DTC P0131

Front HO2S circuit low input

DETECTION CONDITION

• The PCM monitors the input voltage from the front HO2S and the front HO2S output current when the engine is running. If the input voltage is less than 1.8 V or the output current is less than –5 mA, the PCM determines that the front HO2S circuit voltage is low.

Diagnostic support note

• This is a continuous 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.

• 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

• Front HO2S malfunction

• Connector or terminal malfunction

• Open circuit in wiring harness between front HO2S terminal A and PCM terminal 2AD

• Short to ground in wiring harness between front HO2S terminal A and PCM terminal 2AD

• Open circuit in wiring harness between front HO2S terminal B and PCM terminal 2Z

• Short to ground in wiring harness between front HO2S terminal B and PCM terminal 2Z

• PCM malfunction

STEP

INSPECTION

ACTION

1

• 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 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

• Turn the ignition switch off, then to the ON position (Engine off).

• Verify the pending code or stored DTCs using the 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

• Is DTC P0131 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

• Turn the ignition switch off.

• Disconnect the front HO2S connector.

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

• Is there any malfunction?

Yes

Repair or replace the terminal, then go to Step 10.

No

Go to the next step.

6

• Turn the ignition switch off.

• Inspect for continuity between the following terminals and body ground:

• Front HO2S terminal A (wiring harness-side) and body ground

• Front HO2S terminal B (wiring harness-side) and body ground

• Is there continuity?

Yes

Repair or replace the wiring harness for a possible short to ground, then go to Step 10.

No

Go to the next step.

7

• Turn the ignition switch off.

• Inspect for continuity between the following circuits:

• Front HO2S terminal A (wiring harness-side) and PCM terminal 2AD (wiring harness-side)

• Front HO2S terminal B (wiring harness-side) and PCM terminal 2Z (wiring harness-side)

• Is there continuity?

Yes

Go to the next step.

No

Repair or replace the wiring harness for a possible open circuit, then go to Step 10.

8

• Turn the ignition switch off.

• Disconnect the PCM connector.

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

• Is there any malfunction?

Yes

Repair or replace the terminal, then go to Step 10.

No

Go to the next step.

9

• Inspect the front HO2S.

  (See FRONT HEATED OXYGEN SENSOR (HO2S) INSPECTION [LF].)

• Is there any malfunction?

Yes

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

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

No

Go to the next step.

10

• 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.

11

• Perform the “AFTER REPAIR PROCEDURE”.

  (See AFTER REPAIR PROCEDURE [LF].)

• Are any DTCs present?

Yes

Go to the applicable DTC inspection.

(See DTC TABLE [LF].)

No

DTC troubleshooting completed.