1994 MAZDA MX-5 engine

DECHOKE CONTROL SYSTEM DECHOKE CONTROL SYSTEM DESCRIPTION To clean out excess fuel in cylinders, as in the case of engine flooding, when the engine is cold, no fuel will be injected when the accelerator is held fully depressed while cranking the engine. CRANKSHAFT POSITION SENSOR (NE-SIGNAL) n POWERTRAIN CONTROL MODULE ENGINE COOLANT TEMPERATURE SENSOR I (ENGINE) 1 DETERMINA- TION OF FUEL CUT SPEED Gartner Banana

COOLANT FAN CONTROL COOLANT FAN CONTROL OUTLINE The PCME controls the coolant fan and the condenser fan to provide more efficient fan control. This 4 improves the performance reliability and stability during idling of an engine. The coolant fan is normal when it start to operate with the data link connector TEN terminal grounded and the accerelator pedal is depressed (Ignition switch ON). IGNITION SWITCH OFF CONDENSER FAN MOTOR PCME RELAY I& MAGNETIC CLUTCH I COOLANT FAN RELAY Q COOLANT FAN MOTOR Gartner Banana

COOLANT FAN CONTROL F COOLANT FAN The coolant fan rotates at a constant velocity. 'L / Operation Condition TEN TERMINAL (DATA LINK CONNECTOR) IDLE SWITCH -----' OFF EXCEPT AT STARTING 'I ENGINE COOLANT TEMPERATURE ABOVE 97C0 (206.6F0) 1 COOLANT FAN - - ENGINE COOLANT TEMPERATURE SENSOR FAILED I A/C OPERATING CONDENSER FAN The condenser fan is operated by PCME. r The condenser fan rotates at a constant velocity. Operation Condition Except during acceralation Except at starting Other than wide open throttle Air conditioner is operating The condenser fan operates when above-mentioned conditions are satisfied. Engine coolant temperature is above 108°C (226.4OFj. TEN terminal grounded and idle switch off. Gartner Banana

CONTROL SYSTEM CONTROL SYSTEM PREPARATION 49 9200 162 Engine Signal Monitor Self-Diagnosis Checker 49 GO1 8 904 Sheet For inspection of powertrain control module (engine) For inspection of heated oxygen sensor For inspection of powertrain control module (engine) 49 GO18 903 For inspection of Adapter powertrain harness control module 49 B019 9AO For inspection of System heated oxygen Selector sensor Gartner Banana

CONTROL SYSTEM STRUCTURAL VIEW i 1. Powertrain control module (engine) 6. Heated oxygen sensor Inspection . . . . . . . . . . . . . . . . . . page F-144 Inspection . . . . . . . . . . . . . . . . . . page F-156 Removal / Installation . . . . . . . . page F-143 Replacement . . . . . . . . . . . . . . . page F-156 2. Crankshaft position sensor 7. Main relay Removal . . . . . . . . . . . . . . . . . . . page F-153 Inspection . . . . . . . . . . . . . . . . . . page F-156 lnspection . . . . . . . . . . . . . . . . . . page F-153 8. Clutch switch Installation . . . . . . . . . . . . . . . . . page F-153 Inspection . . . . . . . . . . . . . . . . . . page F-157 3. Mass airflow sensor Replacement . . . . . . . . . . . . . . . page F-157 System inspection . . . . . . . . . . . page F-152 9. Neutral switch Inspection . . . . . . . . . . . . . . . . . . page F-152 Inspection . , . . . . . . . . . . . . . . . . page F-157 4. Engine coolant temperature sensor Replacement . . . . . . . . . . . . . . . page F-157 Removal . . . . . . . . . . . . . . . . . . . page F-154 10. Steering pressure sensor Inspection . . . . . . . . . . . . . . . . . . page F-154 Inspection . . . . . . . . . . . . . . . . . . page F-158 Installation . . . , . . . . . . . . . . . . . page F-154 Replacement . . . . . . . . . . . . . . . page F-158 5. Throttle position sensor -,' Inspection . . . . . . . . . . . . . . . . . . page F-155 Adjustment . . . . . . . . . . . . . . . . . page F-155 Replacement . . . . . . . . . . . . . . . page F-156 Gartner Banana

CONTROL SYSTEM F POWERTRAIN CONTROL MODULE (ENGINE) (PCME) Removal l Installation 1. Remove in the order shown in the figure. L 2. Install in the reverse order of removal. 1. Negative battery cable 2. PCME connector 3. PCME Inspection . . . . . . . . . . . . . . . . . . page F-144 Gartner Banana

F CONTROL SYSTEM Inspection 1. Lift up the floormat in front of the passenger's seat. (Refer to section S.) ,i 1 USECONNECTORA TERMINALS /AANDB 2. Connect the SST (Engine Signal Monitor) between the powertrain control module (engine) and the wiring har- ness using the SST (Adapter) as shown. 3. Place the SST (Sheet) on the SST (Engine Signal Mon- itor). 4. Measure the voltage at each terminal. (Refer to pages F-148 to F-151.) 5. If any powertrain control module (engine) terminal volt- age is incorrect, check the input or output device and re- lated wiring. 6. If they are normal, replace the powertrain control module (engine). (Refer to pages F-145 to F-147.) Caution Applying voltage to SST terminals A or B will dam- age the SST. Gartner Banana

CONTROL SYSTEM F Terminal voltage B+: Battery positive voltage Test condition I Voltage I Remark - - - - - - - - - - - - - - - - - - Connection to Battery Constant Ignition switch OFF Main relay - B+ OV lgnition switch (Start position) For backup - Ignition switch ON While cranking Lamp illuminated for 3 sec. after 1 4.5-5.5V ianition switch OFF+ON 1 B+ Approx. 1 OV Ignition switch ON - - OV Data link connector (MEN terminal) Test switch at "SELF-TEST" .. Lamp not illuminated after 3 sec. Test switch at "02 MONITOR" at idle Monitor lam illuminated & 4.5-5.5v . . I Malfunction indicator IighVData link connector (FEN ter- minal) With Self-Diagnosis Checker and System Selector Test switch at "02 MONITOR" at idle Monitor lamp not illuminated Light illuminated and buzzer sounded for 3 sec. after ignition switch OFF-ON B+ tor tesiswitch at "SELF-TEST" With Self-Diagnosis checker and system selector Below 2.5V 1 Light illuminated and buzzer sounded 1 Below 2.5V I With System Selec- Light not illuminated and buzzer not sounded after 3 sec. I Light not illuminated and buzzer 1 n. 1 B+ not sound I D+ 1 - #I, 4 lgniter (in IG COIL) #2,3 Igniter (in IG COIL) Powertrain control module (transmis- sion) - Ignition switch ON Idle Ignition switch ON Idle lgnition switch ON (Engine coolant temp, below 60°C {I 40°F)) Ignition switch ON AtC relay Air conditioning sensor ON at idle Air conditioning sensor OFF at idle Ground (MT) - OV Approx. 0.2V OV Approx. 0.2V Below 1 .OV B+ Below 2.5V B+ - - - - , * Open (AT) - Ignition switch ON ( Below 1 .O V I Engine coolant temp. I Below .OV I ldle Above 97°C (206.6OF1 Ignition switch ON I I B+ Ignition switch ON Coolant fan relay B+ . - Other conditions lgnition switch On dround data link connector TEN terminal I Blow 1.0" I B+ Vehicle speed sensor ldle switch OFF While driving Vehicle sto~wed ldle switch (in throttle position sensor) 2-5V 1 or 7V . , Accelerator pedal released Accelerator ~edal de~ressed - Stoplight switch OV B+ Brake pedal released Brake ~edal deoressed lgnition switch ON Steering pressure sensor OV B+ I I - Ignition switch ON B+ - PIS ON (at idle) PIS OFF (at idle) Air conditioning sensor Air conditioning sensor ON (Igni- tion switch ON) Air conditioning sensor OFF (Igni- tion switch ON) OV B+ - Below 2.5V B+ Blower motor ON Gartner Banana