Engine Controls - System/component Tests - Efi: Other Mazda MX-5 NA

Air By-Pass Valve

Remove air by-pass valve. Connect vacuum pump to port "A" of valve. (Scheme 24) Apply 10 in. Hg 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 24

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.

Charge Relief Valve

Remove charge relief valve. Connect vacuum pump to port "A" of valve. (Scheme 24) Apply 8 in. Hg to port "A", and blow air into port "B". Replace charge relief valve if air does not flow from port "B" to port "C".

Intercooler

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

Solenoid Valves (Turbo Precontrol & Wastegate Control)

1. Remove pressure chamber from intake manifold. Disconnect vacuum hoses. Disconnect solenoid valve connector and solenoid valves. Blow air through air tube and verify air does not flow. If air flows, replace solenoid valve.
2. Apply 12 volts and ground to solenoid valve connector. (Scheme 25) Blow air through air tube and verify air passes freely. If air does not pass freely with 12 volts applied, replace solenoid valve.

Scheme 25

Charge Actuator

1. Ensure engine is cool. Remove hose connected to actuator. Connect vacuum pump to charge actuator. (Scheme 26)
2. Apply 2 in. Hg to charge actuator. Ensure actuator rod moves when vacuum is applied. If actuator rod does not move, replace charge actuator.

Scheme 26

Control Actuator

1. Ensure engine is cool. Remove hose connected to actuator. Connect air pressure source to pressure gauge. (Scheme 27) Apply air pressure to actuator. CAUTION: DO NOT allow pressure to exceed 11 psi (.8 kg/cm 2 ).
2. Apply 7 psi (0.5 kg/cm 2 ) of compressed air. Ensure actuator rod moves when air pressure is applied. If actuator rod does not move, replace control actuator.

Scheme 27

Precontrol Actuator

1. Ensure engine is cool. Remove hose connected to actuator. Connect air pressure source to pressure gauge. (Scheme 28) Apply air pressure to actuator. CAUTION: DO NOT allow pressure to exceed 14 psi (1.0 kg/cm 2 ).
2. Apply 10-14 psi (0.7-1.0 kg/cm 2 ) of compressed air. Ensure actuator rod moves when air pressure is applied. If actuator rod does not move, replace precontrol actuator.

Scheme 28

Wastegate Actuator

1. Ensure engine is cool. Remove hose connected to actuator. Connect air pressure source to pressure gauge. (Scheme 29) Apply air pressure to actuator. CAUTION: DO NOT allow pressure to exceed 14 psi (1.0 kg/cm 2 ).
2. Apply 10-14 psi (0.7-1.0 kg/cm 2 ) of compressed air. Ensure actuator rod moves when air pressure is applied. If actuator rod does not move, replace wastegate actuator.

Scheme 29

System Check

1. With engine cold, start engine. Ensure actuator rod is pulled in. (Scheme 30) If rod is not pulled in, check operation of coolant thermosensor and solenoid valve. Also check and repair any vacuum leaks. Apply vacuum to double throttle actuator. If rod does not pull in, replace double throttle actuator.
2. Warm engine until engine coolant temperature is greater than 176°F (80°C). Ensure actuator rod extends. If rod does not extend, check operation of coolant thermosensor and solenoid valve.

View Of Double Throttle Control System (RX7). Scheme 30

System Check (Protege DOHC)

Connect tachometer to IG terminal of diagnostic connector. (Scheme 31) Start engine, and operate it at idle. Ensure shutter valve actuator rod is retracted at idle. (Scheme 32) Gradually increase engine speed to 5000 RPM and ensure actuator rod extends. If necessary, check Variable Inertia Charging System (VICS) components.

Scheme 31

Scheme 32

System Check (929)

Start engine, and operate it at idle. Ensure shutter valve actuator rod is retracted at idle. (Scheme 32) 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.

Solenoid Valve

Remove solenoid valve. Blow air through port "B". (Scheme 33) Ensure air flows from valve air filter. Connect 12 volts and a ground to solenoid valve terminals. Blow air through valve port "B", and ensure air flows from port "A". Replace solenoid valve as necessary.

Scheme 33

Shutter Valve Actuator (Protege DOHC)

Disconnect vacuum hose from shutter valve actuator. (Scheme 32) 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 32) 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 34) Replace dynamic chamber if valve is stuck or does not rotate smoothly.

Scheme 34

Vacuum Chamber (Protege DOHC)

Remove vacuum chamber. Blow air through port "A" and verify flow through port "B". (Scheme 35) 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 35

System Check (MX-3 DOHC, MX-6 2.5L & 626 2.5L)

Connect tachometer to IG terminal of diagnostic connector. (Scheme 31) 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 36) If necessary, check Variable Resonance Induction System (VRIS) components.

VRIS RPM SPECIFICATIONS

Scheme 36

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 32) Remove shutter valve actuator.
2. Apply vacuum to shutter valve actuator. (Scheme 37) 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 Actuators (MX-3 DOHC, MX-6 2.5L & 626 2.5L)

Disconnect vacuum hose from shutter valve actuators No. 1 and 2. (Scheme 32)or (Scheme 36). Connect vacuum pump to actuator. (Scheme 37) 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 33) Ensure air flows from valve air filter. Disconnect solenoid valve connector, and connect 12 volts and a ground to solenoid valve terminals. 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 37

Ground Circuits

1. Locate Powertrain Control Module (PCM) behind right kick panel. Using a DVOM, check for continuity to ground on PCM terminals No. 40 and 60. (Scheme 38) 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 PCM 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 article in the ENGINE PERFORMANCE section.

Scheme 38

POWERTRAIN CONTROL MODULE (EXCEPT NAVAJO)

1. Locate Electronic Control Unit (ECU) or Powertrain Control Module (PCME). See ECU/PCME LOCATION table. Connect Engine Signal Monitor (49-9200-162) to ECU/PCME. (Scheme 39) Check voltage at each terminal of ECU/PCME. If input and output component voltage readings are not as specified, check faulty component. See «PIN VOLTAGE CHARTS»(ref-18276) article, appropriate information in «TESTS W/CODES»(ref-18270) article in the ENGINE PERFORMANCE section, and testing for appropriate component in this article.
2. If input and output component voltages are as specified and ECU/PCME voltage is incorrect, replace ECU/PCME.

ECU/PCME LOCATION

Scheme 39

A/C SWITCH

See A/C CUT-OFF CONTROL SYSTEM (B2200, B2600i, MIATA, MPV, MX-3, MX-6, RX7, 626 & 929) under A/C CLUTCH under MISCELLANEOUS CONTROLS.

MX-6 2.0L & 626 2.0L

Remove sensor from air cleaner housing. With sensor disconnected, measure resistance between sensor terminals. See ACT SENSOR RESISTANCE table. Replace sensor as necessary.

Navajo

Locate sensor on top left side of engine, behind idle air by-pass valve. With sensor disconnected, measure resistance between sensor terminals. See ACT SENSOR RESISTANCE table. Replace sensor as necessary.

ACT SENSOR RESISTANCE

Miata, MPV 3.0L, MX-3, MX-6 2.5L, Protege, 323, 626 2.5L & 929

Inspect airflow meter for damage, and ensure measuring plate or cone moves smoothly. (Scheme 40), (Scheme 41) or (Scheme 42). 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 40

Scheme 41

Scheme 42

ATMOSPHERIC PRESSURE SENSOR

See PIN VOLTAGE CHARTS article. On MX-6 2.0L A/T and 626 2.0L A/T, see TROUBLE CODE CHART 14 in TESTS W/O CODES article.

RX7

1. Warm engine to operating temperature. Turn all accessories off. Connect positive lead of voltmeter to BARO sensor terminal "A" and negative lead to terminal "B".
2. With engine at idle, voltmeter should read 1.3-1.6 volts. Disconnect hose from BARO sensor and plug. (Scheme 43) Voltmeter should read 2.38-2.78 volts.
3. Connect a vacuum pump to BARO sensor, and apply 29 in. Hg. Voltmeter should read 4.35-4.65 volts. If voltmeter readings do not test as described, replace BARO sensor.

Scheme 43

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.

Camshaft Position Sensor (CMP) is a Hall-Effect switch, located on top rear of engine. See CIRCUIT TEST DR in TESTS W/CODES article in the ENGINE PERFORMANCE section.

MPV, RX7 & 929

CPU acts as an electrical load sensor. On MPV, remove CPU from behind left side of instrument panel. On RX7, remove CPU from right side kick panel above ECU. 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. If voltages are incorrect, check appropriate circuit. If circuits are okay but voltages are still incorrect, replace CPU.

Scheme 44

Scheme 45

Scheme 46

Scheme 47

Scheme 48

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 table. Replace thermoswitch as necessary.

COLD START THERMOSWITCH RESISTANCE

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.

CRANK ANGLE SENSOR

See IGNITION CHECKS in BASIC TESTING article.

ENGINE COOLANT TEMPERATURE (ECT) SENSOR

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

ECT SENSOR RESISTANCE

ECT SENSOR RESISTANCE

ECT SENSOR RESISTANCE

MX-3 DOHC, MX-6 2.5L, RX7, 626 2.5L & 929

See EXHAUST GAS RECIRCULATION (EGR) (MX-3 DOHC, MX-6, RX7, 626 & 929) under EMISSION SYSTEMS & SUB-SYSTEMS .

1. Remove circuit opening relay. Start engine and allow system to fuel pressure to bleed down. Install circuit opening relay. Remove upper intake manifold. Remove fuel temperature sensor from fuel rail.
2. Place sensor and thermometer in container of water. Connect ohmmeter to sensor terminals. Heat water. Note resistance at specified temperatures. See «FUEL TEMPERATURE SENSOR RESISTANCE»(ref-18275-S30049035112000123000000) table. Replace sensor as necessary.

FUEL TEMPERATURE SENSOR RESISTANCE

1. Remove right front seat. Lift floor mat and remove heat hazard sensor. Wrap sensor and a thermometer in aluminum foil. Place foil in a pot of oil. Connect a battery and 12-volt test light in series, to sensor terminals.
2. Heat oil to 221-239°F (105-115°C). Test light should light when sensor reaches specified temperature. If test light does not light, replace heat hazard sensor.

MPV 3.0L, MX-6, 626 & 929

With engine at room temperature, disconnect HO2S connector. Measure resistance across terminals "A" and "B" on MX-6 2.0L and 626 2.0L, or terminals "C" and "D" on all others. (Scheme 49) See HO2S RESISTANCE table. Replace HO2S as necessary. Also see PIN VOLTAGE CHARTS article.

HO2S RESISTANCE

Scheme 49

HO2S 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 article. If no service code has been set, see CIRCUIT TEST H in TESTS W/CODES article for additional sensor specifications and circuit testing procedures. Ensure following conditions do not exist

1. Moisture inside sensor/harness connector.
2. HO2S coated with contaminants.
3. Sensor circuit open or shorted to ground.

Miata, MPV 3.0L, MX-3, MX-6 2.5L, Protege, RX7, 323, 626 2.5L & 929

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

Scheme 50

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

INHIBITOR SWITCH (A/T)

Disconnect inhibitor switch electrical connector. Connect ohmmeter to indicated switch terminals. (Scheme 51)- (Scheme 57). 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 51

Scheme 52

Scheme 53

Scheme 54

Scheme 55

Scheme 56

Scheme 57

Remove sensor from under upper intake manifold. Using a heat light, ohmmeter and thermometer, measure resistance of sensor at various temperatures. (Scheme 60) 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 60) See INTAKE AIR THERMOSENSOR RESISTANCE table. Replace sensor as necessary.

INTAKE AIR THERMOSENSOR RESISTANCE

Scheme 58

Scheme 59

Scheme 60

KNOCK SENSOR

See PIN VOLTAGE CHARTS article.

MASS AIRFLOW (MAF) SENSOR (NAVAJO)

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

MILEAGE SWITCH (RX7)

See PIN VOLTAGE CHARTS article.

Except Navajo (M/T)

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.

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.

1. Warm engine to operating temperature. Operate engine at idle. Disconnect O2 sensor electrical connector. Connect voltmeter between O2 sensor connector terminals "C" and "D" on MX-6 2.5L and 626 2.5L, or terminals "A" and "B" on all others. (Scheme 61)
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 61

POWER STEERING PRESSURE SWITCH (PSPS)

Disconnect power steering pressure switch electrical connector. Connect ohmmeter to PSPS 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 appropriate article

1. «BASIC TESTING»(ref-18260)
2. «TESTS W/CODES»(ref-18270)

Except Navajo & 929

See PIN VOLTAGE CHARTS article.

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

1. Connect positive lead of voltmeter to Green/Red wire of combination meter. Connect negative lead of voltmeter to ground. Raise and support rear wheels. Start engine. Engage Drive and rotate rear wheels. Voltmeter should show 3-4 volts. If not, stop engine.
2. Disconnect connector from combination meter. Measure resistance across Blue/White and Blue/Yellow wires (terminals 1K and 1L). Resistance should be 290 ohms. If resistance is not 290 ohms, check wiring to transmission. If wiring is okay, check resistance of VSS at transmission.
3. If resistance of VSS is not 290 ohms, replace VSS. If resistance of VSS is 290 ohms, replace VSS buffer in instrument cluster.

RX7 (M/T)

1. Disconnect 1-2 switch connector at transmission. Check continuity across White and Yellow wires. In first gear, no continuity should exist. In all other gears, continuity should be present. If switch does not test as described, replace 1-2 switch.
2. Check continuity across Red and Blue wires. In second gear, continuity should be present. In all other gears, no continuity should exist. If switch does not test as described, replace 1-2 switch.

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 62) Ground terminal "D". Check continuity between terminals "A" and "B". Continuity should exists with power applied. Continuity should not exist with power removed.

Note. For additional testing, see CIRCUIT TEST J in TESTS W/CODES article in the ENGINE PERFORMANCE section.

Scheme 62

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 63), (Scheme 64) or (Scheme 65).
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)

Remove relay from vehicle. Connect battery voltage to terminal "C". (Scheme 62) 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 testing, see CIRCUIT TEST B in TESTS W/CODES article in the ENGINE PERFORMANCE section.

Scheme 63

Scheme 64

Scheme 65

SOLENOIDS

Note. All solenoids (used on all vehicles except Navajo) operate the same way. (Scheme 66)to locate specific solenoids used on RX7.

Scheme 66

Backpressure EGR Vacuum Regulator Valve (Navajo)

See EXHAUST GAS RECIRCULATION (EGR) (NAVAJO - CALIFORNIA) under EMISSION SYSTEMS & SUB-SYSTEMS .

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.

Double Throttle Control Solenoid (RX7)

Disconnect vacuum hose from double throttle control solenoid. Blow air through solenoid port "A". (Scheme 67) 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.

EGR Solenoid (MX-3 DOHC, MX-6, RX7, 626 & 929)

See EXHAUST GAS RECIRCULATION (EGR) (MX-3 DOHC, MX-6, RX7, 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 67) 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 67

Purge Control Solenoid

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

Air Injection Solenoid (RX7)

See AIR INJECTION (RX7) under EMISSION SYSTEMS & SUB-SYSTEMS.

Turbocharger Solenoid (RX7)

See TURBOCHARGER (RX7) 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, MX-6 2.5L & 626 2.5L)

See VARIABLE RESONANCE INDUCTION SYSTEM (MPV 3.0L, MX-3 DOHC, MX-6 2.5L & 626 2.5L) 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 under RELAYS & SOLENOIDS. Also see FUEL PRESSURE (FUEL INJECTION) under FUEL SYSTEM in BASIC TESTING article.

Inertia Fuel Shutoff (IFS) Switch (Navajo)

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

Fuel Pressure Regulator (Except Navajo)

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

Scheme 68

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 68) 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»(ref-18260) 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 68) 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 (Navajo & RX7)

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

Pressure Regulator Control (Except Miata, Navajo & 929)

1. Engine must be at or near operating temperature. Turn engine off. Disconnect vacuum hose at fuel pressure regulator and connect a vacuum gauge to hose.
2. Without touching throttle, start engine. Observe vacuum gauge. Vacuum should not exist. If vacuum is present, check pressure regulator control solenoid and related circuits. If no vacuum exists, count seconds until vacuum gauge shows intake manifold vacuum. See PRESSURE REGULATOR SPECIFICATIONS table.
3. If vacuum gauge shows intake manifold vacuum after specified amount of time, system is okay. (Scheme 69) If intake manifold vacuum is not present, check vacuum source, pressure regulator control solenoid and related circuits.

See PRESSURE REGULATOR CONTROL SOLENOID (EXCEPT NAVAJO) under SOLENOIDS under RELAYS & SOLENOIDS.

Scheme 69

PRESSURE REGULATOR SPECIFICATION

See FUEL INJECTORS under SOLENOIDS under RELAYS & SOLENOIDS.

Injector Fuel Leakage (Except Navajo)

1. Relieve fuel system pressure. See «BASIC TESTING»(ref-18260) 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, MX-6, Protege, RX7, 323, 626 and 929, connect a jumper wire between terminals F/P and GND of diagnostic connector located near battery. (Scheme 70)
3. On B2200, B2600i and MPV, 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 70

Air Valve (B2200, B2600i, MPV 2.6L, MX-6 2.0L & 626 2.0L)

1. Remove air valve from throttle body. Blow air through valve from port "A" and ensure air comes out of port "B" when valve is cold. (Scheme 71)
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 72)
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 System (MX-3, MX-6 & 626)

Connect jumper wire between diagnostic connector terminals TEN and GND. Connect tachometer to diagnostic connector terminal IG. (Scheme 73) 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 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 71

Scheme 72

Scheme 73

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 74)

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 74

Idle Speed Control (ISC) Solenoid

1. Solenoid is a by-pass air-type solenoid. Disconnect coolant hoses. Make sure coolant flows through ISC and air valve is open at room temperature.
2. 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.

1. Make sure fast idle cam has released throttle lever. (Scheme 75) Disconnect ISC valve electrical connector. Connect ohmmeter to ISC valve 2-wire connector. (Scheme 76) Measure resistance. Resistance should be 10.7-12.3 ohms at 68°F (20°C). If resistance is not within specification, replace ISC valve.
2. With engine idling at operating temperature, disconnect ISC valve electrical connector. Engine speed should increase to 1000-1500 RPM. If engine speed does not increase, replace ISC valve.

Accelerated Warm-Up System (AWS) Valve

Make sure fast idle cam has released throttle lever. (Scheme 75) Disconnect AWS valve electrical connector. Connect ohmmeter to AWS valve 2-wire connector. (Scheme 77) Measure resistance. Resistance should be 9.3-11.3 ohms at 68°F (20°C). If resistance is not within specification, replace AWS valve.

Scheme 75

Scheme 76

Scheme 77

PINPOINT TESTS (NAVAJO)

Note. Before testing Electronic Distributorless Ignition System (EDIS), ensure all tests in BASIC TESTING and TESTS W/CODES articles have been performed. In following tests, Electronic Distributorless Ignition System (EDIS) or Ignition Control Module (ICM) may be used to describe ignition system.

Note. Use EDIS Diagnostic Cable (49-UN01-057) to diagnose system. Cable is equipped with additional circuits and components to enhance and modify signals for testing purposes. If using an aftermarket test cable or DVOM, become familiar with system wiring diagram and system operation. (Scheme 78)and (Scheme 79).

Scheme 78

Scheme 79

Air Control Valve

1. Remove air control valve. Apply about 15 in. Hg to switching valve port. (Scheme 81) Ensure switching valve opens. If switching valve does not open, replace air control valve.
2. Apply about 19 in. Hg to air relief valve port. (Scheme 82) Ensure air relief valve opens. If air relief valve does not open, replace air control valve.

Scheme 80

Scheme 81

Scheme 82

Air Pump

1. Install a "T" fitting into hose between air pump and air control valve. Connect a pressure gauge to fitting. Start engine. Pressure gauge should show at least .7 psi (.05 kg/cm 2 ) coming from air pump. If pressure is less than specified, replace air pump.
2. Increase engine speed to 3250 RPM and verify air pump magnetic clutch disengages. If air pump magnetic clutch does not disengage, disconnect electrical connector from air pump. Air pump magnetic clutch should disengage.
3. If air pump is still engaged, replace air pump. If air pump magnetic clutch disengaged when electrical connector was disconnected, check air pump relay (located in front engine compartment relay box).

Air Relief Valve

1. Warm engine to normal operating temperature. Disconnect hose from air relief valve. Ensure no air flows from hose. If air does flow, air relief valve may be stuck open.
2. Disconnect electrical connector from relief valve solenoid No. 1. Using jumper wires, energize solenoid. If air flows from air relief valve, air relief valve and relief valve solenoid No. 1 are okay. (Scheme 80) If air does not flow, check vacuum routing, relief valve solenoid No. 1, air pump and air control valve.

Control Solenoids

Disconnect electrical connector from each solenoid. (Scheme 80) Using jumper wires, energize solenoid. Ensure each solenoid clicks. Measure resistance across solenoid terminals. Resistance should be 26-33 ohms at room temperature. If any solenoid does not test as described, replace solenoid.

Port Air & Split Air Check Valves

1. Operate engine at idle. Disconnect hose between air pump and air control valve. (Scheme 80) Ensure exhaust gas is not leaking from port air check valve. If exhaust gas is leaking, replace air control valve.
2. Disconnect hose from split air check valve. (Scheme 80) Increase engine speed to 2000 RPM and verify exhaust gas is not leaking from split air check valve. If valve is not working correctly, replace split air check valve.

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 during deceleration. For adjustment and testing, see ADJUSTMENTS article.

System Check (MX-3 DOHC, MX-6 2.5L, 626 2.5L & 929)

1. Connect Engine Signal Monitor (49-9200-162) and Test Harness (49 G018 903) 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 83)or (Scheme 85).

System Check (MX-6 2.0L & 626 2.0L)

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 to about 2000 RPM, and ensure diaphragm of EGR control valve moves. If no movement is detected, test EGR components as necessary. (Scheme 84)

System Check (RX7)

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 allow it to idle. Ground Blue/Yellow wire at EGR solenoid. Ensure EGR control valve moves and engine idles rough or stalls. If no movement occurs or engine idles smooth, test EGR components as necessary.

Scheme 83

Scheme 84

Scheme 85

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 vacuum. See EGR CONTROL VALVE OPERATING VACUUM table. Engine should run rough or stall. If engine does not operate as specified, clean or replace EGR control valve.

EGR CONTROL VALVE OPERATING VACUUM

EGR Modulator Valve (MX-6 2.0L & 626 2.0L)

Remove EGR modulator valve. Plug port No. 3, and connect a vacuum pump to port No. 1. (Scheme 78)and (Scheme 80). Blow into exhaust gas port. Operate vacuum pump and verify vacuum is held. Release exhaust port and verify vacuum is released. Replace EGR modulator valve if it does not test as described.

Scheme 86

EGR Position Sensor (MX-3 DOHC)

1. Disconnect ECU electrical connector. Connect Engine Signal Monitor (49-9200-162) and Test Harness (49 G018 903) to ECU. Connect vacuum pump to EGR control valve. Turn ignition on. Check voltage at ECU connector terminals. See EGR POSITION SENSOR VOLTAGE table.
2. If voltage is not correct at terminals "A" and "B", check wiring harness and connection at ECU connector terminals 2J and 3D. If voltage is not correct at terminal "C", check sensor resistance, wiring harness and ECU connector terminal 2I.
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 table. If resistance is not within specifications, replace sensor.

EGR Position Sensor (MX-6 2.0L & 626 2.0L)

Disconnect EGR position sensor electrical connector. Check resistance across terminals. (Scheme 87) At room temperature, resistance should be 182-336 ohms. If resistance is not as specified, replace EGR control valve.

Scheme 87

EGR Position Sensor (MX-6 2.5L & 626 2.5L)

1. Disconnect ECU electrical connector. Connect Engine Signal Monitor (49-9200-162) and Test Harness (49 G018 903) between ECU 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 88) See «EGR POSITION SENSOR VOLTAGE»(ref-18275-S37415423002000123000000) table.
3. If voltage is not correct at terminals "A" and "B", check wiring harness and connection at ECU connector terminals 2J and 3C. If voltage is not correct at terminal "C", check sensor resistance, wiring harness and ECU connector terminal 2I.
4. Disconnect EGR position sensor electrical connector. Disconnect vacuum hose from EGR control valve. Apply vacuum to EGR control valve.
5. Check sensor resistance between indicated terminals. See «EGR POSITION SENSOR RESISTANCE»(ref-18275-S09130092782000123000000) table. If resistance is not within specifications, replace sensor.

EGR Position Sensor (929)

1. Disconnect EGR position sensor electrical connector. Connect ohmmeter to EGR position sensor. Disconnect vacuum hose from EGR control valve. Apply vacuum to EGR control valve.
2. Check sensor resistance between indicated terminals. See «EGR POSITION SENSOR RESISTANCE»(ref-18275-S09130092782000123000000) table. If resistance is not within specifications, replace sensor.

EGR Switch (RX7 California)

Measure continuity across switch on EGR control valve. Apply 3.3-4.5 in. Hg to EGR control valve. Continuity should be present. If continuity is not present, replace EGR control valve.

EGR POSITION SENSOR VOLTAGE

EGR POSITION SENSOR RESISTANCE

Scheme 88

EGR Solenoid Valve (MX-3 DOHC, MX-6 2.5L, 626 2.5L & 929)

1. Disconnect vacuum hoses. Blow air through vacuum hose (vacuum side). 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 89) Blow air through vacuum hose and ensure air flows.
2. Blow air through vacuum hose (vent side). Ensure air flows. Disconnect EGR solenoid valve (vent side) electrical connector. Apply 12 volts and a ground to solenoid valve (vent side) terminals. (Scheme 89) Blow air through vacuum hose and ensure air does not flow. Replace solenoid valves as necessary.

Scheme 89

1. 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 allow it to idle.
2. Disconnect vacuum hose at EGR control valve. (Scheme 90) Ensure less than 1 in. Hg is present. If specified amount of vacuum is present, check EGR control valve. If specified amount of vacuum is not present, test EGR components as necessary.

Note. Most EGR problems should set a trouble code in computer memory. For computer control testing of EGR components, see CIRCUIT TEST DL in TESTS W/CODES article.

Bring engine to normal operating temperature and operate at idle. Disconnect and plug vacuum hose at EGR control valve. (Scheme 90) Engine should run smoothly. Connect vacuum pump to EGR control valve, and apply 5-10 in. Hg. Engine should run rough. If engine does not run rough, clean or replace EGR control valve.

Scheme 90

Charcoal Canister

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

1-Way Check Valve (B2200, B2600i & MPV)

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.

2-Way Check Valve (All Except B2200, B2600i & MPV)

Remove check valve. Connect a vacuum pump to one end of check valve. Air should flow with about 1-1.7 in. Hg applied. Connect vacuum pump to other end of check valve. Air should also flow with about 1-1.7 in. Hg applied. Replace valve as necessary.

3-Port Check Valve (Miata A/T & 929)

Note direction of valve installation. Remove check valve. Cap port going to 2-way check valve. Connect a vacuum pump to lower port. Air should flow from port going to fuel tank with 3.0 in. Hg applied. Replace valve as necessary.

Check & Cut Valve (B2200, B2600i, MPV, MX-3, Protege & 323)

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 91)
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 91

Fuel Vapor Valve (B2200, B2600i, Miata, MX-6, RX7, 626 & 929)

Remove fuel vapor valve. Blow air into upper port of valve. Air should flow through valve to lower port. Turn valve upside down. Blow air through lower port of valve. Air should not flow. 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 92) 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 92

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 to manifold vacuum side of solenoid. CANP solenoid should hold vacuum for 20 seconds. Using jumper wires, energize CANP solenoid. Vacuum should flow through solenoid. If CANP solenoid does not test as described, replace solenoid.
3. Faults in CANP solenoid or circuit should set a service code. See QUICK TEST in «TESTS W/CODES»(ref-18270) article. If no service code has been set, see CIRCUIT TEST KD in «TESTS W/CODES»(ref-18270) 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.

Air Cleaner Temperature Sensor

With temperature sensor less than 75°F (24°C), apply 8 in. Hg to source port. Duct door should close. If door does not close, replace sensor.

Air Control Door

When 8 in. Hg 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,MX-6, RX7, 626 & 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 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 article. If no service code has been set, see CIRCUIT TEST KM in TESTS W/CODES article in the ENGINE PERFORMANCE section for testing.

Anti-Afterburn Control (RX7)

Start engine and allow it to idle. Disconnect Idle Speed Control (ISC) connector. Raise engine speed to more than 4000 RPM, and quickly close throttle. Engine should idle rough at 1000-1500 RPM. No other information is available.

Variable Exhaust System (929)

1. With engine idling, ensure exhaust gas comes out of one exhaust pipe. Raise engine speed to 3500 RPM. Exhaust gas should come out of both exhaust pipes.
2. To test control motor, remove inside-rear trunk panel. Disconnect control motor connector. Apply 12 volts to Yellow/Black wire and ground to Blue wire. Control motor should rotate clockwise. Reverse leads and control motor should rotate counterclockwise. If system does not function as specified, check wiring between computer and control motor. See PIN VOLTAGE CHART S article.