Mazda 6. Manual - part 138

F–74

ON-BOARD DIAGNOSTIC 

End Of Sie

DTC P0031

A6E397001084W04

7

VERIFY TROUBLESHOOTING OF DTC P0012 
COMPLETED

• Make sure to reconnect all disconnected 

connectors.

• Clear DTC from PCM memory using WDS or 

equivalent.

• Perform KOER self-test.

(See 

F–66 KOEO/KOER SELF-TEST

.)

• Is same DTC present?

Yes Replace PCM, then go to next step.

(See 

F–43 PCM REMOVAL/INSTALLATION

.)

No

Go to next step.

8

VERIFY AFTER REPAIR PROCEDURE

• Perform “After Repair Procedure”.

(See 

F–66 AFTER REPAIR PROCEDURE

.)

• Is there any DTC present?

Yes Go to applicable DTC troubleshooting.

(See 

F–67 DTC TABLE

.)

No

Troubleshooting completed.

STEP

INSPECTION

ACTION

DTC P0031

Front HO2S heater circuit low input

DETECTION 

CONDITION

• PCM monitors front HO2S heater control signal at PCM terminal 4A. If PCM turns front HO2S heater off but 

front HO2S heater circuit has low voltage, PCM determines that front HO2S heater circuit has malfunction.

Note

• Front HO2S heater is controlled by duty signal.

Diagnostic support note

• This is a continuous monitor (O

2

 sensor heater).

• MIL illuminates if PCM detects above malfunction condition in two consecutive drive cycles or in one drive 

cycle while DTC for the same malfunction has been stored in PCM.

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

• FREEZE FRAME DATA is available.

• DTC is stored in PCM memory.

POSSIBLE 

CAUSE

• Front HO2S malfunction

• Open circuit between ignition switch and front HO2S terminal C

• Open circuit between front HO2S terminal D and PCM terminal 4A

• Short to ground circuit between front HO2S terminal D and PCM terminal 4A

• Poor connection at front HO2S or PCM connector

• PCM malfunction

ON-BOARD DIAGNOSTIC 

F–75

F

Diagnostic procedure

STEP

INSPECTION

ACTION

1

PERFORM DTC CONFIRMATION PROCEDURE

• Perform DTC CONFIRMATION PROCEDURE.

(See 

F–66 DTC CONFIRMATION 

PROCEDURE

.)

• Is same DTC present?

Yes Go to next step.

No

Intermittent concern exists. Go to INTERMITTENT 
CONCERN TROUBLESHOOTING procedure.
(See 

F–227 INTERMITTENT CONCERN 

TROUBLESHOOTING

.)

2

INSPECT POOR CONNECTION OF FRONT 
HO2S CONNECTOR

• Turn ignition key to OFF.

• Disconnect front HO2S connector.

• Inspect for poor connection (damaged, pulled-

out pins, corrosion, etc.).

• Are there any malfunctions?

Yes Repair or replace terminal, then go to Step 8.

No

Go to next step.

3

INSPECT FRONT HO2S HEATER

• Inspect front HO2S heater.

(See 

F–56 HEATED OXYGEN SENSOR 

(HO2S) INSPECTION

.)

• Is front HO2S heater okay?

Yes Go to next step.

No

Replace front HO2S, then go to Step 8.

4

INSPECT POWER CIRCUIT OF FRONT HO2S 
HEATER FOR OPEN CIRCUIT

• Turn ignition key to ON (Engine OFF).

• Measure voltage between front HO2S terminal 

C (harness-side) and body ground.

• Is voltage B+?

Yes Go to next step.

No

Repair or replace harness for open circuit, then go to Step 
8.

5

INSPECT POOR CONNECTION OF PCM 
CONNECTOR

• Turn ignition key to OFF.

• Disconnect PCM connector.

• Inspect for poor connection (damaged, pulled-

out pins, corrosion, etc.).

• Are there any malfunctions?

Yes Repair terminal, then go to Step 8.

No

Go to next step.

DTC P0031

Front HO2S heater circuit low input

F–76

ON-BOARD DIAGNOSTIC 

End Of Sie

DTC P0032

A6E397001084W05

6

INSPECT CONTROL CIRCUIT OF FRONT HO2S 
HEATER FOR SHORT TO GROUND

• Inspect continuity between front HO2S terminal 

D (harness-side) and body ground.

• Is there continuity?

Yes Repair or replace harness for short to ground, then go to 

Step 8.

No

Go to next step.

7

INSPECT CONTROL CIRCUIT OF FRONT HO2S 
HEATER FOR OPEN CIRCUIT

• Remove PCM with PCM connector connected.

• Inspect continuity between front HO2S terminal 

D (harness-side) and PCM terminal 4A.

• Is there continuity?

Yes Go to next step.

No

Repair or replace harness for open circuit, then go to Step 
8.

8

VERIFY TROUBLESHOOTING OF DTC P0031 
COMPLETED

• Make sure to reconnect all disconnected 

connectors.

• Clear DTC from PCM memory using WDS or 

equivalent.

• Perform KOEO/KOER self-test.

(See 

F–66 KOEO/KOER SELF-TEST

.)

• Is same DTC present?

Yes Replace PCM, then go to next step.

(See 

F–43 PCM REMOVAL/INSTALLATION

.)

No

Go to next step.

9

VERIFY AFTER REPAIR PROCEDURE

• Perform “After Repair Procedure”.

(See 

F–66 AFTER REPAIR PROCEDURE

.)

• Is there any DTC present?

Yes Go to applicable DTC troubleshooting.

(See 

F–67 DTC TABLE

.)

No

Troubleshooting completed.

STEP

INSPECTION

ACTION

DTC P0032

Front HO2S heater circuit high input

DETECTION 

CONDITION

• PCM monitors front HO2S heater control signal at PCM terminal 4A. If PCM turns front HO2S heater on but 

front HO2S heater circuit has high voltage, PCM determines that front HO2S heater circuit has malfunction.

Note

• Front HO2S heater is controlled by a duty signal.

Diagnostic support note

• This is a continuous monitor (O

2

 sensor heater).

• MIL illuminates if 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 PCM detects the above malfunction condition.

• FREEZE FRAME DATA is available.

• DTC is stored in PCM memory.

POSSIBLE 

CAUSE

• Short to power circuit between front HO2S terminal D and PCM terminal 4A

• Front HO2S or PCM terminal is shorted

• Front HO2S heater malfunction

• PCM malfunction

ON-BOARD DIAGNOSTIC 

F–77

F

Diagnostic procedure

STEP

INSPECTION

ACTION

1

PERFORM DTC CONFIRMATION PROCEDURE

• Perform DTC CONFIRMATION PROCEDURE.

(See 

F–66 DTC CONFIRMATION 

PROCEDURE

.)

• Is same DTC present?

Yes Go to next step.

No

Intermittent concern exists. Go to INTERMITTENT 
CONCERN TROUBLESHOOTING procedure.
(See 

F–227 INTERMITTENT CONCERN 

TROUBLESHOOTING

.)

2

INSPECT FRONT HO2S TERMINALS

• Turn ignition key to OFF.

• Disconnect front HO2S connector.

• Inspect for bent terminals.

• Is there any malfunction?

Yes Repair or replace terminal, then go to Step 6.

No

Go to next step.

3

INSPECT FRONT HO2S HEATER

• Inspect front HO2S heater.

(See 

F–56 HEATED OXYGEN SENSOR 

(HO2S) INSPECTION

.)

• Is front HO2S heater okay?

Yes Go to next step.

No

Replace the front HO2S, then go to Step 6.

4

INSPECT PCM TERMINAL

• Disconnect PCM connector.

• Inspect for bent terminals.

• Are there any malfunctions?

Yes Repair terminal, then go to Step 6.

No

Go to next step.

5

INSPECT FRONT HO2S HEATER CONTROL 
CIRCUIT FOR SHORT TO POWER CIRCUIT

• Turn ignition key to ON (Engine OFF).

• Measure voltage between front HO2S terminal 

D (harness-side) and body ground.

• Is there voltage B+?

Yes Repair or replace harness for shot to power circuit, then go 

to next step.

No

Go to next step.

DTC P0032

Front HO2S heater circuit high input