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DTC P0031:00 [PCM (SKYACTIV-G 2.0)]

DTC P0031:00

A/F sensor heater control circuit low input

DETECTION CONDITION

  • When the PCM controls the A/F sensor heater, the voltage input to the PCM is too low.

    Diagnostic support note

  • This is a continuous monitor (A/F sensor heater, HO2S heater).

  • The check engine light 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 first drive cycle.

  • FREEZE FRAME DATA/Snapshot data is available.

  • DTC is stored in the PCM memory.

FAIL-SAFE FUNCTION

  • Stops fuel feedback control

POSSIBLE CAUSE

  • A/F sensor connector or terminals malfunction

  • Short to ground or open circuit in A/F sensor heater power supply circuit:

    • Short to ground in wiring harness between ENGINE1 10 A fuse and A/F sensor terminal A

    • ENGINE1 10 A fuse malfunction

    • Open circuit in wiring harness between main relay terminal C and A/F sensor terminal A

  • PCM connector or terminals malfunction

  • Short to ground in wiring harness between A/F sensor terminal E and PCM terminal 1BY

  • A/F sensor heater malfunction

  • Open circuit in wiring harness between A/F sensor terminal E and PCM terminal 1BY

  • PCM malfunction

Diagnostic Procedure

STEP

INSPECTION

ACTION

1

 RECORD FREEZE FRAME DATA/SNAPSHOT DATA AND DIAGNOSTIC MONITORING TEST RESULTS TO UTILIZE WITH REPEATABILITY VERIFICATION

NOTE:

  • Recording can be facilitated using the screen capture function of the PC.

  • Record the FREEZE FRAME DATA/snapshot data and DIAGNOSTIC MONITORING TEST RESULTS (A/F sensor heater, HO2S heater related) on the repair order.

—

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 A/F SENSOR CONNECTOR CONDITION

  • Switch the ignition off.

  • Disconnect the A/F sensor connector.

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

  • Is there any malfunction?

Yes

Repair or replace the connector and/or terminals, then go to Step 9.

No

Go to the next step.

4

 INSPECT A/F SENSOR HEATER POWER SUPPLY CIRCUIT FOR SHORT TO GROUND OR OPEN CIRCUIT

  • Verify that the A/F sensor connector is disconnected.

  • Switch the ignition ON (engine off).

    NOTE:

    • Another DTC may be stored by the PCM detecting an open circuit.

  • Measure the voltage at the A/F sensor terminal A (wiring harness-side).

  • Is the voltage B+?

Yes

Go to the next step.

No

Inspect the ENGINE1 10 A fuse.

  • If the fuse is blown:

    • Refer to the wiring diagram and verify whether or not there is a common connector between ENGINE1 10 A fuse and A/F sensor terminal A.

        • If there is a common connector:

      • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for a short to ground.

      • Repair or replace the malfunctioning part.

        If there is no common connector:

      • Repair or replace the wiring harness which has a short to ground.

      • Replace the fuse.

  • If the fuse is damaged:

    • Replace the fuse.

  • If the fuse is normal:

    • Refer to the wiring diagram and verify whether or not there is a common connector between main relay terminal C and A/F sensor terminal A.

        • If there is a common connector:

      • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for an open circuit.

      • Repair or replace the malfunctioning part.

        If there is no common connector:

      • Repair or replace the wiring harness which has an open circuit.

Go to Step 9.

5

 INSPECT PCM CONNECTOR CONDITION

  • Switch the ignition 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 connector and/or terminals, then go to Step 9.

No

Go to the next step.

6

 INSPECT A/F SENSOR HEATER CONTROL CIRCUIT FOR SHORT TO GROUND

  • Verify that the A/F sensor and PCM connectors are disconnected.

  • Inspect for continuity between A/F sensor terminal E (wiring harness-side) and body ground.

  • Is there continuity?

Yes

Refer to the wiring diagram and verify whether or not there is a common connector between A/F sensor terminal E and PCM terminal 1BY.

    If there is a common connector:

  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for a short to ground.

  • Repair or replace the malfunctioning part.

    If there is no common connector:

  • Repair or replace the wiring harness which has a short to ground.

Go to Step 9.

No

Go to the next step.

7

 INSPECT A/F SENSOR HEATER

Yes

Replace the A/F sensor, then go to Step 9.

(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [SKYACTIV-G 2.0].)

No

Go to the next step.

8

 INSPECT A/F SENSOR HEATER CONTROL CIRCUIT FOR OPEN CIRCUIT

  • Verify that the A/F sensor and PCM connectors are disconnected.

  • Inspect for continuity between A/F sensor terminal E (wiring harness-side) and PCM terminal 1BY (wiring harness-side).

  • Is there continuity?

Yes

Go to the next step.

No

Refer to the wiring diagram and verify whether or not there is a common connector between A/F sensor terminal E and PCM terminal 1BY.

    If there is a common connector:

  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for an open circuit.

  • Repair or replace the malfunctioning part.

    If there is no common connector:

  • Repair or replace the wiring harness which has an open circuit.

Go to the next step.

9

 VERIFY DTC TROUBLESHOOTING COMPLETED

Yes

Repeat the inspection from Step 1.

Go to the next step.

No

Go to the next step.

10

 VERIFY AFTER REPAIR PROCEDURE

Yes

Go to the applicable DTC inspection.

(See DTC TABLE [PCM (SKYACTIV-G 2.0)].)

No

DTC troubleshooting completed.
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Free to use workshop manual for your 2015+ Mk4 'ND' Mazda MX-5

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