Home

< Previous   Next >

2008 - MX-5 - Engine

DTC P0038 [LF]



DTC P0038

Rear HO2S heater circuit high input

DETECTION CONDITION

  • The PCM monitors the rear HO2S heater control voltage when the PCM turns the rear HO2S heater off. If the control voltage exceeds 25% of the battery voltage, the PCM determines that the rear HO2S heater control circuit voltage is high.

    Diagnostic support note
  • This is a continuous monitor (HO2S heater).

  • 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.

  • 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 heater malfunction

  • Connector or terminal malfunction

  • Short to power supply in wiring harness between rear HO2S terminal D and PCM terminal 2BE

  • PCM malfunction


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 heater 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

INSPECT REAR HO2S CONNECTOR FOR POOR CONNECTION
  • Turn the ignition switch off.

  • Disconnect the rear HO2S connector.

  • Inspect for poor connection (such as damaged/pulled-out pins, and corrosion).

  • Is there any malfunction?

Yes

Repair or replace the terminal, then go to Step 7.

No

Go to the next step.

4

INSPECT REAR HO2S HEATER CONTROL CIRCUIT FOR SHORT TO POWER SUPPLY
  • Turn the ignition switch to the ON position (Engine off).

  • Measure the voltage between rear HO2S terminal D (wiring harness-side) and body ground.

  • Is the voltage B+?

Yes

Repair or replace the wiring harness for a possible short to power supply, then go to Step 7.

No

Go to the next step.

5

INSPECT PCM CONNECTOR FOR POOR CONNECTION
  • Turn the ignition switch off.

  • Disconnect the PCM connector.

  • Inspect for poor connection (such as damaged/pulled-out pins, and corrosion).

  • Is there any malfunction?

Yes

Repair or replace the terminal, then go to Step 7.

No

Go to the next step.

6

INSPECT REAR HO2S HEATER

Yes

Replace the rear HO2S, then go to the next step.

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

No

Go to the next step.

7

VERIFY TROUBLESHOOTING OF DTC P0038 COMPLETED
  • Make sure to reconnect all disconnected connectors.

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

  • Perform the KOEO self-test (using M-MDS) or the HO2S heater, HO2S, and TWC Repair Verification Drive Mode (not using M-MDS).

    (See KOEO/KOER SELF TEST [LF].)

    (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.

8

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.