1994 MAZDA MX-5 engine

OUTLINE F COMPONENT DESCRIPTIONS Component Air cleaner housing Air valve Remark Function Filters air entering throttle body When cold, supplies bypass air into dynamicchamber w Engine speed increased to shorten warm-up period Thermowax type Barometric absolute pressure sensor Detects barometric absolute pressure; sends signal to powertrain control module (engine) 3uilt-in PCME Charcoal canister Clutch switch (MT) Stores gas tank fumes while engine stopped Detects in-gear condition: sends signal to powertrain control module (engine) --- ~witch OFF when clutch pedal released Crankshaft position sen- sor Detects No.1 cylinder TDC; sends signal to powertrain control module (engine) Detects crank angle at 180" intervals; sends signal to powertrain control module (engine) Data link connector Concentrated service connector Concentrated terminals are: 1. CIS on-board diagnosis terminal 2. Initial set terminal 3. Fuel pump check terminal Dynamic chamber Interconnects all cylinders Detects coolant temperature; sends signal to powertrain control module (engine) Recircurates oortion of exhaust aas Engine coolant temperature sensor EGR control valve lnstalled in EGR control valve EGR function sensor Detects EGR control valve operating position; send sig- nal to PCME EGR solenoid valve (vent) Controls vacuum to EGR control valve (vent side) Controlled by duty signal from PCME . - EGR solenoid valve (vac- Controls vacuum to EGR control valve (vacuum side) 0 Controlled by duty signal from PCME uum) Fuel filter Filters particles from fuel Injects fuel into intake port Fuel injector Controlled by signals from powertrain control module (engine) High-ohmic injector 0 Sinale port injector nozzle Fuel pump Provides fuel to fuel injectors 0 operates while engine running lnstalled in fuel tank Fuel pump relay Voltage for fuel pump while engine running Fuel vapor valve Prevents fuel from entering canister during vehicle roll over Heated oxygen sensor Detects oxygen concentration; sends signal to power- train control module (engine) 0 Zirconia ceramic and platinum coating ldle air control valve Controls bypass air amount Controlled by duty signal from powertrain control module (engine) Controls idle-up lnstalled in throttle position sensor lnstalled in ignition coil ldle switch Igniter Detects idle condition; sends signal to PCME Receives spark signal from powertrain control module (engine) and generates high voltage in ignition coil Detects high voltage ignition; sends substitute ignition signal to powertrain control module (engine) Ignition switch (START position) Sends engine cranking signal to powertrain control mod- ule (engine) Intake air temperature sensor Detects intake air temperature: sends signal to powertrain control module (engine) Installed in mass airflow sensor Main relay Supplies electric current to fuel injectors, powertrain control module (engine), etc. Gartner Banana

Neutral swltch (MT) 7 PCV valve Powertrain control mod- ule (engine) (PCME) Purge solenoid valve Resonance chamber Steering pressure sen- Stoplight swltch I Throttle posltion sensor r [Two-way check valve Function jetects amount of intake air; sends signal to powertrain :ontrol module (engine) Li~ht illuminates when input device malfunctions - Light flashes to indicate trouble code number of input and output devices Detects in-gear condition; sends signal to powertrain :ontrol module (engine) - Controls blow by aas amount introduced into engine Detects the followlng: 1. A/C operation 2. Airlfuel ratio (Oxygen concentration) 3. Barometric absolute pressure 4. Braking signal 5. Cranking signal 6. EIL operation 7. Engine coolant temperature 8. Engine speed 9. In-gear condition 10. lntake air amount 11, lntake air temperature 12. No.1 piston TDC 13. PIS operation 14. Initial set signal 15. Throttle valve opening angle Controls operatlon of the followlng: 1. AIC (Cut off) 2. Fail-safe function 3. Fuel injection system 4. ldle speed control 5. Ignition timing control system 6. Monitor function 7. Purge control system 8. Lockup control svstem Controls vacuum to pressure regulator -- Adjusts fuel pressure supplied to fuel injectors Controls evaporative fumes from canister to intake man- ifold -- lm~roves mid-ranae torque characteristics -. Detects PIS operation; sends signal to powertrain con- trol module (engine) -- Detects braking operation (deceleration); sends signal to powertrain control module (engine) Reduces HC, CO, and NOx by chemical reaction Controls pressurein fuel tank Controls intake air quantity Detects position of the throttle valve closed throttle posi- tion; sends signal to powertrain control module (engine) Detects the throttle valve opening at a preset angle; sends si~nal to powertrain control module (engine) controls pressure in fuel tank Remark lntake air temperature sensor and fuel pump switch included Use Vref (5 volt) as power source ' Data link connector terminal TEN ' Data link connector terminal TEN Switch ON when in neutral 1, Air conditioning sesnor 2. Heated oxygen sensor 3. Barometric absolute pressure sensor 4. Stoplight switch 5. Ignition switch (START position) 6. Coolant fan relay Light and turn relay Blower switch 7. Engine coolant temperature sensor 8. Crankshaft position sensor (SGT-signal) 9. Neutral and dutch switches (MT) Parklneutral switch (AT) 10. Mass airflow sensor 11, lntake air temperature sensor 12. Crankshaft position sensor (SGC-signal) 13. Steering pressure switch 14. Data link connector 15. Throttle position sensor 1. NC relay 2. Self-diagnosis checker and MIL 3. Fuel injector 4. IAC valve 5. Igniter 6. Monitor lamp (Self-diagnosis checker) 7. Purge solenoid valve 8. Powertrain control module (transmission) (AT) D Controlled by duty signal from powertrain control module (engine) D PIS: ON when steering wheel turned Monolith type D Integrated throttle position sensor, Idle air control valve, and dashpol Gartner Banana

TROUBLESHOOTING GUIDE F TROUBLESHOOTING GUIDE ENGINE CONTROL OPERATION CHART Output Devices and Engine Conditions ENGINE CONDITION CRANK- WARMING MEDIUM LOAD ING UP (DUR- ACCEL- HEAVY (COLD ERATION LOAD OUTPUT ENGINE) INGIDLE) COLD WARM DEVICE u I I I FUEL INJEC- FUELIN- nON Rich Normal JECToR AMOUNT Rich FUEL PUMP RELAY I IG: ON DECEL (ENGINE ERATION NOT RUNNING] No Injec- Fuel cut I Normal I tion IGNITER Depends on engine condition I PURGE SOLENOID VALVE OFF ON (Purge) OFF I I IDLE AIR ON ON ON CONTROL (Fixed (Closed ON (Fixed duty) (Closed OFF BAC VALVE duty) loop duty) loop duty) VALVE AIR VALVE OPEN CLOSED - AIC RELAY I OFF PRC SOLENOID VALVE OFF (Vacuum to pressure regulator) I I EGR SO- VENT ON LENOID OFF (System operates: amount of OFF JALVE VACUUM EGR changes) Gartner Banana

TROUBLESHOOTING GUIDE RELATIONSHIP CHART Fuel injector TEN Terminal (Data link connector) Ignition Switch (Start Position) Steering Pressure Sensor X X X X X X X X X X X X X X X xoo Blower Switch Headlight Switch Stoplight Switch Neutral and Clutch Switches (MT) Parklneutral switch (AT) Air Conditioning Sensor Idle Switch Throttle I BDL) Position Sensor I Sensor (NO) Barometric Absolute Pres- sure Sensor IGF Signal Heated Oxygen Sensor Engine Coolant Temperature Sensor Sensor Mass Air- flow Sensor Intake Air Temperature Sensor Crankshaft SGTSignal Position Sensor SGC-Signal Gartner Banana

F TROUBLESHOOTING GUIDE Troubleshooting chart F TROUBLESHOOTING GUIDE 7 I - page F-79 CRANKS NORMALLY BUT HARD TO START - AFTER WARM-UP 1 Check if PCME terminal voltaoes are OK Check If '00" is displayed on Sell-Diagnosis Check- er wilh lonillon switch ON I (2D* 2R and *) page 6145 'SCRIPTION Enginecranks at normal speed but requires excessive cranking time (more than 5 sec.) before starting after run- ning and hot soaked Battery In normal condition Engine starts normally when cold TROUBLESHOOTING HINTS] D AidFuel mixture too rich @ Vapor lock Fuel injection control malfunction . Fuel pressure not held In fuel line after engine stop Fuel injector fuel leakage . High RVP (winter) fuel used In warm weather ITEP I INSPECTlON Yes "88" flashes I Check PCME terminal I E ~Itg " p8gO F-I45 1 ACVON Go to next slep No Speclflcatlon: Baltery porltlve voltage (Ignition rwltch 1 ON) Diagnostic Trouble Code No. dlrplayed Check lor cause (Refer lo specified check sequence) a page F-81 If OK, replace PCME rr F-143 I:, if not OK, check wiring between PCME and Sell-Diagno- sis Checker LQ page M I No Check for cause (Refer to 'Check Pdnt for Each Terml- nal') page F-1 I -- ~ Yes Go lo next step I p- / Yes DESCRIPTION: Further describes the symptom. Confirm that the chart addresses the actual symptom before beginning troubleshooting. Go to next slep TROUBLESHOOTING HINTS: This describes the possible point of malfunction. STEP: This shows the order of troubleshooting. Proceed with troubleshooting as indicated. INSPECTION: This describes an inspection to quickly determine the malfunction of parts. If a detailed procedure is nec- essary to perform the INSPECTION, refer to the page shown by the "UW' mark. ACTION: This recommends the appropriate action to take as a result (YesINo) of the INSPECTION. How to per- form the action is described on the reference page shown by the "=" mark. Gartner Banana

TROUBLESHOOTING GUIDE DIAGNOSTIC INDEX Cranks normally but will not start (No com- Engine cranks at normal speed but shows no sign of bustion) I #firingN I F-17 I No. 1 TROUBLESHOOTING ITEM Will not crank or cranks slowly -- -- Cranks normally but will not start (Partial combustion) -When engine is cold Cranks normally but will not start (Partial combustion) - After warm-up Cranks normally but hard to start - Always Cranks normally but hard to start - When engine is cold - Engine cranks at normal speed but shows partial com- bustion and will not continue to run Engine cranks at normal speed but shows partial com- bustion and will not continue to run after running and hot soaked Engine cranks at normal speed but requires excessive cranking time (more than 5 sec.) before starting Same condition as No.5 when engine is cold Restarts OK after warm-up 8 DESCRIPTION Refer to Engine Electrical System Low idle speed1Rough idle - Before warm- UP Low idle speed/Rough idle -After warm-up PAGE SECTION G Cranks normally but hard to start - After warm-up Rough idle - Always Engine speed low or engine vibrates excessively at idle during warm-up Engine runs normally at idle during warm-up but vi- brates excessively after warm-up High idle speed - After warm-up Low idle speed - When NC, PIS, or EIL ON l5 1 Engine stalls at idle - Always Engine starts normally but vibrates excessively and stalls at idle in every condition I F40 1 13 14 Same condition as No.5 after running and hot soaked Starts normally when cold Engine vibrates excessively at idle in every condition Engine idle excessive for operation mode Engine speed decreases at idle when NC, PIS, or EIL is ON 18 1 Engine stalls during start-up 1 Engine unexpectedly stops running while starting I F-45 F-26 F-27 F-34 F-36 Rough idle just after starting Idle moves up and down 16 17 l9 1 Engine stalls on deceleration I Engine unexpectedly stops running while decelerating or after deceleration Engine starts normally but vibrates excessively only just after starting Engine speed up and down periodically at idle Engine stalls at idle - Before warm-up Engine stalls at idle - After warm-up Engine stalls at idle -When AIC, PIS, or EIL running at idle when 1 20 1 ON I F-50 1 F-37 F-38 I I . . I 21 1 Engine stalls suddenly (Intermittent) I Engine intermittently stops running I F-52 Engine starts normally but vibrates excessively and stalls at idle before warm-up Engine runs normally at idle during warm-up but be- comes rouclh and stalls after warm-up F-43 F-44 24 1 Lack of power Performance is poor under load Maximum speed re- 1 duced I F-57 I Hesitates/Stumbles on acceleration Surges while cruising I I I 25 / Poor acceleration I Performance is poor while accelerating 1 F-61 I Flat spot occurs just after accelerator is depressed or mild jerking occurs during acceleration Unexpected, usually repetitive change in engine speed Knocking F-53 F-55 Runs rough on deceleration1Afterburn Abnormal combustion accompanied by audible "ping- ing" noise I F-67 I Engine runs rough while decelerating and abnormal combustion in exhaust system 1 30 1 High oil consumption I Oil consumption excessive I F-70 1 F-65 28 1 Fuel odor 29 / Exhaust sulfur smell 1 31 1 Poor fuel economy I Fuel economy unsatisfactory I F-71 I Gasoline odor in cabin Exhaust gas smells abnormal (rotten egg smell) F-69 F-70 Gartner Banana

TROUBLESHOOTING GUIDE Warning Fuel vapor is hazardous. It can very easily ignite, causing serious injury and damage. Always keep sparks and flames away from fuel. Fuel in the fuel system is under high pressure when the engine is not running. 4 Warning Fuel line spills and leaks are dangerous. Fuel can ignite and cause serious injuries or death and damage. Fuel can also irritate skin and eyes. To prevent this, always complete the following "Fuel Line Safety Procedures". 35UOFX-008 F-73 F-73 F-74 Fuel Line Safety Procedures A. Release the fuel pressure before disconnecting a fuel line. 1. Start the engine. u 2. Disconnect the fuel pump relay connector. 3. After the engine stalls, turn the ignition switch to OFF. 4. Reconnect the fuel pump relay connector. B. Avoid leakage. 1. When disconnecting a fuel line hose, wrap a rag around it to protect against fuel leakage. 2. Plug the hose after removal. C. Install hose clamps to secure the fuel pressure gauge connections. Self-Diagnosis Checker does not indicate Diagnostic Trouble Code No. but MIL comes on Self-Diagnosis Checker indicates Diagnostic Trouble Code No, of input device but MIL never comes ON Blower fan operates but no cool air is discharged 32 33 34 Pinching Hose When pinching an air hose or fuel hose with pliers, wrap the hose with a rag to prevent damage. MIL always ON MIL never ON NC does not work Checking ignition spark When checking ignition spark condition, hold the high- tension lead with insulated pliers. Note If a timing light is used to check for spark, some lights do not light at the number 2 and 4 cylinders even if the ignition system is normal. J Gartner Banana

TROUBLESHOOTING GUIDE SYMPTOM TROUBLESHOOTING 2 CRANKS NORMALLY BUT WILL NOT START (NO COMBUSTION) Engine cranks at normal speed but shows no sign of "firing" ESCwPTION : Battery in normal condition Throttle valve not held wide open throttle while cranking Fuel in tank rROUBLESHOOTlNG HINTS] ecause of no combustion, possibly no fuel is injected to engine or no ignition at all cylinders 1 No spark O Low fuel line pressure lanition control malfunction @ Low engine compression ignition system component malfunction I No fuel injection Fuel pump does not operate Fuel injector does not operate INSPECTION ACTION :heck if strong blue spark is visible at disconnected iigh-tension lead while cranking engine :heck if "00" is displayed on Self Diagnosis Checker ~ith ignition switch ON page F-79 Sonnect data link connector terminals F/P and GND ~ith jumper wire and check for fuel pump operating sound with ignition switch ON page F-114 Yes - No - Yes No - Yes - No Go to Step 3 Go to Step 2 Check ignition system (Refer to Troubleshooting "Misfire") mf Section G Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) page F-81 "88" flashes Check PCME terminal 1 E voltage ojg. page F-145 Specification: Battery positive voltage (Ignition switch ON) 0 If OK, replace PCME us? page F-143 Q If not OK, check wiring between PCME and Self-Diagno- sis Checker page F-7 Check if engine starts in this condition 0 If starts, check fuel pump relay f@ page F-117 r3 If does not start, go to Step 5 Go to Step 4 Gartner Banana