Engine Controls - System/component Tests - Efi Mazda Navajo I

INTRODUCTION

Before testing separate components or systems, perform procedures in BASIC TESTING article. Since many computer-controlled and monitored components set a trouble code if they malfunction, also perform procedures in appropriate TESTS W/CODES article.

Note. Testing individual components does not isolate shorts or opens. Perform all voltage tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use ohmmeter to isolate wiring harness shorts or opens.

Air By-Pass Valve

Remove air by-pass valve. Connect vacuum pump to port "A" of valve. (Scheme 44) Apply 10-16 in. Hg vacuum to port "A", and blow air into port "B". Replace air by-pass valve if air does not flow from port "B" to port "C".

Scheme 44

Boost Pressure

Ensure engine is cool. Disconnect hose from solenoid valve, and connect pressure gauge to vacuum hose. (Scheme 45) Warm engine to normal operating temperature. Increase engine speed to 4000 RPM and verify boost pressure is greater than zero psi. If boost pressure is not as specified, test turbocharger components as necessary.

Scheme 45

Compressor & Turbine Wheel Deflection

Allow engine to cool. Remove air intake tube. Turn compressor wheel. Replace turbocharger if wheel does not turn freely or if wheel touches housing.

Intercooler

Remove intercooler. Inspect for cracks, restriction or damage. Replace as necessary.

Oil Passage Inspection

Ensure engine is cool. Remove oil return pipe. Verify oil passage in turbocharger and oil return pipe are not blocked with carbonized oil. Replace turbocharger and return pipe as necessary.

Overboost Warning

Start engine, and operate it at 2000 RPM. Lift air cleaner upper case, and push measuring plate completely open. Warning buzzer should sound and engine speed should drop or engine should stall.

Solenoid Valve

Disconnect small air tube from air hose. Disconnect solenoid valve connector. Blow air through air tube and verify air does not flow. If air flows, replace solenoid valve and turbocharger as an assembly. Apply 12 volts and ground to solenoid valve connector. (Scheme 46) Blow air through air tube and verify air passes freely. If air does not pass freely with 12 volts applied, replace solenoid valve and turbocharger as an assembly.

Scheme 46

Wastegate Actuator

1. Ensure engine is cool. Remove exhaust manifold insulator and side insulator. Remove hose connected to actuator. Connect air pressure source to pressure gauge. (Scheme 47) Apply air pressure to actuator. CAUTION: DO NOT apply more than 14 psi (1.0 kg/cm 2 ) of air pressure.
2. Apply 8.5 psi (0.6 kg/cm 2 ) of compressed air. Ensure actuator rod moves when air pressure is applied.

Scheme 47

System Check (Protege DOHC)

Connect tachometer to IG terminal of diagnostic connector. (Scheme 48) Start engine, and operate it at idle. Ensure shutter valve actuator rod is retracted at idle. (Scheme 49) Gradually increase engine speed to 5000 RPM and ensure actuator rod extends. If necessary, check Variable Inertia Charging System (VICS) components.

Scheme 48

Scheme 49

System Check (929)

Start engine, and operate it at idle. Ensure shutter valve actuator rod is retracted at idle. (Scheme 49) Actuator rod should extend when engine is started, for 5 seconds after engine is started and when engine is operating at 1100-4800 RPM with throttle opened in "D" range. If necessary, check Variable Inertia Charging System (VICS) components.

Check Valve (929)

Remove check valve. Blow air through port "A" and verify flow through port "B". Ensure air does not flow in reverse direction. Replace as necessary.

Remove solenoid valve. Blow air through port "B". (Scheme 50) Ensure air flows from valve air filter. Connect 12 volts and a ground to solenoid valve terminals. (Scheme 50) Blow air through valve port "B" and ensure air flows from port "A". Replace solenoid valve as necessary.

Scheme 50

Shutter Valve Actuator (Protege DOHC)

Disconnect vacuum hose from shutter valve actuator. (Scheme 49) Ensure shutter valve rod moves in and out smoothly. Place finger over hose. Ensure vacuum is present at idle. Reconnect vacuum hose on actuator and ensure rod retracts. Replace as necessary.

Shutter Valve Actuator (929)

Disconnect vacuum hose from shutter valve actuator. (Scheme 49) Connect vacuum pump to actuator. Apply vacuum and verify shutter valve rod retracts. Replace as necessary.

Shutter Valve (929)

Shutter valve stopper bolt is preset at factory. DO NOT adjust shutter valve stopper bolt. Remove shutter valve actuator. Ensure shutter valve rotates smoothly. (Scheme 51) Replace dynamic chamber if valve is stuck or does not rotate smoothly.

Scheme 51

Vacuum Chamber (Protege DOHC)

Remove vacuum chamber. Blow air through port "A" and verify flow through port "B". (Scheme 52) Ensure air does not flow in reverse direction. Replace as necessary.

Vacuum Chamber (929)

Remove vacuum chamber. Visually inspect vacuum chamber for clogging, cracks and damage. Replace as necessary.

Scheme 52

System Check (MX-3 DOHC)

Connect tachometer to IG terminal of diagnostic connector. (Scheme 48) Start engine, and operate it at idle. Manually open throttle valve. Ensure shutter valve actuator rods No. 1 and 2 retract at specified RPM. See VRIS RPM SPECIFICATIONS table. (Scheme 53) If necessary, check Variable Resonance Induction System (VRIS) components.

VRIS RPM SPECIFICATIONS

Scheme 53

Check Valve

Remove check valve. Blow air through port "A" and verify flow through port "B". Ensure air does not flow in reverse direction. Replace as necessary.

Shutter Valve Actuator (MPV 3.0L)

1. Remove shutter valve actuator protector cover. Remove "C" clip. Disconnect shutter valve actuator vacuum hose. (Scheme 49) Remove shutter valve actuator.
2. Apply vacuum to shutter valve actuator. (Scheme 54) Ensure rod retracts into actuator. Replace shutter valve actuator if rod does not retract. With shutter valve actuator removed, ensure shutter valve rod moves smoothly. Replace as necessary.

Shutter Valve Actuator (MX-3 DOHC)

Disconnect vacuum hose from shutter valve actuators No. 1 and 2. (Scheme 49) Connect vacuum pump to actuator. (Scheme 54) Apply vacuum to each actuator separately and verify shutter valve rod retracts. Replace actuator as necessary.

Disconnect vacuum hose from solenoid valve port "A". Blow air through port "B". (Scheme 50) Ensure air flows from valve air filter. Disconnect solenoid valve connector, and connect 12 volts and a ground to solenoid valve terminals. (Scheme 50) Blow air through valve port "B" and ensure air flows from port "A". Replace solenoid valve as necessary.

Vacuum Chamber

Remove vacuum chamber. Visually inspect chamber for clogging, cracks and damage. Replace as necessary.

Scheme 54

Ground Circuits

1. Locate Electronic Control Assembly (ECA) behind right kick panel. Using a DVOM, check for continuity to ground on ECA terminals No. 40 and 60. (Scheme 55) Reading on DVOM should be zero ohms. If reading is not zero ohms, repair open to ground.
2. Using a voltmeter, touch negative lead of voltmeter to a good ground. Touch positive lead of voltmeter to each ground terminal. With engine running, voltmeter should indicate less than one volt. If reading is one volt or more, check for open, corrosion and loose connection on ground lead.

Power Circuits

Using a voltmeter, check for battery voltage between ECA terminal No. 1 (constant battery power) and ground. Check for battery voltage at terminals No. 37 and 57 with ignition on. If battery voltage is not present, power is not being supplied from EEC power relay. See CIRCUIT TEST B in TESTS W/CODES - NAVAJO article.

Scheme 55

ENGINE CONTROL UNIT (EXCEPT NAVAJO)

1. Locate Engine Control Unit (ECU). See «ECU LOCATION»(/mazda/navajo/i-1990-1994/remont/testing-diagnostics/#engine-controls-systemcomponent-tests-efi) table. Connect Engine Signal Monitor (49-9200-162) to ECU. (Scheme 56) Check voltage at each terminal of ECU. If input and output component voltage readings are not as specified, check faulty component. See PIN VOLTAGE CHART S article, TESTS W/CODES - EXCEPT NAVAJO article and testing for appropriate component in this article.
2. If input and output component voltages are as specified, and ECU voltage is incorrect, replace ECU.

ECU LOCATION

Scheme 56

A/C SWITCH

See A/C CUT-OFF CONTROL SYSTEM (B2200, B2600i, MIATA, MPV, MX-3 & 929) under MISCELLANEOUS CONTROLS .

Navajo

Locate sensor on top left side of engine, behind idle air by-pass valve. Sensor requires a 5-volt reference signal during engine operation. With sensor disconnected, measure resistance between sensor terminals. See ACT SENSOR RESISTANCE table. Replace sensor as necessary.

ACT SENSOR RESISTANCE

B2200, B2600i & MPV 2.6L

1. Pull rubber boot back from airflow sensor connector. Backprobe sensor connector, and check terminal voltages. (Scheme 57) See «AIRFLOW SENSOR TERMINAL VOLTAGES»(/mazda/navajo/i-1990-1994/remont/testing-diagnostics/#engine-controls-systemcomponent-tests-efi) table.
2. If voltages are not correct, check wiring for open or short. If wiring is okay, check burn-off operation. See BURN-OFF OPERATION (B2200, B2600I & MPV 2.6L). If ECU control of burn-off operation is okay but voltages are still incorrect, replace airflow sensor.

AIRFLOW SENSOR TERMINAL VOLTAGES

Scheme 57

Burn-Off Operation (B2200, B2600i & MPV 2.6L)

1. Perform this test if airflow sensor failed voltage test. Disconnect negative battery cable to reset ECU. Reconnect negative battery cable.
2. Bring engine to normal operating temperature. Pull back rubber boot from airflow sensor connector. Operate engine at about 2000 RPM for 3 minutes with transmission in Neutral.
3. Turn ignition off. Backprobe airflow sensor Green/Orange wire at ECU terminal 2H using a voltmeter. Voltage should be zero volts immediately after ignition is turned off. About 8-12 volts should be present momentarily, 2-5 seconds after ignition switch is turned to OFF position.
4. If voltages are as specified, replace airflow sensor. If voltages are not as specified, check voltage and related wiring at ECU terminals 2P, 2Q and 1I (B2200 and B2600i) or ECU terminals 2O, 2Q and 1I (MPV 2.6L). See PIN VOLTAGE CHART S article.

Miata, MPV 3.0L, MX-3, MX-6, Protege, 323, 626 & 929

Inspect airflow meter for damage, and ensure measuring plate or cone moves smoothly. (Scheme 58), (Scheme 59) or (Scheme 60). Disconnect airflow meter electrical connector. Move measuring plate or cone and measure resistance between terminals. See appropriate AIRFLOW METER TERMINAL RESISTANCE table. Replace sensor as necessary.

AIRFLOW METER TERMINAL RESISTANCE

AIRFLOW METER TERMINAL RESISTANCE

AIRFLOW METER TERMINAL RESISTANCE

Scheme 58

Scheme 59

Scheme 60

ATMOSPHERIC PRESSURE SENSOR

See PIN VOLTAGE CHART S article.

Faults in BP sensor or circuit should set a service code. See QUICK TEST in TESTS W/CODES - NAVAJO article. If no service code has been set, see CIRCUIT TEST DF in TESTS W/CODES - NAVAJO article for sensor testing.

BRAKELIGHT SWITCH

Disconnect brakelight switch connector. Measure resistance between terminals of brakelight switch. With brake pedal released, continuity should not exist. With brake pedal depressed, continuity should be present. Replace switch as necessary.

MPV & 929

CPU acts as an electrical load sensor. On MPV, remove CPU from behind left side of instrument panel. On 929, remove CPU from behind left front side trim panel near door. Check voltage at terminals of CPU connector. See appropriate CPU UNIT VOLTAGE CHART. (Scheme 61)- (Scheme 64). If voltages are incorrect, check appropriate circuit. If circuits are okay but voltages are still incorrect, replace CPU.

Scheme 61

Scheme 62

Scheme 63

Scheme 64

CLUTCH SWITCH (M/T)

Disconnect clutch switch electrical connector. Using ohmmeter, check continuity between switch terminals. With clutch pedal depressed, continuity should be present. With clutch pedal released, continuity should not exist. Replace switch as necessary.

929

Remove cold start thermoswitch. Place thermoswitch and thermometer in container of coolant. Connect ohmmeter to thermoswitch terminals. Slowly heat coolant. Note resistance at specified temperatures. See COLD START THERMOSWITCH RESISTANCE (929) table. Replace thermoswitch as necessary.

COLD START THERMOSWITCH RESISTANCE (929)

Miata, MX-3 SOHC, Protege & 323

1. Remove switch from radiator or engine block. Place switch and thermometer in container of coolant. Connect ohmmeter to coolant temperature switch terminals. Slowly heat coolant.
2. Note temperature at which continuity is present between switch terminals. Continuity should be present with coolant temperature greater than 207°F (97°C). Continuity should not exist with temperature less than 194°F (90°C). Replace switch as necessary.

MX-6 & 626

1. Remove both switches from radiator hose flange. (Scheme 65) Place each switch individually with a thermometer in container of engine oil. Connect ohmmeter to coolant temperature switch terminals. Slowly heat engine oil. Note temperature at which continuity is present between switch terminals.
2. Continuity should exist in switch No. 1 at temperatures greater than 207°F (97°C). Continuity should exist in switch No. 2 at temperatures greater than 226°F (108°C). Replace switches as necessary.

Note. DO NOT allow engine oil temperature to exceed 248°F (120°C).

Scheme 65

COOLANT THERMOSENSOR

Remove coolant thermosensor. Place thermosensor and thermometer in container of coolant. Connect ohmmeter to thermosensor terminals. Slowly heat coolant. Note resistance at specified temperatures. See appropriate COOLANT THERMOSENSOR RESISTANCE table. Replace sensor as necessary.

COOLANT THERMOSENSOR RESISTANCE

COOLANT THERMOSENSOR RESISTANCE

CRANK ANGLE SENSOR

See IGNITION CHECKS in BASIC TESTING article.

Sensor is located in intake manifold cooling passage, at front of engine. Sensor requires a 5-volt reference signal during engine operation. With sensor disconnected, measure resistance between sensor terminals. See ECT SENSOR RESISTANCE table. Replace sensor as necessary.

ECT SENSOR RESISTANCE

MX-3 DOHC, MX-6, 626 & 929

See EXHAUST GAS RECIRCULATION (EGR) (MX-3 DOHC, MX-6, 626 & 929) under EMISSION SYSTEMS & SUB-SYSTEMS.

HEATED EXHAUST GAS OXYGEN (HEGO) SENSOR (NAVAJO)

HEGO sensor is located in exhaust pipe, upstream of the catalytic converter. Faults in sensor or circuit should set a service code. See QUICK TEST in TESTS W/CODES - NAVAJO article. If no service code has been set, see CIRCUIT TEST H in TESTS W/CODES - NAVAJO article for additional sensor specifications and circuit testing procedures. Ensure following conditions do not exist

1. Moisture inside sensor/harness connector.
2. HEGO sensor coated with contaminants.
3. Sensor circuit open or shorted to ground.

B2200, B2600i, MPV 2.6L, MX-6 & 626

1. Disconnect idle switch electrical connector. (Scheme 66) Check continuity between switch and ground. Continuity should be present with throttle valve fully closed. Continuity should not exist with throttle valve open.
2. If continuity is not as specified, check wiring harness for open or short circuits. On B2200, B2600i, MX-6 and 626, replace idle switch and throttle body as an assembly if wiring harness is okay. On MPV 2.6L, replace idle switch if wiring harness is okay.

Miata, MPV 3.0L, MX-3, Protege, 323 & 929

Idle switch is part of throttle position sensor. See ADJUSTMENTS article.

Scheme 66

1. Inertia switch is located under dash, right of transmission tunnel. To reset switch, ensure no fuel leaks are present. Push reset button.
2. Disconnect inertia switch electrical connector. Connect ohmmeter set on 200 ohm scale across switch connector terminals. If resistance is greater than .3 volt, replace switch.

INHIBITOR SWITCH (A/T)

Disconnect inhibitor switch electrical connector. Connect ohmmeter to indicated switch terminals. (Scheme 67)- (Scheme 73). Continuity should be present with gearshift in PARK and NEUTRAL positions. Continuity should not exist in any other gear positions. Replace switch as necessary.

Scheme 67

Scheme 68

Scheme 69

Scheme 70

Scheme 71

Scheme 72

Scheme 73

B2200, B2600i & MPV

Disconnect intake air thermosensor connector. Connect ohmmeter to switch terminals. (Scheme 74)or (Scheme 75). Measure resistance of sensor at various temperatures. See INTAKE AIR THERMOSENSOR RESISTANCE table. Replace sensor as necessary.

Remove intake air thermosensor. Using a heat light, ohmmeter and thermometer, measure resistance of sensor at various temperatures. (Scheme 76) See INTAKE AIR THERMOSENSOR RESISTANCE table. Replace sensor as necessary.

INTAKE AIR THERMOSENSOR RESISTANCE

Scheme 74

Scheme 75

Scheme 76

KNOCK SENSOR

See PIN VOLTAGE CHART S article.

Faults in Mass Airflow (MAF) sensor or circuit should set a service code. See QUICK TEST in TESTS W/CODES - NAVAJO article. If no service code has been set, see CIRCUIT TEST DC in TESTS W/CODES - NAVAJO article for sensor and circuit testing and specifications.

M/T Models Except Navajo

Disconnect neutral switch electrical connector. Using ohmmeter, check continuity between switch terminals. Ensure continuity exists with transmission in Neutral. Continuity should not exist with transmission in any other gear. Replace switch as necessary.

Navajo (A/T & M/T)

With ignition switch in OFF position, set DVOM to 200-ohm scale. Locate neutral switch (on transmission). Disconnect neutral switch electrical connector. Using ohmmeter, measure resistance across neutral terminals. If resistance is greater than 5 ohms, replace switch.

B2200, B2600i, Miata, MPV 2.6L, MX-3, MX-6, Protege, 323 & 626

1. Warm engine to operating temperature. Operate engine at idle. Disconnect O2 sensor electrical connector. Connect voltmeter between connector and ground. On B2200, B2600i, MPV 2.6L, MX-3 DOHC, MX-6 and 626, increase engine speed to 4500 RPM until voltmeter indicates about .7 volt. On Miata, MX-3 SOHC, Protege and 323, increase engine speed to 3000 RPM until voltmeter indicates about .55 volt.
2. Observe voltmeter while rapidly accelerating and decelerating engine speed. Voltage should be 0.5-1.0 volt during acceleration and 0.0-0.4 volt during deceleration. Replace O2 sensor as necessary.

MPV 3.0L & 929

1. Warm engine to operating temperature. Operate engine at idle. Disconnect O2 sensor electrical connector. Connect voltmeter between O2 sensor connector terminals "A" and "B". (Scheme 77)
2. Observe voltmeter while rapidly accelerating and decelerating engine speed. Voltage should be 0.5-1.0 volt during acceleration and 0.0-0.4 volt during deceleration. Replace O2 sensor as necessary.

Scheme 77

OXYGEN (O2) SENSOR HEATER

See PIN VOLTAGE CHART S article.

POWER STEERING PRESSURE SWITCH (PSPS)

Disconnect power steering pressure switch electrical connector. Connect ohmmeter to PSPS switch terminals. Start engine, and operate it at idle. Turn steering wheel from side to side, and observe ohmmeter. Ohmmeter should indicate continuity when front wheels are turned. Continuity should not exist when wheels are not turned. Replace switch as necessary.

THROTTLE POSITION SENSOR

See ADJUSTMENTS article for checking and adjustment procedures.

See BASIC TESTING and TESTS W/CODES - NAVAJO articles.

Except Navajo

See PIN VOLTAGE CHART S article.

Disconnect VSS electrical connector. Using DVOM, measure resistance across VSS terminals. Resistance should be 190-250 ohms. Replace sensor as necessary.

Circuit Opening Relay

See FUEL PRESSURE (FUEL INJECTION) under FUEL SYSTEM in BASIC TESTING article.

Cold Start Injector Relay (929)

Remove cold start injector relay. Apply battery voltage to terminal "C", and ground terminal "D". Continuity should be present with battery voltage applied. Continuity should not exist without voltage applied. Replace relay as necessary.

Fuel Pump Relay (Navajo)

Remove relay from vehicle. Connect battery voltage to terminal "C". (Scheme 78) Ground terminal "D". Measure resistance between terminals "A" and "B". Resistance should be less than one ohm with power applied. Continuity should not exist with power removed.

Note. For additional fuel delivery system testing, see CIRCUIT TEST J in TESTS W/CODES - NAVAJO article.

Scheme 78

Main Relay (Except Navajo)

1. Ensure main relay clicks when ignition is turned on and off.
2. If no sound is heard, unplug relay. Apply 12 volts to terminal "A", and ground terminal "B". (Scheme 79), (Scheme 80), (Scheme 81) or (Scheme 82).
3. Using ohmmeter, check continuity between terminals "C" and "D". Continuity should be present with 12 volts applied. Continuity should not exist with no voltage applied. Replace main relay as necessary.

EEC Power Relay (Navajo)

See TESTS W/CODES - NAVAJO article.

Scheme 79

Scheme 80

Scheme 81

Canister Purge (CANP) Solenoid (Navajo)

See FUEL EVAPORATION (NAVAJO) under EMISSION SYSTEMS & SUB-SYSTEMS.

Cold Start Injector Resistance (929)

Disconnect cold start injector electrical connector. Using ohmmeter, measure resistance between injector terminals. Resistance should be 2.7-3.4 ohms at 68°F (20°C). Replace injector as necessary.

EGR Solenoid (MX-3 DOHC, MX-6, 626 & 929)

See EXHAUST GAS RECIRCULATION (EGR) (MX-3 DOHC, MX-6, 626 & 929) under EMISSION SYSTEMS & SUB-SYSTEMS.

Fuel Injectors

Using stethoscope, listen for normal clicking sound at each injector during idle and acceleration. If clicking sound is not heard, check injector wiring circuit, or main relay and circuit.

Fuel Injector Resistance

Disconnect fuel injector electrical connector. Using ohmmeter, measure resistance between injector terminals. Resistance should be 12-16 ohms. Replace injector as necessary.

Pressure Regulator Control Solenoid (Except Navajo)

Disconnect vacuum hose from pressure regulator control solenoid. Blow air through solenoid port "A". (Scheme 82) Ensure air flows through port "B". Disconnect solenoid valve electrical connector. Connect 12 volts and ground to solenoid terminals. Blow air through solenoid port "A". Air should flow through valve air filter. Replace solenoid as necessary.

Scheme 82

Purge Control Solenoid

See FUEL EVAPORATION (EXCEPT NAVAJO) under EMISSION SYSTEMS & SUB-SYSTEMS.

Turbocharger Solenoid (MX-6 & 626)

See TURBOCHARGER (MX-6 & 626) under AIR INDUCTION SYSTEMS.

VICS Solenoid (Protege DOHC & 929)

See VARIABLE INERTIA CHARGING SYSTEM (PROTEGE DOHC & 929) under AIR INDUCTION SYSTEMS.

VRIS Solenoid (MPV 3.0L & MX-3 DOHC)

See VARIABLE RESONANCE INDUCTION SYSTEM (MPV 3.0L & MX-3 DOHC) under AIR INDUCTION SYSTEMS.

FUEL DELIVERY

Note. For fuel system pressure testing, see BASIC TESTING article.

See FUEL PRESSURE (FUEL INJECTION) under FUEL SYSTEM in BASIC TESTING article.

Fuel Pump Circuit

See FUEL PRESSURE (FUEL INJECTION) under FUEL SYSTEM in BASIC TESTING article.

See FUEL PUMP RELAY (NAVAJO) under RELAYS. Also see FUEL PRESSURE (FUEL INJECTION) under FUEL SYSTEM in BASIC TESTING article.

Inertia Switch (Navajo)

See INERTIA SWITCH under ENGINE SENSORS & SWITCHES. Also see FUEL PRESSURE (FUEL INJECTION) under FUEL SYSTEM in BASIC TESTING article.

Scheme 83

1. Ensure ignition is off. Connect fuel pressure gauge to Schrader valve on fuel rail. Ensure manifold vacuum supply tube is connected to fuel pressure regulator. Start engine, and run it for 10 seconds. Stop engine, and wait 10 seconds. Start engine, and operate it for 10 seconds. Stop engine, and remove pressure regulator vacuum hose. (Scheme 83) Check vacuum port for fuel.
2. If fuel is present, replace fuel pressure regulator and repeat test. If fuel is not present, plug pressure regulator vacuum hose. Observe fuel pressure while driving vehicle and accelerating heavily. If fuel pressure remains at 27-48 psi, go to next step. If fuel pressure does not remain at 27-48 psi, check fuel filter. If filter is okay, replace fuel pump. If filter is dirty, replace filter and recheck system.
3. Remove plug from vacuum hose, and connect hose to pressure regulator. Install vacuum gauge to intake manifold. Start engine, and observe fuel pressure gauge and vacuum gauge readings. Increase engine speed. Fuel pressure gauge reading should increase as vacuum gauge reading decreases and vacuum gauge reading should increase as fuel pressure gauge decreases.
4. If gauges responds as specified, no fault is present in fuel system. Check for other causes of driveability symptoms. If gauges do not respond as specified, turn ignition off. Remove vacuum hose from fuel pressure regulator, and plug hose. Install a vacuum pump to pressure regulator. Start engine, and observe fuel pressure. Apply vacuum.
5. If fuel pressure changes as vacuum is applied, check and repair vacuum system. If fuel pressure does not change as vacuum is applied, replace fuel pressure regulator.

Fuel Pressure Regulator Pressure Leakage (Navajo)

1. Ensure ignition is off. Relieve fuel pressure. See FUEL SYSTEM in BASIC TESTING article. Remove fuel pressure regulator. Check "O" ring, gasket and mounting surfaces for cracks, cuts and other damage.
2. Connect vacuum pump to fuel return tube, and apply 20 in. Hg vacuum. (Scheme 83) If maximum vacuum loss exceeds 10 in. Hg in 10 seconds, replace fuel pressure regulator. If maximum vacuum loss does not exceed 10 in. Hg in 10 seconds, fuel pressure regulator is functioning properly.

Pulsation Damper

Start engine, and operate it at idle. Pulsation damper is located at end of fuel rail. Place finger over pulsation damper and ensure damper pulsates. Replace pulsation damper as necessary.

See FUEL INJECTORS under SOLENOIDS .

Injector Fuel Leakage (Except Navajo)

1. Relieve fuel system pressure. See BASIC TESTING article. Remove air valve or dynamic chamber as necessary. Remove delivery pipe with hoses still connected. Remove fuel injectors. Using wire, secure injectors tightly onto delivery pipe. CAUTION: Ensure injectors are securely tied to delivery pipe. If injectors are not properly secured to delivery pipe, fuel may spray from loose connections.
2. On Miata, MX-3, Protege, 323 and 929, connect a jumper wire between terminals F/P and GND of diagnostic connector located near battery. (Scheme 84)
3. On B2200, B2600i, MPV, MX-6 and 626, install a jumper wire between terminals of Yellow fuel pump check connector. Fuel pump check connector is located on firewall, under windshield wiper motor.
4. Turn ignition on for 10 seconds. Turn ignition off, and clean injector nozzles. On 4-cylinder models, tilt injectors about 60 degrees. On all models, turn ignition on. Ensure no fuel leakage exists at injectors. After one minute, a single drop of fuel is acceptable. If fuel leakage is present, replace faulty injector.

Injector Fuel Leakage (Navajo)

Use fuel injector tester/cleaner to test injector fuel leakage. Testing procedures are provided in instructions included with tester/cleaner from manufacturer.

Scheme 84

Air Valve (B2200, B2600i, MPV 2.6L, MX-6 & 626)

1. Remove air valve from throttle body. Blow air through valve from port "A" and ensure air comes out port "B" when valve is cold. (Scheme 85)
2. Place air valve in water at temperature greater than 176°F (80°C) for one minute. Blow air through valve from port "A". No air should come out of port "B". Replace valve as necessary.

Air Valve (MPV 3.0L & 929)

1. Disconnect air hoses from air valve. Blow air through valve from port "A" and ensure air flows through valve when engine is cold. (Scheme 86)
2. Warm engine to normal operating temperature. Blow air through valve from port "A". Air should not flow through valve. Replace valve as necessary.

Air Valve (MX-3)

Connect jumper wire between diagnostic connector terminals TEN and GRD. Connect tachometer to diagnostic connector terminal IG. (Scheme 87) Start engine. Idle speed should decrease as engine reaches normal operating temperature. Replace valve as necessary.

ISC Valve

Disconnect ISC valve electrical connector. Connect ohmmeter to Idle Speed Control (ISC) valve 2-wire connector. Measure resistance. See ISC RESISTANCE SPECIFICATIONS table. If resistance is not within specification, replace ISC valve.

ISC RESISTANCE SPECIFICATIONS

Scheme 85

Scheme 86

Scheme 87

Air Valve

Remove air valve. Cool air valve to temperature less than 32°F (0°C). Using a drier, heat air valve and verify plunger moves in direction of arrow. (Scheme 88)

Disconnect ISC valve electrical connector. Connect ohmmeter to Idle Speed Control (ISC) valve 2-wire connector. Measure resistance. Resistance should be 11-13 ohms at 68°F (20°C). If resistance is not within specification, replace ISC valve.

Scheme 88

Idle Speed Control (ISC) Solenoid

Solenoid is a by-pass air-type solenoid. Ensure ignition is off. Disconnect ISC solenoid electrical connector. Set DVOM to 200-ohm scale. Measure resistance between ISC solenoid terminals. A diode is located in solenoid; connect DVOM positive test lead to VPWR terminal (Red wire) and negative lead to ISC terminal (White/Light Blue wire). Resistance should be 6-13 ohms. Replace solenoid as necessary.

IGNITION SYSTEM

Note. For basic ignition checks, see BASIC TESTING article.

PINPOINT TESTS (NAVAJO)

Note. Before testing Electronic Distributorless Ignition System (EDIS), ensure all tests in BASIC TESTING and TESTS W/CODES - NAVAJO articles have been performed.

Note. Use EDIS Diagnostic Cable (49-UN01-057) to diagnose system. Cable is equipped with additional circuits and components used in enhancing and modifying signals for testing purposes. If using an aftermarket test cable or DVOM, become familiar with system wiring diagram and system operation. (Scheme 81)and (Scheme 83).

Scheme 89

Scheme 90

Pinpoint Test B (IDM Failure Code 212)

1. With ignition off, connect EDIS diagnostic cable to Breakout Box (BOB) and EDIS module. DO NOT connect VR sensor tee or coil tee. Use EDIS "6" overlay. Connect negative and positive leads of EDIS diagnostic cable to battery. Set EDIS diagnostic cable box switch to 4/6 CYLINDER position. Set DVOM on 20-volt AC scale. Start engine. Measure voltage between IDM DETECTOR (30) and BAT- (7) of diagnostic cable Ignition Diagnostic Monitor (IDM) at BOB. If pulses are present, IDM detector output will be 5-7 volts AC. If AC voltage is 5-7 volts, go to next step. If AC voltage is not 5-7 volts, go to step 3).
2. With ignition off, EDIS module and ECA disconnected, disconnect EDIS module from EDIS module tee, leaving EDIS diagnostic cable connected to vehicle harness connector. Set DVOM on 200-ohm scale. Connect ECA Breakout Box (BOB) to ECA harness connector. Measure resistance between IDM E (41) at BOB and terminal No. 4 at ECA BOB. If resistance is less than 5 ohms, IDM signal at ECA is okay, ECA does not respond to IDM signal. Replace ECA. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article. If resistance is 5 ohms or more, IDM is open. Check connections and/or repair open circuit or replace harness. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
3. With ignition off and IDM circuit disconnected, set DVOM on 20-volt AC scale. Push EDIS IDM button at EDIS diagnostic cable connector to BOB. Start engine, and measure voltage between diagnostic cable IDM DETECTOR (30) and BAT- (7) at BOB. If AC voltage is 5-7 volts, go to next step. If AC voltage is not 5-7 volts, IDM output from EDIS module does not exist. Replace EDIS module. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
4. With ignition off and ECA disconnected, set DVOM on 20-volt AC scale. Crank engine, and measure voltage between diagnostic cable IDM DETECTOR (30) and BAT- (7) at BOB. If voltage is less than 5 volts, go to next step. If voltage is 5 volts or more, ECA is loading IDM signal. Replace ECA. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
5. With ignition off and EDIS module and ECA disconnected, disconnect EDIS module from diagnostic cable module tee, leaving EDIS diagnostic cable connected to vehicle harness connector. Set DVOM on 20-k/ohm scale. Measure resistance between IDM E (41) and BAT- (7) at BOB. If resistance is 10-k/ohms or more, go to next step. If resistance is less than 10-k/ohms, IDM is shorted low. Check connections and/or repair short circuit or replace harness. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
6. With ignition off and EDIS module and ECA disconnected, set DVOM on 20-volt DC scale. With Key On, Engine Off (KOEO), measure voltage between IDM E (41) and BAT- (7) at BOB. If DC voltage is .5 volt or more, IDM is shorted high. Check connections and/or repair short circuit or replace harness. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
7. If voltage is less than .5 volt, IDM is shorted to another wire between EDIS module and ECA. Check connections and/or repair short circuit or replace harness. Remove test equipment and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.

Pinpoint Test C (Lack Of Power Or Poor Fuel Economy Code 213)

1. With ignition off, install EDIS diagnostic cable to BOB and EDIS module. DO NOT connect VR sensor tee or coil tee. Use EDIS "6" overlay. Connect negative and positive leads of EDIS diagnostic cable to battery. Set EDIS diagnostic cable box switch to 4/6 CYLINDER position. Connect timing light (must be EDIS compatible). Start engine, and warm it to normal operating temperature. Push and hold down EDIS diagnostic cable SAW detector button. If timing is 8-12 degrees Before Top Dead Center (BTDC), go to next step. If timing is not 8-12 degrees Before Top Dead Center (BTDC), go to step 8).
2. Release EDIS diagnostic cable SAW detector button. Go to next step if timing is not 15 degrees BTDC. If timing is more than 15 degrees BTDC, EDIS is okay. Check for other causes of driveability symptoms.
3. With ignition off, set DVOM on 20-volt AC scale. Start engine and measure voltage between SAW DETECTOR (21) of EDIS diagnostic cable and BAT- (7) at BOB. If AC voltage is 5 volts or more, go to next step. If AC voltage is less than 5 volts, SAW input to EDIS module is okay and no spark advance is present. Replace EDIS module. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
4. With ignition off and SAW circuit disconnected, set DVOM on 20-volt AC scale. Push and hold down SAW detector button at EDIS diagnostic cable connector to BOB. Start engine, and measure voltage between SAW DETECTOR (21) of EDIS diagnostic cable and BAT- (7) at BOB. If AC voltage is less than 5 volts, go to next step. If AC voltage is 5 volts or more, SAW is shorted in EDIS module. Replace EDIS module. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
5. With ignition off and EDIS module and ECA disconnected, disconnect EDIS module from EDIS module tee, leaving EDIS diagnostic cable connected to vehicle harness connector. Set DVOM on 20-k/ohm scale. Disconnect EDIS diagnostic cable positive lead to battery. Measure resistance between SAW E (45) and BAT- (7) at BOB. If resistance is 10 k/ohms or more, go to next step. If resistance is less than 10 k/ohms, SAW is shorted low. Check connections and/or repair open circuit or replace harness. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
6. With ignition off and EDIS module and ECA disconnected, set DVOM on 20-volt DC scale. With Key On, Engine Off (KOEO), measure voltage between SAW E (45) and BAT- (7) at BOB. If DC voltage is less than .5 volt, go to next step. If DC voltage is .5 volt or more, SAW is shorted high. Check connections and/or repair open circuit or replace harness. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
7. With ignition off and EDIS module and ECA disconnected, set DVOM on 200-ohm scale. Connect ECA Breakout Box (BOB) to ECA harness connector. Measure resistance between SAW E (45) at BOB and terminal No. 36 at ECA BOB. If resistance is less than 5 ohms, SAW is open. Check connections and/or repair open circuit or replace harness. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article. If resistance is 5 ohms or more, SAW is not being transmitted by ECU. Replace ECU. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
8. If VR sensor or trigger wheel is loose, misaligned or damaged, repair or replace as necessary. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article. If VR sensor or trigger wheel is not loose, misaligned or damaged, EDIS module has incorrect output. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.

Pinpoint Test D (No Start Or Coil Failure Code 232)

1. Using spark plug tester, check for spark at all spark plug wires while cranking. If spark was consistent on all spark plug wires (one spark per crankshaft revolution), ignition system is okay. Check for other causes of driveability symptoms. If spark was not consistent on all spark plug wires, check spark plug wires for insulation damage, looseness, shorting and other damage. Remove and check spark plugs for wear, carbon deposits, improper gap and damage. If spark plugs and wires are okay, go to next step. If spark plugs and wires are not okay, repair or replace as necessary. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
2. With ignition off, install EDIS diagnostic cable to BOB. Connect EDIS diagnostic cable negative lead to battery. Set EDIS diagnostic cable box switch to 4/6 CYLINDER position. Install coil tee. Use EDIS "6" overlay. Set DVOM on 20-volt DC scale. With Key On, Engine Off (KOEO), measure voltage between VBAT C (5) and BAT- (7) at BOB. If DC voltage is 10 volts or more, go to next step. If DC voltage is less than 10 volts, VBAT is open. Check connections and/or repair open circuit or replace harness. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
3. With Key On, Engine Off (KOEO), measure voltage between C1C (3) and BAT- (7) at BOB. If DC voltage is 10 volts or more, go to next step. If DC voltage is less than 10 volts, go to step 15).
4. With Key On, Engine Off (KOEO), measure voltage between C2C (6) and BAT- (7) at BOB. If DC voltage is 10 volts or more, go to next step. If DC voltage is less than 10 volts, go to step 17).
5. With Key On, Engine Off (KOEO), measure voltage between C3C (6) and BAT- (7) at BOB. If DC voltage is 10 volts or more, go to next step. If DC voltage is less than 10 volts, go to step 19).
6. With ignition off, connect EDIS module tee to EDIS module and vehicle harness connector. Set DVOM on 20-volt DC scale. With KOEO, measure voltage between C1E (53) and BAT- (7) at BOB. If DC voltage is 10 volts or more, go to next step. If DC voltage is less than 10 volts, C1 is open. Check connections and/or repair open circuit or replace harness. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
7. With KOEO, measure voltage between C2E (55) and BAT- (7) at BOB. If DC voltage is 10 volts or more, go to next step. If DC voltage is less than 10 volts, C2 is open. Check connections and/or repair open circuit or replace harness. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
8. With KOEO, measure voltage between C3E (54) and BAT- (7) at BOB. If DC voltage is 10 volts or more, go to next step. If DC voltage is less than 10 volts, C3 is open. Check connections and/or repair open circuit or replace harness. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
9. With ignition off and coil disconnected, disconnect coil pack from coil tee. Leave EDIS diagnostic cable connected to vehicle harness connector. Set DVOM on 20-volt DC scale. With KOEO, measure voltage between C1C (3) and BAT- (7) at BOB. If voltage is less than .5 volt, go to next step. If voltage is .5 volt or more, go to step 21).
10. With KOEO and coil disconnected, measure voltage at BOB between C2C (6) and BAT- (7). If DC voltage is less than .5 volt, go to next step. If DC voltage is .5 volt or more, go to step 22).
11. With KOEO and coil disconnected, measure voltage at BOB between C3C (10) and BAT- (7). If DC voltage is less than 10.5 volts, go to next step. If DC voltage is 10.5 volts or more, go to step 23).
12. With coil disconnected, connect EDIS diagnostic cable positive lead to battery. Connect incandescent test light between C1C (3) and BAT+ (1). Crank engine. If test light blinks consistently and brightly (one blink per engine revolution), go to next step. If test light does not blink consistently and brightly, C1 is open in EDIS module. Replace EDIS module. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
13. With coil disconnected, connect incandescent test light between C2C (6) and BAT+ (1). Crank engine. If test light blinks consistently and brightly (one blink per engine revolution), go to next step. If test light does not blink consistently and brightly, C2 is open in EDIS module. Replace EDIS module. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
14. With coil disconnected, connect incandescent test light between C3C (10) and BAT+ (1). Crank engine. If test light blinks consistently and brightly (one blink per engine revolution), input to coil pack is okay and no high voltage output is present. Replace coil pack. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article. If test light does not blink consistently and brightly, C3 is open in EDIS module. Replace EDIS module. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
15. With ignition off and coil disconnected, set DVOM on 20-k/ohm scale. Disconnect coil from coil tee, leave EDIS diagnostic cable connected to vehicle harness connector. Measure voltage at BOB between C1C (3) and BAT- (7). If resistance is less than 2 k/ohms, go to next step. If resistance is 2 k/ohms or more, C1 is open in coil. Replace coil pack. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
16. With ignition off and EDIS module and coil disconnected, disconnect EDIS module from vehicle harness connector. Set DVOM on 20-k/ohm scale. Measure voltage between C1C (3) and BAT- (7) at BOB. If resistance is less than 10-k/ohms, C1 is shorted low. Check connections and/or repair open circuit or replace harness. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article. If resistance is 10-k/ohms or more, C1 is shorted low. Replace EDIS module. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
17. With ignition off and coil disconnected, set DVOM on 20-k/ohm scale. Disconnect coil from coil tee, leave EDIS diagnostic cable connected to vehicle harness connector. Measure resistance between C2C (6) and BAT- (7) at BOB. If resistance is less than 2 k/ohms, go to next step. If resistance is 2 k/ohms or more, C2 is open in coil. Replace coil pack. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
18. With ignition off and EDIS module and coil disconnected, disconnect EDIS module from vehicle harness connector. Set DVOM on 20-k/ohm scale. Measure resistance between C2C (6) and BAT- (7) at BOB. If resistance is less than 10-k/ohms, C2 is shorted low. Check connections and/or repair open circuit or replace harness. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article. If resistance is 10-k/ohms or more, C2 is shorted low. Replace EDIS module. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
19. With ignition off and coil disconnected, set DVOM on 20-k/ohm scale. Disconnect coil from coil tee, leave EDIS diagnostic cable connected to vehicle harness connector. Measure resistance between C3C (10) and BAT- (7) at BOB. If resistance is less than 2-k/ohms, go to next step. If resistance is 2-k/ohms or more, C3 is open in coil. Replace coil pack. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
20. With ignition off and EDIS module and coil disconnected, disconnect EDIS module from vehicle harness connector. Set DVOM on 20-k/ohm scale. Measure resistance between C3C (10) and BAT- (7) at BOB. If resistance is less than 10-k/ohms, C3 is shorted low. Check connections and/or repair open circuit or replace harness. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article. If resistance is 10-k/ohms or more, C3 is shorted low. Replace EDIS module. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
21. With ignition off and EDIS module and coil disconnected, disconnect EDIS module from EDIS module tee. Leave EDIS diagnostic cable connected to vehicle harness connector. Set DVOM on 20-volt DC scale. With KOEO, measure voltage between C1C (3) and BAT- (7) at BOB. If DC voltage is .5 volt or more, C1 is shorted high. Check connections and/or repair open circuit or replace harness. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article. If DC voltage is less than .5 volt, C1 is shorted high. Replace EDIS module. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
22. With ignition off and EDIS module and coil disconnected, disconnect EDIS module from EDIS module tee. Leave EDIS diagnostic cable connected to vehicle harness connector. Set DVOM on 20-volt DC scale. With KOEO, measure voltage between C2C (6) and BAT- (7) at BOB. If DC voltage is .5 volt or more, C2 is shorted high. Check connections and/or repair open circuit or replace harness. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article. If DC voltage is less than .5 volt, C2 is shorted high. Replace EDIS module. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.
23. With ignition off and EDIS module and coil disconnected, disconnect EDIS module from EDIS module tee. Leave EDIS diagnostic cable connected to vehicle harness connector. Set DVOM on 20-volt DC scale. With KOEO, measure voltage between C3C (10) and BAT- (7) at BOB. If DC voltage is .5 volt or more, C3 is shorted high. Check connections and/or repair open circuit or replace harness. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article. If DC voltage is less than .5 volt, C3 is shorted high. Replace EDIS module. Remove test equipment, and reconnect all components. Clear continuous memory codes, and rerun QUICK TEST. See QUICK TEST in TESTS W/CODES - NAVAJO article.

DECELERATION CONTROL SYSTEM

Note. Deceleration control system is a function of dashpot and ECU. Dashpot prevents sudden closure of throttle valve. ECU controls fuel cut-off during deceleration. For adjustment and testing, see ADJUSTMENTS article.

System Check (MX-3 DOHC & 929)

1. Connect Engine Signal Monitor (49-9200-162) to ECU. Start engine. Increase engine speed, and check voltage at ECU terminals 3O and 3P while engine is cold. See PIN VOLTAGE CHART S article. Voltage should be 12 volts.
2. Warm engine to operating temperature, and operate it at idle. Increase engine speed, and ensure engine signal monitor Green and Red lights flash at ECU terminals 3O and 3P.
3. Disconnect EGR solenoid valve (vacuum side) electrical connector. Apply 12 volts and a ground to solenoid valve. Ensure engine runs rough or stalls at idle. Test EGR components as necessary. (Scheme 91)or (Scheme 95).

System Check (MX-6 & 626)

Check all connectors and hose routings. Check for cracks, leakage and restrictions, and repair as necessary. Start engine, and ensure diaphragm of EGR control valve does not move while engine is cold. Warm engine to operating temperature and operate at idle. Increase engine speed, and ensure diaphragm of EGR control valve moves upward. If no movement is detected, test EGR components as necessary. (Scheme 92)or (Scheme 94).

Scheme 91

Scheme 92

Scheme 93

Scheme 94

EGR Control Valve

Bring engine to normal operating temperature and operate at idle. Disconnect and plug vacuum hose at EGR control valve. Engine should run smoothly. Connect vacuum pump to EGR control valve, and apply 1.6-2.4 in. Hg vacuum. Engine should run rough or stall. If engine does not operate as specified, clean or replace EGR control valve.

EGR Modulator Valve (MX-6 & 626 Non-Turbo)

Remove EGR modulator valve. Plug port No. 1, and connect a vacuum pump to port No. 3. (Scheme 95) Blow into exhaust gas port. Operate vacuum pump and verify vacuum is held. Release exhaust port and verify vacuum is released.

Scheme 95

Note. EGR position sensor testing for 929 is not available.

EGR Position Sensor (MX-3 DOHC)

1. Disconnect ECU electrical connector. Connect Engine Signal Monitor (49-9200-162) to ECU. Connect vacuum pump to EGR control valve. Turn ignition on. Check voltage at ECU connector terminals. See EGR POSITION SENSOR VOLTAGE (MX-3 DOHC) table.
2. If voltage is not correct at terminals "A" and "B", check wiring harness and connection at ECU connector terminals 2I and 3D. If voltage is not correct at terminal "C", check sensor resistance, harness and ECU connector terminal 2F.
3. Disconnect EGR position sensor electrical connector. Connect ohmmeter to EGR position sensor. Disconnect vacuum hose from EGR control valve. Connect vacuum pump to EGR control valve.
4. Check sensor resistance between indicated terminals. See «EGR POSITION SENSOR RESISTANCE»(/mazda/navajo/i-1990-1994/remont/testing-diagnostics/#engine-controls-systemcomponent-tests-efi) table. If resistance is not within specifications, replace sensor.

EGR Position Sensor (MX-6 & 626)

1. Disconnect EGR position sensor electrical connector. Connect Adapter Harness (49-G018-901) between EGR position sensor and wiring harness. Disconnect vacuum hose from EGR control valve. Connect vacuum pump to EGR control valve.
2. Turn ignition on. Check voltage at adapter harness connector terminals. (Scheme 96) See «EGR POSITION SENSOR VOLTAGE (MX-6 & 626)»(/mazda/navajo/i-1990-1994/remont/testing-diagnostics/#engine-controls-systemcomponent-tests-efi) table.
3. If voltage is not correct at terminals "A" and "B", check wiring harness and connection at ECU connector terminals 2A and 2C. If voltage is not correct at terminal "C", check sensor resistance, wiring harness and ECU connector terminal 2F.
4. Check sensor resistance between indicated terminals. See «EGR POSITION SENSOR RESISTANCE»(/mazda/navajo/i-1990-1994/remont/testing-diagnostics/#engine-controls-systemcomponent-tests-efi) table. If resistance is not within specifications, replace sensor.

EGR POSITION SENSOR VOLTAGE

EGR POSITION SENSOR VOLTAGE

EGR POSITION SENSOR RESISTANCE

Scheme 96

EGR Solenoid Valve (MX-3 DOHC, MX-6 Turbo, 626 Turbo & 929)

1. Disconnect vacuum hoses. Blow air through vacuum hose. Ensure air does not flow. Disconnect EGR solenoid valve (vacuum side) electrical connector. Apply 12 volts and a ground to solenoid valve (vacuum side) terminals. (Scheme 97) Blow air through vacuum hose and ensure air flows.
2. Disconnect EGR solenoid valve (vent side) electrical connector. Apply 12 volts and a ground to solenoid valve (vent side) terminals. (Scheme 97) Blow air through vacuum hose and ensure air does not flow. Replace solenoid valves as necessary.

Note. The following figure is Courtesy of Mazda Motors Corp.

Testing EGR Solenoid Valve (MX-3 DOHC Shown; MX-6/626 Turbo & 929 Similar). Scheme 97

EGR Solenoid Valve (MX-6 & 626 Non-Turbo)

1. Disconnect vacuum hose from solenoid valve. Blow air through port "A". Ensure air flows through port "B". (Scheme 98)
2. Disconnect solenoid valve electrical connector. Connect 12 volts and a ground to solenoid valve terminals. Blow air through port "A". Ensure air flows through air filter.

Scheme 98

Vacuum Chamber (MX-6 & 626 Turbo)

Disconnect vacuum hoses from vacuum chamber. Connect vacuum pump to port "A". (Scheme 99) Apply vacuum and verify no vacuum is held. Disconnect vacuum pump from port "A", and connect it to port "B". Apply vacuum and verify vacuum is held. Replace vacuum chamber as necessary.

Scheme 99

System Inspection

Purge system operation takes place when vehicle is accelerating in gear (off idle), engine is at operating temperature and oxygen sensor is functioning normally. (Scheme 100)

Scheme 100

Charcoal Canister

Check for loose, missing, cracked and broken connections and parts. Repair or replace as necessary. No liquid should exist in canister.

Note direction of valve installation. Remove check valve. Blow air into both ends of valve. Air should flow through valve from charcoal canister side but should not flow from airflow meter side (beveled end). Replace valve as necessary.

Check & Cut Valve

1. Remove check and cut valve. Connect pressure gauge with "T" fitting to check and cut valve nipple leading to fuel tank. Cap opposite nipple. (Scheme 101)
2. Blow air through port "A". On MX-3, Protege and 323, valve should open when pressure gauge indicates 0.92-1.20 psi (.065-.085 kg/cm 2 ). On all other models, valve should open when pressure gauge reads 0.78-1.00 psi (.06-.07 kg/cm 2 ). Remove "T" fitting and pressure gauge. Connect "T" fitting to bottom of valve. Blow air through port "B". When pressure gauge reads.14-.71 psi (.01-.05 kg/cm 2 ), valve should open. Replace cut and check valve as necessary.

Scheme 101

Fuel Vapor Valve

Note direction of valve installation. Remove fuel vapor valve. Blow air into upper port of valve. Air should flow through valve from lower port. Blow air through lower port of valve. Air should not flow from upper port. Replace valve as necessary.

Purge Control Solenoid Valve

1. Warm engine to normal operating temperature and operate at idle. Disconnect vacuum hoses from solenoid valve. Ensure vacuum is not present at solenoid valve. Disconnect vacuum hoses from charcoal canister.
2. Ensure air does not flow through solenoid valve. If air flows through solenoid valve, disconnect solenoid valve connector. Connect 12 volts and a ground to solenoid valve terminals. (Scheme 102) Blow air through check valve. Air should flow through valve. Replace valve as necessary.

Separator

Check for loose, missing, cracked and broken connections and parts. Repair or replace as necessary. No liquid should exist in canister.

Scheme 102

Canister Purge (CANP) Solenoid

1. Disconnect CANP solenoid harness connector. Set DVOM to 200-ohm scale. Measure resistance across CANP solenoid terminals. Resistance should be 40-90 ohms. If resistance is not as specified, replace CANP solenoid.
2. Disconnect vacuum hose at CANP solenoid on manifold vacuum side. Apply 16 in. Hg vacuum to manifold vacuum side of solenoid. CANP solenoid should hold vacuum for 20 seconds.
3. Faults in CANP solenoid or circuit should set a service code. See QUICK TEST in TESTS W/CODES - NAVAJO article. If no service code has been set, see CIRCUIT TEST KD in TESTS W/CODES - NAVAJO article for additional solenoid and circuit testing.

EVAP Canister

Check for loose, missing, cracked and broken connections and parts. Repair or replace as necessary. No liquid should exist in canister.

1. Warm engine to normal operating temperature, and operate it at idle. Disconnect Positive Crankcase Ventilation (PCV) valve, together with vent hose, from valve cover. Block PCV valve opening and check for vacuum. If no vacuum is felt, check for collapsed line and blockage.
2. Note direction of valve installation. Remove PCV valve. Blow air into upper port of valve. Air should flow through valve from lower port. Blow air through lower port of valve. Air should not flow from upper port. Replace valve as necessary.

Air Cleaner Temperature Sensor

With temperature sensor less than 75°F (24°C), apply 8 in. Hg vacuum to source port. Duct door should close. If door does not close, replace sensor. Sensor will bleed off vacuum to allow duct door to open and let in fresh air at specific temperatures. See AIR CLEANER TEMPERATURE SENSOR OPENING SPECIFICATIONS table.

AIR CLEANER TEMPERATURE SENSOR OPENING SPECIFICATIONS

Air Control Door

When 8 in. Hg vacuum or more is applied to vacuum motor, door should stay in appropriate position for as long as vacuum is applied. If vacuum bleeds off and door returns to rest position, replace vacuum motor.

A/C Cut-Off Control System B2200, B2600i, Miata, MPV, MX-3, 929

1. Turn A/C, blower and ignition on. DO NOT start engine. Shift transmission into a drive gear. Open throttle fully. Listen for A/C clutch disengaging and re-engaging after a few seconds. See «A/C CUT-OFF TIME SPECIFICATIONS»(/mazda/navajo/i-1990-1994/remont/testing-diagnostics/#engine-controls-systemcomponent-tests-efi) table.
2. If system does not function as specified, check operation of related switches, sensors and relays. See PIN VOLTAGE CHART S article.

A/C CUT-OFF TIME SPECIFICATIONS

Wide Open Throttle A/C Cut-Out (WAC) & A/C Demand Switch (Navajo)

Faults in WAC & A/C demand switch or circuit should set a service code. See QUICK TEST in TESTS W/CODES - NAVAJO article. If no service code has been set, see CIRCUIT TEST KM in TESTS W/CODES - NAVAJO article for testing.

See also:
• VRIS RPM SPECIFICATIONS