Engine Controls - System/component Tests - 2.5L: Other Mazda Millenia I

VARIABLE RESONANCE INDUCTION SYSTEM

VRIS RPM SPECIFICATIONS

Check Valve

Remove check valve. (Scheme 58) Apply air pressure to port "A" (White port) of check valve. Air should flow from port "B". Apply air pressure to port "B" (Green port) of check valve. Air should not flow from port "A". Replace check valve as necessary.

Shutter Valve Actuators

Disconnect vacuum hose from shutter valve actuators No. 1 and 2. (Scheme 58) Connect vacuum pump to actuator. Apply vacuum to each actuator separately and verify shutter valve rod retracts. Ensure both shutter valves move freely. Replace actuator as necessary.

Scheme 58

Solenoid Valve

Remove solenoid valve. Apply air pressure to port "B". Air should flow from "C". Using jumper wires, apply battery voltage to solenoid valve terminals. Apply air pressure to port "B". Air should flow from port "A". Replace solenoid valve as necessary.

Vacuum Chamber

2.5L is equipped with one vacuum chamber. Remove vacuum chamber. Visually inspect vacuum chamber for clogging, cracks and damage. Replace as necessary.

POWERTRAIN CONTROL MODULE (PCM)

Note. For purpose of this article, all references to PCM include ECM unless otherwise specified.

Ground Circuit Checks

1. Using an ohmmeter, check ground circuits to PCM for continuity to ground. See appropriate wiring diagram in «WIRING DIAGRAMS - 2.5L»(ref-18693) article to determine PCM ground terminals. If continuity does not exist, repair open circuit to ground.
2. Using a voltmeter, touch negative lead to a good ground. Touch positive lead to each ground terminal. With vehicle running, voltmeter should indicate less than one volt. If voltage reading is more than one volt, check for open circuit, corrosion, or loose connection on ground lead.

Power Circuit Checks

1. Using a voltmeter, check for battery voltage between PCM constant battery power terminals and ground. See appropriate wiring diagram in «WIRING DIAGRAMS - 2.5L»(ref-18693) article to determine PCM power terminals. If battery voltage is not present, check PCM power supply fuse. If fuse is okay, check for open in power supply or PCM wiring.
2. Turn ignition on. Using a voltmeter, check for battery voltage between PCM ignition power terminals and ground. If battery voltage is not present, check power supply fuse(s). If fuse is okay, check for an open in wiring between fuse and PCM, or check for a defective ignition switch.
3. Connect voltmeter between ground and PCM start (crank) signal terminal. Turn ignition switch to START position. Battery voltage should be present between PCM start terminal and ground only when ignition switch is in START position. If voltage is not present, check fuse(s). If fuse is okay, check for open circuit in wiring harness between fuse and PCM. If wiring harness is okay, check for a defective ignition switch.

PCM LOCATIONS

BRAKELIGHT SWITCH

Disconnect brakelight switch connector. Using ohmmeter, check continuity between brakelight switch terminals. With brake pedal released, continuity should not exist. With brake pedal depressed, continuity should exist. If continuity is not as specified, replace brakelight switch.

CAMSHAFT POSITION (CMP) SENSOR

1. CMP sensor is located inside of distributor. Remove distributor, leaving electrical connector connected. Using analog voltmeter (or oscilloscope), connect negative lead to CMP sensor ground (CMP body or Black/Blue wire).
2. With positive voltmeter lead, backprobe Yellow/Blue wire at CMP connector. Turn ignition on. Rotate CMP shaft and observe voltage reading. Voltmeter should indicate one voltage pulse (5 volts) per revolution. Replace distributor as necessary.

CLOSED THROTTLE POSITION SWITCH

Closed throttle position switch is part of Throttle Position (TP) sensor. To test closed throttle position switch, check TP sensor continuity. See THROTTLE POSITION SENSOR (TP) in ADJUSTMENTS - 2.5L article. Check TP sensor adjustment before replacing TP sensor.

CRANKSHAFT POSITION (CKP) SENSOR

1. CKP sensor is located on front of engine, near crankshaft pulley. Disconnect CKP sensor connector. Using ohmmeter, measure resistance between terminals "A" and "B" at CKP sensor. (Scheme 59) Resistance should be as specified. See «CRANKSHAFT POSITION SENSOR RESISTANCE»(ref-18677-S00793219292000123000000) table.
2. If resistance is not as specified, replace CKP sensor.

CRANKSHAFT POSITION SENSOR RESISTANCE

Scheme 59

EGR BOOST SENSOR

See EXHAUST GAS RECIRCULATION (EGR) SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS

ENGINE COOLANT TEMPERATURE (ECT) SENSOR

Remove ECT sensor. Place ECT sensor and thermometer in a container of water. Connect ohmmeter between ECT sensor terminals. Slowly heat water. Observe resistance reading at specified temperatures. See ENGINE COOLANT TEMPERATURE (ECT) SENSOR SPECIFICATIONS table. If resistance is not as specified, replace ECT sensor.

ENGINE COOLANT TEMPERATURE (ECT) SENSOR SPECIFICATIONS

FUEL TANK PRESSURE SENSOR

1. Fuel tank pressure sensor is located on top of fuel tank. Connect Engine Signal Monitor (49 9200 162A) to ECM/PCM, using proper overlay and adapter cables. Turn ignition on. Measure voltage at ECM/PCM terminal 3U.
2. With 2 psi (6.7 kPa) of pressure applied to sensor, voltage should be 4-5 volts. With 0 psi (0 kPa) of pressure applied to sensor, voltage should be 2.3-2.8 volts. With 2 in. Hg of vacuum applied to sensor, voltage should be.45-.55 volt. If all voltage readings are as specified, fuel tank pressure sensor is functioning properly. If any voltage reading is not as specified, go to next step.
3. Turn ignition off. Check continuity of circuits between fuel tank pressure sensor wiring harness connector and ECM/PCM. See appropriate wiring diagram in «WIRING DIAGRAMS - 2.5L»(ref-18693) article. If continuity exists in all circuits, go to next step. If continuity does not exist in one or more circuits, repair wiring harness as necessary.
4. Turn ignition on. Measure voltage at terminal "B" at fuel pressure sensor wiring harness connector. (Scheme 60) Voltage should be less than one volt. Measure voltage at terminal "C" at fuel tank pressure sensor wiring harness connector. Voltage should be 4.5-5.5 volts. If voltage is as specified, replace fuel tank pressure sensor. If voltage is not as specified, locate and repair short circuit in wiring harness. See appropriate wiring diagram in «WIRING DIAGRAMS - 2.5L»(ref-18693) article.

Scheme 60

(Using Engine Signal Monitor)

1. Warm engine to normal operating temperature. Connect Engine Signal Monitor (49 9200 162A) to ECM, using proper overlay and adapter cables. Measure voltage of suspect sensor at ECM/PCM terminal. See «HO2S ECM/PCM TERMINAL IDENTIFICATION»(ref-18677-S06561546632000123000000) table. Voltage should be.5-1.0 volt under acceleration and 0-.5 volt under deceleration.
2. If voltage is not as specified, check wiring harness and connector between ECM and HO2S. Also check intake manifold system, fuel system and self-diagnostic system. Repair as necessary. If no problems are found, replace HO2S.
3. To test HO2S heating element, allow sensor to cool to room temperature. Disconnect HO2S connector. Using ohmmeter, measure resistance between sensor terminals "C" and "D". (Scheme 61)Resistance should be about 6 ohms with sensor temperature at 68°F (20°C). If resistance is not as specified, replace HO2S.

HO2S ECM/PCM TERMINAL IDENTIFICATION

Scheme 61

INTAKE AIR TEMPERATURE (IAT) SENSOR

Locate and remove IAT sensor from air cleaner housing. Place IAT sensor and thermometer in a container of water. Connect ohmmeter between IAT sensor terminals. Slowly heat water. Observe resistance at specified temperatures. See INTAKE AIR TEMPERATURE SENSOR SPECIFICATIONS table. If resistance is not as specified, replace IAT sensor.

INTAKE AIR TEMPERATURE SENSOR SPECIFICATIONS

KNOCK SENSOR

Disconnect knock sensor connector. Using ohmmeter, measure resistance between knock sensor terminal "A" (White wire) and knock sensor body. Resistance should be about 560,000 ohms at 68°F (20°C). If resistance is not as specified, replace knock sensor.

Using Engine Signal Monitor

1. Visually check MAF sensor for cracks or damage. If any damage is present, replace MAF sensor. If no damage is present, connect Engine Signal Monitor (49 9200 162A) to ECM/PCM. Measure voltage at ECM/PCM terminal 3E. See «MASS AIRFLOW (MAF) SENSOR VOLTAGE»(ref-18677-S20962075792000123000000) table.
2. If voltage is not as specified, check continuity of each circuit between MAF sensor and ECM/PCM. See appropriate wiring diagram in «WIRING DIAGRAMS - 2.5L»(ref-18693) article. Repair as necessary. If continuity exists in all circuits, replace MAF sensor.

POWER STEERING PRESSURE (PSP) SWITCH

Disconnect power steering pressure switch connector. Connect ohmmeter between PSP switch and ground. Start engine and operate at idle. Turn steering wheel from side to side and observe ohmmeter. Continuity should exist when steering wheel is turned. Continuity should not exist when steering wheel is straight ahead. If continuity is not as specified, replace PSP switch.

SPEEDOMETER SENSOR

Speedometer sensor is located in instrument cluster. If sensor is suspect, check speedometer operation. See appropriate INSTRUMENTS PANELS article in the ACCESSORIES/SAFETY EQUIP section. Repair as necessary.

THROTTLE POSITION SENSOR

See ADJUSTMENTS - 2.5L article for TP sensor testing and adjustment procedures.

TRANSMISSION RANGE SWITCH (A/T)

1. Check for starter operation with ignition switch in START position and shift lever in "P" and "N" position only. Ensure back-up lights illuminate with ignition in ON position and selector lever in "R".
2. To test switch, disconnect transmission range switch connector. Check for continuity between specified terminals at transmission range switch. (Scheme 62) If continuity is not as specified, replace switch.

Scheme 62

VEHICLE SPEED SENSOR (VSS)

VSS is located on side of transaxle. Disconnect negative battery cable. Disconnect VSS connector. Rotate front wheels and measure voltage between sensor terminals. (Scheme 63) If voltmeter needle does not fluctuate, replace sensor.

Scheme 63

FUEL PUMP RELAY

Remove fuel pump relay. See FUEL PUMP RELAY LOCATIONS table below. Using ohmmeter, check for continuity between relay terminals "C" and "D". (Scheme 64) Continuity should not exist. Apply battery voltage to terminal "A" and ground terminal "B". Again, check for continuity between relay terminals "C" and "D". Continuity should exist with battery voltage applied. If continuity is not as specified, replace fuel pump relay.

FUEL PUMP RELAY LOCATIONS

Scheme 64

MAIN RELAY

1. Ensure main relay clicks when ignition is turned on and off. If no sound is heard, locate and remove main relay from main fuse block, in left side of engine compartment. Using ohmmeter, check continuity between terminals "C" and "D". (Scheme 64) Continuity should not exist.
2. Using jumper wires, apply battery voltage to relay terminal "A" and ground terminal "B". Check continuity between relay terminals "C" and "D". Continuity should exist with battery voltage applied. If continuity is not as specified, replace main relay.

EGR Vacuum Solenoid Valve

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

EGR Vent Solenoid Valve

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

Pressure Regulator Control (PRC) Solenoid Valve

Disconnect vacuum hose from PRC solenoid valve. Refer to the PRC SOLENOID VALVE LOCATIONS table. Apply air pressure to solenoid port "A". (Scheme 65) Air should flow from port "B". Using jumper wires, apply battery voltage to solenoid terminals. Apply air pressure to solenoid port "A". Air should flow through valve air filter. Replace solenoid valve as necessary.

PRC SOLENOID VALVE LOCATIONS

Scheme 65

Purge Control Solenoid

See FUEL EVAPORATION under EMISSION SYSTEMS & SUB-SYSTEMS.

FUEL PRESSURE RELEASE

Disconnect fuel pump relay. See FUEL PUMP RELAY LOCATIONS table. Start engine (if possible) and allow to die. Turn ignition off.

FUEL PUMP RELAY LOCATIONS

FUEL DELIVERY

Note. For system pressure testing, see BASIC TESTING - 2.5L article.

Fuel Pump Circuit

See FUEL PRESSURE in BASIC TESTING - 2.5L article.

Fuel Pressure Regulator

See FUEL PRESSURE in BASIC TESTING - 2.5L article.

Pressure Regulator Control Solenoid

See PRESSURE REGULATOR CONTROL SOLENOID under SOLENOIDS .

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 connectors. Using ohmmeter, measure resistance between injector terminals. (Scheme 66) Refer to the CHECKING FUEL INJECTOR RESISTANCE table. With sensor temperature at 68°F (20°C), resistance should be about 13.8 ohms. Replace injectors as necessary.

CHECKING FUEL INJECTOR RESISTANCE

Scheme 66

Injector Fuel Leakage

1. Using mechanics wire, secure each fuel injector to fuel rail. Disconnect fuel injector connectors. Remove fuel rail assembly from intake manifold. See appropriate engines article in ENGINES section. Reconnect fuel lines to fuel rail. Locate Data Link Connector (DLC) in left side of engine compartment.
2. Connect a jumper wire between DLC terminals F/P and GND. (Scheme 67) Turn ignition on. Tilt injectors about 60 degrees and check injector nozzles for fuel leaks. Fuel leakage should be less than one drop every 2 minutes. If fuel leakage exists, replace injector.

Scheme 67

Fuel Cut Control System

1. To check system operation, connect New Generation Star (49 T088 0A0) scan tool to Data Link Connector (DLC) 2. DLC 2 is located under left side of instrument panel, right of steering column. Ensure engine is at normal operating temperature. Allow engine to idle. Turn A/C switch off.
2. Using scan tool, access DIAGNOSTIC DATA LINK menu, and select PCM. Highlight and select PID/DATA MONITOR AND RECORD. Select INJR and INJL. Scan tool will measure and display fuel injector pulse width. Increase engine speed to 4000 RPM, then quickly close throttle valve.
3. Fuel injection pulse width should be zero milliseconds until engine speeds drops to about 1200 RPM, then pulse width should return to specification noted prior to increasing engine speed. If pulse width is as specified, A/C cutoff system is functioning properly.
4. If pulse width is not as specified, measure voltage at ECM terminals 3Q (ECT sensor circuit), 3X (closed throttle position switch circuit), 4AH and 4AL (crankshaft position sensor circuit). See «PIN VOLTAGE/PID VALUE CHARTS - 2.5L»(ref-18724) article. Repair as necessary.

Dechoke Control System

1. When spark plugs become fouled (i.e. engine is flooded), fuel injection is cut if throttle valve is held wide open during cranking to facilitate in starting engine. This allows spark plugs to dry and purges excess fuel from cylinders.
2. To check system operation, turn ignition on and verify injector operating sound is present while cranking engine. Turn ignition off. Depress accelerator pedal fully and turn ignition on. Verify injector operating sound is not present while cranking engine.
3. If operation sound is not present, dechoke control system is functioning properly. See «PIN VOLTAGE/PID VALUE CHARTS - 2.5L»(ref-18724) article. Repair as necessary

BY-PASS AIR CONTROL (BAC) VALVE

1. BAC valve is located underneath throttle body.
2. Ensure engine is cold. Start engine and let it idle. Idle speed should gradually decrease as engine reaches normal operating temperature. If idle speed does not decrease, check coolant hose to BAC valve. Repair as necessary. If coolant hose is okay, replace BAC valve.

IDLE AIR CONTROL (IAC) VALVE

IAC valve is part of By-Pass Control (BAC) valve. Disconnect IAC valve connector. Using an ohmmeter, measure resistance between IAC valve terminals. See IAC VALVE RESISTANCE SPECIFICATIONS table. If resistance is not as specified, replace BAC valve.

IAC VALVE RESISTANCE SPECIFICATIONS

IGNITION SYSTEM

Note. For basic ignition checks, see BASIC TESTING - 2.5L article.

System Check

Check all connectors and vacuum hose routing. Check for cracks, leakage and restrictions, and repair as necessary. Start engine and operate throttle. Diaphragm of EGR control valve should not move while engine is cold. Warm engine to operating temperature. Increase engine speed to about 2000 RPM, EGR control valve diaphragm should move. If no movement is detected, check EGR system components.

EGR Boost Solenoid

Remove EGR boost solenoid. See EGR BOOST SOLENOID LOCATIONS table. Apply air pressure to port "B" of solenoid valve. Air should flow from port "C" only. Using jumper wires, apply battery voltage to solenoid valve terminals. Apply air pressure to port "A" of solenoid valve. Air should flow from port "B" only. Replace solenoid valve as necessary.

EGR BOOST SOLENOID LOCATIONS

1. Connect Engine Signal Monitor (49 9200 162A) to ECM, using proper overlay and adapter cables. Turn ignition on. Disconnect vacuum hose from EGR boost sensor. Sensor is located in center rear of engine compartment.
2. Measure voltage at ECM terminal 3F while applying vacuum to EGR boost sensor. Voltage should decrease as vacuum is increased. See «EGR BOOST SENSOR SPECIFICATIONS»(ref-18677-S26068154472000123000000) table. If voltage is as specified, sensor is functioning properly. If voltage is not as specified, go to next step.
3. Turn ignition off. Check continuity of circuits between EGR boost sensor wiring harness connector and ECM. See appropriate wiring diagram in «WIRING DIAGRAMS - 2.5L»(ref-18693) article. If continuity exists in all circuits, go to next step. If continuity does not exist in one or more circuits, repair open in wiring harness as necessary.
4. Turn ignition on. Measure voltage at terminal "B" at EGR boost sensor wiring harness connector. see scheme 11 Voltage should be less than one volt. Measure voltage at terminal "C" at EGR boost sensor wiring harness connector. Voltage should be 4.5-5.5 volts. If voltage is as specified, replace EGR boost sensor. If voltage is not as specified, locate and repair short circuit in wiring harness. See appropriate wiring diagram in «WIRING DIAGRAMS - 2.5L»(ref-18693) article.

EGR BOOST SENSOR SPECIFICATIONS

EGR Valve

Warm engine to normal operating temperature and operate at idle. Disconnect and plug vacuum hose at EGR valve. Engine should run smoothly. Connect vacuum pump to EGR valve, and apply vacuum. Engine should run rough or stall. If engine does not operate as specified, replace EGR valve.

EGR Position Sensor

EGR position sensor is part of EGR valve assembly. Disconnect the EGR position sensor connector. Disconnect the vacuum hose from the EGR control valve. Measure the resistance between the EGR position sensor terminals. Refer to the EGR POSITION SENSOR RESISTANCE table. (Scheme 68) Apply 5.9 in. Hg of vacuum to EGR position sensor and recheck resistance. If resistance is not as specified, replace EGR valve.

EGR POSITION SENSOR RESISTANCE

Scheme 68

Remove EGR vacuum solenoid. See EGR VACUUM/VENT SOLENOID VALVE LOCATIONS table. Apply air pressure to a solenoid valve port. (Scheme 69) Air should not flow from other solenoid port. Using jumper wire, apply battery voltage to solenoid valve terminals. Air should flow with voltage applied. If solenoid valve does not operate as specified, replace valve.

Remove EGR vent solenoid valve. Refer to the EGR VACUUM/VENT SOLENOID VALVE LOCATIONS table. Apply air pressure to port "A". (Scheme 69) Air should flow from ports "B" and "C". Using jumper wires, apply battery voltage to solenoid valve terminals. Apply air pressure to port "A". Air should flow from port "B" only. Replace solenoid valve as necessary.

EGR VACUUM/VENT SOLENOID VALVE LOCATIONS

Scheme 69

Charcoal Canister

Charcoal canister is located under rear of vehicle. Plug Canister Drain Cut Valve (CDCV) port and purge solenoid valve port. (Scheme 70) Apply small amount of air pressure to fuel tank port on charcoal canister. If air leaks, replace charcoal canister.

Scheme 70

Fuel Vapor Rollover Valve

Vehicle is equipped with 2 fuel vapor valves, built into top of fuel tank. With valve in upright position, air should flow through valve. With valve turned upside down, air should not flow through valve. If fuel vapor valve does not operate as specified, replace fuel tank.

Purge Control Solenoid Valve

Disconnect purge control solenoid valve connector. See the PURGE CONTROL SOLENOID VALVE LOCATIONS table. Ensure air does not flow through solenoid valve vacuum ports. Using jumper wires, apply battery voltage to solenoid valve terminals. Apply air pressure to a solenoid valve port. Air should flow from other port. If valve does not operate as specified, replace solenoid valve.

PURGE CONTROL SOLENOID VALVE LOCATIONS