Engine Controls - Tests W/codes Mercury Capri III

INTRODUCTION

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

This article uses many abbreviations for devices, signal names, and wire colors. See SELF-DIAGNOSTICS ABBREVIATIONS table. Abbreviations for wire colors used in individual PINPOINT TEST diagrams are as follows

1. BLK - Black
2. BLU - Blue
3. BRN - Brown
4. GRN - Green
5. LT GRN - Light Green
6. ORG - Orange
7. PNK - Pink
8. RED - Red
9. WHT - White
10. YEL - Yellow

SELF-DIAGNOSTICS ABBREVIATIONS

Hard Failures

Hard failures cause CHECK ENGINE light (MIL) to come on and remain on until problem is repaired. If MIL 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, ECA will use a substitute value in its calculations to permit continued engine operation. In this condition (limp-in mode), vehicle will run but driveability will not be optimum.

Intermittent Failures

Intermittent failures may cause MIL to flicker or come on and go off after intermittent defect goes away. Corresponding trouble code, however, will be retained in ECA memory. If related defect does not reoccur within a certain time frame, related trouble code will be erased from ECA memory. Intermittent failures may be caused by a sensor, connector, or wiring. See INTERMITTENTS in TESTS W/O CODES article in the ENGINE PERFORMANCE Section.

VISUAL CHECK & VEHICLE PREPARATION

Before connecting any equipment to diagnose EEC system, perform following preparatory procedures

1. Verify condition of air cleaner and air ducts.
2. Check all vacuum hoses for leaks, restrictions, or improper routing.
3. Check EEC system wiring harness electrical connections for corrosion, bent or broken pins, loose wires or terminals, or improper routing.
4. Check ECA, sensors, and actuators for physical damage.
5. Check engine oil and coolant level.
6. Perform all necessary safety precautions to prevent personal injury or vehicle damage.
7. Set parking brake. Place shift lever in Park for automatic transmissions, or Neutral for manual transmissions. DO NOT move shift lever during test unless specifically directed.
8. Turn off all lights and accessories. Ensure vehicle doors are closed when measuring voltage or resistance.
9. Start engine. Run at idle until upper radiator hose is hot and pressurized and engine is off fast idle. Check for leaks around exhaust manifold, exhaust gas oxygen sensor, and vacuum hose connections.
10. Turn ignition off. Service items as required. Go to «EQUIPMENT HOOK-UP»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes) .

VOM

1. Turn ignition off. Connect a jumper wire from STI connector to ground. Refer to «SELF-TEST CONNECTOR LOCATION»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes) and «SELF-TEST CONNECTOR WIRE COLORS»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes) tables. (Scheme 4)
2. Connect VOM between STO terminal and engine ground. Set VOM to measure 0-20 volts DC.

CHECK ENGINE Light (MIL)

Connect a jumper wire between STI connector and ground.

SUPER STAR II Tester

Turn ignition off. Connect adapter cable leads to diagnostic tester. Connect service adapter cables to vehicle self-test connectors. Ground adapter cable.

SELF-TEST CONNECTOR LOCATION

SELF-TEST CONNECTOR WIRE COLORS

Scheme 4

Reading Service Codes

Engine control system communicates malfunctions to technician through service codes. These service codes are 2-digit numbers representing a particular defect. Service codes are transmitted through STO connector.

Service codes are displayed as timed pulses, and may be read with a VOM or Super Star II tester. VOM displays codes by needle sweeps. (Scheme 5)

Turn ignition off. Ensure all procedures of EQUIPMENT HOOK-UP have been followed. Engine should be at normal operating temperature.

Scheme 5

Disconnect and reconnect jumper wire from STI terminal to ground. Turn ignition on. Record displayed codes. Erase codes, and repeat test procedure to verify all codes are currently valid. See ERASING CODES & RETESTING . Service only those codes which appear during retest. Refer to TROUBLE CODE DEFINITION table to find appropriate pinpoint test.

MIL

Turn ignition on. Connect a jumper wire between STI connector and ground. Observe MIL, and record pulses to determine codes stored.

Note. If MIL flashes continuously prior to connecting test equipment, go to PINPOINT TEST STI .

Set center button to TEST position. Turn ignition on. Turn tester on. When activated, tester should display 888 for 2 seconds. Release and reset center TEST button. After all codes are displayed, release center button. All codes in tester memory may now be reviewed.

ERASING CODES & RETESTING

Erasing codes and retesting will give an indication of whether codes are hard or intermittent defects. Hard codes reset immediately and will be displayed during retest.

Disconnect negative battery cable. Press brake pedal for 5-10 seconds. Turn off VOM or Super Star II tester. Reconnect battery. Perform tests under RETRIEVING CODES to again display and record codes.

TROUBLE CODE DEFINITION

TROUBLE CODE DEFINITION

Clearing Codes Procedure

Disconnect negative battery cable. Press brake pedal for 5-10 seconds. Turn off VOM or Super Star II tester. Reconnect battery.

ECA LOCATION

ECA is located on center console behind kick panel on Capri, and under instrument panel on driver side of Festiva.

KEY ON, ENGINE OFF (KOEO) SELF-TEST

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

KOEO

1. 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.
2. Erase codes, and repeat self-test. Diagnose only codes occurring during repeat self-test. See «TROUBLE CODE DEFINITION»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes) table. If no codes are present, proceed to «KEY ON, ENGINE RUNNING (KOER) SELF-TEST»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes__key-on-engine-running-koer-self-test) .

KEY ON, ENGINE RUNNING (KOER) SELF-TEST

Note. It is necessary to clear codes in memory before performing this test. DO NOT move throttle during test.

KOER

1. Deactivate self-test. Start and run engine at 2000 RPM for 2 minutes to warm up EGO sensor. Turn off engine and wait 10 seconds.
2. Restart engine, and activate self-test. Record all service codes displayed. See «TROUBLE CODE DEFINITION»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes) table. If no codes are present, proceed to «SWITCH MONITOR TEST»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes__switch-monitor-test) .

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 procedure checks input signals received by ECA from individual switches. Use following procedure to perform switch monitor test

1. Turn engine off and allow it to cool.
2. Ensure all accessories are turned off.
3. Deactivate self-test.
4. Ensure transmission is in Neutral or Park.
5. Turn ignition on.

Connect Super Star II tester adapter cable. Turn on tester. Latch center button. Operate each switch listed in SWITCH MONITOR TEST table. Note output of LED on adapter cable as each switch operates. Record test results.

1. Ground STI connector. Connect VOM positive lead to SML terminal on self-test connector. Connect negative lead to ground. (Scheme 4)
2. Operate each switch listed in «SWITCH MONITOR TEST»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes) table. Note output on VOM as each switch is operated. Go to specified PINPOINT TEST if any switch does not meet specification.

Note. DO NOT move throttle, clutch, or transmission lever unless so directed.

SWITCH MONITOR TEST

Checking Circuitry

1. Visually inspect suspected sensor, switch, or solenoid. Enter WIGGLE TEST if using Super Star II tester. If using VOM, connect it to STO terminal on self-test connector, and ground STI self-test connector terminal. Lightly tap sensor, switch, or solenoid.
2. Push and pull on suspected sensor, switch, or solenoid connector, but DO NOT unplug it. Test and wiggle harness vigorously, working in small sections, from suspected device toward dash panel, and from dash panel to ECA.
3. If VOM or Super Star II tester does not display a positive indication of an intermittent defect, carefully disconnect suspected device. Remove terminals from connector.
4. Inspect terminals at both ends for corrosion, bad crimps, or improperly seated terminals. Reconnect after inspection. Unplug harness from ECA.
5. Inspect ECA and harness connector terminals for corrosion, bad crimps, or improperly seated terminals. If VOM does not indicate any intermittent defect, reconnect wiring and erase codes.

PINPOINT TESTS

Note. Following tests and illustrations are courtesy of Ford Motor Co. Complete EEC system wiring diagrams may be found in WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

HOW TO USE PINPOINT TESTS

Note. Check all wiring, harnesses, connectors, and components for damage, overheating, shorting, or looseness. If any defect is found, repair as necessary before proceeding to any PINPOINT TEST.

1. DO NOT perform any PINPOINT TEST unless directed by a QUICK TESTS procedure. Ensure all non-EEC related defects are corrected. Follow each test step in order until defect is found. DO NOT replace any part unless so directed. When more than one service code exists, start with first code displayed.
2. PINPOINT TESTS require ensuring electrical circuits are okay before replacing sensors or any other components. Always test circuits for continuity between sensor and ECA. Test all circuits for shorts to power, opens, or shorts to ground. VREF and VPWR circuits should be tested with KOEO or as specified in PINPOINT TESTS.
3. DO NOT measure voltage or resistance at ECA, or connect any test light unless specified in testing procedure. DO NOT pierce wiring. Isolate both ends of a circuit and turn key off whenever checking for shorts or continuity, unless otherwise specified.
4. Disconnect solenoids and switches before checking circuit continuity or energizing solenoids.
5. An open is defined as any resistance greater than 10,000 ohms, unless otherwise specified.
6. To help diagnose circuits to ECA, turn ignition off and disconnect ECA harness. Connect BOB between ECA and ECA harness to perform circuit and pinpoint tests.

PINPOINT TEST IDM - IGNITION DIAGNOSTIC MONITOR

Note. Enter this test only when Code 01 is displayed during QUICK TESTS procedure or when directed here from another PINPOINT TEST.

Identifying IDM Circuit & Connector. Scheme 6

IDM CIRCUIT PIN IDENTIFICATION

1.3L

1. Connect spark tester between coil secondary wire and ground. Crank engine several times, leaving ignition on between cranking periods. If continuous sparks jump tester gap, go to next step. If continuous sparks do not jump tester gap, go to step 3).
2. With ignition off, connect BOB, leaving ECA disconnected. Connect test light between test pins IDM and VPWR. Crank engine several times. If test light flashes each time engine cranks, IDM circuit is okay. Return to QUICK TESTS if directed here from there. If test light does not flash, repair IDM wire between ECA and coil.
3. Unplug connector from ignition coil. Connect test light between coil IDM wire and PWR wire. Crank engine several times, leaving ignition on between cranking periods. If test light flashes continuously, go to next step. If test light does not flash continuously, go to step 6).
4. Turn ignition on. Measure voltage between coil harness PWR wire and ground. If voltage is greater than 10 volts, replace coil. If voltage is less than 10 volts, repair wire between ignition switch and coil.
5. Connect test light between PWR and ground terminals at coil harness connector. Turn ignition on. If test light glows, replace coil. If test light does not glow, repair ground wire to coil.
6. Unplug connector from ignition module. Connect jumper wire between SPOUT wire on ignition module harness connector and mating terminal on ignition module. Connect another jumper wire between ignition module GND wire and mating connector. Leave IDM wire disconnected. Connect test light between IDM terminal on ignition module and PWR wire. Crank engine several times, leaving ignition on between cranking periods. If test light flashes each time engine cranks, repair wire between ignition module IDM wire and coil. If test light does not flash, go to next step.
7. Turn ignition off. Unplug ignition module connector. Turn ignition on. Measure voltage between ignition module PWR wire and ground. Turn ignition on. If voltage is not more than 10 volts, repair PWR wire from ignition switch. If voltage is more than 10 volts, go to next step.
8. Turn ignition off. Unplug ignition module connector. Turn ignition on. Connect test light between ignition coil PWR wire and ignition module GND wire. Turn ignition on. If test light glows, go to step 10). If test light does not glow, go to next step.
9. Turn ignition off. Unplug ignition module connector. Connect test light between ignition coil PWR wire and ignition module SPOUT wire. Crank engine. If test light flashes, check ignition module SPOUT wire for short to ground; if no short exists, replace ignition module. If test light does not flash, go to next step.
10. Turn ignition off. Unplug ignition module connector. Install BOB, leaving ECA disconnected. Check SPOUT wire for continuity between BOB test pin and ignition module. If continuity exists, check SPOUT wire for shorts to any other wire. If no short exists, replace ECA. If continuity does not exist, repair SPOUT wire to ECA.

1.6L

1. Connect spark tester between coil secondary wire and ground. Crank engine several times, leaving ignition on between cranking periods. If continuous sparks do not jump tester gap, go to step 3). If continuous sparks jump tester gap, go to next step.
2. Turn ignition off. Connect BOB. Leave ECA disconnected. Connect test light between test BOB pins IDM and VPWR. Crank engine several times. If test light flashes each time engine cranks, IDM circuit is okay. Return to QUICK TESTS if directed here from there. If test light does not flash, repair IDM wire between ECA and coil.
3. Unplug connector from ignition coil. Connect test light between coil IDM wire and PWR wire. Crank engine several times, leaving ignition on between cranking periods. If test light does not flash continuously, go to step 6). If test light flashes continuously, go to next step.
4. Turn ignition on. Measure voltage between coil harness PWR wire and ground. If voltage is greater than 10 volts, replace coil. If voltage is less than 10 volts, repair wire between ignition switch and coil.
5. Connect test light between PWR and ground terminals at coil harness connector. Turn ignition on. If test light glows, replace coil. If test light does not glow, repair ground wire to coil.
6. Unplug connector from ignition module. Connect a jumper wire between PWR wire on ignition module harness connector and mating terminal on ignition module. Leave IDM wire disconnected. Connect test light between IDM terminal on ignition module and PWR wire. Crank engine several times, leaving ignition on between cranking periods. If test light flashes each time engine cranks, repair wire between ignition module IDM wire and coil. If test light does not flash. go to next step.
7. Unplug connector from ignition module. Measure voltage between ignition module PWR wire and ground. If voltage is not higher than 10 volts, repair PWR wire from ignition switch. If voltage is higher than 10 volts, go to next step.
8. Turn ignition off. Unplug ignition module connector. Turn ignition on. Connect test light between ignition module PWR wire and ignition module GND wire. Turn ignition on. If test light glows, replace ignition module. If test light does not glow, repair ignition module ground wire.

PINPOINT TEST CPS - CRANKSHAFT POSITION SENSOR

Note. Enter this test only when Code 02 is displayed during QUICK TESTS procedure or when directed here from another PINPOINT TEST.

Identifying CPS Circuit & Connector. Scheme 7

CPS CIRCUIT PIN IDENTIFICATION

1. Turn ignition off. Install BOB. Leave ECA disconnected. Unplug distributor connector. Measure resistance of CPS, VPWR, and GND wires between ECA and distributor. If all resistances are not less than 5 ohms, repair wire in question. If all resistances are less than 5 ohms, go to next step.
2. Turn ignition off. Unplug distributor connector. Turn ignition on. Measure voltage between distributor VPWR and GND wires. If voltage is more than 10 volts, replace CPS sensor. If voltage is not more than 10 volts, repair distributor GND wire.

PINPOINT TEST CID - CYLINDER IDENTIFICATION SENSOR

Note. Enter this test only when Code 03 is displayed during QUICK TESTS procedure or when directed here from another PINPOINT TEST.

Identifying CID Circuit & Connectors. Scheme 8

CID CIRCUIT PIN IDENTIFICATION

1. Turn ignition off. Install BOB, leaving ECA disconnected. Unplug distributor connector. Measure resistance between BOB pin No. 34 and CID terminal on distributor harness connector. Repair Yellow wire between ECA and distributor if resistance is greater than 5 ohms. If resistance is less than 5 ohms, go to next step.
2. Turn ignition on. Measure voltage between distributor VPWR and GND wires. If voltage is greater than 10 volts, replace CID sensor. If voltage is not greater than 10 volts, repair distributor GND wire.

PINPOINT TEST KC - KNOCK CONTROL

Note. Enter this test only when directed here from QUICK TESTS.

Identifying KC Circuit & Connectors. Scheme 9

1. Disconnect and plug vacuum hose at distributor. Connect timing light. Start engine. Unplug knock control service connector, located near ECA. If timing retards, service knock sensor and/or knock sensor wiring. If timing does not retard, go to next step.
2. Determine and record ignition timing setting. Tap intake plenum with plastic mallet. If timing does not retard, go to step 4). If timing retards, go to next step.
3. Reconnect knock control service connector, located near ECA. Determine and record ignition timing setting. Tap intake plenum with plastic mallet. If timing does not retard, knock control unit is okay; go to next step. If timing retards, replace knock control unit.
4. Turn ignition off. Unplug knock control service connector, located near ECA. Install a known good knock sensor. Start engine. Tap intake plenum with plastic mallet. If timing retards, replace knock sensor. If timing does not retard, go to next step.
5. Check VPWR and GND (Yellow/Green and Black/Yellow wires respectively) to knock control unit for shorts or open circuits. Service wires as necessary. If wires are okay, replace knock control unit.

PINPOINT TEST VSS - VEHICLE SPEED SENSOR

Note. Enter this test only when Code 06 is displayed during QUICK TESTS procedure or when directed here from another PINPOINT TEST.

Identifying VSS Circuit & Connectors. Scheme 10

VSS CIRCUIT PIN IDENTIFICATION

PINPOINT TEST VAF - VANE AIRFLOW METER

Note. Enter this test only when a Code 08 is displayed during QUICK TESTS procedure, or when directed here from another PINPOINT TEST. To avoid unnecessary diagnostic time, check for unmetered air leaks between VAF meter and throttle body. This test is intended to diagnose only VAF and VREF circuits.

Identifying VAF Meter Circuits. Scheme 11

VAF CIRCUIT PIN IDENTIFICATION

1. Turn ignition off. Install BOB. Turn on ignition. Measure voltage between VAF and ground pins while moving vane in VAF meter. Voltage should vary smoothly between .5-1.5 volts with door open, and 4.5-5.0 with door closed. If voltage is as specified, VAF meter is okay; return to QUICK TESTS if sent here from there. If not sent here from QUICK TESTS, replace ECA. If voltage is not as specified, go to next step.
2. Remove connector from VAF meter. Using jumper wires, connect VREF and ground terminals on VAF connector to corresponding terminals on VAF meter. Turn ignition on. Measure voltage between VAF terminal on VAF meter and ground terminal while moving vane in VAF meter. Voltage should vary smoothly between .5-1.5 volts with door open, and 4.5-5.0 with door closed. If voltage is correct, repair VAF circuit between ECA and VAF meter. If voltage is not as specified, go to next step.
3. Turn ignition off. Unplug VAF meter connector. Turn ignition on. Measure voltage between VREF and ground wires. If voltage is 4.5-5.5 volts, replace VAF meter. If voltage is not 4.5-5.5 volts, go to PINPOINT TEST VREF.

1. Turn ignition off. Install BOB. Turn ignition on. Measure voltage between VAF and SIGRTN pins while moving vane in VAF meter. Voltage should be as specified in VAF METER VOLTAGE table. If voltage is not as specified, go to step 3). If voltage is as specified, go to next step.
2. Measure voltage between VMREF and SIGRTN test pins. If voltage is 7-9 volts, circuit is okay; return to QUICK TESTS if sent here from there. If not sent here from QUICK TESTS, replace ECA. If voltage is not as specified, repair VMREF wire to VAF.
3. Unplug connector from VAF meter. Using jumper wires, connect VPWR, VMREF, and SIGRTN terminals on VAF connector to corresponding terminals on VAF meter. Leave VAF wire disconnected. Measure voltage between VAF and SIGRTN pins on harness connector while moving vane in VAF meter. Voltage should be as specified in «VAF METER VOLTAGE»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes) table. If voltage is okay, repair VAF wire to ECA. If voltage is not okay, go to next step. VAF METER VOLTAGE Door Position Volts 1/8 Open 3.24 1/4 Open 5.60 3/8 Open 5.62 1/2 Open 5.83 5/8 Open 6.02 3/4 Open 6.57 7/8 Open 7.46 Full Open 7.87
4. Unplug connector from VAF. Using jumper wires, connect VPWR and SIGRTN terminals on VAF connector to corresponding terminals on VAF meter. Leave VAF and VMREF wires disconnected. Measure voltage between VAF terminal at VAF meter, and SIGRTN pin at harness connector while moving vane in VAF meter. Voltage should be as specified in «VAF METER VOLTAGE»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes) table. If voltage is okay, repair VMREF wire to ECA. If voltage is not okay, go to next step.
5. Unplug connector from VAF meter. Turn ignition on. Measure voltage between SIGRTN and VPWR wire. If voltage is more than 10 volts, replace VAF meter. If voltage is not more than 10 volts, go to next step.
6. Unplug VAF meter connector. Turn ignition on. Measure voltage between VAF meter VPWR wire and ground. If voltage is more than 10 volts, repair VAF wire to ECA. If voltage is not more than 10 volts, go to PINPOINT TEST VPWR.

PINPOINT TEST ECT - ENGINE COOLANT TEMPERATURE SENSOR

Note. Enter this test only when a Code 09 is displayed during QUICK TESTS procedure or when directed here from another PINPOINT TEST. To prevent unnecessary diagnosis, inspect coolant level, oil level, cooling fan, thermostat, and airflow to radiator before testing.

Identifying ECT Sensor Circuits. Scheme 12

ECT CIRCUIT PIN IDENTIFICATION

1. Turn ignition off. Install BOB. Leave ECA disconnected. Unplug ECT connector. Check for continuity between ECT test pin and ECT terminal (Red/Blue wire) on ECT harness connector. If continuity does not exist, repair ECT wire between ECA and ECT sensor. If continuity exists, go to next step.
2. Unplug ECT sensor. Check for continuity between Black wire at ECT sensor and ground. If continuity does not exist, repair Black wire between ECT sensor and ground. If continuity exists, go to next step.
3. Reconnect ECA. Measure resistance between BOB ECT test pin and ground pin. If resistance is 500-1000 ohms, replace ECA. If resistance is not 500-1000 ohms, replace ECT sensor.

1. Turn ignition off. Install BOB. Leave ECA disconnected. Unplug ECT connector. Check for continuity between ECT test pin and ECT terminal (Blue/Red wire) on ECT harness connector. If continuity does not exist, repair ECT wire between ECA and ECT sensor. If continuity exists, go to next step.
2. Install BOB. Connect ECT. Warm engine to normal operating temperature. Measure resistance between ECT test pin and SIGRTN pins. If resistance is 500-1000 ohms, replace ECA. If resistance is not 500-1000 ohms, replace ECT sensor.

PINPOINT TEST VAT - VANE AIR TEMPERATURE SENSOR

Note. Enter this test only when a Code 10 is displayed during QUICK TESTS procedure or when directed here from another PINPOINT TEST. Ambient temperature must be higher than 50°F (10°C) for this test.

Identifying VAT Circuits. Scheme 13

VAT CIRCUIT PIN IDENTIFICATION

1. Turn ignition off. Ensure engine is at operating temperature. With ignition off, install BOB. Turn ignition on. Measure temperature near VAT sensor. Measure voltage between VAT and SIGRTN test pins. Compare voltage to specifications shown in «VAT SENSOR VOLTAGE»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes) table. If voltage is within specification, VAT circuit is okay. If voltage is not within specification, go to next step. VAT SENSOR VOLTAGE Temperature °F (°C) (1) Volts 20 (-6) 3.64 30 (-1) 3.36 40 (4) 3.05 44 (7) 2.79 50 (10) 2.29 60 (16) 2.61 70 (21) 2.35 80 (27) 2.05 90 (32) 1.76 100 (38) 1.57 (1) Values may vary by 15 percent.
2. Turn ignition off. Disconnect ECA. Measure resistance between VAT and SIGRTN test pins. Measure temperature near VAF meter. Compare resistance to specifications shown in «VAT SENSOR RESISTANCE»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes) table. If resistance is within specification, go to next step. If resistance is not within specification, go to step 4).
3. Unplug VAF sensor connector. Measure resistance between VAT test pin and all other test pins. If any resistance is less than 5 ohms, repair VAT wire from ECA to VAF meter. If all measurements are greater than 5 ohms, replace ECA.
4. Turn ignition off. Unplug VAF meter connector. Monitor temperature near VAT sensor. Measure resistance between VAF meter VAT and SIGRTN terminals. Compare resistance to specifications shown in «VAT SENSOR RESISTANCE»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes) table while heating VAT sensor . If resistance is within specification, repair VAT and/or SIGRTN wires from VAF to ECA. If resistance is not within specification, replace VAF meter.

VAT SENSOR RESISTANCE

PINPOINT TEST TP - THROTTLE POSITION SENSOR

Note. Enter this test only when a Code 12 is displayed during QUICK TESTS procedure or when directed here from another PINPOINT TEST.

Identifying TP Circuits. Scheme 14

TP CIRCUIT PIN IDENTIFICATION

1. Turn ignition off. Install BOB. Turn ignition on. Measure voltage between BOB test pins TP and SIGRTN while opening throttle. Compare voltage to specification in «TP SENSOR OUTPUT VOLTAGE»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes) table. Go to next step if output voltage is not within specification. TP SENSOR OUTPUT VOLTAGE Throttle Opening (1) Voltage 1/8 1.00 1/4 1.60 3/8 2.37 1/2 2.74 5/8 3.15 3/4 3.43 7/8 3.60 (1) Voltage may vary by 15 percent.
2. Turn ignition off. Unplug TP sensor connector at throttle body. Using jumper wires, connect VREF and SIGRTN wires on harness connector to corresponding terminals on TP sensor connector. Turn ignition on. Measure voltage between TP and SIGRTN terminals on TP sensor while opening throttle. Compare voltage to specification in «TP SENSOR OUTPUT VOLTAGE»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes) table. If voltage is within specification, repair TP wire to ECA. Go to next step if voltage is not within specification.
3. Turn ignition off. Unplug TP harness connector. Turn ignition on. Measure voltage between VREF and SIGRTN wires on TP harness connect-or. If voltage is 4-5 volts, replace TP sensor. If voltage is not 4.5-5.5 volts, go to next step.
4. Measure voltage between VREF wire on TP harness connector and ground. If voltage is 4-5 volts, adjust or replace throttle position sensor. If voltage is not 4-5 volts, go to «PINPOINT TEST VREF»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes__pinpoint-test-vref-reference-voltage) .

PINPOINT TEST BP - BAROMETRIC PRESSURE SENSOR

Note. Enter this procedure only when a Code 14 is displayed during QUICK TESTS procedure or when directed here from another PINPOINT TEST. To prevent unnecessary replacement of components, note following non-EEC items may be at fault: unusually high or low atmospheric pressure, blocked vacuum lines, or basic mechanical engine components.

Identifying BP Sensor Circuits. Scheme 15

BP sensor is incorporated into ECA; it cannot be checked or serviced separately. If Code 14 is set and cannot be cleared, replace ECA.

Turn ignition off. Connect BOB. Remove dust cover from BP sensor, located on passenger side cowl. Turn ignition on. Connect vacuum pump to BP sensor. Measure voltage between pins BP and SIGRTN on BOB while applying vacuum to BP sensor. See BAROMETRIC PRESSURE SENSOR OUTPUT VOLTAGE table. Replace BP sensor if voltage is not as specified.

BAROMETRIC PRESSURE SENSOR OUTPUT VOLTAGE

PINPOINT TEST EGO - EXHAUST GAS OXYGEN SENSOR

Note. Enter this test only when a Code 15 (lean) or Code 17 (rich) is displayed during QUICK TESTS procedure.

EGO CIRCUIT PIN IDENTIFICATION

1. Warm engine to operating temperature, and let idle. Unplug EGO sensor. Measure voltage between EGO sensor connector (sensor side) and ground. With engine at idle, voltage should fluctuate between 0.2-0.8 volt.
2. Increase and decrease engine speed while reading voltmeter. When engine speed is decreasing, voltage should decrease. When engine speed is increasing, voltage should increase. If voltage is within specification, go to next step. If voltage is not within specification, replace EGO sensor.
3. With ignition off, install BOB. Leave ECA disconnected. Unplug EGO sensor connector. Measure continuity between EGO test pin and EGO sensor connector wire. If continuity exists, EGO circuit is okay; return to QUICK TESTS if sent here from there. If not sent here from QUICK TESTS, replace ECA. If voltage is not as specified, repair VMREF wire to VAF. If continuity does not exist, service EGO sensor wire to ECA.

PINPOINT TEST PRC - FUEL PRESSURE REGULATOR CONTROL SOLENOID

Note. Enter this test only when a Code 25 is displayed during QUICK TESTS procedure or when directed here from another PINPOINT TEST.

Identifying PRC Circuit & Connector. Scheme 16

PRC CIRCUIT PIN IDENTIFICATION

1. Locate Fuel Pressure Control (PRC) solenoid on cowl panel, next to canister purge solenoid. Unplug PRC solenoid connector. Remove both vacuum lines. Plug vacuum port from engine vacuum source. Apply vacuum to remaining port. Replace PRC solenoid if it does not hold vacuum.
2. Turn ignition off. Connect BOB. Leave ECA disconnected. Reconnect wiring to PRC solenoid. Turn ignition on. Apply vacuum to PRC solenoid. Connect jumper wire between PRC test pin on BOB and ground. If vacuum drops to zero, PRC solenoid function is okay. Return to QUICK TESTS if sent here from there. If vacuum does not drop to zero, go to next step.
3. Turn ignition off. Unplug PRC solenoid connector. Turn ignition on. Measure voltage between VPWR wire on harness connector and ground. If voltage is not higher than 10 volts, repair VPWR wire to main relay. If voltage is higher than 10 volts, go to next step.
4. Turn ignition off. Unplug PRC solenoid connector. Turn ignition on. Measure voltage between solenoid connector VPWR wire and solenoid connector SIG wire. Connect jumper wire between PRC test pin on BOB and ground. If voltage is higher than 10 volts only when solenoid is activated, replace solenoid. If voltage is not higher than 10 volts only when solenoid is activated, go to next step.
5. Turn ignition off. Connect BOB. Leave ECA disconnected. Unplug solenoid connector. Measure resistance between SIG test pin and solenoid connector SIG wire. If resistance is not less than 5 ohms, repair SIG wire to ECA. If resistance is less than 5 ohms, go to next step.
6. Turn ignition off. Connect BOB. Leave ECA disconnected. Unplug solenoid connector. Measure resistance between SIG test pin and all other test pins. If resistance between SIG PRC test pin and any other pin is less than 5 ohms, repair PRC wire to ECA. If resistance between PRC test pin and any other pin is greater than 10,000 ohms, replace ECA.

PINPOINT TEST CANP - CANISTER PURGE CONTROL SOLENOID

Note. Enter this test only when a Code 26 is displayed during QUICK TESTS procedure or when directed here from another PINPOINT TEST.

Identifying CANP Circuit & Connector. Scheme 17

CANP CIRCUIT PIN IDENTIFICATION

1. Turn ignition off. Install BOB. Leave ECA disconnected. Turn ignition on. Remove canister purge hose from intake manifold, and apply vacuum. Connect a jumper wire between CANP test terminal and ground. If vacuum releases, solenoid is okay. If vacuum does not release, go to next step.
2. Locate CANP solenoid near center of cowl panel. Unplug solenoid connector. Apply vacuum to port from engine vacuum source. Replace CANP solenoid if it does not hold vacuum.
3. Connect BOB. Leave ECA disconnected. Reconnect wiring to CANP solenoid. Turn ignition on. Apply vacuum to CANP solenoid. Connect jumper wire between CANP test pin on BOB and ground. If vacuum drops to zero, solenoid function is okay. Return to QUICK TESTS if sent here from there. If vacuum does not drop to zero, go to next step.
4. Turn ignition off. Unplug CANP solenoid connector. Turn ignition on. Measure voltage between VPWR wire on harness connector and ground. If voltage is not higher than 10 volts, repair VPWR wire to main relay. If voltage is higher than 10 volts, go to next step.
5. Turn ignition off. Unplug CANP solenoid connector. Turn ignition on. Measure voltage between solenoid connector VPWR wire and solenoid connector SIG wire. Connect jumper wire between CANP test pin on BOB and ground. If voltage is higher than 10 volts only when solenoid is activated, replace solenoid. If voltage is not higher than 10 volts only when solenoid is activated, go to next step.
6. Turn ignition off. Connect BOB. Leave ECA disconnected. Unplug CANP solenoid connector. Measure resistance between SIG test pin and solenoid connector SIG wire. If resistance is not less than 5 ohms, repair SIG wire to ECA. If resistance is less than 5 ohms, go to next step.
7. Turn ignition off. Connect BOB. Leave ECA disconnected. Unplug solenoid connector. Measure resistance between SIG test pin and all other test pins. If resistance between SIG PRC test pin and any other pin is less than 5 ohms, repair CANP wire to ECA. If resistance between CANP test pin and all other pins is greater than 10,000 ohms, replace ECA.

PINPOINT TEST ISC - IDLE SPEED CONTROL

Note. Enter this test only when a Code 34 is displayed during QUICK TESTS procedure or when directed here from another PINPOINT TEST.

Identifying ISC Circuit & Connector. Scheme 18

ISC CIRCUIT PIN IDENTIFICATION

1. Install BOB, leaving ECA disconnected. Turn ignition on. Connect a jumper between BOB test pin No. 41 and ground. Listen for clicking sound from solenoid, mounted on throttle body. If clicking sound occurs, ISC solenoid is okay; return to QUICK TESTS if sent here from there. If no clicking sound occurs, go to next step.
2. Unplug ISC solenoid connector. With ignition on, measure voltage between VPWR wire and ground. If voltage is less than 10 volts, repair VPWR wire to main relay. Go to next step if voltage is not less than 10 volts.
3. Measure voltage between ISC solenoid VPWR wire and solenoid connector SIG wire while cranking engine. Replace solenoid if voltage is more than 10 volts only when engine is cranking. If okay, go to next step.
4. With BOB installed and ECA disconnected, unplug ISC solenoid connector. Check for continuity between BOB SIG test pin and ISC connector SIG wire. If resistance is not less than 5 ohms, repair ISC wire between solenoid and ECA. If okay, go to next step.
5. With BOB installed and ECA disconnected, measure resistance between BOB SIG test pin and all other test pins. If resistance is less than 5 ohms, repair short in SIC wire to ECA. If resistance is not less than 5 ohms, replace ECA.

PINPOINT TEST STI - SELF-TEST INPUT

Note. Enter this test only when sent here from QUICK TESTS.

STI CIRCUIT PIN IDENTIFICATION

1. Turn ignition off. Install BOB. Leave ECA disconnected. Connect test light between STI test pin on BOB and 12-volt source. If test light comes on, go to «PINPOINT TEST STO»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes__pinpoint-test-sto-self-test-output) . If light does not come on, go to next step.
2. Leave test light connected. Ground STI connector. If test light does not come on, repair open circuit between STI connector and ECA.

PINPOINT TEST STO - SELF-TEST OUTPUT

Note. Enter this test only when codes cannot be retrieved or when directed by PINPOINT TEST STI.

STO CIRCUIT PIN IDENTIFICATION

1. Turn ignition off. Install BOB. Leave ECA disconnected. Measure resistance between STO test pin and STO terminal of self-test connector. If resistance is greater than 5 ohms, repair circuit between ECA and self-test connector. If resistance is less than 5 ohms, go to next step.
2. Measure resistance between STO test pin and all other test pins. If resistance between STO test pin and any other test pin is less than 5 ohms, repair short in STO wire to diagnostic connector. If resistance is greater than 5 ohms, go to «PINPOINT TEST PGC»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes__pinpoint-test-pgc-power) .

PINPOINT TEST PGC - POWER & GROUND CONNECTIONS

Note. Enter this test only when directed here from QUICK TESTS or another PINPOINT TEST.

PGC CIRCUIT PIN IDENTIFICATION

1. Turn ignition off. Install BOB, leaving ECA disconnected. Turn ignition on. Measure voltage at BOB pin in question. Compare voltage to specification in «PGC CIRCUIT PIN IDENTIFICATION»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes) table. If voltage is not to specification, repair wire in question.
2. Measure resistance between ground and BOB pin in question. If any measurement is greater than 5 ohms, repair associated wire to ground. If resistance is less than 5 ohms, return to «PINPOINT TEST VREF»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes__pinpoint-test-vref-reference-voltage) if sent here from there, and replace ECA. If not sent here from PINPOINT TEST VREF, return to diagnostic routine.

PINPOINT TEST STG - SWITCH TO GROUND

Note. Enter this test only when directed here from QUICK TESTS or another PINPOINT TEST.

STG CIRCUIT PIN IDENTIFICATION

Note. For 1.3L, blower motor resistor must be disconnected, HEATER fuse must be removed, and blower motor switch must be in position "1" when testing ACS signal.

1. Turn ignition off. Install BOB, leaving ECA disconnected. Measure resistance between switch BOB test pin and ground. Cycle switch. If resistance is greater than 10,000 ohms with switch open and less than 5 ohms when switch is closed, switch is okay; go to step 4). If resistance is not greater than 10,000 ohms with switch open, or greater than 5 ohms when switch is closed, go to next step.
2. Turn ignition off. Disconnect switch. Connect ohmmeter between switch terminals on 2-pin switches, or between ground and switch ECA terminal on multi-pin or one-pin switches. Cycle switch. If resistance is not greater than 10,000 ohms with switch open, or is greater than 5 ohms when switch is closed, replace switch. If resistance is greater than 10,000 ohms with switch open and less than 5 ohms when switch is closed, switch is okay; go to next step.
3. Turn ignition off. Install BOB, leaving ECA disconnected. Measure resistance between BOB pin for suspected switch and BOB pins 26, 37, 57, and 60. If any measurement is less than 10,000, repair shorted wire in question. If all measurements are greater than 10,000 ohms, go to next step.
4. Turn ignition off. Install BOB, leaving ECA disconnected. Measure resistance between BOB pin for suspected switch and switch connector. If resistance is greater than 5 ohms, repair wire in question. If sent here from SWITCH MONITOR TEST in QUICK TESTS, replace ECA; otherwise, return to QUICK TESTS.

PINPOINT TEST STP - SWITCH TO POWER

Note. Enter this test only when directed here from QUICK TESTS.

STP CIRCUIT PIN IDENTIFICATION

1. Turn ignition off. Install BOB, leaving ECA disconnected. Turn ignition on. Cycle switch in question. Measure voltage between switch BOB test pin and ground. If voltage changes from less than 4 volts to more than 10 volts, switch is okay. If sent here from SWITCH MONITOR TEST in QUICK TESTS, replace ECA. If sent here from elsewhere in QUICK TESTS, return to QUICK TESTS. If voltage is not as specified, go to next step.
2. Turn ignition on. Measure voltage at switch in question on wire to ECA. Cycle switch. If voltage changes from less than 4 volts to more than 10 volts, repair wire from switch to ECA. If voltage does not change from less than 4 volts to more than 10 volts, go to next step.
3. Turn ignition on. Install BOB, leaving ECA disconnected. Measure resistance between BOB test pin for switch in question and ground and between BOB test pin and BOB pins 37, 57, and 26. If resistance is greater than 10,000 ohms for all measurements, go to next step. If resistance is not greater than 10,000 ohms for all measurements, repair wire to switch.
4. Disconnect switch. Measure resistance between switch terminals. Cycle switch. If resistance is less than 5 ohms with switch closed and greater than 10,000 ohms with switch open, switch is okay. If sent here from SWITCH MONITOR TEST in QUICK TESTS, return to QUICK TESTS. If sent here from elsewhere in QUICK TESTS, replace ECA. If resistance is not as specified, replace switch.

PINPOINT TEST VPWR - VEHICLE POWER

Note. Enter this test only when directed here from another PINPOINT TEST. To prevent replacement of good components, note following non-EEC components may be faulty: ignition switch, alternator, battery cables, ground straps, or voltage regulator. This test is intended to diagnose only ECA, wiring harness circuits, and battery voltage.

Identifying VPWR Circuit & Connector. Scheme 19

VPWR CIRCUIT PIN IDENTIFICATION

1. Turn ignition off. Install BOB, leaving ECA disconnected. Turn ignition on. Measure voltage between VPWR test pin and battery ground. If voltage is not greater than 10 volts, go to step 3). If voltage is greater than 10 volts, go to next step.
2. Measure voltage between VPWR test pin and GROUND test pin. If voltage is greater than 10 volts, go to next step. Repeat measurement for each ECA ground wire. If all voltages are greater than 10 volts, go to «PINPOINT TEST VREF»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes__pinpoint-test-vref-reference-voltage) . If all voltages are not greater than 10 volts, repair ECA ground wire in question.
3. Turn ignition off. Locate main power relay. On Capri, relay is located on left side of engine compartment. On Festiva, relay is located at left front of engine compartment. Disconnect main power relay 4-wire connector. Using jumper wires, connect BATT, PWR, and GND terminals of relay to corresponding trammels on connector. Leave VPWR wire disconnected.
4. Turn ignition on. Measure voltage between main power relay VPWR terminal (where VPWR wire was) and ground. If voltage is more than 10 volts, repair VPWR circuit between main power relay and ECA. If voltage is not more than 10 volts, go to next step.
5. Unplug main relay connector. Measure voltage between harness connector BATT wire and ground. If voltage is not greater than 10 volts, repair BATT wire from battery to harness connector. If voltage is greater than 10 volts, go to next step.
6. Unplug main relay connector. Measure voltage between harness connector PWR wire and ground. If voltage is not greater than 10 volts, repair PWR wire from ignition switch to harness connector. If voltage is greater than 10 volts, go to next step.
7. Measure voltage between main power relay BATT wire and main power relay GROUND wire. If voltage is less than 10 volts, repair main power relay ground wire. If voltage is not less than 10 volts, ground circuit is okay; replace main power relay.

PINPOINT TEST VREF - REFERENCE VOLTAGE & SIGNAL RETURN

Note. Enter this test only when directed from another PINPOINT TEST.

Identifying VREF Circuit & Connector. Scheme 20

VREF CIRCUIT PIN IDENTIFICATION

1. On 1.3L, go to next step. On 1.6L, turn ignition on. Measure voltage between throttle position switch VREF and SIGRTN wires. See «VREF CIRCUIT PIN IDENTIFICATION»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes) table. If voltage is 10-12 volts, repair short to voltage. If voltage is zero volts, go to next step.
2. Turn ignition on. On 1.3L, measure voltage between Black and White-Black wires at VAF sensor. On 1.6L, measure voltage between White-Black and Blue/Yellow wires at BP sensor. If voltage is 4-5 volts, VREF circuit is okay. If voltage is zero volts, go to next step. If voltage is 10-12 volts, repair short to voltage.
3. Turn ignition off. Install BOB. Install 4EAT tester (if vehicle is equipped with 4EAT transaxle). Unplug connector from VAF, TP, and BP sensors as applicable to vehicle. Measure resistance between VREF terminals on ECA and 4EAT module. Also measure resistance between ECA VREF terminal and TP, BP, and VAF VREF harness connector terminals. If any measurement is greater than 5 ohms, repair wire in question. If resistance is less than 5 ohms for all measurements, go to next step.
4. Turn ignition off. Disconnect 4EAT module (if equipped). Unplug connector from VAF, TP, and BP sensors as applicable to vehicle. Measure resistance between ECA VREF pin on BOB and ground. If resistance is not greater than 10,000 ohms, repair short in VREF circuit. If resistance is greater than 10,000 ohms, go to next step.
5. Turn ignition off. Disconnect ECA. Unplug connector from VAF, TP, and BP sensors as applicable to vehicle. Measure resistance between ECA SIGRTN, 4EAT, and all SIGRTN pins on BOB. If any measurement is greater than 5 ohms, repair wire in question. If resistance is less than 5 ohms for all measurements, go to next step.
6. Turn ignition off. Install BOB. Connect ECA. Connect 4EAT module (if equipped). Turn ignition on. Measure voltage at ECA SIGRTN test pin on BOB. If voltage is 0-1 volt, go to «PINPOINT TEST PGC»(/mercury/capri/iii-1990-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes__pinpoint-test-pgc-power) . If voltage is not 0-1 volt, repair short to voltage on SIGRTN circuit.

SUMMARY

If no hard codes, or only pass codes, are present, and driveability symptoms or intermittent codes still exist, proceed to TESTS W/O CODES article in the ENGINE PERFORMANCE Section for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.

See also:
• SELF-DIAGNOSTICS ABBREVIATIONS
• ERASING CODES & RETESTING
• PINPOINT TEST STI
• KEY ON, ENGINE RUNNING (KOER) SELF-TEST
• SWITCH MONITOR TEST
• PINPOINT TEST VREF
• PINPOINT TEST STO
• PINPOINT TEST PGC