Home

< Previous   Next >

2008 - MX-5 - Engine

DTC P0139 [LF]



DTC P0139

Rear HO2S circuit problem

DETECTION CONDITION

  • The PCM monitors the rich (0.4 V) to lean (0.3 V) response time of the rear HO2S. The PCM measures the response time when the following conditions are met. The PCM determines a rear HO2S response deterioration malfunction when the measured response time is more than the threshold value (80 ms) five consecutive times.

    • MONITORING CONDITIONS
    • PCM Adaptive Memory Production, HO2S heater, HO2S, and TWC Repair Verification Drive Mode

    • Following conditions are met:

      • During deceleration fuel cut

      • Engine speed is above 500 rpm.

      • Engine coolant temperature is above 70 °C {158 °F}.

      • Rear HO2S output voltage ia above 0.4 V.

  • The PCM monitors for a time-out malfunction (when rear HO2S remains above 0.3 V for longer than a specified period of time during fuel cut control). The PCM measures the amount of time from when the following conditions are met until the rear HO2S output voltage drops below 0.3 V. The PCM determines a rear HO2S time-out malfunction when the detected time is more than the threshold value (6 s) three consecutive times.

    • MONITORING CONDITIONS
    • PCM Adaptive Memory Production, HO2S heater, HO2S, and TWC Repair Verification Drive Mode

    • Following conditions are met:

      • During deceleration fuel cut

      • Engine speed is above 500 rpm.

      • Engine coolant temperature is above 70 °C {158 °F}.

      • Rear HO2S is activated (more than 0.55 V)

    Diagnostic support note
  • This is an intermittent monitor. (HO2S)

  • The MIL illuminates if the PCM detects the above malfunction condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM.

  • DIAGNOSTIC MONITORING TEST RESULTS is available.

  • PENDING CODE is available if the PCM detects the above malfunction condition during the first drive cycle.

  • FREEZE FRAME DATA is available.

  • The DTC is stored in the PCM memory.

POSSIBLE CAUSE

  • Rear HO2S deterioration

  • Rear HO2S malfunction

  • Looseness rear HO2S

  • Pressure regulator (built-in fuel pump unit) malfunction

  • Fuel pump malfunction

  • Fuel filter (built-in fuel pump unit) clogged or restricted

  • Fuel leakage on fuel line from fuel distribution pipe and fuel pump

  • Leakage exhaust system

  • Purge solenoid valve malfunction

  • Purge solenoid hoses improper connection

  • Insufficient compression

  • Engine malfunction (Leakage engine coolant)


Diagnostic procedure

STEP

INSPECTION

ACTION

1

VERIFY FREEZE FRAME DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED
  • Have FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS (HO2S related) been recorded?

Yes

Go to the next step.

No

Record the FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS on the repair order, then go to the next step.

2

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.

3

VERIFY RELATED PENDING AND STORED DTC
  • Turn the ignition switch off, then to the ON position (Engine off).

  • Verify pending and /or stored DTCs using the M-MDS.

  • Is DTC P0443 also present?

Yes

Go to DTC P0443 troubleshooting procedures, then go to Step 13.

No

Go to the next step.

4

IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA
  • Is DTC P0139 on FREEZE FRAME DATA?

Yes

Go to the next step.

No

Go to troubleshooting procedures for DTC on FREEZE FRAME DATA.

(See DTC TABLE [LF].)

5

INSPECT INSTALLATION OF REAR HO2S
  • Inspect if the rear HO2S is loosely installed.

  • Is the front HO2S installed securely?

Yes

Go to the next step.

No

Retighten the rear HO2S, then go to Step 10/

(See REAR HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [LF].)

6

IINSPECT GAS LEAKAGE FROM EXHAUST SYSTEM
  • Visually inspect if there is any gas leakage between the exhaust manifold and rear HO2S.

  • Is there gas leakage?

Yes

Repair or replace any malfunctioning exhaust part, then go to Step 10.

No

Go to the next step.

7

INSPECT REAR HO2S

Yes

Replace the rear HO2S, then go to Step 10.

(See REAR HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [LF].)

No

Go to the next step.

8

INSPECT FUEL LINE PRESSURE

Yes

Go to the next step.

No

Repair or replace any malfunctioning exhaust part, then go to Step 10.

9

INSPECT SEALING OF ENGINE COOLANT PASSAGE

Yes

Repair or replace malfunctioning part according to the inspection result. Then go to the next step.

No

Go to the next step.

10

VERIFY TEOUBLESHOOTING OF DTC P0139 COMPLETED
  • Make sure to reconnect all disconnected connectors.

  • Clear the DTC from the PCM memory using the M-MDS or equivalent.

  • Perform the “PCM Adaptive Memory Produce Drive Mode“ and “HO2S heater, HO2S, and TWC Repair Verification Drive Mode“.

    (See OBD-II DRIVE MODE [LF].)

  • Is the PENDING CODE for this DTC present?

Yes

Replace the PCM, then go to the next step.

(See PCM REMOVAL/INSTALLATION [LF].)

No

Go to the next step.

11

VERIFY AFTER REPAIR PROCEDURE

Yes

Go to the applicable DTC inspection.

(See DTC TABLE [LF].).

No

DTC troubleshooting completed.




< Previous   Next >
Back to Top
© 2012 Mazda North American Operations, U.S.A.