Mike's Workshop Manuals: Service manuals for every vehicle
Home >> Mazda >> 2010 >> 5 Touring, 2.3 L >> Repair and Diagnosis >> Engine Performance >> System >> On-Board Diagnostic [Engine Control System L3] >> DTC P0300 >> Diagnostic procedure

Diagnostic procedure

DTC P0300 [L3] DIAGNOSTIC PROCEDURE

STEP INSPECTION ACTION
1 IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA (MODE 2) 
  • Is DTC P0300 on FREEZE FRAME DATA (Mode 2)?
Yes Go to the next step.
No Go to troubleshooting for DTC on FREEZE FRAME DATA (Mode 2).
(See DTC TABLE .)
2 VERIFY FREEZE FRAME DATA (MODE 12) AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED 
  • Have FREEZE FRAME DATA (Mode 12) and DIAGNOSTIC MONITORING TEST RESULTS (Misfire related) been recorded?
Yes Go to the next step.
No Record the FREEZE FRAME DATA (Mode 12) and DIAGNOSTIC MONITORING TEST RESULTS on repair order, then go to the next step.
3 VERIFY RELATED REPAIR INFORMATION AVAILABILITY 
  • Verify related Service Bulletins and/or on-line repair information availability.
  • Is any related repair information available?
Yes Perform repair or diagnosis according to the available repair information.
  • If the vehicle is not repaired, go to the next step.
No Go to the next step.
4 VERIFY RELATED PENDING CODE OR STORED DTC 
  • Turn the ignition switch off then to the ON position (Engine off).
  • Verify related pending code or stored DTCs.
  • Are other DTCs present?
Yes Go to the appropriate DTC troubleshooting.
(See DTC TABLE .)
No Go to the next step.
5 VERIFY CURRENT INPUT SIGNAL STATUS (KEY TO ON/IDLE) 
  • Access PCM PIDs APP1, APP2, ECT, IAT, MAF, RPM, TP REL, and VSS using M-MDS. (See PCM INSPECTION .)
  • Is there any signal that is far out of specification when the ignition switch is turned to the ON position and the engine idles?
Yes Inspect the suspected circuit.
  • If the inspection results are normal:
    • Go to the next step.
  • If the inspection results are not normal:
    • Repair or replace the malfunctioning part according to the inspection results, then go to Step 20.
No Go to the next step.
6 VERIFY CURRENT INPUT SIGNAL STATUS UNDER TROUBLE CONDITION 
CAUTION:
  • While performing this step, always operate the vehicle in a safe and lawful manner.
  • When the M-MDS is used to observe monitor system status while driving, be sure to have another technician with you, or record the data in the M-MDS using the PID/DATA MONITOR AND RECORD capturing function and inspect later.

  • Inspect the same PIDs as in Step 5 while simulating FREEZE FRAME DATA (Mode 2) condition.
  • Is there any signal which causes drastic changes?
Yes Inspect the suspected circuit.
  • If the inspection results are normal:
    • Go to the next step.
  • If the inspection results are not normal:
    • Repair or replace the malfunctioning part according to the inspection results, then go to Step 20.
No Go to the next step.
7 INSPECT CMP SENSOR 
Yes Go to the next step.
No Inspect installation condition and damages on timing chain and gears, repair the malfunctioning part.
  • If it is normal, replace the CMP sensor.

Then go to Step 20.
8 VERIFY CKP SENSOR INSTALLATION CONDITION 
  • Inspect for CKP sensor looseness.
  • Is CKP sensor loosen?
Yes Retighten the CKP sensor, then go to the next step.
No Go to the next step.
9 INSPECT IGNITION SYSTEM OPERATION 
Yes Go to the next step.
No Repair or replace malfunctioning part according to spark test result. Then go to Step 20.
10 INSPECT MAF PID 
  • Start the engine.
  • Access PCM PID MAF using the M-MDS.
  • Race the engine and verify that MAF PID changes quickly according to change in the engine speed.
  • Is MAF PID response normal?
Yes Go to Step 12.
No Go to the next step.
11 INSPECT EXCESSIVE AIR SUCTION IN INTAKE AIR SYSTEM 
NOTE:
  • Engine speed may change when rust penetrating agent is sprayed on the air suction area.

  • Inspect for air leakage at following:
    • Between the MAF sensor and throttle body
    • Between throttle body and intake manifold
  • Is there any malfunction?
Yes Repair or replace suspected part, then go to Step 20.
No Replace the MAF sensor, then go to Step 21.
12 INSPECT FUEL LINE PRESSURE 
Yes Go to Step 14.
No If the fuel line pressure is too low, go to the next step. If the fuel line pressure is excess high, replace the fuel pump unit, then go to Step 20.
13 INSPECT FUEL LINE FROM FUEL PUMP TO FUEL DISTRIBUTOR 
  • Visually inspect fuel line for fuel leakage.
  • Is there any fuel leakage?
Yes Replace suspected fuel line, then go to Step 21.
No Inspect fuel filters for following:
  • Foreign materials or stain inside fuel filter (low-pressure side)

Perform following actions depend on the result above.
  • If foreign materials or stain is found inside fuel filter (low-pressure side), clean the fuel tank and filter (low-pressure side).
  • If normal, replace the fuel pump unit.

Then, go to Step 20.
14 INSPECT VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION 
Yes Go to the next step.
No Repair or replace malfunctioning part according to variable valve timing control system inspection results, then go to Step 20.
15 INSPECT OPERATION OF PURGE CONTROL SOLENOID VALVE 
  • Turn the ignition switch off.
  • Connect the vacuum pump to purge control solenoid valve and apply vacuum to solenoid.
  • Verify that solenoid holds vacuum.
  • Turn the ignition switch to the ON position (Engine off).
  • Access EVAPCP PID in SIMULATION TEST using the M-MDS.
  • Set duty value to 100% for EVAPCP PID.
  • Apply vacuum while turning solenoid from OFF to ON and simulating EVAPCP PID with 100% duty value.
  • Verify that solenoid releases vacuum while solenoid is turned ON.
  • Is purge control solenoid valve operation normal?
Yes Go to the next step.
No Replace the purge control solenoid valve, then go to Step 20.
16 INSPECT OPERATION OF EGR VALVE 
  • Remove the EGR valve.
  • Visually inspect the EGR valve for stuck to open.
  • Is EGR valve stuck to open?
Yes Repair or replace the EGR valve, then go to Step 20.
No Go to the next step.
17 INSPECT SEALING OF ENGINE COOLANT PASSAGE 
Yes Repair or replace malfunctioning part according to inspection results.
Then go to Step 20.
No Go to the next step.
18 INSPECT ENGINE COMPRESSION 
Yes Go to the next step.
No Perform engine overhaul for repairs, then go to Step 20.
19 INSPECT PCV VALVE OPERATION 
Yes Go to the next step.
No Replace the PCV valve, then go to the next step.
20 VERIFY TROUBLESHOOTING OF MISFIRE DTC COMPLETED 
  • Make sure to reconnect all disconnected connectors.
  • Turn the ignition switch to the ON position (Engine off).
  • Clear the DTC from the memory using the M-MDS.
  • Perform the KOER self-test with M-MDS, or A/F sensor heater, HO2S heater, A/F sensor, HO2S, and TWC Repair Verification Drive Mode. (See KOEO/KOER SELF TEST .) (See OBD-II DRIVE MODE .)
  • Is the PENDING CODE for this DTC present?
Yes Replace the PCM, then go to the next step.
(See PCM REMOVAL/INSTALLATION .)
No Go to the next step.
21 VERIFY AFTER REPAIR PROCEDURE 
Yes Go to the applicable DTC troubleshooting.
(See DTC TABLE .)
No Troubleshooting completed.