system.
3. Damaged vacuum reservoir or canister.

DPFE SENSOR SPECIFICATIONS

1) Code 327: Generate Code 337 Code 327 indicates DPFE sensor signal is less than self-test minimum of 0.2 volt. Possible causes for this fault are

1. Faulty DPFE sensor.
2. Open or shorted wiring harness circuits.
3. Faulty PCM.

Turn ignition off. Disconnect DPFE wiring harness connector at sensor. Install a jumper wire between VREF circuit and DPFE circuit at sensor wiring harness connector. Perform KOEO SELF-TEST. If no codes are present, remove jumper wire and go to step 4). If Code 337 is present, ignore all other codes and replace DPFE sensor. Repeat QUICK TEST . If Code 337 is not present, remove jumper wire and go to next step.

2) Measure VREF Circuit Voltage With DPFE sensor disconnected, turn ignition on. Measure voltage between sensor wiring harness connector VREF and SIG RTN terminals. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, go to CIRCUIT TEST C.

3) Check DPFE Circuit Continuity Turn ignition off. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between DPFE terminal at sensor wiring harness connector and test pin No. 27 at breakout box. If resistance is more than 5 ohms, repair open circuit. Repeat QUICK TEST . If reading is 5 ohms or less, go to next step.

4) Check DPFE Circuit For Shorts To Ground & SIG RTN Turn ignition off. Measure resistance between test pin No. 27 and test pins No. 40, 46 and 60 at breakout box. If any resistance is less than 10,000 ohms, repair short circuit. Repeat QUICK TEST. If all resistance readings are 10,000 ohms or more, replace PCM. Repeat QUICK TEST.

5) Code 337: Generate Code 327 Code 337 indicates DPFE sensor signal is greater than self-test maximum of 4.8 volts. Possible causes for this code are

1. Faulty DPFE sensor.
2. Shorted vehicle harness circuits.
3. Open SIG RTN circuit.
4. Faulty Powertrain Control Module (PCM).

Turn ignition off. Disconnect DPFE sensor. Repeat KOEO SELF-TEST. Check for Code 327. Ignore all other codes at this time. If Code 327 is not present, go to step 7). If Code 327 is present, go to next step.

6) Measure VREF Circuit Voltage With DPFE sensor disconnected, turn ignition on. Measure voltage between VREF and SIG RTN terminals at DPFE sensor wiring harness connector. If reading is 4-6 volts, replace DPFE sensor. Repeat QUICK TEST. If reading is not 4-6 volts, go to CIRCUIT TEST C.

7) Check DPFE Circuit For Shorts To Power With ignition off, disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 27 and test pins No. 26, 37 and 57. If any resistance reading is less than 10,000 ohms, repair short circuit. Repeat QUICK TEST . If all resistance readings are 10,000 ohms or more, replace PCM. Repeat QUICK TEST.

8) Code 335: Verify KOER Codes Code 335 indicates DPFE sensor is out of self-test range (2.6-4.2 volts) and may be faulty. DPFE system can detect lack of pressure in exhaust system. A garage exhaust ventilation system, installed during KOEO SELF-TEST, may cause DPFE sensor to generate Code 335. Remove exhaust ventilation system. Repeat KOEO SELF-TEST. Service codes as necessary. If no codes are present during KOEO SELF-TEST, complete QUICK TEST . If Code 335 is present during KOEO SELF-TEST, go to next step.

9) Check DPFE Sensor Pressure Input Hose Remove pressure feed tube from DPFE sensor. Inspect tube, including DPFE inlet, for blockage. Repair if necessary, and repeat QUICK TEST. If no blockage is found, go to next step.

10) Measure VREF Circuit Voltage With ignition off, disconnect DPFE sensor wiring harness connector. Turn ignition on. Measure voltage between VREF and SIG RTN terminals at DPFE sensor wiring harness connector. If voltage is 4-6 volts, replace DPFE sensor and repeat QUICK TEST . If reading is not 4-6 volts, go to CIRCUIT TEST C.

11) Code 558: Measure EVR Solenoid Resistance Code 558 indicates failure in EVR solenoid or circuit.

Possible causes for this code are

1. Faulty EVR solenoid.
2. Faulty Powertrain Control Module (PCM).
3. Open or shorted wiring harness circuit.

Turn ignition off. Disconnect EVR solenoid connector. Measure resistance between terminals. If resistance is 20-70 ohms, go to next step. If resistance is not 20-70 ohms, replace EVR solenoid. Repeat QUICK TEST.

12) Check VPWR Circuit Voltage Turn ignition on. Measure voltage between VPWR terminal at EVR solenoid wiring harness connector and negative battery terminal. 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.

13) Check EVR Circuit Continuity Turn ignition off. Leave EVR solenoid connector disconnected. Disconnect PCM 60-pin connector. Inspect terminals and repair if damaged. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between EVR terminal at EVR solenoid wiring harness connector and test pin No. 33 at breakout box. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST. If reading is less than 5 ohms, go to next step.

14) Check EVR Circuit For Shorts To Power Or Ground Turn ignition off. Measure resistance between test pin No. 33 and pins No. 37, 40, 57 and 60 at breakout box. If any resistance reading is less than 10,000 ohms, repair short circuit and repeat QUICK TEST . If code is repeated, replace PCM. If all readings are 10,000 ohms or more, replace PCM and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 14) to step 21). No test procedures have been omitted.

21) Code 327 Code 327 indicates DPFE sensor signal is less than self-test minimum. Disconnect and plug EGR valve vacuum hose. Perform KOER SELF-TEST. If Code 326 or 327 is present, go to next step. If codes are not present, check EVR vent and vacuum hose to EGR valve for blockage. Repair as necessary. If vent and vacuum hose are okay, replace EVR solenoid and repeat QUICK TEST .

22) Code 326 Or 327: Check DPFE Input Hoses With ignition off, check DPFE sensor pressure input hose for blockage and leaks. Repair as necessary. Connect all lines, and repeat QUICK TEST. If no fault is found, go to next step.

23) Check DPFE Voltage With Engine At Idle Turn ignition off. Disconnect PCM 60-pin connector. Inspect terminals and repair if damaged. Install Breakout Box (T83L-50-EEC-IV). Leave PCM connected to breakout box. Start engine and allow to idle with transmission in Park or Neutral. Measure voltage between test pins No. 27 and 46 at breakout box. If voltage is less than 0.2 volt, replace sensor and repeat QUICK TEST. If voltage is more than 0.2 volt, replace PCM and repeat QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 23) to step 30). No test procedures have been omitted.

30) Code 332: Verify Vacuum At EGR Valve Code 332 indicates DPFE sensor input to PCM did not change after EVR solenoid received signal from PCM to open EGR valve.

Possible causes for this fault are

1. Vacuum hose leaks or restrictions.
2. Faulty DPFE sensor.
3. Faulty EVR solenoid.
4. Faulty EGR valve.
5. Faulty Powertrain Control Module (PCM).

Turn ignition off. Using a vacuum "T", connect vacuum gauge at EGR valve. Perform KOER SELF-TEST while observing vacuum gauge. Disregard code output at this time. If vacuum reading is greater than one in. Hg, go to step 34). If vacuum reading is one in. Hg or less, remove vacuum gauge and go to next step.

31) Check Vacuum Input To EVR Solenoid Turn ignition off. Disconnect EVR vacuum hose. Connect EVR vacuum hose to vacuum gauge. Start engine and allow to idle while observing vacuum gauge. If 15 in. Hg. or more is present, replace EVR solenoid and repeat QUICK TEST . If less than 15 in. Hg. is present, repair vacuum source and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 31) to step 34). No test procedures have been omitted.

34) Check Vacuum At DPFE Inlet Hose(s) Turn ignition off. Inspect vacuum hose for damage and repair if necessary. Using a vacuum "T", connect vacuum gauge at DPFE inlet hose(s). Perform KOER SELF-TEST while observing vacuum gauge. If vacuum momentarily increases, go to next step. If momentary increases in vacuum do not occur, service EGR valve.

35) Attempt To Generate KOEO Code 337 Turn ignition off. Disconnect DPFE sensor. Install jumper wire between DPFE terminal and VREF terminal at DPFE sensor wiring harness connector. Perform KOEO SELF-TEST. If Code 337 is present, ignore all other codes. Replace DPFE sensor and repeat QUICK TEST . If Code 337 is not present, remove jumper wire and go to next step.

36) Measure VREF Circuit Voltage With DPFE sensor disconnected, turn ignition on. Measure voltage between VREF terminal and SIG RTN terminal at DPFE sensor 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.

37) Check DPFE Circuit Resistance Turn ignition off. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between DPFE terminal at DPFE sensor wiring harness connector and test pin No. 27 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 repeat QUICK TEST.

38) Check DPFE Circuit For Short To SIG RTN & Ground Turn ignition off. Measure resistance between DPFE terminal at DPFE sensor wiring harness connector and test pins No. 40, 46 and 60 at breakout box. If any resistance checks are less than 10,000 ohms, repair short circuit and repeat QUICK TEST . If all resistance checks are 10,000 ohms or more, replace PCM and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 38) to step 50). No test procedures have been omitted.

50) Codes 336 & 337: Check EVR Malfunction Code 336 indicates DPFE voltage is too high at zero duty cycle. Possible causes for these codes are

1. Exhaust system restricted.
2. EGR sensor faulty.
3. EVR sensor faulty.
4. PFE sensor faulty.
5. Faulty PCM.

Disconnect and plug EGR vacuum hose. Perform KOER SELF-TEST. If Code 336 or 337 is present, go to next step. If Code 336 or 337 is not present, ensure vacuum hose routing is correct and EVR filter is clean. If okay, replace EVR solenoid.

51) Check DPFE Sensor Output With Engine Idling Turn ignition off. Disconnect PCM 60-pin connector. Inspect terminals and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM connected. Start engine and allow to idle with transmission in Park or Neutral. Measure voltage between test pins No. 27 and 46 at breakout box. If voltage is less than 0.7 volt at idle, replace PCM and repeat QUICK TEST . If voltage is 0.7 volt or more, go to next step.

52) Check EGR Valve Remove EGR valve. Check EGR valve for carbon deposits, binding or other damage. Repair as necessary. Install EGR valve and repeat KOER SELF-TEST. If Code 336 or 337 is still present, replace EGR valve and repeat KOER SELF-TEST. If Code 336 or 337 is still present, replace DPFE sensor and repeat QUICK TEST . If Code 336 or 337 is not present, fault is intermittent and cannot be duplicated at this time. Testing is complete.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 52) to step 90). No test procedures have been omitted.

90) EGR Fault Code(s) In Continuous Memory Repeat QUICK TEST . If fault code(s) are present, go to appropriate circuit test. If fault codes are present in continuous memory only, go to next step.

91) DPFE System Inspection Check for damaged or loose connectors. Check for loose or corroded connector pins. Inspect wiring harness for proper routing and insulation. Ensure component mounting and vacuum hose routing is correct. Ensure EVR solenoid filter is clean. Repair or replace as necessary and repeat QUICK TEST. If no faults are present, go to next step.

92) EGR Fault Code(s) In Continuous Memory Repeat QUICK TEST . If fault code(s) are present, go to appropriate circuit test. If fault code 326, 327, 336 or 337 is present in continuous memory only, go to next step. If fault Code 332 is present in continuous memory only, go to step 105).

93) Continuous Memory Code 326, 327, 336 Or 337 If code is present, possible causes are

1. Damaged connectors or terminals.
2. Open or shorted wiring harness.
3. Faulty EGR valve operation.
4. Faulty EVR solenoid operation.
5. Circuit fault can be in wiring harness, component or PCM.

Enter wiggle test. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST. Observe analog VOM or diagnostic tester for indication of fault while performing following steps. Grasp wiring harness near sensor connector while observing VOM or diagnostic tester for fault indication. Shake and bend small sections of harness, working from sensor toward firewall. Shake and bend harness from firewall to PCM. If fault is indicated, inspect connectors and terminals. Repair as necessary. If connectors and terminals are okay, replace PFE/DPFE sensor. Clear codes and repeat QUICK TEST . If no fault is indicated, go to next step.

94) 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 PCM. If fault is indicated, isolate fault in harness and repair as necessary. Repeat QUICK TEST. If no fault is indicated, go to next step.

95) Check PCM Wiring Harness Connector Turn ignition off, and wait 10 seconds. Disconnect PCM 60-pin connector. Inspect connector and terminals for damage and repair as necessary. Clear codes, and repeat QUICK TEST . If connector and terminals are okay but fault Code 326 or 327 is present, go to next step. If no codes are present, fault is intermittent and cannot be duplicated at this time. Testing is complete.

96) Check EGR Valve Operation Turn ignition off. Disconnect vacuum hose from EGR valve. Connect vacuum pump to EGR valve. While observing EGR valve, slowly apply 10 in. Hg and release. If EGR valve does not operate smoothly, service or replace EGR valve. Repeat QUICK TEST. If EGR valve operation is smooth, go to next step.

97) Check EVR Solenoid & Hoses Turn ignition off. Inspect EVR solenoid vacuum hoses for contamination, moisture or restriction. Ensure EVR solenoid filter is clean. Repair or replace as necessary, and repeat QUICK TEST . If no faults are found, go to next step.

98) Check EVR Solenoid For Short Circuit Turn ignition off. Disconnect vacuum hose from EGR valve. Connect vacuum pump to vacuum hose. Start engine and operate at idle. While observing vacuum gauge, tap on EVR solenoid and wiggle wiring harness connector. If vacuum gauge does not remain less than one in. Hg and has erratic increases, replace EVR solenoid and repeat QUICK TEST. If vacuum gauge remains less than one in. Hg with no erratic increases, leave vacuum gauge connected and go to next step.

99) Check Wiring Harness Between EVR Solenoid & PCM With engine running, observe vacuum gauge while wiggling wiring harness connector between EVR solenoid and dash panel. Wiggle wiring harness between dash panel and PCM. EGR vacuum is an indication of fault. If EGR vacuum increases, isolate short and repair as necessary. Repeat QUICK TEST . If EGR vacuum does not increase, fault is intermittent and cannot be duplicated at this time. Testing is complete.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 99) to step 101). No test procedures have been omitted.

101) Check EGR Vacuum At Start-Up Disconnect and plug EGR vacuum hose. Start engine and allow to idle (if possible). If engine idle is correct, ensure EVR hoses are correctly routed. If hoses are okay, replace EVR solenoid. Clear codes and repeat QUICK TEST . If engine does not idle correctly, go to next step.

102) Check EGR Valve Operation Turn ignition off. Disconnect vacuum hose from EGR valve. Connect vacuum pump to EGR valve. While observing EGR valve, slowly apply 10 in. Hg and release. If EGR valve does not operate smoothly or close completely, service or replace EGR valve. If EGR valve operation is okay, problem is not EGR related. Connect all components and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 102) to step 105). No test procedures have been omitted.

105) Continuous Memory Code 332 Turn ignition off. Disconnect vacuum hose from EGR valve. Connect vacuum pump to EGR valve. While observing EGR valve, apply 1.0-1.5 in. Hg. EGR valve should begin to open. Increase vacuum pump application to 4 in. Hg. EGR valve should be fully open. Increase vacuum pump application to 10 in. Hg. EGR valve should hold and maintain vacuum. If EGR valve does not perform as specified, repair or replace as necessary. Repeat QUICK TEST . If EGR valve is okay, go to next step.

106) With ignition off, remove EVR vacuum hoses. Inspect vacuum hoses for damage or restrictions. Repair as necessary. Repeat QUICK TEST. If EVR vacuum hoses are okay, go to next step.

107) Inspect DPFE Hoses With ignition off, remove DPFE hoses from sensor. Inspect hoses for contamination, leaks or restrictions. Repair as necessary. Repeat QUICK TEST . If DPFE hoses are okay, go to step 108).

108) Check EVR Solenoid Ground Turn ignition off. Disconnect PCM 60-pin connector. Inspect terminals and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM connected. Disconnect vacuum hose from EGR valve. Connect EGR vacuum hose to vacuum pump. Start engine and allow to idle. Connect jumper wire between test pins No. 33 and 40. EVR solenoid should turn on. Observe vacuum gauge while tapping on EVR solenoid. Wiggle wiring harness and connector. A sudden drop in vacuum indicates a fault in the system. If a sudden drop in vacuum occurs, isolate fault and repair as necessary. Repeat QUICK TEST . If no drop in vacuum occurs, problem cannot be identified at this time. Testing is complete.

EVR solenoid receives variable input from PCM, which allows it to control vacuum level to EGR valve. Vacuum not used by EGR is routed to EVR solenoid and vented to atmosphere.

Perform this test when instructed by QUICK TEST or if directed by other test procedures. To prevent replacement of good components, be aware a damaged EGR valve may be cause of problem. This CIRCUIT TEST is intended to diagnose the following

1. EVP sensor.
2. EVR solenoid.
3. EGR valve assembly.
4. Powertrain Control Module (PCM).
5. EGR and EVR vacuum lines.
6. Wiring harness circuits (VREF, EVP, SIG RTN, EVR and VPWR).

EVP Sensor & EVR Solenoid Connector Terminal ID (Bronco). Scheme 16

TEST PIN NO. 26 (VREF) WIRE COLOR ID

TEST PIN NO. 27 (EVP) WIRE COLOR ID

TEST PIN NO. 33 (EVR) WIRE COLOR ID

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

Note. EVR sensor is preloaded when attached to EGR valve. Valve failure causing EVR sensor to lose preload may set Code 31/327.

1) Code 327: Generate Code 337 - Code 327 indicates EVP sensor signal is less than self-test minimum of 0.2 volt.

Possible causes for this fault are

1. Faulty EVP sensor.
2. Faulty EGR valve.
3. Open or grounded harness.
4. Faulty PCM.

Turn ignition off. Disconnect EVP wiring harness connector at sensor. Install a jumper wire between VREF terminal and EVP terminal at EVP sensor wiring harness connector. Repeat KOEO SELF-TEST and KOER SELF-TEST. Check for Code 337. Ignore all other codes at this time. If Code 337 is present, replace EVP sensor and repeat QUICK TEST. If Code 337 is not present, remove jumper wire and go to next step. If no codes are present, remove jumper wire and go to step 4).

2) VREF Circuit Voltage Disconnect EVP sensor. Turn ignition on. Measure voltage between VREF terminal and SIG RTN terminal at EVP sensor wiring harness connector. If voltage is 4-6 volts, go to step 3). If voltage is not 4-6 volts, go to CIRCUIT TEST C.

3) Check EVP Circuit Resistance Turn ignition off, and wait 10 seconds. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between EVP terminal at EVP sensor wiring harness connector and test pin No. 27. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST . If reading is less than 5 ohms, go to next step.

4) Check EVP Circuit For Shorts To Ground Ensure ignition is off and EVP sensor is disconnected. Measure resistance between test pin No. 27 and test pins No. 40, 46 and 60. If any resistance is less than 10,000 ohms, repair short circuit and repeat QUICK TEST. If all readings are 10,000 ohms or more, replace PCM and repeat QUICK TEST.

5) Code 337: Generate Code 327 Code 337 indicates EVP sensor signal is greater than self-test maximum of 4.81 volts.

Possible causes for this fault are

1. Faulty EVP sensor.
2. Faulty PCM.
3. Short to power in vehicle harness.
4. Open in SIG RTN circuit.

Turn ignition off. Disconnect EVP sensor. Perform KOEO SELF-TEST and KOER SELF-TEST. Check for Code 327. Ignore all other codes at this time. If Code 327 is present, go to next step. If Code 327 is not present, go to step 7).

6) Check VREF Circuit Voltage Turn ignition on. Measure voltage between VREF terminal and SIG RTN terminal at EVP sensor wiring harness connector. If reading is 4-6 volts, replace EVP sensor. Repeat QUICK TEST. If reading is not 4-6 volts, go to CIRCUIT TEST C.

7) Check EVP Circuit For Short To Power Turn ignition off. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 27 and test pins No. 26 and 57 at breakout box. If either reading is less than 10,000 ohms, repair short circuit and repeat QUICK TEST . If both readings are 10,000 ohms or more, replace PCM and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 7) to step 10). No test procedures have been omitted.

10) Code 558: Check EVR Solenoid Resistance Code 84/558 indicates fault in EVR solenoid circuit. Possible causes for this fault are

1. Faulty EVR solenoid.
2. Faulty PCM.
3. Shorted or open harness.

Turn ignition off. Disconnect EVR solenoid connector. Measure resistance across EVR solenoid terminals. If reading is not 20-70 ohms, replace EVR solenoid assembly and repeat QUICK TEST . If reading is 20-70 ohms, go to next step.

11) Check VPWR Circuit Voltage Disconnect EVR solenoid. Turn ignition on. Measure voltage between negative battery terminal and VPWR terminal at EVR solenoid wiring harness connector. If reading is less than 10.5 volts, repair open in VPWR circuit and repeat QUICK TEST . If reading is 10.5 volts or more, go to next step.

12) Check EVR Circuit Continuity Turn ignition off. Disconnect EVR solenoid. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between EVR terminal at EVR solenoid wiring harness connector and test pin No. 33. If reading is less than 5 ohms, go to next step. If reading is 5 ohms or more, repair open circuit and repeat QUICK TEST.

13) Check EVR Circuit For Shorts To Power Or Ground Measure resistance between test pin No. 33 and pins No. 37, 40, 46, 57 and 60 at breakout box with ignition off. If any reading is less than 10,000 ohms, repair short circuit and repeat QUICK TEST . If code is repeated, replace EVR solenoid. If all readings are 10,000 ohms or more, replace PCM. Remove breakout box, 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.

20) Code 334: Check For Code 558 Code 334 indicates EGR valve and/or EVP is not fully seated in closed position. EVP voltage signal, in closed position, is greater than self-test maximum of 0.67 volt. Because of EVP sensor preload, determining whether EGR valve is seated or EVP sensor contacts EGR valve stem is difficult. Possible causes for this fault are

1. Poor contact in EVP sensor circuit.
2. EGR valve not seated.
3. Faulty EGR valve.
4. Faulty EVP sensor.
5. Faulty EVP solenoid.
6. Faulty PCM.

Perform KOEO SELF-TEST. If Code 558 is present, return to step 10). If Code 558 is not present, go to next step.

21) Perform SELF-TEST Without EGR Remove and plug vacuum line to EGR valve. Perform KOEO SELF-TEST and KOER SELF-TEST. If Code 334 is still present, go to next step. If Code 334 is not present, check EVR solenoid for obstructions. If no obstructions are present, replace EVR solenoid.

22) Check EGR Valve & EVP Sensor Operation Turn ignition off. Disconnect EVP sensor. Inspect harness and connector, and service if necessary. Remove and plug vacuum hose to EGR valve. Install vacuum gauge at EGR valve vacuum hose. Operate EGR valve by applying and releasing vacuum. Install vacuum hose to EGR valve and wiring harness connector to EVP sensor. Repeat KOEO SELF-TEST and KOER SELF-TEST. If Code 334 is present, go to next step. If Code 334 is not present, original fault was caused by poor continuity at EVP sensor connector or binding/sticking of EGR valve stem.

23) Check EVP Signal Voltage Turn ignition off. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect PCM to breakout box. Turn ignition on. Measure voltage between test pin No. 27 and test pin No. 46 at breakout box. If voltage is less than 0.67 volt, replace PCM and repeat QUICK TEST . If voltage is greater than 0.67 volt, go to next step.

24) EGR Valve/EVP Sensor Fault Isolation Remove EGR valve and EVP sensor. Inspect valve and sensor for binding, carbon deposits, excessive wear and damage. Repair or replace as necessary. Install EGR valve and EVP sensor. Perform KOEO SELF-TEST and KOER SELF-TEST. If Code 334 is still present, replace EGR valve. If Code 334 is not present, testing is complete.

25) Service Code 328 Service Code 328 indicates EVP sensor is lower than normal (0.24 volt) in closed position. Possible causes for this fault are

1. Faulty EGR valve.
2. Faulty EVP sensor.
3. Faulty PCM.
4. Poor continuity in EVP sensor circuit.

Turn ignition off. Disconnect EVP sensor wiring harness connector. Inspect harness and connector, and service as necessary. Remove EGR valve vacuum hose. Attach vacuum pump to EGR valve. Operate EGR valve by applying and releasing vacuum. Install vacuum hose to EGR valve and wiring harness connector to EVP sensor. Repeat KOEO SELF-TEST and KOER SELF-TEST. If Code 328 is not present, original fault was caused by poor continuity at EVP sensor connector or binding/sticking of EGR valve stem. If Code 328 is present, go to next step.

26) Check EVP Signal Voltage Turn ignition off. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect PCM to breakout box. Remove and plug EGR valve vacuum hose. Connect vacuum pump to EGR valve vacuum hose. Turn ignition on. Measure voltage between test pin No. 27 and test pin No. 46 at breakout box while performing following: apply 6 in. Hg to EGR valve and slowly bleed vacuum completely off. If voltage does not drop to less than 0.24 volt, replace PCM and repeat QUICK TEST . If voltage drops to less than 0.24 volt, go to next step.

27) Substitute EVP Sensor On Original EGR Valve Turn ignition off. Install a known good EVP sensor on original EGR valve. Ensure all hoses and electrical connectors are attached. Perform KOEO SELF-TEST and KOER SELF-TEST. If Code 328 is present, check EGR valve for mechanical malfunction. If Code 328 is not present, replace original EVP sensor. Repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 27) to step 40). No test procedures have been omitted.

40) KOER Code 332: Check Vacuum At EGR KOER Code 332 indicates EVP sensor input did not change after PCM signaled operation of EGR. Possible causes for this fault are

1. Leaking vacuum hose.
2. Restricted vacuum hose.
3. Restricted EVR solenoid.
4. Faulty EVR solenoid.
5. Faulty EVP sensor.
6. Faulty EGR valve.

Turn ignition off. Disconnect vacuum hose from EGR valve. Connect a vacuum gauge at open end of hose. Perform KOER SELF-TEST while observing vacuum gauge. If vacuum reading is more than one in. Hg, remove vacuum gauge and go to step 43). If reading is one in. Hg or less, go to next step.

41) Verify Vacuum Supply To EVR Solenoid Turn ignition off. Disconnect EVR solenoid vacuum hose. Install vacuum gauge at vacuum hose. Start engine and check vacuum. If reading is 10 in. Hg or more, go to next step. If reading is less than 10 in. Hg, check vacuum line to EVR solenoid. Repair if necessary. Repeat QUICK TEST .

42) Check Vacuum Between EVR Solenoid & EGR Valve Check vacuum hose for cracks, loose connections, blockage and kinks. Repair or replace vacuum hose if necessary, and repeat QUICK TEST. If vacuum hose is okay, check EVR solenoid filter for obstructions. Replace if necessary. If filter is okay, replace EVR solenoid. After repairs are made, repeat QUICK TEST .

43) Check EVP Sensor & EGR Valve Operation Turn ignition off. Disconnect EVP sensor. Inspect connector and harness for damage, and service as necessary. Remove vacuum hose from EGR valve. Connect vacuum pump to EGR valve. Operate EGR valve operation by applying and releasing vacuum. Connect vacuum line to EGR valve. Connect wiring harness connector to EVP sensor. Repeat KOER SELF-TEST. If Code 332 is still present, go to next step. If Code 332 is not present, original code was set either by poor continuity at EVP sensor connector or sticking EGR valve. Test is complete.

44) Verify EGR Valve Vacuum Control Turn ignition off. Install tachometer. Remove Idle Air Control (IAC) wiring harness connector. Remove and plug vacuum hose from EGR valve. Start engine, and allow it to idle with transmission in Neutral. Ensure idle speed is adjusted correctly. Connect vacuum pump to EGR valve. Slowly apply 5-10 in. Hg. If engine idle decreases more than 100 RPM with vacuum applied and returns to correct idle with vacuum released, replace EVP sensor. Repeat QUICK TEST . If vacuum does not drop more than 100 RPM with vacuum applied, repair or replace EGR valve. Repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 44) to step 90). No test procedures have been omitted.

90) Continuous Memory Code 327, 328 Or 337 Continuous Memory Code 327 or 328 indicates EGR valve closed further than normal or EVP circuit failed with intermittent low voltage sometime during engine operation. Code 337 indicates EVP signal to PCM was above maximum self-test limit sometime during engine operation. Possible causes for these faults are

1. Obstructed vacuum valve.
2. Faulty EVP sensor.
3. Faulty EVP sensor.
4. EGR valve.

Turn ignition off, and wait 10 seconds. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect PCM to breakout box. Turn ignition on. Connect DVOM between test pins No. 27 and 46 at breakout box. Wiggle wiring harness and lightly tap on EVP sensor. If voltage remains steady at .24-.67 volt, go to next step. If voltage is erratic or not within .24-.67 volt range, remove and inspect EVP sensor wiring harness connector. Repair or replace if necessary. Repeat QUICK TEST . If sensor connector is okay, replace EVP sensor. Repeat QUICK TEST.

91) Check Wiring Harness Turn ignition off. Connect DVOM between test pins No. 27 and 46 at breakout box. Observe DVOM for fault indication while wiggling and bending small sections of wiring harness near sensor, working from sensor toward dash panel. Wiggle and bend wiring harness from firewall to PCM. If fault is indicated, isolate fault and repair wiring harness. Clear codes, and repeat QUICK TEST. If fault is not found, go to next step.

92) Measure EVP Signal Voltage While Exercising EVP Sensor Remove and plug vacuum hose to EGR valve. Install vacuum gauge at EGR valve vacuum hose. Turn ignition on. Measure voltage between test pin No. 27 and test pin No. 46 at breakout box while performing following: apply 5-10 in. Hg to EGR valve and slowly bleed vacuum completely off. If voltage steadily fluctuates between 0.24-4.81 volts, problem is intermittent and cannot be duplicated at this time. If voltage does not fluctuate between 0.24-4.81 volts, replace EVP sensor and repeat QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 92) to step 110). No test procedures have been omitted.

110) Continuous Memory Code 332 Code 332 indicates EGR valve did not open with engine at normal operating temperature and with EVR solenoid signal present sometime during engine operation. Possible causes of this fault are

1. Fault in vacuum line.
2. Faulty EGR valve.
3. Open or shorted EVR circuit.

Turn ignition off. Disconnect vacuum hose at EGR valve. Connect vacuum pump to valve. Apply 10-20 in. Hg to EGR valve. If EGR valve opens and holds vacuum, go to next step. If EGR valve does not open and hold vacuum, service or replace EGR valve as necessary and repeat QUICK TEST .

111) EVR Solenoid & Wiring Harness Check Turn ignition off. Disconnect vacuum hose from EGR valve. Connect EGR valve hose to vacuum gauge. Disconnect PCM 60-pin connector and inspect it for damaged terminals. Repair or replace as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect PCM to breakout box.

112) Start engine, and allow it to idle. Connect jumper wire between test pins No. 33 and 40. Tap on EVR sensor and wiggle wiring harness while observing vacuum gauge. If vacuum gauge shows a sudden drop in vacuum, isolate cause and repair as necessary. Repeat QUICK TEST. If vacuum gauge does not show a drop in vacuum, problem is intermittent and cannot be duplicated at this time.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 112) to step 115). No test procedures have been omitted.

115) Continuous Memory Code 334 Code 334 indicates EGR valve was open with engine idling at normal operating temperature. Possible causes for this fault are

1. Faulty EVP sensor.
2. Faulty EVR solenoid.
3. Faulty EGR valve.

Turn ignition off. Disconnect vacuum hose from EGR valve. Connect EGR valve hose to vacuum gauge. Start engine, and allow it to idle. Tap on EVR sensor and wiggle wiring harness while observing vacuum gauge. If vacuum gauge reading does not remain below one in. Hg and/or has sudden vacuum increase, service or replace EVR solenoid. If vacuum gauge reading remains below one in. Hg with no sudden increase, go to next step.

116) EVR Solenoid Check Leave engine idling and vacuum gauge connected to EGR valve hose. Observe vacuum gauge while wiggling and bending small sections of wiring harness near EVR sensor, working from sensor toward dash panel. Wiggle and bend wiring harness from firewall to PCM. If vacuum gauge shows an increase in vacuum, isolate cause and repair as necessary. If vacuum gauge does not show an increase in vacuum, go to next step.

117) Check EVR Signal At PCM Turn ignition off, and wait 10 seconds. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect PCM to breakout box. Start engine, and allow it to idle. Connect DVOM between test pins No. 27 and 46 at breakout box. Wiggle wiring harness and lightly tap on EVP sensor. If voltage increases to more than 0.67 volt, remove and service EGR valve. If voltage is still more than 0.67 volt, replace EVP sensor. Repeat QUICK TEST . If voltage is 0.67 volt or less, problem is intermittent and cannot be duplicated at this time. 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. Powertrain Control Module (PCM).

Vehicle Speed Sensor Circuit (Bronco). Scheme 17

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

1. Programmable Speedometer/Odometer Module (PSOM) output to PCM.
2. PSOM (+) and PSOM (-) wiring harness circuits.
3. PCM.

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. Ring gear inside differential.
4. Instrumentation system.

PSOM Circuit Logic (Bronco). Scheme 18

PSOM Circuit & Connector Terminals (Bronco). Scheme 19

TEST PIN NO. 3 (PSOM +) WIRE COLOR ID

TEST PIN NO. 6 (PSOM -) WIRE COLOR ID

1) Continuous Memory Code 29/452 Code 29/452 indicates PCM detected incorrect output from VSS sometime during vehicle operation. Following are possible causes of code.

1. PSOM Output To PCM
2. PSOM (+) And PSOM (-) Wiring Harness Circuits
3. PCM

Turn ignition off. Remove PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM 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) 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. Measure resistance between test pin No. 6 at breakout box and PSOM (-) circuit at PSOM wiring harness connector. If resistance is more than 5 ohms, repair open circuit and repeat QUICK TEST . If resistance is 5 ohms or less, go to next step.

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 atbreakout 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) Turn ignition off. Remove RABS connector. (Scheme 18) Measure resistance between connector terminals. If resistance is not 1300-1550 ohms, replace RABS and repeat QUICK TEST. If resistance is 1300-1550, go to next step.

5) Turn ignition off. Connect PCM 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. Using an assistant, 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 PCM.

Perform this test when directed by QUICK TEST. This test is intended to diagnose a faulty BOO switch circuit or PCM. 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.

BOO Switch Circuit (Bronco). Scheme 20

TEST PIN NO. 2 (BOO) WIRE COLOR ID

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

1. Brake pedal not applied during self-test.
2. Brake pedal applied during entire self-test.
3. Open brakelight circuit.
4. Short to ground or power.
5. Faulty Powertrain Control Module (PCM).

If brake was not applied during KOER SELF-TEST, repeat test. Depress and release brake pedal only once during test. If pedal was depressed, go to next step.

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

3) Check For BOO Switch Circuit Cycling Turn ignition off. Wait 10 seconds. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure voltage between test pin No. 2 and test pin No. 40 while applying and releasing brake. If voltage cycles, replace PCM and repeat QUICK TEST . If voltage does not cycle, repair open circuit in BOO switch circuit between PCM and BOO switch connection to brakelight circuit. Repeat QUICK TEST.

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) 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) Check For Short To Power In PCM Turn ignition off. Disconnect PCM. Turn ignition on. Check brakelights. If brakelights are on, go to next step. If brakelights are not on, replace PCM and repeat QUICK TEST.

7) Check For Short To Power In Shift Lock Actuator Turn ignition off. Ensure PCM and brakelight switch are disconnected. Disconnect shift lock actuator, cruise control module and ABS module (if equipped). Turn ignition on. If brakelights are still on, repair short to power in BOO or STOPLAMP circuit and repeat QUICK TEST. If brakelights are not on, repair short circuit in shift lock actuator circuit, cruise control system circuit or ABS circuit. Repeat QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 7) to step 90). No test procedures have been omitted.

90) Continuous Memory Code 536: Check For Proper Brakelight Switch Installation Code 536 indicates a BOO circuit failure. Possible causes for this fault are

1. Brakelight switch installed improperly.
2. Open brakelight circuit.
3. Short to ground or power.
4. Faulty brakelight switch.
5. Faulty brakelight switch ground connection.

Check brakelight switch for proper installation (alignment with brake pedal, corrosion or frayed wires). If brakelight switch is okay, go to next step. If brakelight switch is not okay, repair as necessary. Clear codes and repeat QUICK TEST .

91) Check Brakelight Switch Ground Check brakelight switch ground connection. Also, check brakelight connector wires for corrosion or damage. Repair as necessary. Clear codes and repeat QUICK TEST. If connector and wires are okay, go to next step.

92) Check Brakelight BOO Circuits For Short To Power Turn ignition on. Observe brakelights. With brake pedal released, wiggle brakelight BOO circuit wires and connectors. If brakelights flash, isolate short to power and repair as necessary. Clear codes and repeat QUICK TEST. If brakelights do not flash, go to next step.

93) Check Brakelight Circuit Continuity Turn ignition off. Depress and hold-down brake pedal. Observe brakelights and wiggle brakelight circuit wires and connectors. Also, lightly tap on brakelight switch (to simulate road shock). If brakelights flash or go off, isolate open in brakelight circuit and repair as necessary. Clear codes and repeat QUICK TEST . If brakelights stay on (normal operation), go to next step.

94) Check BOO Circuit Continuity Turn ignition off. Release brake pedal. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Connect DVOM between BOO test pin (No. 2 or 5) at breakout box and BOO terminal at brakelight switch. Observe DVOM and wiggle BOO circuit wires and connectors. If resistance at anytime was more than 5 ohms, isolate open in BOO circuit and repair as necessary. Remove breakout box, reconnect all components, and repeat QUICK TEST. If resistance was 5 ohms or less at all times, fault is intermittent and cannot be duplicated at this time. Testing is complete.

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

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

1. Blower (BLR) motor input circuit.
2. Daytime Running Lights (DRL) input circuit.
3. Headlight (HDL) input circuit.
4. Rear window Defroster (DEF) input circuit.
5. Powertrain Control Module (PCM).

SWITCH CIRCUIT LOGIC

Electrical Load Input Circuit (Bronco). Scheme 21

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.

10) Check Blower Motor Switch (Low Speed) Turn ignition and all accessories off. Remove PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM 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.

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 PCM and confirm idle speed fault has been corrected. If voltage is 1.5 volts or more, go to next step.

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 switch or relay. If resistance is 10,000 ohms or less, repair short circuit.

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.

14) Check Blower Circuit For Short To Power Turn ignition off. Leave blower motor relay disconnected. 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.

20) Check DRL Circuit Voltage (Headlights On) Turn ignition and all accessories off. Remove PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM 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.

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 PCM and confirm idle speed fault has been corrected. If voltage is 1.5 volts or more, go to next step.

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.

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. (Scheme 21) 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.

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.

30) Check Headlight Circuit Voltage (Headlights Off) Turn ignition and all accessories off. Remove PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM 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.

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 PCM and confirm idle speed fault has been corrected. If voltage is not 10-17 volts, go to next step.

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. (Scheme 21) 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.

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.

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.

40) Check DEF Circuit Voltage (Defrost Off) Turn ignition off. Turn all accessories off. Remove PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM 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).

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 PCM and confirm idle speed fault has been corrected. If voltage is 3 volts or more, go to next step.

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.

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. (Scheme 21) 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.

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.

The PSP switch is a normally closed switch that opens as pressure in the power steering system increases.

Perform this test when instructed during QUICK TEST or if directed by other test procedures. Some vehicles may not have power steering, but PCM may be equipped with PSP switch software strategy. If a KOEO Code 519 is displayed, check if vehicle is equipped with power steering. If vehicle is not equipped with power steering, disregard code.

This test is only intended to diagnose

1. Power Steering Pressure (PSP) switch.
2. PSP and SIG RTN wiring harness circuits.
3. Powertrain Control Module (PCM).

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

1. Idle speed/throttle stop adjustment.
2. Binding throttle shaft/linkage.
3. Cruise control linkage.
4. Power steering hydraulic system.

Power Steering Pressure (PSP) Switch Circuit (Bronco). Scheme 22

PSP WIRE COLOR IDENTIFICATION

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

1) KOEO Code 519: Attempt To Eliminate Code Code 519 indicates PSP switch circuit is open. Possible causes for this fault are

1. Damaged PSP switch.
2. Open circuit in wiring harness.
3. Faulty PCM.

Turn ignition off. Disconnect PSP switch. Install jumper wire between PSP terminal and SIG RTN terminal at wiring harness connector. Repeat KOEO SELF-TEST. If Code 519 is not displayed, replace PSP switch and repeat QUICK TEST . If Code 519 is displayed, remove jumper wire and go to next step.

2) Check Continuity Of PSP Circuits Turn ignition off, and wait 10 seconds. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 46 and SIG RTN terminal at PSP switch wiring harness connector. Also measure resistance between test pin No. 24 at breakout box and PSP terminal at switch wiring harness connector. If both readings are less than 5 ohms, replace PCM and repeat QUICK TEST. If readings are 5 ohms or more, check for open circuit and repair as necessary. If circuit is okay, go to next step.

3) Check PSP Switch Operation Turn ignition off. Connect tachometer, and start engine. Allow engine to idle with transmission in Park or Neutral. Disconnect PSP switch wiring harness connector. If RPM increases, replace PSP switch and recheck system. If RPM does not increase, go to next step.

4) Check PSP Switch Circuits For Shorts Turn ignition off. Disconnect PSP switch wiring harness connector. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 24 and test pin No. 46 at breakout box. If resistance is 10,000 ohms or less, repair short in harness and recheck symptom. If reading is more than 10,000 ohms, replace PCM and recheck symptom.

5) KOER Code 521 Disregard this code if vehicle does not have power steering. Code 521 indicates PSP switch did not change states due to open or closed switch. Possible causes for this fault are

1. Damaged PSP switch.
2. Open or shorted circuit in wiring harness.
3. Front wheels turned but not centered.
4. Faulty PCM.

If steering wheel was turned 1/2 turn within 2 seconds after engine ID code and then returned to center, go to next step. If steering wheel was not turned, repeat QUICK TEST .

6) Check PCM Open Circuit Identifying Capabilities Turn ignition off. Disconnect PSP switch. Perform KOEO SELF-TEST. If Code 519 is present, go to step 8). If Code 519 is not present, go to next step.

7) Check PSP Switch Circuits For Shorts Turn ignition off. Disconnect PSP switch. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between PSP test pin and test pin No. 46 at breakout box. If reading is 10,000 ohms or less, repair short circuit and repeat QUICK TEST. If reading is more than 10,000 ohms, replace PCM and repeat QUICK TEST .

8) Check PSP Switch Position Comparison Turn ignition off. With PSP switch connected, turn ignition on. Measure resistance between test pin No. 24 and test pin No. 46 at breakout box. Start engine. Measure resistance between test pin No. 24 and test pin No. 46 at breakout box. If reading shows less than 10 ohms difference between key on engine off and key on engine running, go to next step. If reading is not as described, replace PSP switch and repeat QUICK TEST.

9) Check PSP Switch With Engine Running (Load & No Load) Connect PSP switch. Start engine, and allow it to idle. Measure resistance between test pin No. 24 and test pin No. 46 at breakout box. Turn steering wheel 1/2 turn and return to center position. If resistance changes from less than 10 ohms to infinity and then returns to 10 ohms or less (when steering wheel is centered), PSP switch system is okay. Testing is complete. If reading does not change as indicated, replace PSP switch. Repeat QUICK TEST .

10) Code 519: Attempt To Eliminate Code 519 Disregard this code if vehicle does not have power steering. Code 519 indicates PSP switch circuit is open. Possible causes for this fault are

1. Damaged PSP switch.
2. Open or shorted circuit in wiring harness.
3. Front wheels turned but not centered.
4. Faulty PCM.

Turn ignition off. Disconnect PSP switch connector. Repeat KOEO SELF-TEST. Measure resistance between test pin No. 24 and test pin No. 46 at breakout box. If Code 519 is not present, replace PSP switch. If Code 519 is present, go to next step.

11) Check PSP Circuit For Short Turn ignition off. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 24 and test pin No. 46 at breakout box. If reading is 10,000 ohms or less, repair short circuit and repeat QUICK TEST . If reading is more than 10,000 ohms, replace PCM and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 11) to step 15). No test procedures have been omitted.

15) Check PSP Switch Operation Connect tachometer, and start engine. Allow engine to idle in Park or Neutral. Disconnect PSP switch connector. Using jumper wire, connect PSP switch wiring harness connector terminals. If RPM increases, replace PSP switch and recheck system. If RPM does not increase, go to next step.

16) Check Continuity Of PSP Switch Circuits Turn ignition off, and wait 10 seconds. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM connected. Measure resistance between test pin No. 46 and SIG RTN terminal at PSP switch wiring harness connector. Also measure resistance between test pin No. 24 at breakout box and PSP terminal at PSP switch wiring harness connector. If both readings are less than 5 ohms, replace PCM and repeat QUICK TEST . If any reading is 5 ohms or more, repair open circuit 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.

20) KOER Code 521 Disregard this code if vehicle does not have power steering. Code 521 indicates PSP switch did not change states due to open or closed switch. Possible causes for this fault are

1. Damaged PSP switch.
2. Open or shorted circuit in wiring harness.
3. Front wheels turned but not centered.
4. Faulty PCM.

If steering wheel was turned 1/2 turn within 2 seconds after engine ID code and then returned to center, go to next step. If steering wheel was not turned, repeat QUICK TEST .

21) Check PCM Closed Circuit Identifying Capabilities Turn ignition off. Disconnect PSP switch. Connect jumper wire between PSP terminal and SIG RTN terminal at PSP switch wiring harness connector. Perform KOEO SELF-TEST. If Code 519 is present, remove jumper wire and go to step 23). If Code 519 is not present, remove jumper wire and go to next step.

22) Check Continuity Of PSP Switch Circuits Turn ignition off, and wait 10 seconds. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 24 at breakout box and PSP terminal at PSP switch wiring harness connector. Also measure resistance between test pin No. 46 at breakout box and SIG RTN terminal at PSP switch wiring harness connector. If both readings are less than 5 ohms, replace PCM and repeat QUICK TEST . If either reading is 5 ohms or more, repair open circuit and repeat QUICK TEST.

23) Check PSP Switch Position Comparison Turn ignition off. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM connected. Reconnect PSP switch. Turn ignition on. Measure resistance between PSP test pin and test pin No. 46 at breakout box. Start engine. If reading shows less than 10 ohms difference between key on engine off and key on engine running, go to next step. If reading is not as described, replace PSP switch and repeat QUICK TEST.

24) Check PSP Switch With Engine Running (Load & No Load) Start engine, and allow it to idle. Measure resistance between test pin No. 24 and test pin No. 46 at breakout box. Turn steering wheel 1/2 turn and return to center position. If resistance changes from less than 30 ohms to infinity and then returns to 30 ohms or less (when steering wheel is centered), PSP switch system is okay. Testing is complete. If reading does not change as indicated, replace PSP switch. Repeat QUICK TEST .

Perform this test when instructed during QUICK TEST or if directed by other test procedures. To prevent replacement of good components, be aware the following non-EEC related areas may be at fault

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

This test is only intended to diagnose

1. MAP/BARO sensor.
2. Throttle Position (TP) sensor.
3. Mass Airflow (MAF) sensor.
4. Intake Air Temperature (IAT) sensor.
5. Fuel injectors.

1) Continuous Memory Code 121, 124 Or 125: TP Sensor Integrity Code 121 indicates TP sensor is inconsistent with MAF value. Code 124 indicates TP sensor value is higher than expected. Code 125 indicates TP sensor value is lower than expected.

Turn ignition off. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect PCM to breakout box. Connect DVOM to test pins No. 46 and 47. Slowly apply throttle to WOT, and release to closed position. Voltage should change smoothly from 0.4-4.5 volts. See CIRCUIT TEST DH for schematics and specific engine values. If voltage change is incorrect or erratic, ensure TP sensor is properly installed. If TP sensor is properly installed, replace TP sensor and repeat QUICK TEST . If voltage is okay, go to step 7) for Code 121 or next step for all other codes.

2) Check Idle Ensure idle is correct. If idle is correct, go to next step. If idle is incorrect, see IDLE SPEED in ADJUSTMENTS article in this section.

3) Check Throttle Body Check throttle and/or cruise control linkage for binding and 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. If problems are found, repair as necessary and repeat QUICK TEST . If no problems are found, go to next step.

4) Check MAP/BARO Sensor Output See CIRCUIT TEST DF for MAP/BARO sensor output check. (Scheme 12)for connector terminal identification and MAP/BARO tester hookup. With tester connected and ignition on, measure sensor output voltage. If output voltage is within range for specified altitude, remove MAP/BARO tester and go to next step. See MAP SENSOR VOLTAGE OUTPUT table. If output voltage is not within range, replace MAP/BARO sensor and repeat QUICK TEST.

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

MAP SENSOR VOLTAGE OUTPUT

5) Check IAT Sensor Ensure ambient temperature is more than 50°F (10°C) before performing this test. Check and repair any air leaks in front of IAT sensor. Turn ignition off. Connect breakout box to PCM. Set DVOM to 20-volt scale. Connect DVOM to test pins No. 25 and 46. Start engine, and let it idle. Observe voltage as engine warms. See CIRCUIT TEST DA for voltage specifications. If voltage decreases smoothly and stabilizes when engine reaches operating conditions, system is operating properly at this time. Testing is complete. If voltage does not decrease smoothly and stabilize after engine reaches operating conditions, replace IAT sensor and repeat QUICK TEST .

6) Continuous Memory Code 184 Or 185: 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 Idle Air Control (IAC) 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 9).

7) Check MAF Sensor Circuit Voltage Turn ignition off. Disconnect PCM 60-pin connector. Inspect and repair any damaged terminals. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect PCM to breakout box. Start engine, and warm it to normal operating temperature. Measure voltage between MAF test pin and test pins No. 40 and 60 at breakout box. See MAF WIRE COLOR & TEST PIN IDENTIFICATION table. If voltage is not within specification, replace MAF sensor and repeat QUICK TEST. See MAF SENSOR DATA table. If voltage is within acceptable range, system is operating normally at this time. See SUMMARY in this article.

MAF WIRE COLOR & TEST PIN IDENTIFICATION

MAF SENSOR DATA

8) Continuous Memory Code 186 Or 187: Visual Vacuum Checks Code 186 indicates pulse width is lower than expected (rich). Code 187 indicates pulse width is higher than expected (lean). Inspect air cleaner and air inlet duct. Replace or repair an necessary. Check for unmetered air leaks between MAF sensor and IAC 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.

9) Check Fuel Pressure Turn ignition off. Install fuel pressure gauge. Ensure vacuum hose is connected to fuel pressure regulator (if applicable). Start engine, and run it at idle. If fuel pressure is within specification, go to next step. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. If fuel pressure is not within specification, repair as necessary. See FUEL SYSTEM in SYSTEM/COMPONENT TESTS article in this section.

10) Verify Fuel Pressure Retention Ability Turn ignition on. If fuel pressure remains at specification for 60 seconds, go to next step for models with SFI system or go to CIRCUIT TEST H, step 7) for models with MFI system. If fuel pressure 6does not remain at specification, repair fuel delivery system as necessary. See FUEL SYSTEM in SYSTEM/COMPONENT TESTS article in this section.

11) 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 6). If Code 90 is not present after test, proceed to CIRCUIT TEST H, 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. HO2S and sensor connection.
2. Vacuum systems.
3. Fuel injector and/or fuel injector circuitry.
4. Powertrain Control Module (PCM).
5. Electrical circuits (HO2S, HO2S GND, INJ 1-8, VPWR and SIG RTN).

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

1. Ignition system.
2. Faulty evaporative emission system.
3. EGR and/or PCV system.
4. Air intake system.
5. Engine oil contamination.
6. Fuel system.
7. Intake, supercharger, or charge air cooler leaks.
8. Exhaust system leaks or restriction.
9. Electrical system.
10. Secondary air injection system.
11. Engine cooling system.

INDIVIDUAL INJECTOR RESISTANCE

MFI INJECTOR BANK RESISTANCE

CIRCUIT TEST H ACRONYMS

Test Schematic (Bronco - 5.0L MFI & 5.8L). Scheme 23

Test Schematic (Bronco - 5.0L SFI). Scheme 24

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 KOEO and KOER SELF-TEST. Service ignition continuous memory code (if present) before KOER codes. If vehicle is a no-start, KOER Code 136, 137, 172, 173 or Continuous Memory Code 139, 144, 171, 175, 176, or 177 is set, install PCV valve and go to next step. 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) Check Fuel Pressure Turn ignition off. Release fuel pressure. 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 appropriate SYSTEM/COMPONENT TESTS article in this section.

3) Check System Ability To Hold Fuel Pressure Turn ignition on. Check fuel system for leaks. Repair or replace as necessary. If fuel system does not leak and pressure remains at specification for 60 seconds, go to next step (no-starts), step 5) (MFI) or step 6) (SFI).

4) Fuel Delivery Test Release fuel system pressure. With fuel pressure gauge installed, 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 appropriate TESTS W/O CODES article in this section. If fuel pressure drop is less than 5 psi, remove fuel pressure gauge. Connect inertia switch. Go to step 7) for MFI or step 8) for SFI.

5) Cylinder Balance Test (MFI) 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. IAC 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, perform the following. For Codes 172, 136 or 176, go to step 13). For Codes 173, 137 or 177, go to step 24). For all others, go to step 14).

6) Cylinder Balance Test (SFI) 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 table. If cylinder balance fault codes are present, go to step 8). If Code 136, 172 or 176 is present, go to step 13). If Code 137, 173 or 177 is present, go to step 24). If any other codes are present, go to step 14).

CYLINDER BALANCE TEST SERVICE CODES

7) Check Injector & Harness Resistance (MFI) Turn ignition off. Disconnect PCM 60-pin connector. Inspect pins for damage. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance of injector bank No. 1 between test pins No. 37 and 58 at breakout box. Measure resistance of injector bank No. 2 between test pins No. 37 and 59 at breakout box. Record resistances. See MFI INJECTOR BANK RESISTANCE 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.

8) Check Injector & Harness Resistance (SFI) Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure and record resistance between suspected injector circuit test pin and test pin No. 37. For no-start, measure and record resistance between injector circuit test pin and test pin No. 37. Refer to INJECTOR BANK RESISTANCE 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 next step for all other conditions.

9) Check Continuity Of Fuel Injector Harness Turn ignition off. Disconnect injector wiring harness connector at injectors. Set DVOM on ohm scale. Measure resistance between test pins No. 37 and 57 atbreakout box and each injector VPWR terminal at wiring harness connector. (Scheme 23)and (Scheme 24). 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 next step. 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) Check Injector Harness Circuit For Short To Power Or Ground Turn ignition off, and wait for 10 seconds. With breakout box installed and PCM disconnected, disconnect fuel injector wiring harness connector. 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 (SFI models) or go to next step (MFI models). 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) Isolate Faulty Injector Circuit Turn ignition off. Leave Install breakout box, and disconnect PCM. Disconnect all injectors on suspect bank. With DVOM set on 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 table. 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) Check Injector Drive Signal With ignition off and breakout box installed, connect PCM to breakout box. Use a non-powered 12-volt test light, and connect as follows

1. MFI Connect test light between test pins No. 37 and 58 at breakout box. Connect test light between test pins No. 37 and 59 at breakout box.
2. SFI Connect test light between test pin No. 37 and suspect injector test pin at breakout box.

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 PCM. Reconnect all components. Drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST .

13) Check Thermactor Operation If vehicle is equipped with pulse-air or does not have secondary air injection system, go to next step. A HO2S which is always lean could be caused by thermactor air being diverted upstream from HO2S. With dual HO2S, Code 172 applies to right or rear HO2S and Code 136 or 176 applies to left or front HO2S. Turn ignition off. Disconnect secondary air hose(s) from pump and vent to atmosphere. Perform KOER SELF-TEST. If Code 172, 136 or 176 is present, reconnect air hose(s) and go next step. If Continuous Memory Code 139, 144, 171, 176 or 177 is present, go to step 90). If code(s) is not present, repair air injection system as necessary.

14) Check HO2S Integrity A HO2S which is always lean, slow to switch or does not switch could be caused by

1. Moisture inside HO2S or connector causing a short to ground.
2. HO2S coated with contaminants.
3. HO2S circuit open.
4. HO2S circuit shorted to ground.

Turn ignition off. Inspect HO2S wiring harness for damage. Inspect HO2S 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).

15) Check HO2S (Engines With MAP Sensors) Vacuum or air leaks in non-EEC-IV areas could cause Code 41/172, 91/136 or 176. Check following possibilities before continuing

1. Leaking vacuum actuated motor.
2. Leaking intake gasket.
3. EGR system.
4. PCV system.
5. Lead-contaminated HO2S.

Turn ignition off. Ensure MAP sensor output voltage is correct. See CIRCUIT TEST DF, step 3). Disconnect appropriate HO2S from wiring harness connector. On 3-wire HO2S, connect DVOM to HO2S terminal at sensor wiring harness connector and negative battery terminal. On 4-wire HO2S, connect DVOM to HO2S and HO2S GND or SIG RTN terminal at sensor wiring harness connector. 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 HO2S and repeat QUICK TEST .

16) Check HO2S (Engines With MAF Sensor) Purpose of this test is to verify HO2S can generate a voltage signal of greater than 0.5 volt during KOER SELF-TEST. Vacuum or air leaks in non-EEC-IV areas could cause Code 41/172, 91/136 or 176. Check following possibilities before continuing

1. Leaking vacuum actuated motor.
2. Leaking intake gasket.
3. EGR system.
4. PCV system.
5. Unmetered air between MAF sensor and throttle body.
6. Lead-contaminated HO2S.

Turn ignition off. Disconnect appropriate HO2S from harness. On 3-wire HO2S, connect DVOM to HO2S terminal at sensor wiring harness connector and negative battery terminal. On 4-wire HO2S, connect DVOM between HO2S terminal and HO2S GND or HO2S GND terminal at HO2S wiring harness connector. Run engine at 2000 RPM for 2 minutes. Repeat KOER SELF-TEST and monitor HO2S 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 HO2S and repeat QUICK TEST .

17) Check Continuity Of HO2S Ground Circuits Turn ignition off. Install breakout box, leaving PCM disconnected. Disconnect suspect HO2S wiring harness connector. Inspect connector for damage, moisture and corrosion. Repair as necessary. Measure resistance between HO2S test pin at breakout box and HO2S terminal at sensor wiring harness connector. On 3-wire HO2S, measure resistance between HO2S GND test pin at breakout box and negative battery terminal. On 4-wire HO2S, measure resistance between SIG RTN test pin at breakout box and SIG RTN terminal at sensor wiring harness connector. Where applicable, measure resistance between HO2S GND and SIG RTN at breakout box. 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 .

18) Check HO2S Circuit For Short To Ground Turn ignition off. Leave breakout box installed and PCM disconnected. Disconnect HO2S. Measure resistance between HO2S circuit test pin and test pins No. 40, 46 and 49 at breakout box. If any reading is less than 10,000 ohms, repair short to ground. Drive vehicle at 55 MPH for 5 minutes and repeat QUICK TEST. If reading is 10,000 ohms or more, go to next step.

19) Check HO2S For Short To Ground Ensure ignition is off and PCM is disconnected. With HO2S disconnected, measure resistance between PWR GND and HO2S terminal at HO2S connector. On 4-wire HO2S, also measure resistance between HO2S GND and/or SIG RTN terminal at sensor wiring harness connector. If resistance is less than 10,000 ohms, replace HO2S. Drive vehicle for 5 miles at 55 MPH and repeat QUICK TEST . If resistance is 10,000 ohms or more, perform following procedure as applicable.

1. For Codes 139, 144, 171, 174, 175 and 178, go to step 90).
2. For all other codes, go to next step if engine is equipped with MAP sensor. If engine is equipped with MAF sensor, replace PCM. Drive vehicle for 5 miles at 55 MPH, and repeat QUICK TEST.

20) Attempt To Eliminate Code 136, 172 Or 176 (Engines With MAP Sensor) Turn ignition off. Connect PCM to breakout box. Connect HO2S. Disconnect and plug MAP sensor vacuum hose. Start engine and apply 10-14 in. Hg to MAP sensor. Increase engine speed to 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 136, 172 or 176 is still present, remove breakout box. Connect all components. If engine runs rough, go to CIRCUIT TEST S, step 2). If engine does not run rough, replace PCM, drive vehicle 5 miles at 55 MPH and repeat QUICK TEST . If code is not present, remove breakout box and connect all components. HO2S input circuit and fuel delivery are okay; fault is in area common to all cylinders. See appropriate TESTS W/O CODES article in this section.

21) Check Resistance Of HO2S Heating Element Turn ignition off. Disconnect suspect HO2S. Inspect both ends of connector for damage, moisture and corrosion. Repair if necessary. Measure resistance between IGNITION RUN circuit and PWR GND circuit at HO2S 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 HO2S and repeat QUICK TEST .

22) Check For Power At HO2S Harness Connector Disconnect HO2S. Turn ignition on. Measure voltage between IGNITION RUN and PWR GND circuits at HO2S wiring harness connector. If voltage is 10.5 volts or more, HO2S system and fuel delivery are okay. HO2S may have cooled before KOER SELF-TEST. If driveability symptom continues, fault is in area common to all cylinders. See appropriate TESTS W/O CODES article in this section. If voltage is less than 10.5 volts, go to next step.

23) Check Continuity Of Power Ground Circuit Turn ignition off. Measure resistance between PWR GND circuit at HO2S 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.

24) Diagnostic Test Code 137, 173 Or 177: Check HO2S SIGNAL For Short To Power On dual HO2S systems, Code 173 applies to right or rear sensor. Codes 137 and 177 apply to left or front sensor. HO2S continuously rich could be caused by

1. Moisture inside wiring harness causing short to power.
2. HO2S shorted to power.

Turn ignition off. Disconnect appropriate HO2S. Inspect connector for damage and repair as necessary. Turn ignition on. Measure voltage between HO2S and PWR GND terminal at HO2S 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.

25) Check For Short To Power Turn ignition off. Disconnect HO2S. Inspect wiring harness for damage and repair as necessary. Disconnect PCM 60-pin connector. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Disconnect suspect HO2S. Measure resistance between VPWR test pin and HO2S SIG test pin at breakout box. If reading is 10,000 ohms or more, replace PCM. Remove breakout box, and reconnect all components. Drive vehicle 5 miles at 55 MPH. Repeat QUICK TEST . If reading is less than 10,000 ohms, repair short circuit. Remove breakout box, and reconnect all components. Drive vehicle 5 miles at 55 MPH. Repeat QUICK TEST.

26) Check HO2S For Short To IGNITION RUN Circuit Turn ignition off. Disconnect HO2S. Measure resistance between IGNITION RUN terminal and HO2S terminal at HO2S wiring harness connector. If resistance is 10,000 ohms or more, go to next step for Codes 173, 137 and 177 or step 28) for Codes 171, 174, 175 and 178 (MAP sensor) or step 30) on models with MAF sensor. If resistance is less than 10,000 ohms, replace HO2S. Drive vehicle for 5 miles at 55 MPH, and repeat QUICK TEST .

27) Attempt To Generate Code 172, 136 Or 176 Turn ignition off. Disconnect appropriate HO2S. Using jumper wire, connect HO2S terminal at HO2S wiring harness connector to negative battery terminal. Repeat KOER SELF-TEST. If Code 172, 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 172, 136 and 176 are not present, remove jumper wire. Disconnect PCM connector, and inspect it for damage. If connector is okay, replace PCM. Drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST.

Because MAP sensor greatly influences fuel control, MAP sensor may malfunction without setting Code 126. Next 2 steps test MAP vacuum circuit.

28) Check MAP Sensor For Vacuum Leaks Turn ignition off. Disconnect vacuum hose from MAP sensor. Inspect hose for damage and repair as necessary. 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 next step.

29) Check For Loss Of Vacuum To MAP Sensor Using vacuum "T", connect vacuum gauge in MAP sensor vacuum circuit. Start engine. Note vacuum reading after 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 one 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 .

30) HO2S Check Turn ignition off. Disconnect HO2S. For 4-wire HO2S, connect DVOM to HO2S terminal and HO2S GND or SIG RTN terminal at HO2S connector. For 3-wire HO2S, connect DVOM to HO2S terminal at HO2S connector and negative battery terminal. Cause a vacuum leak to force HO2S to go lean. Remove PCV valve hose. Start engine. Raise engine speed to about 2000 RPM. DVOM should indicate less than 0.4 volt within 30 seconds. If voltage is not as specified, replace HO2S. Reconnect vacuum hoses, and drive vehicle for 5 miles at 55 MPH. Repeat QUICK TEST. If voltage is as specified, go to step 90).

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.

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) under QUICK TEST . While observing DVOM or scan tester, shake or bend small sections of wiring harness from HO2S to PCM. Wiggle, shake or bend small sections of wiring harness from HO2S GND to PCM. 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.

91) Continuous Monitor Test Drive Check While still in KOER wiggle test, 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 HO2S 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.

92) Check HO2S Switching Turn ignition off. Inspect wiring harness for proper routing and insulation. Check for burnt, chaffed or open wires. Repair as necessary. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install breakout box. Connect PCM to breakout box. Connect analog voltmeter to suspect HO2S test pin and HO2S GND at breakout box. Test drive vehicle for 5 miles at 55 MPH while observing voltmeter. HO2S should switch from .3 volt to .9 volt within 3 seconds. If HO2S does not switch as described, replace HO2S. Connect all components, and repeat QUICK TEST. If HO2S switches as described, fault cannot be identified or duplicated at this time. See INTERMITTENTS in TESTS W/O CODES article in this section.

CIRCUIT TEST HA - ADAPTIVE FUEL

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

Perform this test when directed by QUICK TEST. PCM 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/BARO sensors. Average voltage reading will be typical for location and day of testing.

MAP SENSOR VOLTAGE OUTPUT

CIRCUIT TEST HA ACRONYMS

1) Continuous Memory Codes 181, 183, 189 & 192 These codes identify a lean fuel condition resulting in adaptive fuel strategy enriching fuel system to compensate.

1. Code 183 Indicates single right or rear HO2S detected a problem and adaptive fuel rich limit has been reached at idle.
2. Code 192 Indicates left or front HO2S detected a problem and adaptive fuel rich limit has been reached at idle.
3. Code 181 Indicates single right or rear HO2S detected a problem and adaptive fuel rich limit has been reached.
4. Code 189 Indicates left or front HO2S detected a problem and adaptive fuel rich limit has been reached.

When ignition switch is in the ON or START position, the PCM connects FUEL PUMP circuit (PCM terminal No. 22) to ground. The fuel pump relay is energized and electrical current flows to the fuel pump. If PCM does not receive ignition PIP signal within 2 seconds, FUEL PUMP circuit is opened and fuel pump operation is terminated. Perform this test when instructed by QUICK TEST or CIRCUIT TEST AA.

This test is only intended to diagnose

1. Fuel pump relay.
2. Inertia Fuel Shutoff (IFS) switch.
3. Wiring harness circuits (B+, VPWR, FUEL PUMP, GND and POWER-TO-PUMP).
4. Faulty Powertrain Control Module (PCM).

Fuel Pump Monitor Schematic Diagram (Bronco). Scheme 25

Fuel Pump Monitor Circuit Diagram (Bronco). Scheme 26

1) Code 556: Check VPWR To Fuel Pump Relay Code 556 indicates a fuel pump primary circuit failure.

Possible causes for this fault are

1. IFS switch not reset or circuit open.
2. Open or shorted circuit.
3. Faulty fuel pump relay.
4. Faulty PCM.

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 IFS 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 .

2) Check Fuel Pump Relay Turn ignition off. Disconnect fuel pump relay. On ISO relays, measure resistance between terminals No. 85 and 86. (Scheme 27) 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 10-k/ohm scale. On ISO 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 B+ 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.

Fuel Pump Relay Connector Terminal ID (Bronco). Scheme 27

3) Check For Short To Power Turn ignition off. Disconnect fuel pump relay. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Turn ignition on. Measure voltage between test pin No. 22 and negative battery terminal. If voltage is less than one volt, go to next step. If voltage is one volt or more, repair short circuit. Reconnect PCM, and attempt to start vehicle. If vehicle fails to start, replace PCM. Repeat QUICK TEST .

4) Check For Shorts To Ground Turn ignition off. Leave fuel pump relay and PCM 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 circuit and repeat QUICK TEST. If resistance is 10,000 ohms or more, go to next step.

5) Check Fuel Pump Circuit Continuity Turn ignition off. Leave fuel pump relay and PCM 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 PCM and repeat QUICK TEST. If resistance is 5 ohms or more, repair open circuit 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.

10) Code 542 A KOEO Code 542 indicates one of the following conditions

Due to internal circuitry of PCM, a left/front HO2S signal short to power could produce a Code 542 or 543.

25) Check Left/Front HO2S Sensor For Short To Power Turn ignition off. Disconnect left or front HO2S sensor. Measure resistance between HO2S SIGNAL terminal and KEY POWER terminal at HO2S sensor wiring harness connector. (Scheme 28)and (Scheme 29). If resistance is 10,000 ohms or more, go to next step. If resistance is less than 10,000 ohms, replace HO2S sensor. Clear KAM, and repeat QUICK TEST.

HO2S Sensor Connector (Bronco). Scheme 28

HO2S Sensor Wiring Harness Connector (Bronco). Scheme 29

26) Check HO2S Circuit For Short To Power Turn ignition off. Leave left or front HO2S sensor disconnected. Disconnect PCM. Inspect and repair any damaged terminals. Turn ignition on. Measure voltage between HO2S SIGNAL at HO2S wiring harness connector and chassis ground. If voltage is less than 2 volts, replace PCM and repeat QUICK TEST. If voltage is 2 volts or more, repair short circuit. Clear KAM, and repeat QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 26) to step 90). No test procedures have been omitted.

90) Continuous Memory Code 542 Code 542 indicates one of the following conditions

1. Faulty ground circuit at fuel pump.
2. FPM or POWER-TO-PUMP circuit short to power.
3. IFS switch not reset.
4. Fuel pump relay contacts stuck closed.
5. Open circuit in or between fuel pump and FPM circuit at PCM.
6. Left or front HO2S circuit short to power (dual HO2S system).
7. FUEL PUMP circuit is activated at a time that is not programmed into PCM strategy.
8. Engine stall due to excessive load.

Start engine. Check for engine miss or intermittent fuel pump deactivation while performing following

1. Shake and bend POWER-TO-PUMP circuit wiring harness connector between fuel pump relay and fuel pump.
2. Shake and bend fuel pump ground circuit between fuel pump and ground.
3. Lightly tap fuel pump to simulate road shock.
4. Lightly tap IFS switch to simulate road shock.

Turn 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.

91) Check FPM Circuit Turn ignition off. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Connect test light between test pin No. 8 and test pin No. 37 at breakout box. With test light lit, perform wiggle test on FPM circuit between fuel pump and PCM. 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.

92) Check For Shorts To Power Connect a test light between breakout box test pins No. 8 and 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 HO2S) or step 99) (single HO2S).

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

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

1. An open in B+ circuit between B+ and fuel pump relay.
2. Fuel pump relay contacts open.
3. Open in POWER-TO-PUMP circuit between fuel pump relay to FPM splice (if applicable).
4. Left/front HO2S circuit short to power (dual HO2S).

Start engine. Check for engine miss or intermittent fuel pump deactivation while performing the following

1. Shake and bend B+ circuit wiring harness between power source and fuel pump relay.
2. Shake and bend POWER-TO-PUMP circuit wiring harness connector between fuel pump relay and FPM splice (if applicable).
3. Lightly tap fuel pump relay to simulate road shock.

Turn ignition off. Inspect all fuel pump relay and B+ connectors for damage and corrosion. If fault is found, repair as necessary and repeat QUICK TEST . If no fault is found, a Continuous Memory Code 543 may have been set without a Continuous Memory Code 556, even though a fault has occurred in fuel pump primary circuit. go to next step for fuel pump primary circuit check.

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

1. Open in VPWR circuit between EEC power relay and fuel pump relay.
2. Open coil in fuel pump relay.
3. Open in fuel pump circuit (pin No. 22).
4. Faulty IFS switch.

Start engine. Check for engine miss or intermittent fuel pump deactivation while performing the following

1. Shake and bend VPWR circuit wiring harness between EEC and fuel pump relay.
2. Shake and bend FP circuit wiring harness connector between fuel pump relay and PCM.
3. Lightly tap fuel pump relay to simulate road shock.
4. Lightly tap IFS switch to simulate road shock (if equipped).

Turn ignition off. Disconnect fuel pump relay connector and PCM 60-pin connector. Inspect terminals. If fault is found, isolate and repair as necessary. Repeat QUICK TEST . If no faults are found but Code 543 is present, go to next step (dual HO2S) or go to step 99) (all others).

Due to internal circuitry of PCM, an intermittent left/front HO2S signal short to power could produce a Continuous Memory Code 542 or 543.

96) Check Left/Front HO2S Circuit For Short To Power Turn ignition off. Breakout box should be installed with PCM disconnected. Connect test light between left/front HO2S test pin and pin No. 40 at breakout box. See CIRCUIT TEST H for left/front HO2S test pin identification. Test light should be off. Observe test light while bending and shaking left/front HO2S circuit from HO2S sensor to PCM. Lightly tap HO2S SENSOR to simulate road shock. Fault is indicated if test light comes on. If fault is indicated, isolate and repair as necessary, and repeat QUICK TEST . If no fault is indicated, go to step 99).

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.

99) Road Test Vehicle Purpose of this test is to identify faults by monitoring certain controlled parameters while trying to recreate a drive-ability or MIL symptom. To prepare for road test

1. Install fuel pressure gauge and if available, a MAP/BARO tester.
2. Disconnect PCM 60-pin connector, install breakout box and reconnect PCM to breakout box.
3. Connect "T" vacuum gauge into manifold vacuum line.
4. 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

1. 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.
2. 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.
3. OPTIONAL GROUNDS: HO2S GND (pin No. 49), CSE GND (pin No. 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 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, PCM 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 556 is set again, replace fuel pump relay. If only FP voltage goes low, fault is in FP circuit or PCM. To diagnose FP circuit and PCM, connect DVOM between breakout box test pins No. 1 and 22. If voltage goes low as symptom occurs, replace PCM. If voltage stays high as symptom occurs, fault is in FP circuit. For fuel pump secondary circuit Codes 542 and 543, circuits B+, 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 this section for other possible causes of symptom.

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

1. Damaged vacuum hoses.
2. Damaged EGR Pressure Transducer (EPT).
3. EGR valve.

This test is only intended to diagnose

1. EGR Vacuum Regulator (EVR) solenoid.
2. PCM.
3. Wiring harness circuits (EVR and VPWR).

EVR solenoid regulates vacuum to EGR valve by way of EVT. 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.

EGR Vacuum Regulator (EVR) Solenoid Ckt. & Connector Terminal ID (Bronco). Scheme 30

1) Code 558 Code 558 indicates failure in EVR solenoid circuit. Possible causes for this fault are

1. Faulty EVR solenoid.
2. Faulty vacuum hoses.
3. Open or ground circuit in wiring harness.
4. Faulty Powertrain Control Module (PCM).

Turn ignition off. Remove scan tester (if applicable). Disconnect cruise control servo wiring harness connector. Connect DVOM negative lead to STO terminal at Data Link Connector (DLC). Connect positive lead to positive battery terminal. Install a jumper wire between STI terminal and SIG RTN terminal at DLC. (Scheme 7) Perform KOEO SELF-TEST until continuous memory test is complete. DVOM will read less than one volt when test is complete to indicate PCM 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. If voltage increases, remain in OUTPUT STATE CHECK and go to next step.

2) Check EVR Solenoid Electrical Turn ignition off. Remove 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 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 EPT 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 terminal at 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 PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM 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. Leave EVR solenoid disconnected. Measure resistance between test pin No. 31 and test pins No. 37 and 57 at breakout box. Measure resistance between test pin No. 31 and test pins No. 40, 46 and 60 at breakout box. If each resistance is 10,000 ohms or more, replace PCM and repeat QUICK TEST . If reading is less than 10,000 ohms, repair short circuit and repeat QUICK TEST.

CANP valve is controlled by the PCM. CANP valve is used to regulate the flow of fuel vapors from the EVAP canister to the fuel system. The CANP valve operates on manifold vacuum and a duty cycle from the PCM.

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

1. CANP valve.
2. Faulty Powertrain Control Module (PCM).
3. Wiring harness circuits (CANP and VPWR).

CANP Circuit Schematic (Bronco). Scheme 31

CANP Valve Circuit & Connector Terminal ID (Bronco). Scheme 32

1) KOEO Code 565 Code 565 indicates failure in CANP valve. Possible causes for this fault are

1. Faulty CANP valve.
2. Faulty vacuum hoses.
3. Open or ground circuit in wiring harness.
4. Faulty Powertrain Control Module (PCM).

Turn ignition off. Remove scan tester (if applicable). Disconnect cruise control servo wiring harness connector (if equipped). Connect DVOM negative lead to STO terminal at Data Link Connector (DLC). Connect positive lead to positive battery terminal. Install a jumper wire between STI terminal and SIG RTN terminal at DLC. (Scheme 7) Perform KOEO SELF-TEST until continuous memory test is complete. DVOM will read less than one volt when test is complete to indicate PCM has entered OUTPUT STATE CHECK. Fully apply and release throttle. If voltage does not increase, fully apply throttle and release. If voltage remains low, fully apply and release throttle. If voltage does not increase, go to CIRCUIT TEST QC. If voltage increase can be obtained, remain in OUTPUT STATE CHECK and go to next step.

2) Check CANP Valve Electrical Turn ignition off. Remove CANP valve wiring harness connector. Connect DVOM positive lead to VPWR terminal and negative test lead to CANP terminal at CANP valve wiring harness connector. Depress and release throttle 3-5 times to cycle voltage output. If 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 7).

3) Measure CANP Valve Resistance Leave ignition off and CANP valve connectors disconnected. Measure resistance between connector terminals. If resistance is not 30-36 ohms, replace CANP valve and repeat QUICK TEST . If resistance is 30-36 ohms, go to next step.

4) Check CANP Valve For Vacuum Leaks Leave CANP valve connectors disconnected. Remove vacuum hose from input port of CANP valve. (Scheme 33) Using a vacuum pump, apply 16 in Hg. to input port. Replace valve if it does not hold vacuum for 20 seconds. If valve holds vacuum for 20 seconds, go to next step.

Locating CANP Valve Vacuum Input Port (Bronco). Scheme 33

5) Check CANP Valve Electrical/Mechanical Reconnect Leave CANP valve connector. Ensure 16 in Hg. is applied to input port. Fully apply and release throttle. If vacuum is not released, replace CANP valve and repeat QUICK TEST . If vacuum is released, remove jumper wire between SIG RTN and STI terminals of DLC. go to next step.

6) Check Vacuum At CANP Valve Input Port Leave CANP valve wiring harness connected. Start engine and allow to idle. Remove CANP valve vacuum input hose. If vacuum is not present at hose, check hose for blockage, leaking or incorrect routing. If vacuum is present at hose, EEC system is okay. Testing is complete.

7) Check VPWR Circuit Voltage Leave CANP valve wiring harness disconnected. Turn ignition on. Measure voltage CANP valve wiring harness connector terminal VPWR and battery ground. If 10.5 volts or more is present, go to next step. If less than 10.5 volts is present, repair open circuit and repeat QUICK TEST .

8) Check CANP Circuit Continuity Turn ignition off. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 11 and CANP terminal of CANP valve 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.

9) Check For CANP Circuit Short To Power Leave ignition off and CANP valve connector disconnected. Measure resistance between breakout box test pin No. 11 and pins No. 37 and 57. 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.

10) Check For Short To Ground Leave ignition off and CANP valve connector disconnected. Measure resistance between breakout box test pin No. 11 and pins No. 40, 46 and 60. If any reading is less than 10,000 ohms, repair short to ground and repeat QUICK TEST. If all readings are 10,000 ohms or more, replace PCM and repeat QUICK TEST.

PCM uses secondary air injection solenoids to control Air Injection By-pass (AIRB) and Air Injection Diverter (AIRD) valves. AIRB and AIRD are used to direct air to either engine or exhaust system.

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

1. AIRB/AIRD solenoid valve assembly.
2. Wiring harness circuits (AIRB, AIRD and VPWR).
3. Vacuum supply.
4. Powertrain Control Module (PCM).

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

1. Secondary air injection system (belt, pump, valve or reservoir).
2. Blocked or restricted secondary air passages in engine.

Sec. Air System Elect. Ckt. & Wiring Harness Conn. Term. ID (Bronco). Scheme 34

AIRB WIRE COLOR & TEST PIN IDENTIFICATION

AIRD WIRE COLOR & TEST PIN IDENTIFICATION

VREF WIRE COLOR & TEST PIN IDENTIFICATION

1) Codes 311, 312, 313 & 314 Code 311 or 314 indicates that secondary air injection system is inoperative. Code 312 indicates that secondary air is incorrectly routed. Code 313 indicates that secondary air is not by-passed when directed. Possible causes for these faults are

1. Vacuum hoses leaking, blocked or kinked.
2. Secondary air injection valve inoperative.
3. Secondary air injection solenoid defective or blocked.

Check for correct vacuum hose routing to AIRB/AIRD solenoids and by-pass diverter valve. See Vehicle Emission Control Information (VECI) label. Check for kinked or blocked vacuum hoses. Check for kinked or blocked air hoses. Check for disconnected vacuum hoses. If faults are detected, repair as necessary and repeat QUICK TEST . If no faults are detected and Code 311 or 314 is present, go to step 4). If Code 313 is present, go to step 3). If Code 312 is present, go to next step.

2) Attempt To Eliminate Code 312 Disconnect and plug vacuum hose at AIRD valve. Repeat KOER SELF-TEST. If Code 312 is present, EEC-IV system is okay. Inspect diverter valve and check valve for faults. If Code 312 is not present, go to step 4).

3) Attempt To Eliminate Code 313 Disconnect and plug vacuum hose at by-pass valve. Repeat KOER SELF-TEST. If Code 313 is present, EEC-IV system is okay. Check by-pass valve for problem. If Code 313 is not present, go to next step.

4) OUTPUT STATE CHECK Use only a VOM or DVOM for this step. DO NOT use scan tester. Turn ignition off. Disconnect cruise control servo (if equipped). Connect DVOM negative lead to STO terminal at Data Link Connector (DLC). Connect positive lead to positive battery terminal. Using jumper wire, connect STI to SIG RTN at DLC. (Scheme 7) Perform KOEO SELF-TEST until continuous memory test is complete. DVOM will read less than one volt when test is complete. Depress and release throttle. If voltage increases, OUTPUT STATE CHECK has been entered. go to next step. If voltage does not increase, depress throttle to WOT and release. If STO voltage does not increase, go to CIRCUIT TEST QC.

5) Check Solenoid Electrical Operation Set DVOM on 20-volt scale. Disconnect AIRB/AIRD solenoids. Connect DVOM positive lead to VPWR terminal and negative lead to AIRB terminal at AIRB solenoid wiring harness connector. While observing DVOM, depress and release throttle several times to cycle output on and off. Repeat test for AIRD solenoid. Connect DVOM positive lead to VPWR terminal and negative test lead to AIRD terminal on AIRD solenoid wiring harness connector. Cycle AIRD solenoid on and off. If either solenoid does not cycle more than 0.5 volt, remove jumper and go to step 9). If both solenoids cycle more than 0.5 volt, stay in OUTPUT STATE CHECK. Reconnect solenoids and go to next step.

6) Check Solenoids For Vacuum Cycling Connect vacuum pump to solenoid vacuum supply port. Connect vacuum gauge to output port. Maintain 15 in. Hg at vacuum source while depressing and releasing throttle to cycle output on and off. Observe vacuum gauge. Repeat for other solenoid. If either output does not cycle on and off, replace solenoid assembly and repeat QUICK TEST . If both outputs cycle on and off, go to next step.

7) Check Solenoids For Internal Vacuum Leaks Connect a vacuum pump to AIRB solenoid supply port. Connect a vacuum gauge to AIRB solenoid output port. Apply 15 in. Hg at vacuum source. Observe gauge while depressing and releasing throttle to cycle output on and off. Repeat test for AIRD solenoid. If solenoids cycle on and off, fault is in secondary air injection system (belt, pump, valve or reservoir). If solenoids do not cycle on and off, replace solenoid assembly and repeat QUICK TEST.

8) Codes 553 & 552 Codes 553 and 552 indicate voltage output for secondary air injection solenoid did not change when activated. Possible causes for this fault are

1. AIRB/AIRD circuit(s) shorted or open.
2. Fault in solenoid or PCM.

Disconnect both solenoid connectors. Turn ignition on. Measure voltage between VPWR terminal of wiring harness connector and battery ground for both solenoids. If either voltage reading is less than 10.5 volts, repair wiring harness open circuit, and repeat QUICK TEST. If both readings are 10.5 volts or more, go to next step.

9) Measure Solenoid Resistance Turn ignition off. Leave solenoid connectors disconnected. Measure resistance of both solenoids. If either reading is not 50-100 ohms, replace solenoid assembly and repeat QUICK TEST . If both readings are 50-100 ohms, go to next step.

10) Check Circuit Continuity Leave ignition off. Disconnect PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between AIRB test pin at breakout box and AIRB terminal at wiring harness connector. Measure resistance between AIRD test pin at breakout box and AIRD terminal at wiring harness connector. If either reading is 5 ohms or more, repair open circuit and repeat QUICK TEST . If both readings are less than 5 ohms, go to next step.

11) Check For Short To Ground Leave ignition off and solenoids disconnected. Measure resistance between AIRB test pin at breakout box and test pins No. 40, 46 and 60 at breakout box. Measure resistance between AIRD test pin at breakout box and test pins No. 40, 46 and 60. If any reading is less than 10,000 ohms, repair short to ground and repeat QUICK TEST. If all readings are 10,000 ohms or more, go to step 12).

12) Check For Short To Power Circuit Turn ignition off. Leave solenoids and PCM disconnected. Measure resistance between AIRB test pin and test pins No. 37 and 57 at breakout box. Measure resistance between AIRD test pin and test pins No. 37 and 57 at breakout box. If any resistance is less than 10,000 ohms, repair short to power and repeat QUICK TEST . If code is repeated, replace PCM. If all resistances are 10,000 ohms or more, replace PCM 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. Powertrain Control Module (PCM).

Canister Purge (CANP) Circuit (Bronco). Scheme 35

CANP WIRE COLOR & TEST PIN IDENTIFICATION

TEST PINS NO. 37 & 57 (VPWR) WIRE COLOR IDENTIFICATION

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 Data Link Connector (DLC). Connect positive lead to positive battery terminal. Install a jumper wire between STI terminal and SIG RTN terminal at DLC. (Scheme 7) Perform KOEO SELF-TEST until continuous memory test is complete. DVOM will read less than one volt when test is complete to indicate PCM 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 does not increase, leave test equipment hooked up and go to CIRCUIT TEST QC.

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 7). 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 blockage or kinks. 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 side. Start engine. If vacuum is present at vacuum hose, engine control 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 mechanical cause of low vacuum.

6) Code 565 Or 569: Check CANP Solenoid Resistance Code 565 or 569 indicates fault in CANP solenoid circuit.

Possible causes for this fault are

1. Faulty CANP solenoid.
2. Open or short circuit in wiring harness circuit.
3. Faulty PCM.

Turn ignition off. Disconnect CANP solenoid connector. Measure CANP solenoid resistance. If resistance is 30-90 ohms, go to next step. If resistance is not 30-90 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 reading is 10.5 volts or more, go to next step. If reading 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 PCM connector. Inspect terminals, and repair if damaged. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between CANP test pin atbreakout box and CANP terminal at solenoid wiring harness connector. If reading is less than 5 ohms, go to next step. If reading 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 CANP test pin and pins No. 40, 46 and 60 at breakout box. If all readings are 10,000 ohms or more, go to next step. If any reading 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 and PCM disconnected, measure resistance between CANP test pin and test pins No. 37 and 57 at breakout box. If all readings are 10,000 ohms or more, replace PCM and repeat QUICK TEST . If any reading is less than 10,000 ohms, repair short to power and repeat QUICK TEST.

The IAC solenoid controls engine idle speed and dashpot functions by regulating the volume of air by-passing the throttle plate. IAC solenoid positioning is determined by signals sent from the PCM.

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

1. RPM during SELF-TEST mode.
2. IAC solenoid.
3. Wiring harness circuits (IAC and VPWR).
4. Powertrain Control Module (PCM).

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

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

Idle Air Control Circuit (Bronco). Scheme 36

TEST PIN NO. 21 (ISC) WIRE COLOR IDENTIFICATION

TEST PINS NO. 37 & 57 (VPWR) WIRE COLOR IDENTIFICATION

1) Code 412 Code 412 indicates engine RPM could not be controlled within upper RPM limit during KOER SELF-TEST. Possible causes for this fault are

1. Open or shorted circuit.
2. Sticking or binding throttle linkage.
3. Incorrect idle airflow setting.
4. Throttle body or IAC solenoid contaminated.
5. Faulty IAC solenoid.
6. Faulty PCM.
7. Mechanical faults unrelated to EEC-IV which could affect RPM.

Turn ignition off. Connect tachometer to engine. Start engine. Disconnect Idle Air Control (IAC) 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) Check For EGR Codes If EGR service Code 213, 232, 326, 327, 328, 332, 334 or 336 is displayed, reconnect IAC solenoid. Go to appropriate CIRCUIT TEST. See SERVICE CODE REFERENCE CHARTS . If these codes are not displayed, go to next step.

3) Check For Other Diagnostic Test Codes If Code 126, 136, 137, 172 or 173 is displayed, reconnect IAC solenoid. Go to appropriate CIRCUIT TEST. See SERVICE CODE REFERENCE CHARTS. If these codes are not displayed, go to next step.

4) Measure IAC Solenoid Resistance Turn ignition off. Disconnect IAC solenoid. Connect DVOM positive lead to VPWR terminal and negative lead to IAC terminal. (Scheme 37) Measure resistance of IAC solenoid. If resistance is not 6-13 ohms, replace IAC solenoid and repeat QUICK TEST. If resistance is 6-13 ohms, go to next step.

IAC Solenoid Connector (Bronco). Scheme 37

5) Check For Internal Short To IAC Solenoid Case Turn ignition off. With IAC solenoid disconnected, measure resistance from either IAC terminal pin to IAC solenoid housing. If reading is more than 10,000 ohms, go to next step. If reading is 10,000 ohms or less, replace IAC solenoid. Repeat QUICK TEST.

6) Check VPWR Circuit Voltage Leave IAC harness disconnected. Turn ignition on. Measure voltage between VPWR terminal at IAC 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) Check IAC Circuit Continuity Turn ignition off. Leave IAC solenoid disconnected. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 21 and IAC terminal at IAC wiring harness connector. If reading is 5 ohms or less, go to next step. If reading is more than 5 ohms, repair open circuit and repeat QUICK TEST.

8) Check IAC Circuit For Short To Ground Turn ignition off. Leave IAC solenoid and PCM disconnected. Measure resistance between test pin No. 21 and test pins No. 40, 46 and 60. If any reading is less than 10,000 ohms, repair short to ground and repeat QUICK TEST . If all readings are 10,000 ohms or more, go to next step.

9) Check IAC Circuit For Short To Power Leave IAC solenoid and PCM disconnected. Turn ignition on. Measure voltage between breakout box test pin No. 21 and chassis ground. If voltage is more than one volt, repair short circuit and repeat QUICK TEST. If code or symptom is still present, replace PCM. If voltage is one volt or less, go to next step.

10) Check IAC Signal From PCM Turn ignition off. Reconnect IAC solenoid. Connect PCM to breakout box. 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 IAC solenoid to confirm that it is not stuck open. If IAC is okay, replace PCM and repeat QUICK TEST .

11) Check Base Idle Verify base idle speed is correct. See ADJUSTMENTS article in this section. If base idle speed is within specification, remove IAC solenoid and inspect for contamination. Repair or replace as necessary. Repeat QUICK TEST. If code or symptom is still present, replace IAC 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 next step.

12) Check For Faults Affecting Idle Speed Check following mechanical items for faults

1. Throttle linkage and/or cruise control linkage (sticking or binding).
2. Throttle body (contamination).
3. Vacuum hoses. Check Vehicle Emission Control Information (VECI) label.
4. Check for leaks around IAC solenoid (gaskets, etc.).

If any of these items are faulty, service as necessary, and repeat QUICK TEST . If all of these items are okay, remove IAC solenoid and inspect for contamination. Repair or replace as necessary. Repeat QUICK TEST. If code or symptom is still present, replace IAC solenoid. 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.

15) Code 411 Code 411 indicates engine RPM could not be controlled within lower RPM limit during KOER SELF-TEST. Possible causes for this fault are

1. Incorrect idle airflow setting.
2. Vacuum leaks.
3. Sticking or binding throttle linkage.
4. Throttle plates open.
5. Incorrect ignition timing (Distributor ignition only).
6. Throttle body or IAC solenoid contamination.
7. IAC circuit shorted to ground.
8. Faulty IAC solenoid.

If listed items are okay and idle is set to specification, remove IAC solenoid and inspect for contamination. Repair or replace as necessary. Repeat QUICK TEST . If code or symptom is still present, replace IAC solenoid. If idle speed is not within specification, adjust as necessary and repeat QUICK TEST. If idle speed cannot be set to specification, go to next step.

16) Check For Conditions Affecting Idle Speed Check the following mechanical components

1. Vacuum hoses. Check Vehicle Emission Control Information (VECI).
2. Throttle linkage and/or cruise control linkage (sticking or binding).
3. Ensure throttle plates are fully closed.
4. Induction system (vacuum leaks).
5. Throttle body (contamination).
6. Ensure CANP solenoid is not stuck open.
7. Ensure base ignition timing is to specification on emission decal.

If everything checks okay, go to next step. If fault is found, service as necessary and repeat QUICK TEST .

17) Check For Internal Short To IAC Solenoid Case Turn ignition off. Disconnect IAC solenoid wiring harness connector. Measure resistance from either IAC terminal pin to IAC solenoid housing. (Scheme 38) If reading is more than 10,000 ohms, go to next step. If reading is 10,000 ohms or less, replace IAC solenoid. Repeat QUICK TEST.

IAC Solenoid Schematic (Bronco). Scheme 38

18) Check IAC Circuit For Short To Ground Turn ignition off. Leave IAC solenoid disconnected. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 21 and test pins No. 40, 46 and 60. If any reading is less than 10,000 ohms, repair short to ground. Reconnect components, and repeat QUICK TEST . If all readings are 10,000 ohms or more, go to next step.

19) Check IAC Signal From PCM Turn ignition off. Connect PCM to breakout box. Reconnect IAC 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 IAC solenoid and inspect for contamination. Repair or replace as necessary, and repeat QUICK TEST. If voltage is not 3.0-11.5 volts, replace PCM and repeat QUICK TEST.

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

1. Refrigerant charge.
2. Low ambient temperature (less than 45°F). This test is only intended to diagnose
3. Wiring harness circuits (WAC, VPWR, GND, POWER-TO-CLUTCH and ACD).
4. WAC relay.
5. A/C fan controller.
6. Faulty Powertrain Control Module (PCM).

WOT A/C Cut-Out Circuit (Bronco). Scheme 39

TEST PIN NO. 10 (ACCS) WIRE COLOR IDENTIFICATION

1) Low/No Voltage To 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. Disconnect WAC relay connector. Measure resistance between power side of A/C clutch harness connector and POWER-TO-CLUTCH terminal at WAC relay harness connector. If resistance is less than 5 ohms, reconnect A/C switch and go to next step. If resistance is 5 ohms or more, repair open circuit. Reconnect all components and check system operation.

2) Check For Power On A/C Demand Circuit Turn ignition on. Leave WAC relay disconnected. Turn A/C switch to A/C position. Measure voltage between chassis ground and A/C DEMAND SWITCH input terminal at WAC relay wiring harness connector. If voltage is more than 10.5 volts, go to step 5). If voltage is 10.5 volts or less, verify operation of A/C clutch cycling pressure switch and A/C demand switch. If components are okay, repair open circuit and recheck system.

3) Check Continuity Between WAC Relay & A/C Relay Turn ignition off. Remove WAC and A/C relay wiring harness connectors. Measure resistance between A/C RELAY terminal at WAC relay connector and A/C RELAY terminal at A/C relay connector. If resistance is less than 5 ohms, check A/C relay for low output voltage. Repair as necessary. If resistance is 5 ohms or more, repair open circuit. Connect relays, and check system operation.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 3) to step 5). No test procedures have been omitted.

5) Check WAC Circuit For Short To Ground Turn ignition off. Leave WAC relay disconnected. Disconnect 60-pin PCM connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Leave PCM disconnected. Measure resistance between WAC terminal at WAC relay wiring harness connector and chassis ground. If resistance is less than 10,000 ohms, repair short and check system operation. If resistance is 10,000 ohms or more, go to next step.

6) Check For Voltage At ACCS Input To PCM Turn ignition off. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Set A/C switch to A/C position. Turn ignition on. Measure voltage between test pins No. 10 and 40 at breakout box.

7) Check WAC Relay Turn ignition off. Connect WAC relay, leaving A/C clutch disconnected. Leave A/C and blower switch positioned as listed in step 6). Turn ignition on. Measure voltage between POWER-TO-CLUTCH terminal of A/C clutch wiring harness connector and negative battery terminal. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, replace WAC relay. Reconnect all components and check system operation.

8) Check Engine Coolant Temperature (ECT) Sensor & Throttle Position (TP) Sensor Voltage Turn ignition off. Reconnect PCM connector to breakout box. Reconnect A/C clutch connector. Turn A/C on. Start engine. Measure voltage between test pins No. 7 and 40 at breakout box. Ensure ECT sensor voltage is as specified. See ACT & ECT SENSOR SPECIFICATIONS table in CIRCUIT TEST DA. Also, measure voltage between test pins No. 40 and 47 at breakout box. With throttle plate at specified position, ensure voltage is as specified. (Scheme 15)in CIRCUIT TEST DH. If ECT sensor and TP sensor voltages are as specified, replace PCM. Remove breakout box and check system operation. If either ECT sensor or TP sensor voltage is not as specified, perform QUICK TEST. Service any codes that are present. See DIAGNOSTIC TROUBLE CODE DEFINITION CHARTS. If no codes are present, check ECT/TP sensor wiring for opens and shorts. Repair as necessary. Remove breakout box, reconnect all components, and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 8) to step 15). No test procedures have been omitted.

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 Data Link Connector (DLC). (Scheme 40)Connect positive lead to positive battery terminal. Install a jumper wire between STI terminal and SIG RTN terminal at DLC. Perform KOEO SELF-TEST until continuous memory test is complete. DVOM will read less than 1.0 volt when test is complete to indicate PCM has entered OUTPUT STATE CHECK. Depress and release throttle. If voltage increases to more than 10.5 volts, remain in OUTPUT STATE CHECK and go to next step. If voltage does not increase to more than 10.5 volts, depress throttle to WOT and release. If STO voltage does not go high, go to CIRCUIT TEST QC, step 2).

DLC Terminal ID (Bronco). Scheme 40

16) Check For VPWR To Relay With vehicle in OUTPUT STATE CHECK, disconnect wiring harness from WAC relay. Measure voltage between VPWR terminal at WAC relay wiring harness connector and chassis ground. If voltage is 10.5 volts or less, repair open in VPWR circuit between EEC power relay and WAC relay and retest system. If voltage is more than 10.5 volts, go to next step.

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 terminal. Connect negative test lead to WAC terminal at WAC relay wiring harness connector. Check DVOM while depressing and releasing throttle several times to cycle output on and off. If voltage cycles about one volt high to low, replace WAC relay. Remove jumper wire and check system operation. If voltage does not cycle, remove test leads and jumper wire. Reconnect speed control servo, and go to next step.

18) Check Continuity Of WAC Circuit Turn ignition off. Disconnect 60-pin PCM connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 54 at breakout box and WAC terminal at WAC relay wiring harness connector. If reading is 5 ohms or more, repair open circuit. Reconnect all components and check system operation. If reading is less than 5 ohms, go to next step.

19) Check WAC Circuit For Short To Power Turn ignition off. Leave PCM and WAC relay disconnected. Turn ignition on. Measure voltage between test pin No. 54 and chassis ground. If voltage is less than 1.0 volt, replace PCM and retest system. If voltage is 1.0 volt or more, repair short circuit. If symptom is still present, replace PCM.

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.

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

31) Check A/C Input Circuit Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install breakout box, leaving PCM disconnected. Turn A/C on. Turn ignition on. Measure voltage between test pins No. 10 and 40. If voltage is more than 10.5 volts, replace PCM and connect all components. Repeat QUICK TEST . If voltage is 10.5 volts or less, repair open A/C circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST.

32) Cycle A/C Demand Switch Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install breakout box, leaving PCM disconnected. Connect DVOM positive lead to test pin No. 43. Connect negative lead to test pin No. 40. Turn ignition on. Turn A/C on and off. If voltage cycles high and low when switch is cycled, EEC-IV system is okay and testing is complete. If voltage does not cycle, repair open in ACD circuit, and repeat QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 32) to step 40). No test procedures have been omitted.

Before entering this test, ensure A/C selector is in OFF position and shift selector is in Park (A/T). If A/C was on, repeat QUICK TEST . If Code 67 or 79/539 is present, go to step 40).

40) Code 67 Or 79/539: Check A/C Input Code 79/539 indicates ACCS input to PCM 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 PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. 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, replace PCM and repeat QUICK TEST.

41) Check For Short To Power In PCM Turn ignition off. Connect 60-pin PCM connector to breakout box. Ensure A/C clutch is disconnected. Turn ignition on. Measure voltage between test pins No. 10 and 40 at breakout box. If voltage is 5 volts or more, replace PCM and repeat QUICK TEST. If voltage is less than 5 volts, go to CIRCUIT TEST TD.

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.

Octane Adjust Circuit (Bronco). Scheme 41

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

1) Code 341 Code 341 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 octane adjust shorting bar was removed as a factory authorized procedure, testing is complete. If engine is detonating, go to TESTS W/O CODES article in this section. If vehicle does not have modification decal, go to next step.

3) Check For Code 341 Replace octane adjust shorting bar. Perform KOEO SELF-TEST. If Code 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 this 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 PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM 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 PCM and repeat QUICK TEST.

5) Check For Code 111 Start engine. Warm to normal operating temperature. Turn ignition off. Perform KOEO SELF-TEST. If Code 111 is present, go to next step. If Code 341 is present, return to step 1). 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 octane adjust shorting bar was removed as a factory authorized procedure, testing is complete. If engine is detonating, go to TESTS W/O CODES article in this 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 octane adjust shorting bar exists, go to next step. If a TSB authorizing removal of octane adjust shorting bar does not exist, testing is complete. If driveability faults are present, go to TESTS W/O CODES article in this section.

9) Remove Octane Adjust Shorting Bar Turn ignition off. Remove octane adjust shorting bar. Test drive vehicle to verify complaint. If detonation is present, go to next step. If detonation is not present, system is okay. Testing is complete.

10) Check Octane Adjust Circuit For Short To Ground Turn ignition off. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between OCT ADJ terminal at in-line connector and test pins No. 40, 46 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 PCM Turn ignition off. Disconnect octane adjust shorting bar. Turn ignition on. Measure voltage between OCT ADJ test pin terminal and test pins No. 40 and 60 at breakout box. If voltage is 4 volts or less, replace PCM. Repeat QUICK TEST . If engine still detonates, go to TESTS W/O CODES article in this section. If voltage is 4 volts or more, remove breakout box and go to TESTS W/O CODES article in this section.

To prevent replacing good components, be aware the 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. Engine did not go over 2000 RPM during WOT. This test is only intended to diagnose
3. Throttle movement (minimum 3/4 throttle).
4. 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: System Failed To Recognize WOT Test Repeat KOER SELF-TEST as follows

1. Activate SELF-TEST.
2. Start engine.
3. Observe ID Code start of test.
4. Observe Dynamic Response Code 1 (Code 0 with Star tester).
5. Perform brief WOT.
6. Testing is complete; Diagnostic Test Code (DTC) output begins.

Ensure vehicle speed reached 2000 RPM during WOT. If Code 77/538 is present, replace PCM. If Code 77/538 is not present, vehicle has passed dynamic response test. Service other codes if necessary.

The MIL is turned on when PCM detects a fault in EEC circuit(s). The light will remain on as long as fault remains in system.

Perform this test only when instructed by QUICK TEST or if directed by CIRCUIT TEST QA. This test does not include procedure for models with electronic instrument panel. 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. Faulty PCM.

TEST PIN NO. 17 (STO/MIL) WIRE COLOR IDENTIFICATION

DATA + TEST PIN & WIRE COLOR IDENTIFICATION

DATA - TEST PIN & WIRE COLOR IDENTIFICATION

1) Malfunction Indicator Light (MIL) Always On If vehicle will not start, go to appropriate circuit test

1. For distributor ignition systems, CIRCUIT TEST AA.

Service all KOEO and continuous memory codes before proceeding with this test. Turn ignition off. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pins No. 17 and 40 at breakout box. If resistance is more than 5 ohms, replace PCM and repeat QUICK TEST . If reading is 5 ohms or less, repair short between test pin No. 17 and Diagnostic Link Connector (DLC) terminal No. 17 or MIL. 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.

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 and 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.

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/B+ circuit. Verify repair by turning ignition switch to RUN position.

6) Check Voltage At B+ Circuit Turn ignition on. Measure voltage between B+ side of MIL bulb socket 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.

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, remove jumper wire, and go to next step. If MIL light does not come on, remove jumper wire. Replace MIL bulb socket. Turn ignition on to verify correct MIL operation.

8) Check Continuity Of MIL Circuit Turn ignition off. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 17 at breakout box and MIL wiring harness connector terminal. If resistance is less than 5 ohms, replace PCM. 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.

10) MIL On Intermittently, Check For Intermittent Short From STO To Ground If vehicle does not start, go to step 1). MIL 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) under QUICK TEST. Check DVOM for indication of fault while performing wiggle test on harness in the following areas

1. From Diagnostic Link Connector (DLC) to dash panel.
2. Dash panel to PCM.
3. Dash panel to Malfunction Indicator Light (MIL).

If a fault is indicated, repair short to ground 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.

15) MIL Flashes With Erratic Idle Symptoms indicate STI is grounded and PCM is performing self-test without tester installed. Turn ignition off. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Measure resistance between STI connector and engine ground. If resistance is 10,000 ohms or less, repair short circuit. Reconnect PCM, 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.

20) CHECK ENGINE Message Displayed If vehicle will not start, go to step 1). Perform KOEO SELF-TEST. If result is 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.

25) Continuous Memory Code 529 Or 533 CHECK ENGINE Or CHECK DLC Message Displayed. Codes 529 and 533 indicate circuit fault has occurred on Data Link Connector (DLC). These codes can occur alone or with another code. Fault will occur under following conditions

The IDM is an input signal to the PCM that verifies spark plug fire based on ignition coil primary discharge. IDM signal consists of a single pulse for each engine RPM. No IDM pulse indicates secondary ignition misfire.

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 SYSTEM/COMPONENT TESTS article in this section. To prevent replacing good components, be aware the following non-EEC related areas may be cause of problem

1. Ignition Control Module (ICM).
2. Ignition coil.
3. Spark plugs and/or wires.
4. Distributor.
5. Secondary ignition short to ground. This test is intended to diagnose
6. IDM circuit.
7. Faulty Powertrain Control Module (PCM).

IDM Circuit Schematic (Bronco). Scheme 42

TEST PIN NO. 4 (IDM) WIRE COLOR IDENTIFICATION

TEST PIN NO. 36 (SPOUT) WIRE COLOR IDENTIFICATION

1) Continuous Memory Code 211 Code 211 indicates 2 successive erratic Profile Ignition Pick-Up (PIP) pulses occurred, resulting in a possible engine miss or stall. Check for the following possible causes of fault

1. Loose wires or connectors.
2. Secondary ignition short to ground.
3. On-board transmitter equipment (2-way radio).

Repair if necessary and repeat QUICK TEST . If the problem is not found, go to the next step. If vehicle does not start, proceed to CIRCUIT TEST AA.

2) Continuous Memory Code 212: Check IDM Circuit Continuity Continuous Memory Code 212 indicates loss of IDM input to PCM. Possible causes for this fault are

1. Open or shorted circuit in wiring harness.
2. Faulty ICM.
3. Faulty PCM.

If vehicle is a no-start, go to CIRCUIT TEST AA. If vehicle starts, go to next step.

3) Check IDM Circuit Continuity Turn ignition off. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Disconnect ICM. Measure resistance between test pin No. 4 at breakout box and IDM terminal at ICM wiring harness connector. If resistance is 5 ohms or less, go to step 5). If resistance is more than 5 ohms, repair open circuit, and repeat QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 3) to step 5). No test procedures have been omitted.

5) Check IDM Circuit For Short To Power (Except VREF) Turn ignition off. Leave ICM and PCM disconnected. Measure voltage between breakout box test pin No. 4 and negative battery terminal. Turn ignition on. Measure voltage between test pin No. 4 and test pins No. 40 and 60 at breakout box. If voltage is more than 10.5 volts, repair short circuit. Clear codes, and repeat QUICK TEST . If voltage is 10.5 volts or less, go to next step.

6) Check IDM Circuit For Short To PIP & VREF Turn ignition off. Leave PCM and ICM disconnected. Disconnect ignition coil wiring harness connector (non-CCD). Remove scan tester (if applicable). For shorts to PIP, measure resistance between test pins No. 4 and 56 at breakout box. For shorts to VREF, measure resistance between test pin No. 4 and test pins No. 26 at breakout box. If any 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.

7) Check IDM Circuit For Short To Ground Turn ignition off. Remove scan tester (if applicable). Leave ignition coil, ICM and PCM disconnected. Measure resistance between test pin No. 4 and test pins No. 20, 40, 46 and 60 at breakout box. If each resistance is more than 10,000 ohms, reconnect scan tester and go to next step. If any resistance is 10,000 ohms or less, repair short to ground in IDM circuit. Clear codes, and repeat QUICK TEST.

8) Check ICM Turn ignition off. Connect PCM to breakout box. Reconnect ICM and ignition coil to wiring harness connectors. Connect DVOM between test pins No. 4 and 16 at breakout box. Start engine. Observe DVOM for voltage surge while lightly tapping on ICM and Camshaft Position (CMP) sensor to simulate road shock. Wiggle all ICM and CMP sensor wiring and harness connectors. If fault (voltage surge) is indicated, disconnect and inspect wiring harness connectors and terminals for damage. If fault is not indicated, go to next step.

9) Check PCM & Harness Connectors Ensure engine is still running and DVOM is still connected between test pins No. 4 and 16 at breakout box. While observing DVOM, wiggle and bend wiring harness, a small section at a time, from ICM and CMP sensor (if equipped) to cowl. Also, check harness from cowl to PCM. If fault is indicated, isolate fault and repair as necessary. Remove breakout box, reconnect all components, and repeat QUICK TEST . If no fault is found, go to next step.

10) Check PCM & Harness Connectors Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. If connector is damaged, repair as necessary. Clear codes, and repeat QUICK TEST. If connector is okay, go to next step.

11) Check PCM For Short To Power Turn ignition off. Connect PCM to breakout box. On models with remote mounted ICM, disconnect CMP wiring harness connector. On all other models, disconnect ICM wiring harness connector. Measure voltage between test pin No. 4 at breakout box and chassis ground. Turn ignition on. Measure voltage between test pin No. 4 and test pins No. 40 and 60 at breakout box. If either voltage reading is more than 10.5 volts, replace PCM and repeat QUICK TEST . If both voltage readings are 10.5 volts or less, go to next step.

12) Check PCM For Short To Ground Turn ignition off. Leave PCM connected to breakout box. Measure resistance between test pin No. 4 and test pins No. 40, 46 and 60 at breakout box. If resistance is more than 10,000 ohms, check ignition system. See SYSTEM/COMPONENT TESTS article in this section. If resistance is 10,000 ohms or less, replace PCM and repeat QUICK TEST.

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

1. SPOUT wiring harness circuit.
2. Base timing.
3. Powertrain Control Module (PCM).

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

1. Basic engine condition (compression, valve timing, etc.).
2. Distributor.
3. Ignition Control Module (ICM).

Spark Timing Check Circuit (Bronco). Scheme 43

TEST PIN NO. 36 (SPOUT) WIRE COLOR IDENTIFICATION

1) Check For Power To PCM Turn ignition off. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Turn ignition on. Measure voltage between test pins No. 37 and 40 and between test pins No. 57 and 60 at breakout box. If either voltage reading is less than 10.5 volts, go to CIRCUIT TEST B. If both voltage readings are 10.5 volts or more, go to next step.

2) Check SPOUT Circuit For Continuity Turn ignition off. Disconnect ICM wiring harness connector. Measure resistance between test pin No. 36 at breakout box and SPOUT terminal at ICM wiring harness connector. If resistance is more than 5 ohms, repair open circuit. Reconnect all components, and check ignition timing. If resistance is 5 ohms or less, go to next step.

3) Check SPOUT Circuit For Short To B+ Turn ignition off. Leave PCM and ICM disconnected. Turn ignition on. Measure voltage between test pin No. 36 and test pins No. 40 or 60. If voltage 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 SPOUT Circuit For Short To PIP, VREF & Ground Turn ignition off. Leave PCM and ICM disconnected. To check for shorts to VREF, use DVOM to measure resistance between test pins No. 26 and 36 at breakout box. To test for shorts to PIP, measure resistance between test pins No. 36 and 56 at breakout box. To test for shorts to ground, measure resistance between test pin No. 36 and test pins No. 16, 20, 40, 46 or 60. If either resistance is 10,000 ohms or less, repair short circuit and repeat QUICK TEST. If each resistance measures more than 10,000 ohms, the EEC system is okay. Check the ignition system. Proceed to IGNITION SYSTEMS in the appropriate SYSTEM/COMPONENT TESTS article.

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 .

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

1. Powertrain Control Module (PCM).
2. EEC power relay.
3. Wiring harness circuits (HO2S, SIG RTN, STO, STI, VPWR and VREF).

No Codes/Codes Not Listed Circuits (Bronco). Scheme 44

TEST PIN NO. 17 (STO/MIL) WIRE COLOR IDENTIFICATION

TEST PINS NO. 37 & 57 (VPWR) WIRE COLOR IDENTIFICATION

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

TEST PIN NO. 48 (STI) WIRE COLOR IDENTIFICATION

1) Check VREF Voltage At Data Link Connector (DLC) Turn ignition off. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect PCM to breakout box. Turn ignition on. Measure voltage between test pin No. 26 at breakout box and SIG RTN terminal at DLC. 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 PCM from breakout box. Measure resistance between test pin No. 46 at breakout box and SIG RTN terminal at DLC. If reading is less than 5 ohms, go to CIRCUIT TEST C. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST.

3) Check STI Circuit Continuity Turn ignition off. Disconnect PCM 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 reading is less than 5 ohms, go to next step.

4) Check STO Circuit Continuity Leave ignition off and PCM disconnected. Measure resistance between test pin No. 17 at breakout box and STO terminal at DLC. If reading is less than 5 ohms, go to next step (except 7.3L) or step 7) (7.3L). If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST.

A right/rear HO2S short to power could prevent EEC system from entering self-diagnostics.

5) Check HO2S Signal For Short To Power Leave PCM disconnected. Turn ignition on. Measure voltage between test pin No. 40 or 60 and HO2S SIGNAL test pin No. 29 or 44 at breakout box. For HO2S circuit schematics, see 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 HO2S Sensor Turn ignition off. Leave PCM disconnected. Disconnect right/rear HO2S sensor connector. Turn ignition on. Measure voltage between HO2S SIGNAL test pin No. 29 or 44 and test pins No. 40 and 60 at breakout box. If any measurement is 2 volts or more, repair short to power in HO2S SIGNAL circuit, and repeat QUICK TEST . If voltage is less than 2 volts, replace right/rear HO2S sensor and repeat QUICK TEST.

7) Check STO Circuit For Short To Ground Turn ignition off. Leave PCM disconnected. Measure resistance between STO at DLC and engine ground. If reading 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 Leave ignition off and PCM disconnected. 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 changes from 10.5 volts (or more) to less than one volt, go to step 10). If voltage does not change from 10.5 volts (or more) to less than one volt, go to next step.

9) Check VPWR Circuit For Short To Power Turn ignition off. Leave PCM disconnected. Disconnect EEC power relay. Connect DVOM to test pin No. 37 or 57 and test pin No. 40 or 60 at breakout box. If voltage is more than one volt, repair VPWR circuit short to power and repeat QUICK TEST. If voltage is one volt or less, replace EEC power relay and repeat QUICK TEST.

10) Check Malfunction Indicator Light (MIL) Function If MIL is always on, go to CIRCUIT TEST ML, step 1). If MIL is always off, go to CIRCUIT TEST ML, step 4). If MIL is working normally, replace PCM and repeat QUICK TEST .

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

1. Faulty Powertrain Control Module (PCM).
2. KAPWR wiring harness circuits.

KAPWR Circuit Schematic (Bronco). Scheme 45

TEST PIN NO. 1 (KAPWR) WIRE COLOR IDENTIFICATION

Diagnostic Aid

Continuous Memory Code 15/512 may be displayed when power between PCM and KAPWR is interrupted. This code may be set when a breakout box is installed or battery is disconnected.

1) Continuous Memory Code 15/512: Check KAPWR Circuit Voltage Code 15/512 indicates PCM power interruption in Keep-Alive Memory (KAM). Clear codes and repeat QUICK TEST . If Code 15/512 is repeated, turn ignition off. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure voltage between test pin No. 1 and test pins No. 40 or 60 at breakout box. Observe voltage reading while wiggling small sections of EEC wiring harness from PCM 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.

2) Inspect Wiring Harness Routing Ensure EEC wiring is not routed close to ignition components and 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 not repeated, testing is complete. If Continuous Memory Code 15/512 is still present, replace PCM and repeat QUICK TEST .

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

1. Faulty Powertrain Control Module (PCM).
2. Throttle plate linkage.

1) Check For Codes 23/121, 53/123 & 63/122 Disconnect cruise control servo wiring harness connector (if equipped). Perform KOEO SELF-TEST. If Code 23/121, 53/123 or 63/122 is present, go to appropriate CIRCUIT TEST. See SERVICE CODE REFERENCE CHARTS . If Code 11/111 (pass code) is displayed, go to next step. If no code is displayed, go to CIRCUIT TEST QA.

2) Check Throttle Linkage Check throttle and linkage for sticking and binding. If throttle and linkage are okay, replace Throttle Position (TP) sensor 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 AA, CIRCUIT TEST AB or CIRCUIT TEST AC. This test is intended to diagnose

1. IAC system.
2. MAP/BARO system.
3. EGR system.
4. MAF system.

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

1. Faulty power or ground connections.
2. Secondary ignition (distributor cap, rotor, wires, coil and plugs).
3. Engine mechanical components (compression, timing, valves, etc.).

1) IAC Check Try to start engine at part throttle. If engine starts and runs smoothly at part throttle, go to CIRCUIT TEST KE, step 4). If engine does not run as described, go to step 3). If engine starts and idles smoothly, go to next step.

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

3) Power To MAP/BARO Sensor If vehicle is not equipped with a MAP/BARO sensor, go to step 8). Turn ignition off. Disconnect MAP/BARO sensor. Connect MAP/BARO tester between wiring harness and MAP/BARO sensor. (Scheme 46) Connect banana plugs of tester into DVOM. Turn ignition on. If Green light is on, go to next step. If Green light is not on, repair open in VREF circuit and check system operation.

MAP/BARO Tester & Circuit (Bronco). Scheme 46

4) MAP/BARO Tester Output Reading Measure several known good MAP/BARO sensors to obtain average voltage for location and day of testing. With MAP/BARO tester and DVOM connected, turn ignition on. Measure MAP/BARO voltage at MAP sensor. If voltage is not within specification for specific altitude, replace MAP/BARO sensor. See MAP VOLTAGE OUTPUT table below. If voltage is in within specification for specific altitude, go to step 8) (MAF vehicles) or go to next step (except MAF vehicles).

MAP VOLTAGE OUTPUT

5) Check Vacuum Lines Check vacuum hoses for correct routing. Refer to VECI decal. Check MAP sensor vacuum hose for leaks and blockage. If vacuum hoses are okay, go to next step. If vacuum hoses are not okay, repair as necessary. Repeat QUICK TEST .

6) Check MAP Sensor Turn ignition off. Disconnect vacuum hose from manifold vacuum source. Connect vacuum pump to MAP sensor hose. Apply 18 in. Hg vacuum to MAP sensor. If MAP sensor holds vacuum, 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 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 and repeat QUICK TEST .

8) Check EGR Vacuum If vehicle is not equipped with EGR system, go to CIRCUIT TEST H, step 2). Disconnect and plug vacuum line at EGR valve. Attempt to start engine. If vehicle did not start previously but starts now or if driveability symptoms are eliminated, go to CIRCUIT TEST DN, step 42) (vehicles with EVP) or CIRCUIT TEST DL, step 50) (except vehicles with EVP). If vehicle could not start previously and still does not start or if vehicle driveability fault is still present, go to next step.

9) Check EGR Valve Inspect EGR valve for leaks. If valve is fully closed, go to CIRCUIT TEST H. 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 Pedal Position (CPP) switch.
2. Park/Neutral Position (PNP) switch.
3. Powertrain Control Module (PCM).
4. Wiring harness circuits (CPP, PNP and SIG RTN).

CPP Sw. Ckt. Schematic (Bronco W/ C6 Transmission). Scheme 47

CPP Sw. Ckt. Schematic (4.9L Bronco W/ M/T). Scheme 48

CPP Switch Circuit Schematic (All Other Models With M/T). Scheme 49

TEST PIN NO. 30 (CPP/PNP) WIRE COLOR ID

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

1) Code 522, 525 Or 528 Code 522, 525 or 528 is a result of voltage being high at either pin No. 10 (A/C input) or No. 30 (CPP/PNP input) while cranking engine or during KOEO SELF-TEST. Possible causes for these faults are

1. A/C circuit shorted to power.
2. CPP or PNP circuit open.
3. Faulty Powertrain Control Module (PCM).
4. Starter relay disconnected during self-test.

On all A/T models, go to step 8). For 4.9L M/T models, go to step 7). On all other M/T models, go to next step.

2) Check CPP/PNP Input Turn ignition off. Turn A/C off (if equipped). Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM 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 next step. If resistance is 5 ohms or more, go to step 5).

3) Check CPP/PNP Switch Integrity Leave ignition off and PCM disconnected. Measure resistance between test pins No. 30 and 46 with transmission in any gear and clutch pedal up. (Scheme 50) If resistance is less than 5 ohms, go to CIRCUIT TEST KM, step 40) (models with A/C) or replace PCM and repeat QUICK TEST (except models with A/C). If resistance is 5 ohms or more, go to next step.

Neutral Gear/Clutch Input Circuit (Bronco). Scheme 50

4) Check For CPP Short To Ground Leave ignition off and PCM disconnected. Disconnect CPP switch. Measure resistance between test pins No. 30 and 46. If resistance is 10,000 ohms or more, go to CIRCUIT TEST KM, step 40) (models with A/C), or replace PCM 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) Check CPP/PNP Switch Leave ignition off and PCM disconnected. Locate PNP switch (on transmission) and CPP switch (at clutch pedal linkage). Disconnect wiring harness at both switches. Measure resistance across PNP switch terminals with transmission in Neutral. Measure resistance across CPP 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 switch and repeat QUICK TEST.

6) Check CPP/PNP Wiring Harness Leave ignition off and PCM disconnected. Measure resistance between test pin No. 30 and the following terminals

1. PNP switch wiring harness connector CPP and/or PNP terminal.
2. CPP switch wiring harness connector CPP and/or PNP terminal.

Measure resistance between test pin No. 46 and the following terminals

1. PNP switch wiring harness connector SIG RTN terminal.
2. CPP switch wiring harness connector SIG RTN terminal.

If any resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST . If each resistance is less than 5 ohms, go to CIRCUIT TEST KM, 6step 40) (models with A/C) or replace PCM and repeat QUICK TEST (except models with A/C).

7) Check CPP Switch Turn ignition and A/C off. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Push clutch pedal down. Measure resistance between test pins No. 30 and 46 at breakout box. If resistance is less than 5 ohms, go to CIRCUIT TEST KM, step 40) (models with A/C) or replace PCM and repeat QUICK TEST (except models with A/C). If each resistance is 5 ohms or more, repair open circuit. Reconnect all components, and repeat QUICK TEST.

8) Check PNP Input Turn ignition and A/C off. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect PCM to breakout box. Ensure transmission is in Neutral or Park. 6Turn ignition on. Measure voltage between test pin No. 30 and chassis ground. If voltage is less than one volt, go to CIRCUIT TEST KM, step 40) (models with A/C) or replace PCM and repeat QUICK TEST (except models with A/C). If voltage is one volt or more, go to next step.

9) Check PNP Switch Resistance Turn ignition off. Disconnect PCM from breakout box. Disconnect PNP wiring harness connector. Measure resistance across switch terminals. If resistance is less than 5 ohms, repair open in PNP circuit and repeat QUICK TEST. If resistance is 5 ohms or more, replace PNP switch 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 (compression, valve timing, etc.).
2. Brakes.
3. Transmission fluid, friction elements and cooling.
4. Transfer case linkage or internal condition. This test is only intended to diagnose
5. Harness circuits (4x4 LOW, TCIL and TCS).
6. Faulty PCM.

4x4 Low & Overdrive Cancel Circuits (Bronco - Touch Drive Option). Scheme 51

4x4 Low & Overdrive Cancel Ckts. (Bronco - W/O Touch Drive Option). Scheme 52

1) Code 47/633 & 691 Code 47/633 indicates 4x4 Low selector lever is not in 4x2 or 4x4 HIGH position during KOEO SELF-TEST. Code 691 indicates 4x4 selector fault is set when KAM value for engine speed/vehicle speed disagrees with PCM logic regarding engine speed/vehicle speed verses TCS position. Possible causes for these faults are

1. Faulty 4x4 Low switch or 4x4 selector lever position.
2. Transfer case damaged internally.
3. Wiring harness circuit open or grounded.
4. Faulty PCM.

Ensure that 4x4 Low selector lever was in 4x2 or 4x4 HIGH position during KOEO SELF-TEST and go to step 4).

2) Code 65/632 & 653 Code 65/632 and 653 indicate TCS is not cycled between engine ID code and WOT check during KOER SELF-TEST. Possible causes for these faults are

1. Faulty TCS or switch not cycled.
2. Wiring harness circuit open or grounded.
3. Faulty PCM.

Ensure that TCS switch is cycled between engine ID code and WOT check during KOER SELF-TEST and go to step 4).

3) Code 97/631 & 623 Code 97/631 and 623 indicate TCS light circuit fault during KOEO SELF-TEST. Possible causes for these faults are

1. TCS bulb burned out.
2. Wiring harness circuit open or grounded.

Ensure that TCS switch is cycled during KOEO SELF-TEST and go to step 5).

4) Cycle 4x4 Or Overdrive Cancel Switch Turn ignition off. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Turn ignition on.

1. To check 4x4 LOW circuit, measure voltage between test pin No. 12 and test pins No. 40 and 60 at breakout box while cycling switch between in and out of 4x4 Low position.
2. To check TCS circuit, measure voltage between test pin No. 41 and test pins No. 40 and 60 at breakout box while cycling overdrive cancel switch.

On all models, if voltage cycles, replace PCM and repeat QUICK TEST . If voltage does not cycle, go to next step if diagnosing a trouble code or step 7) if diagnosing driveability symptom only.

5) Check Circuits For Short To Ground Turn ignition off. Leave PCM disconnected from breakout box. Disconnect switch connector. Inspect for damage and repair as necessary.

1. To check 4x4 LOW circuit, measure resistance between test pin No. 12 and test pins No. 40 and 60 at breakout box.
2. To check TCS circuit, measure resistance between test pin No. 41 and pins No. 40 and 60 at breakout box.

Measure resistance between test pin No. 32 and pins No. 40 and 60 at breakout box. If all resistance is more than 10,000 ohms, go to next step (Code 97/631 or 623) or step 8) (Code 47/633, 65/632, 633 or 691). If any resistance is 10,000 ohms or less, repair short circuit. Repeat QUICK TEST. If code is still present, go to step 7).

6) Check Power Through TCIL Circuit Turn ignition off. Leave PCM 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 PCM and repeat QUICK TEST . If voltage is 10.5 volts or less, go to next step.

7) Check Output Driver Voltage Signal Leave PCM disconnected from breakout box. Turn ignition on.

1. To check 4x4 LOW circuit, disconnect switch. Connect DVOM positive lead to test pin No. 12 and negative lead to PWR GND terminal of breakout box.
2. To check TCIL circuit, connect DVOM positive lead to test pin No. 32 and negative lead to PWR GND terminal of breakout box.

On all models, 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 all voltage readings are 2 volts or more, go to next step.

KEY POWER Terminal in Fuse Panel ID (Bronco). Scheme 53

8) Check Circuit Continuity Turn ignition off. Leave PCM disconnected from breakout box. Leave switch disconnected.

1. To check 4x4 LOW circuit, measure resistance between test pin No. 12 at breakout box and 4x4 LOW LED circuit at switch wiring harness connector.
2. To check TCS/TCIL circuit, connect DVOM positive lead on KEY POWER terminal of fuse panel and negative lead on power side of TCS wiring harness connector. Also connect DVOM positive lead on test pin No. 41 at breakout box and negative lead on power side of TCS wiring harness connector.

On all models, if any resistance reading is 5 ohms or more, repair open circuit and repeat QUICK TEST . If all resistance readings are less than 5 ohms, go to next step.

9) Check Circuits For Short To Power Turn ignition off. Leave PCM disconnected from breakout box. Leave switch disconnected.

1. To check 4x4 LOW circuit, measure resistance between test pin No. 12 and test pins No. 37 and 57 at breakout box.
2. To check TCS 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.

On all models, 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 the following non-EEC areas may be at fault

1. Engine condition (compression, cam timing, valves, etc.).
2. Charging system or battery.
3. Transmission linkage, internal components or cooling.

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

1. Wiring harness circuits (TCC, CCS, EPC, SS3/4, SS1, SS2, SS3, SIG RTN, EPC PWR and VPWR).
2. Faulty Powertrain Control Module (PCM).

CIRCUIT TEST TC ACRONYMS

TEST PIN NO. 35, 37 & 57 WIRE COLOR IDENTIFICATION

E4OD Solenoid Circuit ID (Bronco). Scheme 54

E4OD SERVICE CODE IDENTIFICATION

1) OUTPUT STATE CHECK 91/621, 92/622, 93/626, 94, 629 641, or 652 indicates shift solenoid did not respond to PCM command. Code 566 or 629 indicate CCO or SS3/4-4/3 did not change state when requested by PCM. Possible causes for these faults are

1. Faulty solenoid assembly.
2. Circuit open or grounded.
3. Faulty Powertrain Control Module (PCM).

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 Data Link Connector (DLC). Connect positive lead to positive battery terminal. Install a jumper wire between SIG RTN terminal and STI terminal at DLC. (Scheme 44) Perform KOEO SELF-TEST until continuous memory test is complete. DVOM will read less than one volt when test is complete to indicate PCM 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, step 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 wiring harness connector VPWR terminal. Connect negative test lead to appropriate shift solenoid terminal at transmission wiring harness connector. Turn ignition on. 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) Check Solenoid & VPWR Circuit Continuity Turn ignition off. Leave transmission wiring harness disconnected. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between transmission wiring harness connector terminal and corresponding test terminal at breakout box. Measure resistance between breakout box test pins No. 37 and 57 and VPWR terminal at transmission wiring harness connector. If each resistance is less than 5 ohms, go to next step. If any resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST.

4) Check Solenoid Circuit For Short To Power Or Ground Leave ignition off and PCM disconnected. Leave transmission wiring harness disconnected. Measure resistance between PCM output signal test pin and test pins No. 37 and 57 at breakout box. Measure resistance between PCM output signal test pin and pins No. 40, 46 and 60 at breakout box. Measure resistance between PCM 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, check solenoids. If solenoids are okay, replace PCM and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 4) to step 10). No test procedures have been omitted.

10) Code 99/624 Or 625: Check VPWR To Solenoid Code 99/624 indicates failure of EPC circuit. Code 625 indicates EPC driver failure. Possible causes for these faults are

1. Faulty solenoid.
2. Circuit open or grounded.

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/battery 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.

11) Check Solenoid Signal & VPWR Circuit Continuity Turn ignition off. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between VPWR/EPC PWR terminal at transmission wiring harness connector breakout box test pins No. 37 and 57 (test pin No. 35 for 7.3L). Measure resistance between test pin No. 38 at breakout box and EPC 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.

12) Check Circuit For Short To Power Or Ground Leave ignition off and PCM disconnected. Leave transmission wiring harness connector disconnected. Measure resistance between test pins No. 37 and 57 (test pin No. 35 for 7.3L) and suspect solenoid test pin at breakout box. Measure resistance between test pins No. 40, 46 and 60 and suspect solenoid test pin 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, check solenoids. If solenoids are okay, replace PCM and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 12) to step 20). No test procedures have been omitted.

20) Code 621, 622, 641 Or 643: Check Solenoid Resistance KOEO Code 621 (SS1), 622 (SS2), 641 (SS3) or 643 (TCC) indicate failure in shift solenoid circuit. Possible causes for these faults are

1. Faulty shift solenoid.
2. Circuit open or grounded.
3. Faulty PCM.

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 13-27 ohms, go to next step. If resistance is not 13-27 ohms, go to step 25).

21) Check Shift Solenoid For Short To Power Turn ignition off. Disconnect transmission wiring harness connector. Disconnect 60-pin PCM 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.

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 any 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.

23) Check Shift Solenoid Circuit Continuity Turn ignition off. Leave transmission wiring harness connector disconnected. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between suspect shift solenoid test pin 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.

24) Check Shift Solenoid For Short To Power In Transmission Leave ignition off and PCM disconnected. Reconnect transmission wiring harness connector. Turn ignition on. Measure voltage between test pin No. 60 and suspect shift solenoid test pin at breakout box. If voltage is 0.5 volt or more, repair solenoid short to power. If voltage is less than 0.5 volt, replace PCM and repeat QUICK TEST.

25) Check Transmission Wiring Leave ignition off. Check transmission wiring harness circuits and connectors breaks or corrosion in insulation. Check for open or grounded circuits. Repair or replace as necessary. If connectors and circuits are okay, replace suspect solenoid and repeat QUICK TEST .

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 25) to step 30). No test procedures have been omitted.

30) Continuous Memory Codes 621, 622, 641 & 643 Continuous Memory Code 621 (SS1), 622 (SS2), 641 (SS3) or 643 (TCC) indicates a failure was detected in shift solenoid circuit during last 80 warm-up cycles. Possible causes for these faults are

1. Faulty shift solenoid.
2. Circuit open or grounded.

Turn ignition off. Check shift solenoid circuit between PCM and transmission. Repair or replace as necessary. If circuits are okay, go to next step.

31) Check For Intermittent Short Or Open Turn ignition off. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Turn ignition on. Connect test light between test pin No. 37 and suspect shift solenoid test pin at breakout box. See the IDENTIFYING SHIFT SOLENOID TEST CIRCUITS table below. Test light should be at partial brightness. Observe test light while wiggling and bending shift solenoid circuit between transmission and PCM. An open or short to power will be indicated by light going off. A short to ground will be indicated by light getting brighter. Repeat procedure for all solenoids. If fault is indicated, isolate and repair as necessary. If no fault is indicated, go to next step.

IDENTIFYING SHIFT SOLENOID TEST CIRCUITS

32) Check For Intermittent Short To Ground Leave ignition off and PCM disconnected. Disconnect transmission wiring harness connector. Turn ignition on. Connect test light between test pin No. 37 and suspect shift solenoid test pin at breakout box. Test light should be off. Observe test light while wiggling and bending shift solenoid circuit between transmission and PCM. 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 the following non-EEC areas may be at fault

1. Transmission linkage and internal components.
2. Electrical (alternator, battery, add-on devices, etc.).

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

1. Wiring harness circuits (MLP, TRD, TRL, TRR, TROD and SIG RTN).
2. Powertrain Control Module (PCM).

MLP Connector Terminal ID (Bronco - AODE). Scheme 55

MLP Connector Terminal ID (Bronco - E40D). Scheme 56

TEST PIN NO. 30 (MLP) WIRE COLOR IDENTIFICATION

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

1) Codes 67, 522, 634 & 654 KOEO Codes 67, 522, 634 and 654 indicate MLP sensor is out of self-test range (3770-4607 ohms) when gear selector is in Park.

Possible causes for these faults are

1. Linkage not adjusted correctly.
2. Faulty Manual Lever Position (MLP) sensor.
3. Circuit open or grounded.
4. Faulty Powertrain Control Module (PCM).

Turn ignition off. Apply parking brake. Place transmission gear selector in Neutral. Place MLP Sensor Gauge (T91P-7010-AHT) in sensor slot. If gauge does not fit, loosen MLP mounting bolts and adjust sensor as necessary. If gauge fits, remove gauge and go to next step.

2) Check MLP Sensor Circuit Continuity Turn ignition off. Disconnect MLP sensor wiring harness connector. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM 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) Check MLP Sensor For Short To Power & Ground Turn ignition off. Leave PCM and MLP sensor disconnected. Measure resistance between test pin No. 30 and test pins No. 37, 57, 40, 46 and 60 at break-out box. Measure resistance between test pin No. 30 and chassis ground. If any 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) Check MLP Sensor Resistance Turn ignition off. Connect MLP sensor. Leave PCM disconnected. Unlock steering column. Measure resistance between test pins No. 30 and 46 at breakout box while cycling gear selector. See the MLP SENSOR RESISTANCE table below. If resistance is within specification, replace PCM and repeat QUICK TEST. If resistance is not within specification, replace MLP sensor and repeat QUICK TEST.

MLP SENSOR RESISTANCE

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

1. Engine and/or transmission fluid level.
2. Engine and/or transmission fluid temperature.
3. Ambient temperature. This test is intended to diagnose
4. TFT sensor.
5. Wiring harness circuits (TFT and SIG RTN).
6. Faulty Powertrain Control Module (PCM).

AODE Connector Terminal Sensor Circuit ID (Bronco). Scheme 57

E4OD Conn. Terminal Sensor Ckt. ID (Bronco). Scheme 58

TFT SENSOR SPECIFICATIONS

1) Code 26/636 KOEO Code 636 indicate TFT sensor is out of self-test range.

Possible causes for these faults are

1. Transmission fluid level incorrect.
2. Transmission fluid temperature incorrect.
3. Sensor resistance out of specification.
4. Faulty Powertrain Control Module (PCM).

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) Check VREF At Throttle Position (TP) Sensor Turn ignition off. Disconnect TP sensor wiring harness connector. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect PCM to breakout box. Turn ignition on. Measure voltage between VREF and SIG RTN terminals at TP sensor wiring harness connector. (Scheme 59) If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, go to CIRCUIT TEST C.

3) Check TOT Sensor Resistance Turn ignition off. Disconnect PCM from breakout box. Allow transmission to cool. Measure and record resistance between test pin No. 46 and TFT test pin at breakout box. Drive vehicle until transmission fluid is at normal operating temperature. Disconnect PCM from breakout box. Measure resistance voltage between test pin No. 46 and TFT test pin at breakout box. If cold resistance measurement is different than warm resistance measurement, and warm resistance is within specification, replace PCM and repeat QUICK TEST . If voltage is not as specified, replace TFT sensor.

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.

10) KOEO Code 56/637 KOEO Code 56/637 indicate TOT sensor output exceeds self-test maximum voltage (4.8 volts). Possible causes for these faults are

1. Transmission fluid level incorrect.
2. Open wiring harness circuit.
3. Faulty TOT sensor.
4. Faulty PCM.

Turn ignition off. Disconnect TFT wiring harness connector. Inspect terminals, and repair if damaged. Connect jumper wire between TFT and SIG RTN terminals. Perform KOEO SELF-TEST. If Code 66/638 is present, go to step 25). If Code 66/638 is not present, remove jumper wire and go to next step. If no codes are present, go to step 12).

11) Check TOT & SIG RTN Circuit Continuity Turn ignition off. Leave TFT sensor disconnected. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box(T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between TFT circuit at TFT wiring harness connector and TFT test pin at breakout box. Measure resistance between SIG RTN circuit at TFT 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 each resistance is 5 ohms or less, go to next step.

12) Check TFT Sensor For Short To VPWR Turn ignition off. Leave PCM and TFT sensor disconnected. Measure resistance between TFT test pin and test pins No. 37 and 57 at breakout box. If resistance is more than 10,000 ohms, replace PCM 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.

20) KOEO Code 66/638 KOEO Code 638 indicates TFT sensor output is lower than self-test minimum voltage. Possible causes for these faults are

1. Incorrect fluid level.
2. Damaged TFT sensor.
3. Shorted wiring harness circuit.
4. Faulty PCM.

Turn ignition off. Disconnect transmission wiring harness connector. Inspect terminals, and repair if damaged. Perform KOEO SELF-TEST. If Code 56/637 is present, go to step 25). If Code 56/637 is not present, go to next step.

21) Check VREF At Throttle Position (TP) Sensor Turn ignition off. Disconnect TP sensor wiring harness connector. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect PCM to breakout box. Turn ignition on. Measure voltage between VREF and SIG RTN terminals at TP sensor wiring harness connector. (Scheme 59) If voltage is 4-6 volts, reconnect TP sensor and go to next step. If voltage is not 4-6 volts, go to CIRCUIT TEST C.

Throttle Position (TP) Sensor Connector Terminal ID (Bronco). Scheme 59

22) Check TFT Circuit For Short To Ground Turn ignition off. Disconnect PCM from breakout box. Measure resistance between TFT test pin at breakout box and test pins No. 40, 46 and 60. If resistance is more than 10,000 ohms, replace PCM 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.

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 TFT 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.

90) Continuous Memory Code 637 Or 638 Continuous Memory Code 637 or 638 indicates a fault has been detected in TFT circuit during previous 80 warm-up cycles. Possible causes for these faults are

1. Incorrect fluid level.
2. Intermittent fault in TFT sensor.
3. Intermittent short or open in wiring harness.

Turn ignition off. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect PCM to breakout box. Connect DVOM between test pins No. 2 and 46 at breakout box. Turn ignition on. Shake and bend TFT and SIG RTN wires between transmission and PCM. Voltage should remain stable or change gradually. If voltage drops to zero, a short to ground is indicated. If voltage increases up to 5 volts, an open circuit is indicated. If voltage increases to more than 5 volts, a short to power is indicated. If fault is indicated, isolate and repair as necessary. If no faults are found, problem is intermittent and cannot be located at this time. See SUMMARY in this article.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 90) to step 100). No test procedures have been omitted.

100) Continuous Memory Code 68/657 Continuous Memory Code 68/657 indicates excessive transmission temperatures. Possible causes for these faults are

1. Damage in transmission cooling system.
2. Pulling overweight trailer.
3. Incorrect fluid level.
4. Damaged clutch.
5. Fault in TFT sensor.
6. Intermittent short or open in wiring harness.

Turn ignition off. Disconnect transmission wiring harness connector. Inspect terminals, and repair if damaged. Perform KOEO SELF-TEST. If no codes are present, fault is in transmission. If Code 68/657 is present, check for fault causing transmission to overheat. If any other code(s) is present, service as necessary and repeat QUICK TEST.

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

1. Wiring harness circuit (OSS).
2. Faulty Powertrain Control Module (PCM).

Output Shaft Speed (OSS) Sensor Circuit (Bronco). Scheme 60

TEST PIN NO. 5 (OSS+) WIRE COLOR IDENTIFICATION

1) KOER Code 639 KOER Code 639 indicates input from Output Shaft Speed Sensor (OSS) to PCM is out of calibration. Possible causes for this fault are

1. Faulty OSS sensor.
2. Circuit open or grounded.
3. Faulty Powertrain Control Module (PCM).

Turn ignition off. Disconnect OSS wiring harness connector. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between OSS+ terminal at OSS wiring harness connector and test pin No. 5 at breakout box. Measure resistance between SIG RTN terminal at OSS wiring harness connector and test pin No. 46 at breakout box. For E Series 5.0L, measure resistance at SIG RTN terminal at OSS connector and test pin No. 29 at breakout box. On all models, 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

2) Check Circuit For Short To Power Or Ground Leave ignition off and OSS disconnected. Measure resistance between test pin No. 5 and test pins No. 37 and 57 at breakout box. Measure resistance between test pin No. 5 and test pins No. 40, 46 and 60 at breakout box. If any 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.

3) Measure OSS Resistance Leave ignition off and OSS disconnected. Measure resistance between sensor terminals. Resistance should be 450-750 ohms. If resistance is not correct, replace OSS and repeat QUICK TEST . If resistance is correct, check internal transmission components. If okay, replace PCM 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.

10) KOEO Code 639 Code 639 indicates incorrect input signal from OSS. Possible causes for this fault are

1. Faulty OSS.
2. Circuit open or grounded.
3. Faulty PCM.

Turn ignition off. Disconnect transmission 12-pin connector. Measure resistance between OSS (-) and OSS (+) terminal at sensor wiring harness connector. (Scheme 61) If resistance is not 200-600 ohms, check wiring for damage and repair as necessary. If wiring is okay, replace OSS sensor. If resistance is 200-600 ohms, go to next step.

Transmission 12-Pin Connector Terminal ID (Bronco). Scheme 61

11) Check OSS Circuit For Short To Power Leave ignition off and transmission 12-pin connector removed. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Turn ignition on. Measure voltage between OSS (+) terminal at sensor wiring harness connector and chassis ground. Measure voltage between OSS (-) terminal at sensor wiring harness connector and chassis ground. If both voltages are less than 0.5 volt, turn ignition off and go to next step. If either voltage is 0.5 volt or more, repair short circuit and repeat QUICK TEST .

12) Leave ignition off. Leave transmission connector and PCM disconnected. Measure resistance between OSS (+) terminal at sensor wiring harness connector and chassis ground. Measure resistance between OSS (-) terminal at sensor wiring harness connector and chassis ground. Measure resistance between OSS (+) terminal and OSS (-) terminal at 12-pin connector. If any resistance is less than 10,000 ohms, repair short circuit and repeat QUICK TEST. If any resistance is 10,000 ohms or more, go to next step.

13) Check OSS Circuit Continuity Leave ignition off and transmission 12-pin connector removed. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between TSS (+) terminal at 12-pin connector and test pin No. 24 at breakout box. Measure resistance between OSS (-) terminal at 12-pin connector and test pin No. 44 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.

14) Check PCM For Internal Shorts Turn ignition off. Connect PCM to breakout box. Leave transmission wiring harness connector removed. Measure resistance between test pin No. 24 and pins No. 37, 40, 44, 57 and 60 at breakout box. If any resistance is less than 500 ohms, replace PCM and repeat QUICK TEST. If each resistance is 500 ohms or more, go to next step.

15) Check OSS Output Turn ignition off. Leave PCM connected to breakout box. Reconnect transmission 12-pin connector. Set DVOM on AC voltage scale. Start engine. Measure voltage between breakout box test pins No. 24 and 44 while varying engine speed. If AC voltage varies more than 0.5 volt, replace PCM and repeat QUICK TEST . If AC voltage does not vary more than 0.5 volt, replace OSS and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 15) to step 90). No test procedures have been omitted.

90) Continuous Memory Code 639 Code 639 indicates PCM detected incorrect output signal from OSS during previous 40-80 warm-up cycles. Possible causes for this fault are

1. Faulty OSS.
2. Faulty transmission.
3. Circuit open or grounded.
4. Faulty PCM.

Record and clear continuous memory codes. While test driving vehicle, stop, ensure transmission gear selector is in Drive, and accelerate heavily to 35 MPH. After test drive, perform KOEO Self-Test and record all codes. If Continuous Memory Code 639 does not repeat, problem cannot be duplicated at this time. See SUMMARY in this article. If Continuous Memory Code 639 is repeated, go to next step.

91) Check OSS Circuit Continuity Turn ignition off. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Disconnect OSS wiring harness connector. Measure resistance between OSS+ terminal at OSS connector and test pin No. 5 at breakout box. Measure resistance at SIG RTN terminal at OSS connector and test pin No. 46 at breakout box. For E Series 5.0L, measure resistance at SIG RTN terminal at OSS connector and test pin No. 29 at breakout box. On all models, if either resistance is more than 5 ohms, repair short circuit and repeat QUICK TEST. If all resistances are 5 ohms or less, go to next step.

92) Check Circuit For Short To Power Or Ground Turn ignition off. Leave OSS disconnected. Measure resistance between test pin No. 5 and test pins No. 37 and 57 at breakout box. Measure resistance between test pin No. 5 and test pins No. 40, 46 and 60 at breakout box. If either resistance is less than 500 ohms, repair short circuit and repeat step 90). If both resistances are 500 ohms or more, go to next step.

93) Measure Sensor Resistance Turn ignition off. Leave sensor disconnected. Measure resistance between sensor terminals. OSS terminal resistance should be 450-750 ohms. If resistance is correct, replace PCM and repeat step 90) to verify code elimination. If resistance is not correct, replace OSS sensor and repeat step 90) to verify code elimination.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 93) to step 95). No test procedures have been omitted.

95) Continuous Memory Code 639 Continuous Memory Code 639 indicates an error in OSS sensor output during previous 80 warm-up cycles. Possible causes for this fault are

1. Intermittent fault in OSS sensor.
2. Intermittent short or open in wiring harness.
3. Transmission placed in gear when fluid level is low.

Turn ignition off. Visually inspect OSS wires and connectors for damage. Disconnect 60-pin PCM connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect PCM to breakout box. Connect DVOM between test pins No. 24 and 44 at break-out box. Start engine. Shake and bend OSS wires between transmission and PCM. Lightly tap circuit connectors. 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, go to next step.

96) Check PCM & Harness Connectors Turn ignition off. Disconnect all connectors related to OSS circuit. Inspect circuits and connectors for damage. Repair as necessary and repeat QUICK TEST . If fault cannot be found, problem is intermittent and cannot be duplicated at this time. See SUMMARY .

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

1. Wiring harness circuits (CCS, SS1, SS2, SS3, EPC, TCC, TOT, and MLP).
2. Powertrain Control Module (PCM).

A0DE Transmission Ckt. & Wiring Conn. Terminal ID (Bronco). Scheme 62

E4OD Trans. Ckt. & Wiring Conn. Terminal (Bronco). Scheme 63

TEST PINS NO. 37 & 57 (EPC PWR) WIRE COLOR ID

Note. Procedure begins with step 90). No test procedures have been omitted.

90) Drive Cycle Test (AODE & E4OD) Ensure all components are connected. Ensure transmission fluid is correct level. Warm engine to normal operating temperature. Perform KOEO and CONTINUOUS MEMORY CODE SELF-TEST. Clear all codes.

With transmission gear selector in Drive, press Transmission Control Switch (TCS). Transmission Control Indicator Light (TCIL) should come on. Moderately accelerate vehicle to 40 MPH for at least 15 seconds (30 seconds above 4000 feet elevation). Transmission should be in 3rd gear. While holding speed steady, press TCS. TCIL should go off. Accelerate from 40 MPH to 50 MPH. Transmission should shift from 3rd gear to 4th gear. Hold speed steady for 15 seconds. While holding speed steady, lightly apply and release brakes to turn brakelights on. Maintain 50 MPH for about 5 seconds. Stop and park vehicle for a minimum of 20 seconds with transmission gear selector in Drive. Repeat procedure 5 times.

After completing DRIVE CYCLE TEST, perform KOEO and CONTINUOUS MEMORY CODE SELF-TEST. If Code 11/111 is present, fault cannot be duplicated at this time. If Code 99/624, 67/634 or 651 is present, go to next step. If Code 29/452 is present, go to CIRCUIT TEST DP. If any other code(s) is present, go to step 92).

MLP Sensor Circuit & Wiring Connector Terminal ID (Bronco - AODE). Scheme 64

MLP Sensor Circuit & Wiring Connector Terminal ID (Bronco - E4OD). Scheme 65

91) Code 624, 634 Or 651 Code 624 and 651 indicate Electronic Pressure Control (EPC) failure. Code 634 indicates that Manual Lever Position (MLP) sensor is out of calibration. Possible causes for these faults are

1. Faulty EPC solenoid.
2. Faulty MLP sensor.
3. Circuit open or grounded.
4. Damaged PCM connector pins.

Turn ignition off. Disconnect 60-pin PCM connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect PCM to breakout box. To test EPC solenoid, connect DVOM to EPC test pin and EPC VPWR test pin at breakout box. To test MLP sensor, connect DVOM to MLP test pin and test pin No. 46 at breakout box. For EPC solenoid and MLP sensor, turn ignition on. Voltage for EPC should be less than 10 volts. Voltage for MLP should be less than 5 volts. Shake and bend EPC/MLP wiring harness. Lightly tap on components to simulate road shock. Voltage should remain stable. If voltage changes or exceeds specification, fault in circuit is indicated. If fault is indicated, isolate and repair as necessary. Clear continuous memory codes, and repeat QUICK TEST . If no faults are found, problem cannot be located at this time.

92) Check Circuit Harness & Connectors Enter CONTINUOUS MONITOR MODE. Shake and bend EEC wiring harness while observing analog VOM or scan tool. Lightly tap on components to simulate road shock. If VOM indicator has erratic movement or scan tool beep, fault is indicated. If fault is indicated, isolate and repair as necessary. Clear continuous memory codes, and repeat QUICK TEST. If no faults are found, problem cannot be located at this time.

CIRCUIT TEST KOEO CONTINUOUS MEMORY CODES

93) Check For Code 659 Code 659 indicates high vehicle speed detected while vehicle was in Park. Possible causes for this fault are

1. Faulty Manual Lever Position (MLP) sensor.
2. Faulty Powertrain Control Module (PCM).

If Code 659 was present after performing drive cycle test in step 90), go to step 103). If Code 659 was not present after performing drive cycle test in step 90), go to next step.

94) Check For Code 675 Code 675 indicates MLP circuit voltage was out of range.

Possible causes for this fault are

1. Faulty MLP sensor.
2. Open or short circuit.
3. Short to power or ground in SIG RTN circuit.
4. Faulty Powertrain Control Module (PCM).

If Code 675 was present after performing drive cycle test in step 90), go to next step. If Code 675 was not present after performing drive cycle test in step 90), go to step 98).

95) Check For Codes 675 & 667 Code 667 indicates MLP circuit voltage was less than self-test minimum voltage allowed. Possible causes for this fault are

1. Faulty MLP sensor.
2. Open or short in MLP circuit.
3. Short to power in MLP circuit.
4. Faulty Powertrain Control Module (PCM).

If Codes 675 and 667 were present after performing drive cycle test in step 90), go to step 99). If Codes 675 and 667 were not present after performing drive cycle test in step 90), go to next step.

96) Check For Codes 675 & 668 Code 668 indicates MLP circuit voltage was more than self-test maximum voltage allowed. Possible causes for this fault are

1. Faulty MLP sensor.
2. Open MLP circuit.
3. Short to power in SIG RTN circuit.
4. Faulty Powertrain Control Module (PCM).

If Codes 675 and 668 were present after performing drive cycle test in step 90), go to step 101). If Code 675 and 668 were not present after performing drive cycle test in step 90), go to next step.

97) Check MLP Alignment Turn ignition off. Apply parking brake. Place transmission gear selector in Neutral position. Place MLP Sensor Gauge (T91P-7010-AHT) in sensor slot. If gauge does not fit, loosen MLP mounting bolts and adjust sensor as necessary. Clear codes and repeat QUICK TEST . If gauge fits, remove gauge and go to next step.

98) Check For Code 667 Code 667 indicates MLP circuit voltage less than self-test minimum voltage allowed. Possible causes for this fault are

1. Faulty MLP sensor.
2. Open or short to ground in MLP circuit.
3. Faulty Powertrain Control Module (PCM).

If Code 667 was present after performing drive cycle test in step 90), go to next step. If Code 667 was not present after performing drive cycle test in step 90), go to step 101).

99) Check MLP Circuit Resistance Turn ignition off. Disconnect 60-pin PCM connector. Disconnect MLP sensor. Inspect connectors for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pin No. 30 at breakout box and MLP terminal at MLP sensor connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST .

100) Check For Shot To Ground In MLP Circuit Turn ignition off. Ensure breakout box is installed and MLP sensor and PCM are disconnected. Measure resistance between test pin No. 30 and chassis ground. If resistance is more than 10,000 ohms, go to step 103). If resistance is 10,000 or less, repair short circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST.

101) Code 668 Code 668 indicates MLP circuit voltage was more than self-test maximum voltage allowed. Possible causes for this fault are

1. Faulty MLP sensor.
2. Open MLP circuit.
3. Faulty MLP sensor circuit.
4. Faulty Powertrain Control Module (PCM).

Turn ignition off. Disconnect 60-pin PCM connector. Disconnect MLP sensor. Inspect connectors for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Measure resistance between test pins No. 46 at breakout box and SIG RTN terminal at MLP sensor connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST .

102) Check For Short To Power Ensure PCM and MLP sensor are disconnected. Measure resistance between test pin No. 30 and test pins No. 37, 40, 46, 57 and 60 at breakout box. If all readings are more than 10,000 ohms, go to next step. If any reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST.

103) Check MLP Sensor Resistance Turn ignition off. Connect MLP sensor. Leave PCM disconnected. Unlock steering column. Measure resistance between test pins No. 30 and 46 at breakout box while cycling gear selector. See the MLP SENSOR RESISTANCE table below. If resistance is within specification, replace PCM and repeat QUICK TEST . If resistance is not within specification, replace MLP sensor and repeat QUICK TEST.

MLP SENSOR RESISTANCE