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Home >> Mazda >> 2010 >> 5 Touring, 2.3 L >> Repair and Diagnosis >> Engine Performance >> System >> On-Board Diagnostic [Engine Control System L3] >> DTC P0140 >> Diagnostic procedure
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Diagnostic procedure

DTC P0140 [L3] DIAGNOSTIC PROCEDURE

STEP INSPECTION ACTION
1 IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA (MODE 2) 
  • Is DTC P0140 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 (A/F sensor, HO2S related) been recorded?
 Yes Go to the next step.
No Record the FREEZE FRAME DATA (Mode 12) and DIAGNOSTIC MONITORING TEST RESULTS on the 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 AND STORED DTC 
NOTE:
  • If fuel monitor DTC, DTC P0132 is retrieved, ignore it until P0140 is fixed.

  • Turn the ignition switch off, then to the ON position. (Engine off)
  • Verify pending and stored DTCs using M-MDS.
  • Is other DTC present?
 Yes Go to the appropriate DTC troubleshooting procedures. (See DTC TABLE .)
No Go to the next step.
5 INSPECT INSTALLATION OF HO2S 
  • Check if HO2S is loosely installed.
  • Is sensor installed securely?
 Yes Go to the next step.
No Install sensor securely, then go to Step 12.
6 INSPECT GAS LEAKAGE FROM EXHAUST SYSTEM 
  • Visually check if any gas leakage is found between exhaust pipe and HO2S.
  • Is there any gas leakage?
 Yes Repair or replace any malfunctioning exhaust part, then go to Step 12.
No Go to the next step.
7 INSPECT HO2S 
 Yes Go to Step 10.
No Go to the next step.
8 INSPECT SIGNAL CIRCUIT OF HO2S FOR SHORT TO GROUND 
  • Turn the ignition switch off.
  • Disconnect the HO2S connector.
  • Inspect for continuity between HO2S terminal A (wiring-harness-side) and body ground.
  • Is there continuity?
 Yes If the short to ground circuit could be detected:
  • Repair or replace for a possible short to ground.

If the short to ground circuit could not be detected:

Then go to Step 12.
No Go to the next step.
9 INSPECT SIGNAL CIRCUIT OF HO2S FOR OPEN CIRCUIT 
  • HO2S connector is disconnected.
  • Turn the ignition switch off.
  • Disconnect the PCM connector.
  • Inspect for continuity between HO2S terminal A (wiring-harness-side) and PCM terminal 2Q (wiring-harness-side).
  • Is there continuity?
 Yes Replace the HO2S, then go to Step 12.
(See AIR FUEL RATIO (A/F) SENSOR, HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION .)
No Repair or replace the wiring harness for open circuit, then go to Step 12.
10 INSPECT SEALING OF ENGINE COOLANT PASSAGE 
WARNING:
  • Removing the radiator cap when the radiator is hot is dangerous. Scalding coolant and steam may shoot out and cause serious injury.
  • When removing the radiator cap, wrap a thick cloth around and turn it slowly.

  • Remove radiator cap.
  • Perform procedure to bleed air from the engine coolant, then run the engine at idle.
  • Is there any small bubble, which makes the engine coolant white at filling opening?
    NOTE:
    • Large bubbles are normal since they are remaining air coming out from the engine coolant passage.
 Yes Air gets in from poor sealing on head gasket or other areas between combustion chamber and engine coolant passage.
Repair or replace the malfunctioning part, then go to Step 12.
No Go to the next step.
11 INSPECT ENGINE COMPRESSION 
 Yes Go to the next step.
No Perform engine overhaul for repairs, then go to the next step.
12 VERIFY TROUBLESHOOTING OF DTC P0140 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 KOEO self-test with M-MDS, or the "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.
13 VERIFY AFTER REPAIR PROCEDURE 
 Yes Go to the applicable DTC troubleshooting.
(See DTC TABLE .)
No Troubleshooting completed.
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