1994 MAZDA MX-5 Workshop Manual

F ON-BOARD DIAGNOSIS SYSTEM CODE No. I 03 (SGT SIGNAL) iTEP I INSPECTION ACTION - Yes - No ' I Are there any poor connections in crankshaft posi- tion sensor circuit? Repair or replace connector I Go to next step I 1 Is Code No.04 present at same time? Yes - No Go to next ste~ I GO to Step 5 I Yes - No 3 Go to next step I Is there continuity between crankshaft position sen- sor terminal A and ground? Check for open circuit in wiring from crankshaft position sensor to ground Go to next step Check for open circuit in wiring from crankshaft position sensor to main relay 1 Is there battery positive voltage at crankshaft posi- tion sensor terminal B Yes - No Yes 5 6 Go to next step Is there continuity between crankshaft position sen- sor and PCME? Crankshaft position sensor I PCME C I 2 E Is there approx. 5V at PCME terminal 2E? (With crankshaft position sensor connector discon- nected) Check for open circuit in wiring from crankshaft position sensor to PCME Yes Go to next step I Replace PCME as page 6143 Replace crankshaft position sensor page F-153 Yes - No - 7 Check for short circuit in wiring from crankshaft position sensor to PCME 15UOFX-026 Is there approx. 5V at crankshaft position sensor terminal C? (At harness-side connector with con- nector disconnected) I CODE No. I 04 (SGC SIGNAL) I STEP I INSPECTION 1'1 Are there any poor connections in crankshaft posi- tion sensor circuit? Repair or replace connector Go to next step Go to next step 121 Is Code No.03 also present? Go to Step 5 Go to next step Is there continuity between crankshaft position sen- sor terminal A and ground? Check for open circuit in wiring from crankshaft position sensor to ground Go to next step Check for open circuit in wiring from crankshaft position sensor to main relay 4 Is there continuity between crankshaft position sen- sor and PCME? Go to next step Is there battery positive voltage at crankshaft posi- tion sensor terminal B? Yes - No No - Yes - No 6 Check for open circuit in wiring from crankshaft position sensor to PCME Go to next step Replace PCME page F-143 Crankshaft position sensor I PCME D Replace crankshaft position sensor page F-153 Check for short circuit in wiring from crankshaft position sensor to PCME 2G 7 Is there approx. 5V at PCME terminal 2G? (With crankshaft position sensor connector discon- nected) Is there approx. 5V at crankshaft position sensor terminal D? (At harness-side connector with con- nector disconnected) Yes No Gartner Banana

ON-BOARD DIAGNOSIS SYSTEM F Circuit Diagram TO IGNITION SWITCH TO BATTERY MAIN RELAY :AF*, CRANKSHAFT POSITION SENSOR Gartner Banana

F ON-BOARD DIAGNOSIS SYSTEM CODE No. ACTION Yes I Repair or replace connector 08 (MASS AIRFLOW SENSOR) iTEP 1 No I Go to next step INSPECTION Are there any poor connections in mass airflow sensor circuit? Yes 2 Check for open circuit in wiring from mass airflow sensor terminal E to wound Is Code No.10 present at same time? No ( Go to next step 1 Is there continuity between mass airflow sensor connector and PCME? Yes Go to next step Mass airflow sensor E B I Yes I Replace PCME . us page F-143 PCME 2F 20 No Check for short circuit in wiring from mass airflow sensor to PCME Are PCME terminals 20 and 2F voltages OK? page F-146 Check for open circuit in wiring from mass airflow sensor to PCME CODE No. ACTION 09 (ENGINE COOLANT TEMPERATURE SENSOR) STEP 1 Repair or replace connector Go to next step INSPECTION Are there any poor connections in engine coolant temperature sensor circuit? Go to next step Yes - No 2 Engine coolant temperature sensor PCME Check for open circuit in wiring from engine coolant tem- perature sensor to PCME Is there continuity between engine coolant temper- ature sensor and PCME? 4 Is resistance of engine coolant temperature sensor 1 /om I yes Yes Go to next step Coolant temp. Resistance 1 I 20°C ( 68°F) 1 2.21-2.69 kR Replace engine coolant temperature sensor page F-154 Is same Code No. present after performing after repair procedure? page F-94 Go to next step Engine coolant temperature sensor and circuit OK Are PCME terminals 2Q and 2D voltages OK? page F-146 Re~lace PCME ~aae F-143 Check for short circuit in wiring from engine coolant tem- perature sensor to PCME Gartner Banana

ON-BOARD DIAGNOSIS SYSTEM I CODE No. I -- -- 10 (INTAKE AIR TEMPERATURE SENSOR - IN MASS AIRFLOW SENSOR) INSPECTION Are there any poor connections in intake air tem- Yes perature sensor circuit? No Is there continuity between intake air temperature Yes sensor (in mass airflow sensor) and PCME? Intake air temperature sensor PCME I D 2 P Is resistance of intake air temperature sensor (in Yes mass airflow sensor) OK? Terminal I Temperature I Resistance No C-D I 20°C {68"F) 1 2.21-2.69 kR Is same Code No. present after performing after Yes repair procedure? page F-94 No Are powertrain control module (engine) terminals 2P and 2D voltages OK? @= page F-146 ACTION Repair or replace connector Go to next step Go to next step Check for open circuit in wiring from intake air temperature sensor (in mass airflow sensor) to PCME Go to next step Replace mass airflow sensor @= page F-152 -- Go to next step Intake air temperature sensor and circuit OK Replace PCME IS= page F-143 Check for short circuit in wiring from intake air temperature sensor to PCME CODE No. 12 (THROTTLE POSITION SENSOR) I Check throttle position sensor circuit for poor con- nection Throttle position sensor PCME D 2K 2 Repair or replace STEP 1 INSPECTION Yes No ACTION Repair or replace connector Go to next step Check wire harness between throttle position sen- sor and PCME for continuity 3 Replace PCME IS= page F-143 15UOFX-032 Yes CODE No. Go to next step 35UOFX-04 Check if PCME terminal 2M voltage is OK page F-146 14 (BAROMETRIC ABSOLUTE PRESSURE SENSOR) Yes No Replace PCME I@= page F-143 Check for short circuit in wiring from throttle position sen- sor to PCME Gartner Banana

F ON-BOARD DIAGNOSIS SYSTEM CODE No. 15 (HEATED OXYGEN SENSOR: INACTIVATION) 111 Are there any poor connections in heated oxygen sensor circuit? Note a If Code Nos.15 and 17 are both present, first perform the checking procedure for Code No.17 STEP 1 INSPECTION I ACTION 2 3 Circuit Diagram I Yes No 4 5 ENGINE COOLANT MASS AIRFLOW TEMPERATURE SENSOR SENSOR ~ Repair or replace connector Go to next steD Is heated oxygen sensor output voltage OK? page F-155 Is there continuity between heated oxygen sensor and PCME terminal 2N? THROTTLE POSITION SENSOR 35UOFX-065 Is PCME terminal 2N voltage OK? Is sensitivity of heated oxygen sensor OK? * page F-156 PCME Yes No Yes No Go to next step Replace heated oxygen sensor r@ page F-156 Go to next step Check for open circuit in wiring from heated oxygen sen- sor to PCME Yes No Yes No Go to next step Check for short circuit in wiring from heated oxygen sen- sor to PCME Replace PCME aPi. page F-143 Replace heated oxygen sensor r@ page F-156 Gartner Banana

ON-BOARD DIAGNOSIS SYSTEM F CODE No. 16 (EGR FUNCTION SENSOR) 1 ACTION INSPECTION Does EGR function sensor circuit have a poor con- nection? Is EGR control valve OK? page F-125 Is resistance of EGR function sensor OK? Resistance: (A) o (6) Approx. 2.7 kR (A) o (C) 0.5-2.7 kS2 (B) i+ (C) 0.1-2.4 kR Is there continuity between EGR function sensor and PCME? I EGR function sensor I PCME I Is there 4.5-5.5V at C terminal of EGR function sensor connector? page F-124 Is PCME terminal 2J voltage OK? page F-146 Circuit Diagram Yes No Yes I No I Replace EGR control valve Repair or replace connector Go to next step Go to next step No Yes Replace EGR control valve Go to next step Yes Replace PCME No Check for open circuit in wiring from EGR function sensor to PCME Yes No EGR FUNCTION SENSOR Go to next step Check for short circuit in wiring from EGR function sensor terminal C to PCME Yes No Replace PCME Short circuit in wiring harness EGR function sensor termi- nal C to PCME 39UOFX-106 Gartner Banana

F ON-BOARD DIAGNOSIS SYSTEM CODE No. 17 (HEATED OXYGEN SENSOR: INVERSION) I Circuit Diagram INSPECTION Warm up engine and run it at 2,500-3,000 rpm for 3 min. HEATED OXYGEN SENSOR ACTION Does monitor lamp of Self-Diagnosis Checker illu- minate at idle? Are spark plugs clean? Is heated oxygen sensor voltage OK? * page F-156 Is same Code No. present after performing after repair procedure? ESI= page F-90 Is there continuity between heated oxygen sensor and PCME terminal 2N? Is PCME terminal 2N voltage OK? * page F-146 PCME Yes No Yes No Yes No Yes No Yes No Yes No Go to next step Check for air leak in vacuum hoses or emission compo- nents Check for contaminated heated oxygen sensor Check for insufficient fuel injection Go to next step Clean or replace spark plugs Go to next step Replace heated oxygen sensor page F-156 Go to next step Check for short circuit in wiring from heated oxygen sen- sor to PCME terminal 2N Go to next step Check for open circuit in wiring from heated oxygen sen- sor to PCME Replace PCME page F-143 Check for short circuit in wiring from heated oxygen sen- sor to PCME Gartner Banana

ON-BOARD DIAGNOSIS SYSTEM CODE No. 25 (PRC SOLENOID VALVE) I Condition Ignition switch ON ACTION Repair connector and/or wiring harness Go to next step Go to next step STEP 1 2 Check for open or short circuit in wiring harness (PRC Battery positive solenoid valve terminal A - Main relay terminal D) voltaae 3 CODE No. 26 (PURGE SOLENOID VALVE) iTEP I INSPECTION I ACTION 4 ' I Are there any poor connections in purge solenoid valve circuit? INSPECTION I . - I Is continuity between PRC solenoid valve terminal B and PCME terminal 2R? I 2 Is resistance of purge solenoid valve OK? Does PRC solenoid valve circuit have a poor con- nection? Is connector terminal A voltage OK with PRC sole- noid valve connector disconnected? 36UOF2-039 Is PRC solenoid valve OK? as page F-123 Is there battery positive voltage at terminal A of purge solenoid valve circuit? Yes No Yes Yes Solenoid valve Check for short circuit in wiring harness (PRC solenoid valve terminal B - PCME terminal 2R) No Yes ' No 5 Is PCME terminal 2X voltage OK? page F-147 Q If OK, go to next step e If not OK, repair wiring harness Repair wiring harness Replace PCME page F-143 Replace PRC solenoid valve Yes Repair or replace connector No Go to next step Yes Go to next step No Replace purge solenoid valve page F-132 Yes Go to next step No Check for open circuit in wiring from purge solenoid valve I to main relay I No Check for open circuit in wiring from purge solenoid valve I to PcME I Yes I Replace PCME page F-143 No Check for short circuit in wiring from purge solenoid valve to PCME 15UOF2-035 Gartner Banana