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2008 - MX-5 - Engine

DTC P0137 [LF]



DTC P0137

Rear HO2S circuit low input

DETECTION CONDITION

  • The PCM monitors input voltage from rear HO2S. If the input voltage from the rear HO2S is below 0.1 V for 35.2 s the PCM determines that circuit input is low.

    • MONITORING CONDITIONS
    • HO2S, HO2S heater and TWC repair verification drive mode

    • Following conditions are met.

      • Engine speed is above 1,500 rpm.

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

      • Fuel injector control in rear HO2S closed loop control.

  • The PCM monitors the input voltage from the rear HO2S when the following conditions are met. Under the following monitoring conditions, if the input voltage from the rear HO2S does not even exceed 0.1 V though the short term fuel trim is controlled up to 20.5 % for 9.6 s, the PCM determines that sensor circuit input is low.

    • MONITORING CONDITIONS
    • HO2S, HO2S heater and TWC repair verification drive mode

    • Following conditions are met for above 20.8 s.

      • Engine speed is above 1,500 rpm.

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

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

  • The MIL illuminates if the PCM detects 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 malfunction

  • Short to body ground circuit in wiring between rear HO2S terminal A and PCM terminal 2Q

  • Open circuit in wiring between rear HO2S terminal A and PCM terminal 2Q

  • Open circuit in wiring between rear HO2S terminal B and PCM terminal 2BH

  • 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 related) been recorded?

Yes

Go to 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 OR STORED DTCS
  • Turn the ignition switch off, then to the ON position. (Engine off)

  • Verify pending code or stored DTCs using M-MDS.

  • Is other DTC present?

Yes

Go to the appropriate DTC troubleshooting procedures.

(See DTC TABLE [LF].)

No

Go to the next step.

4

IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA
  • Is DTC P0137 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 REAR HO2S CONNECTOR FOR POOR CONNECTION
  • Turn the ignition switch off.

  • Disconnect rear HO2S connector.

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

  • Is there any malfunctions?

Yes

Repair terminal, then go to Step 11.

No

Go to the next step.

6

INSPECT PCM CONNECTOR FOR POOR CONNECTION
  • Disconnect PCM connector.

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

  • Is there any malfunctions?

Yes

Repair terminal, then go to Step 11.

No

Go to the next step.

7

INSPECT REAR HO2S SIGNAL CIRCUIT FOR OPEN
  • Inspect continuity between rear HO2S terminal A (harness-side) and PCM terminal 2Q (harness-side).

  • Is there any continuity?

Yes

Go to the next step.

No

Repair or replace harness for open circuit, then go to Step 11.

8

INSPECT REAR HO2S SIGNAL CIRCUIT FOR SHORT TO GROUND CIRCUIT
  • Inspect continuity between rear HO2S terminal A (harness-side) and body ground.

  • Is any voltage reading?

Yes

Replace short to power supply circuit, then go to Step 11.

No

Go to the next step.

9

INSPECT REAR HO2S GROUND CIRCUIT FOR OPEN
  • Inspect continuity between rear HO2S terminal B (harness-side) and PCM terminal 2BH(harness-side).

  • Is there any continuity?

Yes

Go to the next step.

No

Repair or replace harness for open circuit, then go to Step 11.

10

INSPECT REAR HO2S

Yes

Go to the next step.

No

Repair or replace the rear HO2S, then go to the next step.

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

11

VERIFY TROUBLESHOOTING OF DTC P0137 COMPLETED
  • Make sure to reconnect all disconnected connectors.

  • Turn the ignition switch off. (Engine OFF).

  • Clear DTC from PCM memory using M-MDS.

  • Perform the KOEO self-test with M-MDS, or “PCM Adaptive Memory Procedure Drive Mode” and “HO2S Heater, HO2S, and TWC Repair Verification Drive Mode”.

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

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

  • Is PENDING CODE of same DTC present?

Yes

Replace the PCM, then go to the next step.

(See PCM REMOVAL/INSTALLATION [LF].)

No

Go to the next step.

12

VERIFY AFTER REPAIR PROCEDURE

Yes

Go to the applicable DTC inspection.

(See DTC TABLE [LF].)

No

Troubleshooting completed.




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