1994 MAZDA MX-5 sensor

TROUBLESHOOTING GUIDE INSPECTION Check if "00" is displayed on Self-Diagnosis Check- er with ignition switch ON page F-79 14 - -- Check for correct idle speed page F-77 IDLE MOVES UP AND DOWN Idle speed: 850 2 50 rpm (MT) 800 + 50 rpm (AT) GND TEN I DESCRIPTION I Engine speeds up and down periodically at idle [TROUBLESHOOTING HINTS] O Fuel cut occurs at idle O Air leakage of intake air system Air valve not closing after warm-up and idle speed @ Poor ignition spark reaches to fuel cut speed 8 AirIFuel mixture too rich Q Fuel injection amount fluctuating Fuel evaporative system malfunction Bad contact point inside mass airflow sensor 8 Low engine compression 5'=€% CONNECT TERMINAL AIR ADJUSTING SCREW Check for correct ignition timing at idle * page F-76 Ignition timing: 10" 2 lo BTDC - Yes - No - Yes - No Yes ACTION Go to next step Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) @r page F-81 "88" flashes Check PCME terminal 1 E voltage re page F-145 Specification: Battery positive voltage (Ignition switch ON) 3 If OK, replace PCME page 6143 3 If not OK, check wiring between PCME and Self-Diagno- sis Checker page F-7 So to next step 2heck if idle speed can be adjusted by turning air adjust ;crew 3 If OK, adjust idle speed 3 If not OK, check air valve page F-105 20 to next step idjust I@= page F-76 Gartner Banana

TROUBLESHOOTING GUIDE F 18 ENGINE STALLS DURING START-UP DESCRIPTKlN I Engine unexpectedly stops running while starting VROUBLESHOOTING HINTS] @ Misfire occurs when depressing accelerator Q Lack of engine torque for start-up AirIFuel mixture too rich or too lean AirIFuel mixture too rich or too lean Incorrect ignition timing Weak ignition INSPECTION Check if brakes are dragging Section P Check if "00 is displayed on Self-Diagnosis Check- er with ignition switch ON * page F-79 SELECT SW A Check switches for correct operation with Self- Diagnosis Checker Monitor Lamp and ignition switch ON @ page F-95 Disconnect heated oxygen sensor connector and :heck if condition improves SENSOR CONNECTOR -3 I I - Yes - No Yes Yes No - Yes Low intake air amount Low en~ine com~ression ACTION Repair us Section P Go to next step Go to next step -- Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) page F-81 "88" flashes Check PCME terminal 1 E voltage us page F-145 Specification : Battery positive voltage (Ignition switch ON) If OK, replace PCME rc+r page F-143 6 If not OK, check wiring between PCME and Self-Diagno- sis Checker e page F-7 Go to next step Lamp not ONIOFF with specified switch Check for cause (Refer to specified check sequence) uw page F-96 Lamp always ON Check wiring between PCME terminal 1 D and Self-Diag- nosis Checker page F-7 Check heated oxygen sensor @s page F-156 Go to next step Gartner Banana

TROUBLESHOOTING GUIDE 3ESCRIPTION ( Engine unexpectedly stops running while decelerating or after deceleration JROUBLESHOOTING HINTS] Ingine speed drops too much when releasing accelerator D Idle speed control malfunction Q Engine feedback control malfunction D Fuel cut control malfunction @ Idle speed misadjustment 19 INSPECTION :heck if "00" is displayed on Self-Diagnosis Check- 3r with ignition switch ON page F-79 ENGINE STALLS ON DECELERATION >heck switches for correct operation with Self- Diagnosis Checker Monitor Lamp and ignition switch ON page F-95 SELECT SW A MONITOR kt \A SYSTEM SELECT 1 Disconnect heated oxygen sensor connector and :heck if condition improves >heck if PCME terminal voltages are OK [2D, 20,2U, 2V 2Q, 2Y and 22) its page F-146 - Yes - No Yes Yes No - Yes ACTION Go to next step Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) page Fa1 "88" flashes Check PCME terminal 1 E voltage us? page F-145 Specification: Battery positive voltage (Ignition switch ON) 6 If OK, replace PCME page F-143 o If not OK, check wiring between PCME and Self-Diagno. sis Checker page F-7 Go to'next step Lamp not ONJOFF with specified switch Check for cause (Refer to specified check sequence) page F-96 Lamp always ON Check wiring between PCME terminal 1 D and Self-Diag- nosis Checker page F-7 Check heated oxygen sensor @Tage F-156 Go to next step Go to next step Check for cause (Refer to "Check Point for Each Termi- nal") E%= page F-148 Gartner Banana

TROUBLESHOOTING GUIDE DESCRIPTION I Engine intermittently stops running Before stallina, ennine condition OK 21 [TRO~ESHOOTING HINTS] O Intermittently no spark or no fuel injection Poor connection in wiring harness ENGINE STALLS SUDDENLY (INTERMITTENT) INSPECTION Check if "00" is displayed on Self-Diagnosis Check- er with ignition switch ON page F-79 Tap, move, and wiggle harness and connectors to check if PCME terminal voltages are OK (1 B, 2A, 2B and 2C) @ page F-146 ACTION Go to next step Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) @S page F-81 When checking wiring harness and connectors, tap, move, and wiggle suspect sensor and/or harness to recre- ate problem "88" flashes Check PCME terminal 1 E voltage @S page F-145 Specification: Battery positive voltage (Ignition switch ON) 0 If OK, replace PCME page F-143 0 If not OK, check wiring between PCME and Self-Diagno- sis Checker IS= page F-7 Go to Troubleshooting No.2 "CRANKS NORMALLY BUT WILL NOT START (NO COM- BUSTION)" page F-17 Check for cause (Refer to "Check Point for Each Termi- nal") page F-148 Gartner Banana

TROUBLESHOOTING GUIDE F b AirIFuel mixture leaning when depressing accelerator Fuel injection control malfunction (Correction for accelerating condition) Air leakage of intake air system Fuel line Pressure low 22 park adbance control malfunction HESITATESISTUMBLES ON ACCELERATION 0 - STEF DESCRIPTION] Flat spot occurs just after accelerator depressed or mild jerking occurs during acceleration rrROUBLESHOOTlNG HINTS] ACTION INSPECTION Check if "00" is displayed on Self-Diagnosis Check- er with ignition switch ON page F-79 SELECT SWA SYSTEM SELECT 1 - Yes Go to next step No - Yes - No Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) uz page F-81 "88'1 flashes Check PCME terminal 1 E voltage page F-145 Specification: Battery positive voltage (Ignition switch ON) 6 If OK, replace PCME page F-143 Q If not OK, check wiring between PCME and Self-Diagno- sis Checker US page F-7 Check switches for correct operation with Self- Diagnosis Checker Monitor Lamp and ignition switch ON Go to next step page F-95 SELECT SW A Lamp not ON/OFF with specified switch Check for cause (Refer to specified check sequence) page F-96 Lamp always ON Check wiring between PCME terminal 1 D and Self-Diag- nosis Checker page F-7 Disconnect heated oxygen sensor connector and :heck if condition improves Yes - No - Yes -- -- Check heated oxygen sensor @s page F-156 Go to next step - :heck if PCME terminal voltages are OK :2M, 20, and 2Q) page F-146 Go to next step Check for cause (Refer to "Check Point for Each Termi- nal") page F-148 Gartner Banana

TROUBLESHOOTING GUIDE PROUBLESHOOTING HINTS] 3 Air/Fuel mixture too lean or too rich Fuel injection control malfunction Air leakage of intake air system 23 Fuel line pressure low Fuel evaporative malfunction 0 Spark advance control malfunction -- SURGES WHILE CRUISING - STEP DESCRIPTION ( Unexpected change in engine speed which is usually repetitive INSPECTION ACTION - Yes - No - Yes - No Check if "00" is displayed on Self-Diagnosis check- er with ignition switch ON page F-79 Go to next step SELECTSW A SYSTEM SELECT 1 Diagnostic Trouble Code No. displayed Check for cause (Refer to specified check sequence) page ~-81 -- - "88" flashes Check PCME terminal 1 E voltage @i= page F-145 Specification: Battery positive voltage (Ignition switch ON) 0 If OK, replace PCME @ page F-143 o If not OK, check wiring between PCME and Self-Diagno- sis Checker US page F-7 Check switches for correct operation with Self- Diagnosis Checker Monitor Lamp and ignition Go to next step switch ON w page F-95 SELECT SW A Lamp not ONIOFF with specified switch Check for cause (Refer to specified check sequence) page F-96 Lamp always ON Check wiring between PCME terminal 1 D and Self-Diag- nosis Checker @ page F-7 Disconnect heated oxygen sensor connector and check if condition improves Yes No - Yes Check heated oxygen sensor page F-156 Go to next step :heck if PCME terminal voltages are OK (1 R, 1 T, 2M, 20, and 2Q) as page F-146 Go to next step Check for cause (Refer to "Check Point for Each Termi- nal") * page F-148 Gartner Banana

F TROUBLESHOOTING GUIDE DESCRIPTION I Blower fan operates but cool air not expelled ITROUBLESHOOTING HINTS] Open or short circuit in wiring harness NC relay malfunction 34 Air conditioning sensor malfunction Magnetic clutch malfunction PCME malfunction AIC DOES NOT WORK INSPECTION ;round terminal B at NC relay with jumper wire Yes tnd check if condenser fan operates when ignition ;witch is turned ON #C RELAY I ;round terminal B at PCME 1 J terminal with jump- Yes ,r wire and check if condenser fan operates when gnition switch is turned ON - No :heck if Air conditioning sensor is OK Yes Section U ACTION 30 to next step 30 to A/C system Troubleshooting Section U 30 to next step qepair wire between PCME and A/C relay page F-7 Try known good PCME page F-144 ;heck Air conditioning sensor and wiring Section U Gartner Banana

ENGINE TUNE-UP 8. If the marks are not aligned, remove the ignition coil bracket and push the ignition coil aside for easy access and then loosen the crankshaft position sensor lock bolts, and turn the crankshaft position sensor to make the adjustment. 9. Tighten the distributor lock bolts to the specified torque. Tightening torque: 19-25 N-m (1.9-2.6 kgfem, 14--18 ftqlbf) 10. After adjusting the ignition timing, disconnect the jumper wire or SST from the data link connector. 11. Increase the engine speed and verify that the ignition timing advances. 12. Verify that the ignition timing is within the specification. Ignition timing: BTDC 6-18' ldle Speed 1. Perform Preparation. (Refer to page F-76.) 2. Set switch A to position 1. 3. Set test switch to SELF TEST. 4. With the coolant fan off, verify that the idle speed is within specification. ldle speed (Neutral): 800-900(850 + 50) rpm [MT] (P range): 750--850(800 -c 50) rpm [AT] 5. If not within the specification, adjust the idle by turning the air adjusting screw. 6. Disconnect the SST. Gartner Banana