Tests W/codes - Mpfi Ford Festiva I

INTRODUCTION

If no faults were found while performing BASIC TESTING , proceed with self-diagnostics. If no fault codes or only pass codes are present, proceed to TESTS W/O CODES article for diagnosis by symptom (i.e. ROUGH IDLE, NO START, etc.).

Testing procedures for some of the components are the same for symptom testing as for testing when codes are present. For these testing procedures see the SYMPTOM/TEST MENU in this article.

HARD FAILURES

Hard failures cause "malfunction" light to illuminate and remain on until the malfunction is repaired. If light comes on and remains on (light may flash) during vehicle operation, cause of malfunction must be determined using diagnostic (code) charts. If a sensor fails, control unit will use a substitute value in its calculations to continue engine operation. In this condition, vehicle is functional, but loss of good driveability will most likely be encountered.

INTERMITTENT FAILURES

Intermittent failures may cause "malfunction" light to flicker or illuminate and go out after the intermittent fault goes away. The corresponding trouble code, however, will be retained in control unit memory. If related fault does not reoccur within a certain time frame, related trouble code will be erased from control unit memory. Intermittent failures may be caused by sensor, connector or wiring related problems. See INTERMITTENTS in TESTS W/O CODES article.

SUMMARY

If no hard fault codes are displayed, perform TEST Q. If only Code 88 is present, perform TEST NB. If there are no codes, perform KOEO SELF-TEST. If symptom is still present proceed to TESTS W/O CODES article for diagnosing by symptom (i.e. ROUGH IDLE, NO START, etc.), or for intermittent diagnosis procedures. Also see I - SYS/COMP TESTS article to test systems and/or components.

Scheme 5

PREPARATION

Correct results of the testing are dependent on the proper operation of related non-electronic components. It may be necessary to disconnect harness assemblies to perform some of the inspections. Pin locations should be noted before disassembly. If the engine will not start, starts but stalls, idles rough or runs rough, proceed to Key On Engine Off (KOEO) test.

VISUAL CHECK

Inspect air cleaner and inlet ducting. Check all engine vacuum hoses for damage, leaks, cracks, blockage, ensure proper routing, etc.

VEHICLE PREPARATION

Perform all safety steps required to start and run vehicle tests. Turn off all electrical loads. Start engine and run until operating temperature is reached. Turn engine off and proceed to EQUIPMENT HOOK-UP.

EQUIPMENT HOOK-UP - MIL EQUIPPED VEHICLES

1. Turn ignition off and connect color coded adapter cable to STAR tester.
2. Connect adapter cable leads to the proper self-test connectors and latch center button. Slide switch in "MECS" position and turn ignition on. Ensure that "Fast-Slow" switch is in "Slow" position.

EQUIPMENT HOOK-UP - USING ANALOG VOLT/OHM METER (VOM)

1. Turn ignition off and connect a jumper wire from the self-test input connector to ground. Set volt/ohmmeter on a DC voltage range to read from 0-20 volts.
2. Connect volt/ohmmeter between White/Green wire terminal on 6-pin self-test output connector and battery negative terminal.

EQUIPMENT HOOK-UP - NON-MIL EQUIPPED VEHICLES W/ ANALOG VOM

1. Turn ignition off and set volt/ohmmeter on a DC voltage range to read from 0-20 volts.
2. Connect volt/ohmmeter between Green terminal and Black terminal on the 6-pin self-test connector, located under dash.

CLEARING CODES

A fault code will remain in ECA memory until erased. To erase memory, disconnect negative battery cable and depress brake pedal for at least 5 seconds. Reconnect battery cable and ensure malfunction indicator light is off.

QUICK TEST

Note. The following charts used in this portion of the article, are provided courtesy of Ford Motor Co.

READING SERVICE CODES

The engine control system communicates malfunctions to the technician through service codes. These service codes are 2 digit numbers representing a particular fault. The service codes are transmitted through the Self-Test Output (STO) line found in the vehicle self-test connector.

Codes are displayed in the form of timed pulses and read by the technician on a voltmeter or STAR tester. (Scheme 6) When using analog volt/ohmmeter, codes are displayed in the form of needle sweeps on the volt/ohmmeter.

Scheme 6

KEY ON/ENGINE OFF (KOEO) SELF-TEST

Note. DO NOT depress throttle during KOEO self-test.

This is a test of electronic engine control system, conducted with power (voltage) applied and engine not running. Activate self-test and record all codes displayed. Erase codes and repeat self-test. Diagnose only codes that occur during repeat self-test. After codes have been noted, refer to FAULT CODE/TEST MENU to find the proper test procedure.

FAULT CODE/TEST MENU

FAULT CODE-TO-TEST MENU (1)

KEY ON/ENGINE RUNNING (KOER) SELF-TEST

This test is conducted of the engine control system with the engine running. The sensors are checked under actual operating conditions and at normal operating temperatures.

Note. It is necessary to clear codes in memory before continuing with this test. Also DO NOT depress throttle during test.

PERFORMING TESTS

1. If the symptom is a no-start, proceed to CONTINUOUS SELF-TEST. Verify a pass Code 00 was received in the KOEO SELF-TEST before continuing.
2. Deactivate self-test. Start and run engine at 2000 RPM for 5 minutes to warm up EGO sensor. Turn engine off and wait 10 seconds.
3. Restart engine and activate self-test. Record all service codes displayed and refer to FAULT CODE/TEST MENU to find the proper test procedure.

CONTINUOUS MEMORY/MONITOR SELF-TEST

These codes are issued as a result of information stored during continuous self-test and are stored in permanent memory until they are erased. These codes are displayed only during KOEO testing. These codes should be used for diagnosis only when KOEO and KOER SELF-TESTS result in Code 00 and all QUICK TEST steps have been successfully completed.

Note. Verify that a Pass Code 00 was received in both KOEO and KOER SELF-TESTS before continuing with this test. Clear codes before continuing with test.

CLEARING CONTINUOUS MEMORY CODES

1. Run KOEO SELF-TEST.
2. When service codes are being displayed, deactivate self-test. On STAR tester, unlatching center button (switch in "UP" position) will deactivate self-test. On analog volt/ohmmeter, remove jumper wire from between self-test input (STI) connector and ground.
3. Disconnect negative battery cable and depress brake pedal for 5-10 seconds.

DETERMINING CONTINUOUS MEMORY CODES TO BE TESTED

The cause of some of the continuous memory codes may have been eliminated during either KEY ON/ENGINE OFF (KOEO) or KEY ON/ENGINE RUNNING (KOER) SELF-TEST repairs. Diagnose only those continuous memory codes for which a similar code has not been previously serviced. Once this has been determined, go to KOEO & KOER SELF-TEST procedures.

KOEO SELF-TEST PROCEDURES

1. Connect STAR tester or volt/ohmmeter as described in EQUIPMENT HOOK-UP. Turn on STAR tester and latch center button or ground STI if using volt/ohmmeter.
2. Turn ignition key to the "ON" position to place system in "CONTINUOUS MONITOR" mode. Tap, move and wiggle the suspect sensor and/or harness.
3. If a fault is detected, a service code will be stored in memory and will be indicated. Proceed to FAULT CODE/TEST MENU to find the proper test procedure.

KOER SELF-TEST PROCEDURES

1. Connect STAR tester or volt/ohmmeter as described in EQUIPMENT HOOK-UP. Start engine and run until operating temperature is reached.
2. Activate self-test and wait 2 minutes. Deactivate and reactivate self-test. DO NOT turn off engine. System is now in Engine Running "CONTINUOUS MONITOR" Mode.
3. Tap, move and wiggle the suspect sensor and/or harness. If a fault is detected, a service code will be stored and indicated. Refer to FAULT CODE/TEST MENU to find the proper test procedure.

SWITCH MONITOR TEST

Note. All switches must be tested individually. Allowing a switch to remain on while testing another will lead to false test results.

This test checks input signals from the individual input switches to the ECA. Before activating this test, deactivate self-test and turn all accessories off. Place transmission selector in Neutral and proceed to Using STAR Tester or Using Analog Volt/Ohmmeter. If all switches are okay, proceed to CIRCUIT TEST Q.

USING STAR TESTER

Connect STAR tester adapter cable. Note output of LED on the adapter cable as each switch is actuated. Record all tests results and proceed to SWITCH MONITOR TEST CHART.

USING ANALOG VOLT/OHMMETER

1. Ground STI connector. Connect volt/ohmmeter between Red/Blue (Pos.) and Yellow/Green (Neg.) wire terminals on 6-pin self-test output connector.
2. Note output of the analog volt/ohmmeter as each switch is actuated. Record all tests results and proceed to SWITCH MONITOR TEST CHART.

Note. DO NOT depress throttle, clutch or engage transmission, unless directed.

Switch Monitor Test Chart. Scheme 7

CONTINUOUS MONITOR (WIGGLE) TEST - SYSTEMATIC USE

1. Visually inspect sensor, switch or solenoid affected. Enter CONTINUOUS SELF-TEST and lightly tap sensor, switch or solenoid.
2. Push/pull on sensor, switch or solenoid connector while not disconnecting. Test and wiggle (shake) harness vigorously, working from sensor, switch or solenoid toward dash panel and from the dash panel to ECA in small sections.
3. If volt/ohmmeter does not have a positive indication of an intermittent fault, carefully disconnect sensor, switch or solenoid from harness. Remove terminals from connector.
4. Inspect terminals at both ends for corrosion, bad crimps and improperly seated terminals. Reconnect after inspection and unplug processor from harness.
5. Inspect terminals for corrosion, bad crimps and improperly seated terminals. If volt/ohmmeter does not indicate an intermittent fault plug in connector and erase CONTINUOUS SELF-TEST codes. See CONTINUOUS SELF-TEST for clearing codes.

Fault Code & Component Identification Chart (1 of 2). Scheme 8

Fault Code & Component Identification Chart (2 of 2). Scheme 9

Fault Code Identification Chart - Non-Mil Equipped Vehicles. Scheme 10

Note. If there is trouble in more than 2 places, the fault indication will be for the lowest code number first. If after a malfunction has occurred, and the ignition is turned off, the malfunction indicator will not be displayed. The ECA has a built-in, fail-safe mechanism. If a malfunction occurs during driving, the ECA will operate on its own initiative as shown in the above chart and driving performance will be affected. If the problem is corrected during indication, ECA memory must be erased by disconnecting negative battery cable for 5 or more seconds.

Note. If there is trouble in more than 2 places, the fault indication will be for the lowest code number first. Even if the problem is corrected during indication, 1 cycle will be indicated. If after a malfunction has occurred, and the ignition is turned off, the malfunction indicator will not be displayed. The ECA has a built-in, fail-safe mechanism. If a malfunction occurs during driving, the ECA will operate on its own initiative as shown in the above chart and driving performance will be affected.

HOW TO USE CIRCUIT TESTS

1. DO NOT perform any CIRCUIT TEST unless specified by QUICK TEST. Ensure all non-ECA related faults are corrected. Do not replace any part unless directed to do so. When more than one service code is received, start with first code displayed.
2. Do not measure voltage or resistance at ECA or connect any test light to ECA unless specified. All measurements are made by probing REAR of the connector. Isolate both ends of a circuit and turn key off whenever checking for shorts or continuity, unless specified.
3. Disconnect solenoids and switches from harness before measuring continuity, resistance, or applying 12 volts. Follow each test step in order until fault is found. After each repair, check all component connections and repeat CIRCUIT TEST(S).
4. An "open" is defined as any resistance reading greater than 5 ohms, unless otherwise specified. A "short" is defined as any resistance reading less than 10,000 ohms to ground, unless otherwise specified.
5. On CIRCUIT TEST Q, to prevent replacement of good components, be aware that non-ECA related areas may also be at fault.

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

DIAGNOSTIC ROUTINES

Note. The following acronyms are used throughout the circuit test portion of this article, and can be described as Self-Test Output (STO), Self-Test Input (STI), Switch Monitor Lamp (SML), Reference Voltage (VREF), Signal Return (SIGRTN), Vehicle Power (VPRW) and Keep Alive Power (KAPWR).

SYMPTOM/TEST MENU

Note. Diagnosis by symptom should only be attempted after all codes have been cleared, but the problem still exists. Also refer to H - 4-CYL TESTS W/0 CODES article in this section.

DIAGNOSIS BY SYMPTOM MENU

IGNITION DIAGNOSTIC MONITOR (IDM) CHECK

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: fuel quantity and quality, ignition system damage, cracks, moisture, etc., engine mechanical conditions such as valves, timing belt, etc. Also included are starter and battery circuit problems.

1. System integrity check. Visually inspect all wiring, wiring harness, connectors and components for evidence of overheating, insulation damage, looseness, shorting or other damage. Is there any cause to be concern? If yes, service as required. If no, go to step 2.
2. Distributor pulse check. Connect distributor. On vehicles built before 11/2/87 connect test lamp between black wire and ground. On vehicles built after 11/2/87 connect test lamp between yellow/blue wire and ground. On all models crank engine. If lamp flashes, go to step 6. If lamp does not flash, go to step 3.
3. Voltage at distributor. Set VOM on 20 volt scale. Turn key on. On vehicles built before 11/2/87 measure voltage between distributor black/white wire and ground and between distributor blue/red wire and ground. On vehicles built after 11/2/87 measure voltage between distributor black/white wire and ground and between distributor white/black wire and ground. On all models, is voltage above 10 volts? If yes, return to Diagnostic routine. If no, on black/white wire go to step 4, on white/black wire go to step 5, on blue/red wire go to step 5.
4. Ignition switch power check. Set VOM on 20 volt scale. Turn key on. Measure voltage between ignition switch black/white wire and ground. Is voltage reading above 10 volts? If yes, service black/white wire from ignition switch to coil and/or distributor (check fuses). If no, go to step 1 of CIRCUIT TEST FC.
5. Voltage at ECA. Install breakout box. Set VOM on 20 volt scale. Turn key on, engine off. On vehicles built before 11/2/87 measure voltage between test pin 56 and ground pin 40. On vehicles built after 11/2/87 measure voltage between test pin 36 and ground pin 40. Is reading greater than 10 volts? If no, go to step 1 of CIRCUIT TEST FC. If yes, on vehicles built before 11/2/87 service open in Blue/Red wire from distributor to ECA. If yes, on vehicles built after 11/2/87 service open in White/Black wire from distributor to ECA.
6. Coil-Pulse check. Connect coil. Connect test lamp between tach pulse connector and ground. Crank engine. If light flashes, go to step 7. If light does not flash, service black wire from coil to ECA on vehicles built before 11/2/87. If light does not flash, service yellow/blue wire from coil to ECA on vehicles built after 11/2/87.
7. Voltage at coil (+). Set VOM on 20 volt scale. Turn key on. Measure voltage between ignition coil (+) black/white wire and ground. Is voltage reading above 10 volts? If yes, go to step 8. If no, go to step 4.
8. PIP signal check. Install breakout box. On vehicles built before 11/2/87, connect test lamp between pin 47 and ground pin 40. On vehicles built after 11/2/87, connect test lamp between pin 6 and ground pin 40. On all models crank engine. If light flashes, go to step 9. If light does not flash, service black wire from distributor to ECA on vehicles built before 11/2/87. If light does not flash, service yellow/blue wire from distributor to ECA on vehicles built after 11/2/87.
9. Spark at plugs. Connect spark tester between plug wire (at each plug) and ground. Crank engine. Does spark jump the tester air gap? If yes, replace ECA. If no, return to Diagnostic routine.

Note. When replacing ECA, verify timing is within specifications.

Ignition Diagnostic Module (IDM) Circuit Schematic. Scheme 11

TEST B - VEHICLE BATTERY

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: battery cables and ground straps, voltage regulator and alternator, and ignition switch.

1. Power Check. With ignition off, install breakout box. Using DVOM on 20-volt scale, measure voltage between pin No. 1, ignition switch (Black wire) and battery ground. Also measure voltage between power relay (Blue wire) and battery ground. If reading is greater than 10 volts, proceed to step 3. If reading is 10 volts or less, proceed to next step.
2. Check for Opens. Install breakout box and remove 30, 60 and 80 amp fuses. Disconnect battery. Using DVOM on 200-ohm scale, measure resistance between battery and 30, 60 and 80 amp fuses. Also between 60 and 15 amp fuses, and both relay (Blue wires). If resistance is greater than 5 ohms, repair open in wire(s) in question or replace main fuse block as required. If resistance is 5 ohms or less, proceed to next step.
3. Relay Ground Check. With ignition off and DVOM on 200-ohm scale, measure resistance between power relay (Black wire) and battery negative terminal. If resistance is 5 ohms or more, repair open Black wire in question from power relay(s) to ground. If resistance is less than 5 ohms, proceed to next step.
4. ECA Ground Check. With ignition off and DVOM on 200-ohm scale, measure resistance between ECA case, pins No. 49, 46, 20 and 40, and battery negative terminal. If resistance is 5 ohms or more, repair open in wire(s) in question from power relay(s) to ground. If resistance is less than 5 ohms, proceed to next step.
5. ECA Ground Fault Isolation. With ignition off, install breakout box. Unplug harness from ECA. With DVOM on 200-ohm scale, measure resistance between pins No. 46 and 49, pins No. 46 and 20, and pins No. 46 and 40. If resistances are less than 5 ohms, ECA is okay. Repeat QUICK TEST. If resistance is 5 ohms or more, replace ECA.

Vehicle Battery Circuit Schematic. Scheme 12

VANE AIR TEMPERATURE (VAT) SENSOR

To prevent replacement of good components, ensure that the following conditions are met

1. Test not performed in unusually cold or hot ambient temperature conditions.
2. Ambient temperature must be greater than 50°F (10°C) for this test.
3. Inspect all wiring, harness, connectors and components for evidence of overheating, insulation damage, looseness, shorting or other damage. If none of the above mentioned is present, proceed to test step 1.

1. VAT Resistance Check. With ignition off, install breakout box and unplug ECA. Using DVOM on 10K scale, measure resistance between pins No. 25 and 46. If resistance is not within specification, proceed to step 5. If resistance is within specification, proceed to next step. TYPICAL VANE AIR TEMP. (VAT) SENSOR RESISTANCE Ambient Temperature °F (°C) Ohms Between Test Pins No. 25 & 46 1.3L 40 (4) 3000-6000 68 (20) 2000-3000 90 (32) 500-2000 1.6L 32 (0) 5800 65 (18) 2700 185 (85) 300 220 (104) 180 240 (116) 125
2. VAT Voltage Check. Install breakout box. Using DVOM on 10-volt scale, turn ignition on and measure voltage between pins No. 25 and 46. At 68°F (30°C), voltage reading should be 2-3 volts. Measure voltage between pins No. 46 and 20. At 68°F (30°C), voltage reading should be zero. If all readings are within specification, replace ECA. If all readings are not within specification, proceed to next step.
3. Short Between VAT & ECA Check. Turn ignition off and disconnect battery negative terminal. Install breakout box and unplug ECA. With DVOM on 200-ohm scale, measure resistance between the following pins: No. 25 and No. 1. No. 25 and No. 37. No. 25 and No. 40 (ground). No. 46 and No. 1. No. 46 and No. 37. If any of the resistances are less than 10,000 ohms, repair wire(s) in question. If all resistances are 10,000 ohms or more, reconnect battery and proceed to next step.
4. Signal Return Check. With ignition off and ECA unplugged, install breakout box. Using DVOM on 200-ohm scale, measure resistance between pins No. 46 and 40 (ground), and pin No. 40 (ground) and chassis ground. If resistance is less than 5 ohms, replace ECA. If resistance is 5 ohms or greater, repair open wire(s) in question.
5. Opens Between ECA & VAT. With ignition off and ECA unplugged, install breakout box. Using DVOM on 200-ohm scale, measure resistance between pin No. 25 and pin No. 46 (VAF meter Brown/Yellow wire), and VAF meter Blue/Yellow wire. If resistance is 5 ohms or more, repair wire(s) in question. If resistance is less than 5 ohms, reconnect ECA and proceed to next step.
6. VAF Sensor Resistance Check. With ignition off, unplug VAF connector. Using DVOM on 10-k/ohm scale, measure resistance between VAF meter terminals (Brown/Yellow and Yellow/Green wires, and Brown/Yellow and Blue/Yellow wires). If resistance is 2000-2500 ohms, repair short in Brown/Yellow wire from VAF to ECA. If resistance is not within specification, replace VAF meter.

VAT Sensor Circuit Schematic. Scheme 13

ENGINE COOLANT TEMPERATURE SENSOR

To help prevent replacement of good components, check coolant level, oil level, cooling fan operation, thermostat and other related components for proper condition and operation.

1. Engine Coolant Temperature (ECT) Sensor Resistance Check. Turn ignition off and install breakout box. Unplug ECA. Using DVOM on 200-k/ohm scale, measure resistance between Pins No. 7 and 46. Resistances should indicate as shown in «ENGINE COOLANT TEMPERATURE SENSOR RESISTANCE»(/ford/festiva/i-1986-1993/remont/testing-diagnostics/#tests-wcodes-mpfi) . If resistance is within specification, proceed to next step. If resistance is not within specification, proceed to step 5. ENGINE COOLANT TEMPERATURE SENSOR RESISTANCE Ambient Temperature °F (°C) Ohms Between TEST Pins No. 7 & 46 50 (10) 58,750 65 (18) 40,500 180 (82) 3,600 220 (104) 1,840
2. ECT Sensor Voltage Check. Install breakout box. Using DVOM on 20-volt scale and ignition on, measure voltage between Pins No. 7 and 46. Voltage reading should indicate 2.5 volts at 68°F (20°C). After warming up, voltage reading should indicate 0.3-0.6 volts. If voltage reading is within specification, replace ECA. If voltage reading is not within specification, proceed to next step.
3. Short Between ECT & ECA Check. Turn ignition off and disconnect battery negative terminal. Install breakout box and unplug ECA. Using DVOM on 200-k/ohm scale, measure resistance between the following pins: No. 7 and No. 1. No. 7 and No. 26. No. 7 and No. 37. No. 7 and No. 40. No. 46 and No. 1. No. 46 and No. 19. No. 46 and No. 37. If resistances are 10,000 ohms or more, proceed to next step. If resistances are less than 10,000 ohms, repair wire(s) in question.
4. Signal Return Check. Turn ignition off and install breakout box. Using DVOM on 200-ohm scale, measure resistance between pins No. 46 and 40, and pin No. 40 and chassis ground. If resistance is less than 5 ohms, replace ECA. If resistance is 5 ohms or more, repair ground wire.
5. Open Between ECT Sensor & ECA Check. Turn ignition off and install breakout box. Using DVOM on 200-ohm scale, measure resistance between ECT Blue/Red wire and pin No. 7, and ECT Blue/Yellow wire and pin No. 46. If resistance is 5 ohms or greater, repair wire(s) in question. If resistance is less than 5 ohms, proceed to next step.
6. ECT Sensor Resistance Check. Turn ignition off and unplug ECT sensor. Using DVOM on 200-ohm scale, measure resistance across ECT sensor. See «ENGINE COOLANT TEMPERATURE SENSOR RESISTANCE.»(/ford/festiva/i-1986-1993/remont/testing-diagnostics/#tests-wcodes-mpfi) If resistance is within specification, repair short in wire(s). If resistance is not within specification, replace ECT.

ECT Sensor Circuit Schematic. Scheme 14

TEST DF - BARO SENSOR

Inspect for obstructed vacuum lines, basic engine mechanical operation, wiring, wiring harness and insulation condition, before proceeding with test procedures.

1. VREF & Signal Return Check. Install breakout box and connect ECA. Using DVOM on 20-volt scale, turn ignition on and measure voltage between the following pins: No. 26 and No. 46. No. 26 and No. 40. No. 46 and No. 40. Voltage reading should indicate 4-6 volts on all except those readings taken from pins No. 46 and 40. Voltage reading on pins No. 46 and 40 should indicate zero volts. If voltage readings are within specification, proceed to next step. If voltage reading is greater than specification, proceed to step 5. If voltage reading is less than specification, proceed to step 6.
2. Check For BARO Sensor Voltage. Connect vacuum pump to BARO sensor and install breakout box. Using DVOM on 20-volt scale, with ignition on, measure voltage between pins No. 45 and 46. With zero vacuum, reading should be 3.5-4.5 volts. At 30 in. Hg, reading should indicate zero volts. If reading is within specification, replace ECA. If reading is not within specification, proceed to next step.
3. BARO Sensor Power Check. Using DVOM on 20-volt scale and ignition turned on, measure voltage between wires indicated in «BARO POWER CHECK»(/ford/festiva/i-1986-1993/remont/testing-diagnostics/#tests-wcodes-mpfi) . If voltage is not within specification, repair appropriate wire(s) in question. If voltage is within specification, proceed to next step. BARO POWER CHECK Between Voltage White/Black Wire & Ground 4-6 White/Black & Blue/Yellow Wires Zero Blue/Yellow Wire & Ground Zero
4. BARO Sensor Voltage Check. Connect vacuum pump to BARO sensor. Unplug BARO sensor connector. Using DVOM on 20-volt scale, turn ignition on and measure voltage between Light Green wire and ground. With zero vacuum, reading should be zero volts. At 30 in. Hg, reading should be 3.5-4.5 volts. If reading is within specification, repair open in Light Green wire from BARO sensor to ECA. If reading is not within specification, replace BARO sensor.
5. VREF Short Check. Turn ignition off and install breakout box. Unplug ECA and using DVOM on 200-k/ohm scale, measure resistance between VREF pin No. 26 and KAPWR pin No. 1, and VREF pin No. 26 and VPWR pin No. 37. If resistances are less than 10,000 ohms, repair short to voltage in White/Black wire. If resistances are 10,000 ohms or more, replace ECA.
6. ECA Power Check. Install breakout box. Using DVOM on 20-volt scale, with ignition on, measure voltage between pins No. 1 and 40 (ground), and pins No. 37 and 40 (ground). If reading is greater than 10 volts, proceed to next step. If reading is 10 volts or less, proceed to CIRCUIT TEST FC.
7. Signal Return To Ground Check. Turn ignition off and install breakout box. Plug in ECA. Using DVOM on 200-ohm scale, measure voltage between pin No. 40 and chassis ground. If resistance is less than 5 ohms, replace ECA. If resistance is 5 ohms or greater, repair open in ground (Black wire).
8. ECA Ground Check. Turn ignition off and install breakout box. Using DVOM on 200-ohm scale, measure resistance between pin No. 40 and chassis ground. If resistance is less than 5 ohms, replace ECA. If resistance is 5 ohms or greater, repair open in ground (Black wire).

BARO Sensor Circuit Schematic. Scheme 15

THROTTLE POSITION SENSOR (TPS) CIRCUIT

To prevent replacement of good components, check throttle stop adjustment, speed control linkage, wiring, wiring harness, connectors and other mechanically related components.

1. TPS Voltage Check. Install breakout box and turn ignition key to "ON" position. Using DVOM on 20-volt scale, measure voltage between pins No. 28 and 40, and pins No. 47 and 40. With accelerator depressed, reading should be greater than 10 volts on pin No. 28 and less than 1.5 volts on pins No. 47 and 24. With accelerator released, reading should be less than 1.5 volts on pin No. 28 and greater than 10 volts on pins No. 47 and 24.
2. Signal Return Check. Turn ignition off and install breakout box. Using DVOM on 200-ohm scale, measure resistance between pin No. 46 and TPS Blue/Yellow wire, and pin No. 46 and chassis ground. If resistance is 5 ohms or more, repair open in wire(s) in question. If resistance is less than 5 ohms, proceed to next step.
3. TPS Operation Check. With ignition off and using DVOM on 200-ohm scale, measure resistance between Green/Orange and Blue/Yellow wires. With accelerator depressed, reading should be less than 5 ohms. With accelerator released, reading should be greater than 10,000 ohms. Measure resistance between Orange and Blue/Yellow wires. With accelerator depressed, reading should be greater than 10,000 ohms. With accelerator released, reading should be less than 5 ohms. If all resistances are within specification, replace ECA.

Note. If referred here through another circuit test, do not replace ECA, proceed to CIRCUIT TEST DK, test step 8.

Throttle Position Sensor Circuit Schematic. Scheme 16

VANE AIRFLOW (VAF) METER

Check for unmetered air leaks between VAF meter and throttle body. Check for vacuum leaks. Inspect wiring, wiring harness, connectors and other related components for visible damage.

1. VAF Voltage Check. Install breakout box and unplug ECA. Using DVOM on 20-volt scale, with ignition on, measure voltage between pins No. 18 and 40. If reading is not 7-9 volts, proceed to next step. If reading is 7-9 volts, proceed to step 5.
2. VAF Power Check. With VAF meter connected and using DVOM on 20-volt scale, turn ignition on and measure voltage between VAF meter terminal (Light Green wire) and ground. If reading is 7-9 volts, repair open or short in Light Green wire from VAF meter to ECA. If reading is not 7-9 volts, proceed to next step.
3. VAF Power Check. Using DVOM on 20-volt scale and ignition on, measure voltage between VAF meter terminal (Yellow/Green wire) and ground. If reading is greater than 10 volts, replace VAF meter. If reading is 10 volts or less, proceed to next step.
4. Relay Power Check. Using DVOM on 20-volt scale and ignition on, measure voltage between relay (Yellow/Green wire) and ground. If reading is greater than 10 volts, repair open or short in Yellow/Green wire from relay to VAF meter. If reading is 10 volts or less, proceed to CIRCUIT TEST FC.
5. Signal Return Check. Turn ignition off and install breakout box. Using DVOM on 200-ohm scale, measure resistance between pins No. 46 and 40, pin No. 46 and chassis ground. If resistance is less than 5 ohms, proceed to next step. If resistance is 5 ohms or more, replace ECA.
6. VAF Signal Return Check. Turn ignition off and install breakout box. Using DVOM on 200-ohm scale, measure resistance between VAF meter terminal (Blue/Yellow wire) and pin No. 46. If resistance is 5 ohms or more, repair Blue/Yellow wire from VAF meter to ECA. If resistance is less than 5 ohms, proceed to next step.
7. VAF Voltage Check. Install breakout box and using DVOM on 20-volt scale, measure voltage between pins shown in appropriate «VAF VOLTAGE CHECK»(/ford/festiva/i-1986-1993/remont/testing-diagnostics/#tests-wcodes-mpfi) . If reading is within specifications, replace ECA. If reading is not within specifications, proceed to next step. VAF VOLTAGE CHECK Between Pins Key On Idle No. 43 & 40 2 Volts 4-6 Volts No. 43 & 46 2 Volts 4-6 Volts No. 40 & 46 Zero Volts Zero Volts
8. VAF Signal Check. Plug in VAF meter connector. Using DVOM on 20-volt scale and ignition turned on, measure voltage as indicated in appropriate «VAF SIGNAL CHECK»(/ford/festiva/i-1986-1993/remont/testing-diagnostics/#tests-wcodes-mpfi) . If readings are within specification, repair wire from VAF meter to ECA. If readings are not within specification, replace VAF meter.

VAF SIGNAL CHECK

VAF Meter Circuit Schematic. Scheme 17

NEUTRAL GEAR SWITCH & CLUTCH ENGAGE SWITCH

To prevent replacement of good components, check clutch switch adjustment, pedal operation, transaxle operation and neutral switch installation. Also check wiring, wiring harness and other related components for visible damage.

1. Check For Open Circuit. Install breakout box and unplug ECA. Using DVOM on 200-ohm scale, measure resistance between pins No. 8 and No. 40 (ground). With clutch released, resistance should be zero to 5 ohms. With clutch depressed, resistance should be 10,000 ohms or more. With clutch released and depressed (transmission in Neutral), resistance should be 0-5 ohms. With clutch depressed (transmission in gear), resistance should be 0-5 ohms. If readings are within specification, proceed to step 4. If readings are not within specification, proceed to next step.
2. Clutch Engage Switch Operation Check. Unplug clutch engage switch. Using DVOM on 200-ohm scale, measure resistance between terminals on clutch engage switch with pedal depressed and released. With pedal depressed, resistance should be greater than 10,000 ohms. With pedal released, resistance should be less than 5 ohms. If readings are within specification, proceed to next step. If readings are not within specification, adjust or replace clutch engage switch.
3. Neutral Gear Switch Operation Check. Unplug neutral gear switch. Using DVOM on 200-ohm scale, measure resistance between terminals on neutral gear switch connector. Resistance should be less than 5 ohms in gear and greater than 10,000 ohms in neutral. If readings are within specification, repair open in wire between ECA and clutch switch, or between clutch switch and neutral switch (or ground wire). If readings are not within specification, replace neutral gear switch.
4. Check For Short To VPWR & KAPWR. Install breakout box and unplug ECA. Unplug neutral gear and clutch engage switch. Turn ignition key to "ON" position. Using DVOM on 20-volt scale, measure voltage between pins No. 8 and No. 40 (ground). Also measure voltage between pins No. 8 and No. 20 (ground). If reading is greater than one volt, repair short in wiring harness to VPWR or KAPWR as required. If reading is one volt or less, proceed to next step.
5. ECA Pin Voltage Check. Install breakout box and plug in ECA. Place transaxle in gear. Turn ignition on. Using DVOM on 20-volt scale, measure voltage between pins No. 8 and No. 40. Reading should be greater than 10 volts with clutch pedal depressed and less than 4 volts with clutch pedal released. If readings are within specification, replace ECA. If readings are not within specification, repair short to ground in wiring harness between ECA terminal No. 1G and neutral switch Brown/Black wire terminal.

Neutral Gear & Clutch Engage Switch Circuit Schematic. Scheme 18

INHIBITOR SWITCH (AUTOMATIC TRANSAXLE)

To prevent possible replacement of good components, check transaxle operation and inhibitor switch installation. Also, visually inspect wiring, wiring harness and other related components for damage.

1. Voltage At ECA From Inhibitor Switch. Using DVOM on 20-volt scale, measure voltage between pins No. 2 and 40 (ground). With ignition on, reading should be less than 1.5 volts. With engine cranking, reading should be 7-9 volts. Also, measure voltage between pins No. 5 and 40 (ground). With transaxle in Park or Neutral and ignition on, reading should be less than 1.5 volts, and with engine cranking, reading should be 7-9 volts. If readings are within specification, replace ECA. If readings are not within specification, proceed to next step.
2. Power At Inhibitor Switch. Using DVOM on 20-volt scale, measure voltage between inhibitor switch (Black/Yellow wire) and ground. With ignition on, reading should be less than 1.5 volts. With engine cranking, reading should be 7-9 volts. If reading is within specification, proceed to next step. If reading is not within specification, proceed to step 4.
3. Continuity Across Inhibitor Switch. Turn ignition off and unplug switch. Using DVOM on 200-ohm scale, measure resistance between inhibitor switch Black terminals in transaxle gear ranges. With transaxle in Park and Neutral, reading should be greater than 5 ohms. With transaxle in all other ranges, reading should be less than 5 ohms. If resistances are within specification, repair open in Black/Yellow wire from ignition switch to inhibitor switch. If resistances are not within specification, replace inhibitor switch.
4. Power At Ignition Switch. Plug in inhibitor switch. Using DVOM on 20-volt scale, measure voltage between ignition switch (Black/Yellow wire) and ground. With ignition on, reading should be less than 1.5 volts. With engine cranking, reading should be 7-9 volts. If readings are okay, repair open in Black/Yellow wire from ignition switch to inhibitor switch. If readings are not okay, diagnose battery and charging system.

Inhibitor Switch Circuit Schematic. Scheme 19

TEST FC - VEHICLE POWER

To prevent replacement of good components, check ignition switch, fuses, battery and charging system. Inspect wiring, wiring harness, connectors and other related components for visible damage.

1. Check For VPWR To ECA. Install breakout box. Unplug ECA and turn ignition on. Using DVOM on 20-volt scale, measure voltage between pins No. 37 and 40 (ground). If reading is 10 volts or less, proceed to step 4. If reading is greater than 10 volts, proceed to next step.
2. Check For Cranking Power To ECA. Install breakout box. Unplug ECA and turn ignition on. Using DVOM on 20-volt scale, measure voltage between pins No. 5 and 40 (ground) while cranking engine. If reading is greater than 10 volts, proceed to next step. If reading is 10 volts or less, repair open circuit between ECA terminal No. 3B and starter (Black/Red wire). If circuit is okay, diagnose battery and charging system.
3. Check For ECA Grounds. Install breakout box and unplug ECA. Using DVOM on 200-ohm scale, measure resistance between ground pins No. 20, 40, and 49, and chassis ground. If reading is greater than 5 ohms, repair open in wiring harness between ground terminal in question and chassis ground. If reading is 5 ohms or less, proceed to CIRCUIT TEST B.
4. Check Power At Relay. Turn ignition on. Using DVOM on 20-volt scale, measure voltage at power relay White/Green wire terminal. If all readings are greater than 10 volts, proceed to next step. If all readings are 10 volts or less, check wire(s) for opens or shorts.
5. Check Power To Relay. Turn ignition on. Using DVOM on 20-volt scale, measure voltage at power relay Blue and Black wire terminals. If readings are greater than 10 volts, proceed to next step. If readings are 10 volts or less, check wire(s) for opens or shorts.
6. Check Ground At Relay. Unplug power relay. Using DVOM on 200-ohm scale, measure resistance between power relay(s) connector (Black terminal) and ground. If reading is less than 5 ohms, proceed to next step. If reading is 5 ohms or more, repair open in wiring harness between power relay(s) Black terminal and ground.
7. Power Relay Operation Check. Unplug power relay and ground Black terminal. Using DVOM on 200-ohm scale, measure the resistance between Blue and Black/White wire terminals, and Blue and White/Green wire terminals. Jumper battery voltage to power relay Black/White wire terminal. Measure resistance between relay No. 1, Black/White and Yellow/Green wires, relay No. 2, Blue and Black/White wires, relay No. 1, Black/White and Black wires, and relay No. 2, Black/White and Black wires. If reading is less than 5 ohms with voltage applied and greater than 10,000 ohms with voltage removed, proceed to CIRCUIT TEST B. If reading is 5 ohms or more with voltage applied and 10,000 ohms or less with voltage removed, replace power relay(s).

Vehicle Power Circuit Schematic. Scheme 20

TEST FD - BRAKE ON/OFF SWITCH

Perform a comprehensive visual inspection of wiring and harness connectors at ECA and brake switch assembly. Repair or replace defective wiring or components as necessary.

1. Brake Switch Operation At ECA. Install breakout box. Disconnect ECA connector. Turn ignition on. Using a DVOM, measure voltage between pins No. 3 and 40. Measure voltage between pins No. 3 and 20. Voltmeter should read less than 4 volts with brake pedal released and more than 10 volts with pedal depressed. If DVOM readings were correct, replace ECA assembly. If DVOM readings were incorrect, proceed to next step.
2. Voltage From Brake Switch. With key on, measure voltage between brake switch White/Green wire and ground. Voltmeter should read less than 4 volts with brake pedal released and more than 10 volts with pedal depressed. If DVOM readings were correct, repair open or short to power in wiring harness between ECA terminal No. 1J and brake switch. If DVOM reading is incorrect, proceed to next step.
3. Power To Brake Switch. With key on, measure voltage between brake switch Green/White wire and ground. If DVOM reads more than 10 volts, adjust or replace brake switch. If DVOM reads less than 10 volts, go to next step.
4. Power At Battery. With key on, measure voltage across vehicle battery terminals. If DVOM reading is more than 10 volts, replace bad fuse or repair open in Green/Yellow wire between vehicle battery and brake switch. If DVOM reads less than 10 volts, proceed to CIRCUIT TEST B1.

Brake On/Off Switch Circuit Schematic. Scheme 21

ELECTRICAL LOAD UNIT (ELU) CIRCUIT

1. System Inspection. Perform a visual inspection of wiring and harness connectors. Ensure cooling fan motor, blower motor, lighting system, BAC valve, alternator condition, idle adjustment and general engine performance are not malfunctioning before proceeding with test. If a problem is found with wiring or harness connectors, repair or replace as necessary. If cooling fan is not operating properly, go to next step. If blower control is not functioning properly, go to step 4. If defroster is not functioning properly, go to step 6. If combination switch is not functioning properly, go to step 8.
2. Coolant Fan Temperature Switch Operation. Disconnect cooling fan switch. Turn ignition on. Using a DVOM, measure voltage between fan switch Yellow/Green wire and ground without piercing wire. With coolant temperature more than 206°F (97°C), DVOM should read no voltage. With coolant temperature less than 206°F (97°C), DVOM should read 10 volts. If DVOM reads correctly, go to next step. If DVOM does not read correctly, diagnose heating and air conditioning system.
3. Coolant Fan Switch Operation At ELU. With ignition on, measure voltage between ELU Yellow wire and ground. With coolant temperature more than 206°F (97°C), DVOM should read no voltage. With coolant temperature less than 206°F (97°C), DVOM should read 10 volts. If DVOM reads correctly, go to step 10. If DVOM does not read correctly, repair Yellow wire between ELU and cooling fan switch.
4. Blower Control Switch Operation. With ignition on, measure voltage between blower switch Blue/Green wire and ground with blower switch connected. With blower switch in "OFF" position, DVOM should read 10 volts. With blower switch in "LO", "ML", "MH", or "HI" position, DVOM should read no voltage. If DVOM reads correctly, go to next step. If DVOM does not read correctly, diagnose heating and air conditioning system.
5. Blower Control Switch Operation At ELU. With ignition on, measure voltage between ELU Blue/Green wire and ground. With blower switch in "OFF" position, DVOM should read 10 volts. With blower switch in "LO", "ML", "MH", or "HI" position, DVOM should read no voltage. If DVOM reads correctly, go to step 10. If DVOM does not read correctly, repair Blue/Green wire between blower control and ELU.
6. Defroster Switch Operation. With ignition on, measure voltage between defroster switch Black/Yellow wire and ground with switch connected. With defroster switch on, DVOM should read 10 volts. With defroster switch off, DVOM should read no voltage. If DVOM reads correctly, go to next step. If DVOM does not read correctly, diagnose heating and air conditioning system.
7. Defroster Switch Operation At ELU. With ignition on, measure voltage between ELU Black/Yellow wire and ground. With defroster switch on, DVOM should read 10 volts. With defroster switch off, DVOM should read no voltage. If DVOM reads correctly, go to step 10. If DVOM does not read correctly, repair Black/Yellow wire between ELU and defroster switch.
8. Combination Switch Operation. With ignition on, measure voltage between combination switch White wire and ground with switch connected. With headlight switch on, DVOM should read 10 volts. With headlight switch off, DVOM should read no voltage. If DVOM reads correctly, go to next step. If DVOM does not read correctly, diagnose lighting system.
9. Combination Switch Operation At ELU. With ignition on, measure voltage between ELU White wire and ground. With headlight switch on, DVOM should read 10 volts. With headlight switch off, DVOM should read no voltage. If DVOM reads correctly, go to next step. If DVOM does not read correctly, repair White wire between ELU and combination switch.
10. ELU Operation At ECA. Disconnect ECA connector. Install breakout box. Turn ignition on. Using a DVOM, measure voltage between pins No. 24 and 40. Operate one switch at a time leaving all other switches off. See «SWITCH VOLTAGE SPECIFICATIONS»(/ford/festiva/i-1986-1993/remont/testing-diagnostics/#tests-wcodes-mpfi) . If DVOM reads correctly, replace ECA assembly. If DVOM does not read correctly, go to next step. SWITCH VOLTAGE SPECIFICATIONS Switch Position Approximate Voltage Blower Control "OFF" 10 Blower Control "ON" 2.5 Combination "OFF" 10 Combination "ON" 2.5 Cooling Fan "OFF" 10 Cooling Fan "ON" 2.5 Defroster "OFF" 10 Defroster "ON" 2.5
11. ELU Operation. With ignition on, measure voltage between ELU Black wire and ground. Operate one switch at a time leaving all other switches off. See «SWITCH VOLTAGE SPECIFICATIONS»(/ford/festiva/i-1986-1993/remont/testing-diagnostics/#tests-wcodes-mpfi) . If DVOM reads correctly, repair Black wire between ELU and ECA. If DVOM does not read correctly, go to next step.
12. Power At ELU. With ignition on, measure voltage between ELU Yellow/Green wire and ground. If DVOM reads more than 10 volts, go to step 14. If DVOM reads less than 10 volts, go to next step.
13. Power At Power Relay. With ignition on, measure voltage between power relay Yellow/Green wire and ground with relay connected. If DVOM reads more than 10 volts, repair Yellow/Green wire between power relay and ELU. If DVOM reads less than 10 volts, go to CIRCUIT TEST FC.
14. Ground At ELU. With ignition off, measure resistance between ELU Black wire and ground. If DVOM reads more than 5 ohms, replace ELU. If DVOM reads less than 5 ohms, repair Black wire between ELU and ground.

ELU Circuit Schematic. Scheme 22

TEST FH - WOT CIRCUIT

To prevent replacement of good components, inspect all related wiring, wiring harness, connectors and components for evidence of overheating, looseness and other visible damage. Visually inspect throttle linkage, throttle operation and WOT adjustment.

1. WOT Signal To ECA. Install breakout box. Disconnect ECA Yellow wire from breakout box Pin No. 24. Measure resistance between Pin No. 24 and ground. With the throttle released, ohmmeter should read open. With throttle fully open, resistance should be below 5 ohms. If resistance is reading correctly, replace the ECA. If resistance readings are not reading correctly, go to step 2.
2. WOT Signal From WOT Switch. DO NOT disconnect the WOT switch. Disconnect the Yellow wire from the WOT switch. Measure resistance between Yellow wire and ground. With the throttle released, ohmmeter should read open. With throttle fully open, resistance should be below 5 ohms. If resistance is reading correctly, service Yellow wire from WOT switch to ECA. If resistance readings are not reading correctly, go to step 3.
3. Signal Return To WOT Switch. Measure resistance between WOT switch Yellow/Green wire and ground. Resistance should be below 5 ohms. If resistance is below 5 ohms, replace the WOT switch. If not below 5 ohms, service Yellow/Green wire from WOT switch to ECA.

TEST HA - FUEL CONTROL

To prevent replacement of good components, inspect all related wiring, wiring harness, connectors and components for evidence of overheating, looseness and other visible damage. Visually inspect intake air cleaner, duct, fuel delivery system for leaks or severe wear.

1. EGO Sensor Sensitivity Test. With STAR tester adapter connected to STO and ground (STI open), start engine and run until operating temperature is reached. Increase engine speed to 2500 RPM. If the monitor light flashes 8 times in 10 seconds, proceed to step 4. If monitor light does not flash 8 times in 10 seconds, proceed to next step.
2. Check EGO Sensor Output. Warm engine and allow to idle. Unplug EGO sensor. Using DVOM on 5-volt scale, measure voltage between EGO sensor connector (sensor side) and ground. Raise engine speed to 4000-4500 RPM until voltmeter indicates 0.7 volts. Decrease and increase engine RPM rapidly and note voltmeter reading. At 1000-2500 RPM, reading should be 0-0.4 volts. At 3000-4500 RPM, reading should be 0.5-1.0 volts. If readings are within specification, proceed to next step. If readings are not within specification, proceed to CIRCUIT TEST HE.
3. Check EGO Switching Voltage. With EGO sensor connected and breakout box installed, start engine and bring to operating temperature. Using DVOM on 5-volt scale, measure voltage between pins No. 29 and 40. Decrease and increase engine RPM rapidly and note voltmeter reading. At 1000-2500 RPM, reading should be 0-0.4 volts. At 3000-4500 RPM, reading should be 0.5-1.0 volts. If readings are within specification, proceed to next step. If readings are not within specification, proceed to CIRCUIT TEST HE.
4. Injector Drive Signal Check. Install breakout box and connect standard 12-volt non-power test light between pins No. 58 and 37. Crank or start engine and note test light. Repeat test between pins No. 37 and 59. If test light glows dim on both tests, proceed to step 7 If test light does not illuminate on one or both tests, proceed to next step. If test light illuminates brightly on one or both tests, proceed to step 6.
5. ECA Power Test. Install breakout box and unplug ECA. Turn ignition on. Using DVOM on 20-volt scale, measure voltage between pins No. 1 and 40, and between pins No. 37 and 40. If readings are greater than 10 volts, replace ECA. If readings are 10 volts or less, proceed to CIRCUIT TEST FC.
6. Injector Circuit Check For Shorts. Unplug ECA and disconnect battery. Install breakout box. Using DVOM on 200,000-ohm scale, measure resistance between pins No. 59 and 37, 20, 40, 1 and 49. Repeat test between pins No. 58 and 37, 20, 40, 1 and 49. If any of the readings are less than 10,000 ohms, check for shorts to ground or VPRW in related harness. If any of the readings are 10,000 ohms or more, replace ECA.
7. Injector Balance Test. Unplug ISC connector. Start and run engine at 2000 RPM. Unplug and plug in injectors one at a time while noting RPM drop for each injector. Plug in ISC. If each injector produced at least 150 RPM drop, proceed to next step. If each injector did not produce at least 150 RPM drop, repair circuit of injector in question. If operation is okay, replace faulty injector.
8. Deceleration Fuel Cut-Off Test. Install breakout box and plug in ECA. Connect standard non-powered 12-volt test light between pins No. 58 and 37. Start engine and allow to idle. Increase and decrease engine speed between idle and 4000 RPM and note test light. During idle, test light should flash. During deceleration (2000-4000 RPM range), test light should not illuminate. Repeat test between pins No. 59 and 37. If test light responds as described, diagnose for mechanical problem. If test light does not respond as described, replace ECA.

Fuel Control Circuit Schematic. Scheme 23

TEST HE - EGO SENSOR

To prevent replacement of good components, inspect wiring, wiring harness and connectors for visible damage.

1. EGO Output Voltage Check. Start and run engine to operating temperature. Unplug EGO sensor and allow engine to idle. Using DVOM on 5-volt scale, connect DVOM between EGO sensor and ground. Raise engine speed to 4000-4500 RPM until DVOM indicates about 0.7 volts. Increase and decrease engine RPM rapidly and note DVOM reading. Reading at 3000-4500 RPM should be 0.5-1.0 volts. Reading at 1000-2500 RPM should be 0-0.4 volts. If readings are correct, proceed to step 4. If readings are not correct, proceed to next step.
2. Isolate EGO Sensor Open. Unplug EGO sensor and turn ignition off. Inspect wire from EGO sensor connector for possible opens. If wire is okay, proceed to next step. If wire is not okay, repair wire or replace EGO sensor (if open is between sensor and connector).
3. Isolate EGO Sensor Short. Unplug EGO sensor and turn ignition off. Using DVOM on 20-k/ohm scale, measure resistance between EGO sensor connector (sensor side) and ground. If resistance is greater than 10,000 ohms, replace EGO sensor. If resistance is 10,000 ohms or less, repair short in EGO sensor wire or replace EGO sensor.
4. EGO Sensor Sensitivity Test. With EGO sensor connected, start engine. Connect STAR tester adapter cable to STO connector and ground (STI connector open). Raise engine speed to 2500 RPM. If monitor light flashes 8 or more times in 10 seconds, proceed to step 7. If monitor light does not flash 8 or more times in 10 seconds, proceed to next step.
5. Check EGO Sensor Circuit. Turn ignition off and install breakout box. Unplug ECA and EGO sensor. Using DVOM on 200-ohm scale, measure resistance between EGO sensor connector (harness side) and pin No. 29 at breakout box. If resistance is greater than 10 ohms, repair open circuit and reconnect EGO sensor. If resistance is 10 ohms or less, proceed to next step.
6. Check EGO Sensor Circuit. Turn ignition off and install breakout box. Unplug ECA and EGO sensor. Using DVOM on 200-ohm scale, measure resistance between pins No. 29 and No. 1, 20, 37 and 40. If any of the resistances are less than 10,000 ohms, repair short in EGO sensor circuit to VPWR, VREF, KAPWR or ground. If any of the resistances are 10,000 ohms or more, replace EGO sensor.
7. ECA Input Voltage. Start engine and bring to operating temperature. Install breakout box and unplug ECA. Using DVOM on 5-volt scale, measure voltage between pins No. 29 and 49 while increasing and decreasing engine speed between 1500 and 4000 RPM. If reading varies between 0.5-1.0 volts, inspect ECA and ECA connector for damage, looseness, corrosion or damaged pins. If reading does not vary between 0.5-1.0 volts, replace ECA.

EGO Sensor Circuit Schematic. Scheme 24

TEST KD - CANISTER PURGE

To prevent replacement of good components, inspect wiring, wiring harness, connectors and other related components for visible damage.

1. Measure Voltage At ECA. Install breakout box and unplug ECA. Turn ignition on. Using DVOM on 20-volt scale, measure voltage between pins No. 32 and 40 (ground). If reading is less than 10 volts, proceed to next step. If reading is 10 volts or more, repair wire between ECA and CANP solenoid.
2. Measure Voltage From Canister Purge Solenoid. Turn ignition on and unplug ECA. CANP should remain connected. Using DVOM on 20-volt scale, measure voltage between CANP solenoid Yellow wire and ground. If reading is less than 10 volts, proceed to next step. If reading is 10 volts or more, repair wire between ECA and CANP solenoid.
3. Measure Voltage To Canister Purge Solenoid. Turn ignition on and unplug ECA. Using DVOM on 20-volt scale, measure voltage between CANP solenoid Yellow/Green wire and ground. If reading is less than 10 volts, proceed to next step. If reading is 10 volts or more, replace CANP solenoid.
4. Measure Voltage From Power Relay. Turn ignition on. Power relay should remain connected. Using DVOM on 20-volt scale, measure voltage between power relay Yellow/Green wire and ground. If reading is less than 10 volts, proceed to CIRCUIT TEST FC. If reading is 10 volts or more, repair Yellow/Green wire between CANP solenoid and power relay.
5. Check Canister Purge Circuit For Short To VPWR. Install breakout box and unplug ECA. Unplug CANP solenoid connector. Turn ignition on. Using DVOM on 20-volt scale, measure voltage between pins No. 32 and 40 (ground). If reading is greater than zero volts, repair short to VPWR. If reading is zero volts, replace ECA.

CANP Solenoid Circuit Schematic. Scheme 25

IDLE SPEED CONTROL CIRCUIT

To prevent replacement of good components, ensure idle speed is properly adjusted and inspect vehicle for vacuum leaks. Perform a visual inspection of all wiring and wiring harness connectors.

1. Measure Voltage At ECA. Install breakout box. Disconnect ECA connector. Turn ignition on. Wait 2 minutes. Using a DVOM, measure voltage between pins No. 40 and 41. If DVOM reads less than 10 volts, go to next step. If DVOM reads more than 10 volts, go to step 5.
2. Measure Voltage From ISC Solenoid. With ignition on, wait 2 minutes. With ISC solenoid connected, measure voltage between ISC solenoid Green wire and ground without piercing wire. If DVOM reading is less than 10 volts, go to next step. If DVOM reading is more than 10 volts, repair Green wire between ECA and ISC solenoid.
3. Measure Voltage To ISC Solenoid. With ignition on, measure voltage between ISC solenoid Yellow/Green wire and ground. If DVOM reading is less than 10 volts, go to next step. If DVOM reading is more than 10 volts, replace ISC solenoid.
4. Measure Voltage From Power Relay. With ignition on and power relay connected, measure voltage between power relay Yellow/Green wire and ground. If DVOM reading is less than 10 volts, go to CIRCUIT TEST FC1. If DVOM reading is more than 10 volts, repair the Yellow/Green wire between ISC solenoid and power relay.
5. Check ISC Circuit For Short To VPWR. Disconnect ISC solenoid connector. With ignition on, measure voltage between breakout box pins No. 40 and 41. If DVOM indicates voltage (amount of voltage is not important), repair short to VPWR. If DVOM indicates no voltage, replace ECA.

Idle Speed Control Circuit Schematic. Scheme 26

CANISTER PURGE REGULATOR (CPR) CIRCUIT

To prevent replacement of good components, inspect vehicle for vacuum leaks and canister purge regulator for obvious defects. Visually inspect all wiring and harness connectors. Repair components as necessary.

1. Measure Voltage At ECA. Install breakout box. Disconnect ECA connector. Turn ignition on. Wait 2 minutes. Measure voltage between pins No. 22 and 40. If DVOM reads less than 10 volts, go to next step. If DVOM reads more than 10 volts, go to step 5.
2. Measure Voltage From CPR Solenoid. With ignition on and CPR solenoid connected, measure voltage between CPR solenoid Blue wire and ground without piercing wire. If DVOM reads less than 10 volts, go to next step. If DVOM reads more than 10 volts, repair open wire between ECA and CPR solenoid.
3. Measure Voltage To CPR Solenoid. With ignition on, measure voltage between CPR solenoid Yellow/Green wire and ground. If DVOM reads less than 10 volts, go to next step. If DVOM reads more than 10 volts, replace CPR solenoid.
4. Measure Voltage From Power Relay. With ignition on and power relay connected, measure voltage between power relay Yellow/Green wire and ground. If DVOM reads less than 10 volts, go to CIRCUIT TEST FC. If DVOM reads more than 10 volts, repair Yellow/Green wire between CPR solenoid and power relay.

5) Check CPR Circuit For Short To VPWR. With ignition on and CPR solenoid disconnected, measure voltage between pins No. 22 and 40. If DVOM indicates voltage (amount of voltage is not important), repair short to VPWR. If DVOM indicates no voltage, replace ECA.

Canister Purge Regulator Circuit Schematic. Scheme 27

MALFUNCTION INDICATOR LAMP "CHECK ENGINE" LIGHT

To prevent replacement of good components, check fuse, bulb or socket. Inspect wiring, wiring harness and connectors for visible damage.

1. Determine If ECA Is Providing Ground. Install breakout box and unplug ECA. Turn ignition on. Using jumper wire, jumper pins No. 51 to 40 (ground). If MIL illuminates, proceed to CIRCUIT TEST FC. If MIL does not illuminate, proceed to next step.
2. Check MIL Circuit For Power. Turn ignition on and plug in MIL. Ground Light Green wire using a jumper at terminal C-01 connector at rear of instrument panel. If MIL illuminates, repair Light Green wire between MIL light and ECA. If MIL does not illuminate, problem is in instrument cluster.

MIL Lamp Circuit Schematic. Scheme 28

CODE 88 CONTINUOUSLY FLASHING

Visually inspect all wiring, wiring harness, connectors and other related components for damage.

1. Measure STI Voltage At ECA. Install breakout box and turn ignition on. Using DVOM on 20-volt scale, measure voltage between pins No. 48 and 40 (ground). If reading is less than 10 volts, proceed to nest step. If reading is 10 volts or greater, proceed to step 5.
2. Check STI Continuity To ECA. Install breakout box and unplug ECA. Turn ignition off. Using DVOM on 200-ohm scale, measure resistance between pin No. 48 and STI Yellow wire connector. If reading is less than 5 ohms, proceed to next step. If reading is 5 ohms or more, repair Yellow wire between ECA and Self-Test Input (STI) connector.
3. Check STI For Short To Ground. Install breakout box and unplug ECA. Turn ignition off. Using DVOM on 200,000-ohm scale, measure resistance between pin No. 48 and ground pins No. 20, 40 and 49. If reading is greater than 10,000 ohms, proceed to next step. If reading is 10,000 ohms or less, repair short to ground.
4. Check STI For Short To VPWR. Install breakout box and unplug ECA. Turn ignition on. Using DVOM on 20-volt scale, measure voltage between pins No. 48 and 40 (ground). If reading is greater than zero volts, repair short to VPWR. If reading is zero volts, replace ECA.
5. Measure STO Voltage At ECA. Install breakout box. Jumper STI connector to ground. Turn ignition on and wait 10 seconds. Using DVOM on 20-volt scale, measure voltage between pins No. 17 and 40 (ground). If reading is less than 10 volts, proceed to next step. If reading is 10 volts or more, proceed to step 9.
6. Check STO Continuity To ECA. Install breakout box and unplug ECA. Turn ignition off. Using DVOM on 200-ohm scale, measure the resistance between pin No. 17 and Self-Test Output (STO) Green/Black wire connector. If reading is less than 5 ohms, proceed to next step. If reading is 5 ohms or more, repair Green/Black wire between ECA and STO connector.
7. Check STO For Short To Ground. Install breakout box and unplug ECA. Turn ignition off. Using DVOM on 200,000-ohm scale, measure resistance between pin No. 17 and ground pins No. 20, 40 and 49. If readings are greater than 10,000 ohms, proceed to next step. If readings are 10,000 ohms or less, repair short to ground.
8. Check STO For Short To VPRW. Install breakout box and unplug ECA. Turn ignition on. Using DVOM on 20-volt scale, measure voltage between pins No. 17 and 40 (ground). If reading is greater than zero volts, repair short to VPWR. If reading is zero volts, replace ECA.
9. Measure SML Voltage At ECA. Install breakout box and turn ignition on. Wait 10 seconds and Using DVOM on 20-volt scale, measure voltage between pins No. 38 and 40 (ground). If reading is less than 10 volts, proceed to next step. If reading is 10 volts or more, proceed to step 13.
10. Check SML Continuity To ECA. Install breakout box and unplug ECA. Turn ignition off. Using DVOM on 200-k/ohm scale, measure resistance between pin No. 38 and STO Red/Blue wire. If reading is less than 5 ohms, proceed to next step. If reading is 5 ohms or greater, repair Red/Blue wire between ECA and STO connector.
11. Check SML For Short To Ground. Install breakout box and unplug ECA. Turn ignition off. Using DVOM on 200-k/ohm scale, measure resistance pin No. 38 and ground pins No. 20, 40 and 49. If reading is greater than 10,000 ohms, proceed to next step. If reading is 10,000 ohms or less, repair short to ground.
12. Check SML For Short To VPWR. Install breakout box and unplug ECA. Turn ignition on. Using DVOM on 20-volt scale, measure voltage between pins No. 38 and 40 (ground). If reading is greater than zero volts, repair short to VPWR. If reading is zero volts, replace ECA.
13. Measure Voltage At Self-Test Connector. Turn ignition on. Using DVOM on 20-volt scale, measure voltage between STO Yellow/Green wire connector and ground. If reading is less than 10 volts, proceed to next step. If reading is 10 volts or more, proceed to CIRCUIT TEST B.
14. Measure Voltage From Power Relay. Turn ignition on. Power relay should remain connected. Using DVOM on 20-volt scale, measure voltage between power relay Yellow/Green wire and ground. If reading is less than 10 volts, proceed to CIRCUIT TEST FC. If reading is 10 volts or more, repair Yellow/Green wire between STO connector and power relay.

Self-Test Connector Circuit Schematic. Scheme 29

NO CODES/CODES NOT LISTED

Perform visual inspection of wiring, harness connectors and components. Repair or replace components as necessary.

1. Signal Return Check. Ensure ignition is off. Install breakout box with ECA connected. Using a DVOM, measure resistance between signal return pin No. 46 and ground pin No. 40. Measure resistance between signal return pin No. 46 and chassis ground. If DVOM reads less than 5 ohms, go to next step. If DVOM reads more than 5 ohms, repair ground wires of ECA.
2. Check Voltages At ECA. With ignition on, measure voltage between pins on breakout box indicated in «ECA VOLTAGE SPECIFICATIONS»(/ford/festiva/i-1986-1993/remont/testing-diagnostics/#tests-wcodes-mpfi) . If DVOM readings are within specification, go to step 5. If DVOM readings are not within specification, go to next step. ECA VOLTAGE SPECIFICATIONS Pins No. Voltage 17 & 40 (1) More Than 10 38 & 40 More Than 10 48 & 40 More Than 10 16 & 40 (2) 7.3 19 & 40 (3) More Than 10 (1) Self-Test Input connector grounded. (2) Radiator temperature must be below 63°F (17°C). (3) Front wheels straight.
3. Check Circuits For Continuity. With breakout box installed, ECA disconnected and ignition off, measure resistance between breakout box pin indicated and switch or connector in «CIRCUIT CONTINUITY CHECK»(/ford/festiva/i-1986-1993/remont/testing-diagnostics/#tests-wcodes-mpfi) . If DVOM readings are less than 5 ohms, go to next step. If DVOM readings are more than 5 ohms, repair circuit. CIRCUIT CONTINUITY CHECK Pins No. Wire Color Self-Test Output Connector 17 GRN/BLK 38 RED/BLU 48 YEL ECT Switch & 16 BRN/WHT Power Steering Switch & 19 GRN/RED
4. Check Circuits For Shorts To Ground. With breakout box installed, ECA disconnected and ignition off, measure resistance between breakout box pins indicated in «SHORTS TO GROUND CHECK»(/ford/festiva/i-1986-1993/remont/testing-diagnostics/#tests-wcodes-mpfi) . If DVOM readings are less than 10,000 ohms, go to CIRCUIT TEST FC. If DVOM readings are less than 10,000 ohms, repair shorted circuit. Refer to «CIRCUIT CONTINUITY CHECK»(/ford/festiva/i-1986-1993/remont/testing-diagnostics/#tests-wcodes-mpfi) for circuit identification. SHORTS TO GROUND CHECK Ground Pins No. Pin No. 20, 40, 46, 49 16, 17, 19, 38, 48
5. Check Voltage At Self-Test Connector. With ignition on, measure voltage between Self-Test output connector Yellow/Green wire and ground. If DVOM reads less than 10 volts, go to next step. If DVOM reads more than 10 volts, diagnose for mechanical problem.
6. Check Voltage At Power Relay. With ignition on and power relay connected, measure voltage between power relay Yellow/Green wire and ground without piercing wire. If DVOM reads less than 10 volts, go to CIRCUIT TEST FC. If DVOM reads more than 10 volts, repair Yellow/Green wire between STO connector and power relay.

Self-Test Connector Circuit Schematic. Scheme 30

See also:
• ENGINE COOLANT TEMPERATURE SENSOR RESISTANCE