Mazda 6. Manual - part 139

F–78

ON-BOARD DIAGNOSTIC 

End Of Sie

DTC P0037

A6E397001084W06

6

VERIFY TROUBLESHOOTING OF DTC P0032 
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.

7

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 P0037

Rear HO2S heater circuit low input

DETECTION 

CONDITION

• PCM monitors rear HO2S heater control signal at PCM terminal 4D. If PCM turns rear HO2S heater off but 

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

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 DTC for the same malfunction has been stored in PCM.

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

• FREEZE FRAME DATA is available.

• DTC is stored in PCM memory.

POSSIBLE 

CAUSE

• Rear HO2S malfunction

• Open circuit between the ignition switch and rear HO2S terminal C

• Open circuit between the rear HO2S terminal D and PCM terminal 4D

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

• Poor connection at rear HO2S or PCM connector

• PCM malfunction

ON-BOARD DIAGNOSTIC 

F–79

F

Diagnostic procedure

End Of Sie

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 REAR HO2S 
CONNECTOR

• Turn ignition key to OFF.

• Disconnect rear 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 REAR HO2S HEATER

• Inspect rear HO2S heater.

(See 

F–56 HEATED OXYGEN SENSOR 

(HO2S) INSPECTION

.)

• Is rear HO2S heater okay?

Yes Go to next step.

No

Replace rear HO2S, then go to Step 8.

4

INSPECT REAR HO2S HEATER POWER 
CIRCUIT FOR OPEN CIRCUIT

• Turn ignition key to ON (Engine OFF).

• Measure voltage between rear HO2S terminal 

C (harness-side) and body ground.

• Is there 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.

6

INSPECT REAR HO2S HEATER CONTROL 
CIRCUIT FOR SHORT TO GROUND

• Inspect continuity between rear HO2S terminal 

D (harness-side) and body ground.

• Is there any continuity?

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

Step 8.

No

Go to next step.

7

INSPECT HREAR HO2S HEATER CONTROL 
CIRCUIT FOR OPEN CIRCUIT

• Remove PCM with PCM connector connected.

• Inspect continuity between rear HO2S terminal 

D (harness-side) and PCM terminal 4D.

• Is there any continuity?

Yes Go to next step.

No

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

8

VERIFY TROUBLESHOOTING OF DTC P0037 
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.

F–80

ON-BOARD DIAGNOSTIC 

DTC P0038

A6E397001084W07

Diagnostic procedure

DTC P0038

Rear HO2S heater circuit high input

DETECTION 

CONDITION

• PCM monitors rear HO2S heater control signal at PCM terminal 4D. If PCM turns rear HO2S heater on but 

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

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 during first drive cycle.

• FREEZE FRAME DATA is available.

• DTC is stored in PCM memory.

POSSIBLE 

CAUSE

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

• Rear HO2S or PCM terminal is shorted

• Rear HO2S heater malfunction

• PCM malfunction

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 REAR HO2S TERMINAL

• Turn ignition key to OFF.

• Disconnect rear 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 REAR HO2S HEATER

• Inspect rear HO2S heater.

(See 

F–56 HEATED OXYGEN SENSOR 

(HO2S) INSPECTION

.)

• Is rear HO2S heater okay?

Yes Go to next step.

No

Replace the rear HO2S, then go to Step 6.

ON-BOARD DIAGNOSTIC 

F–81

F

End Of Sie

DTC P0101

A6E397001084W08

Diagnostic procedure

4

INSPECT PCM TERMINAL

• Disconnect PCM connector.

• Inspect for bent terminals.

• Is there any malfunctions?

Yes Repair terminal, then go to Step 6.

No

Go to next step.

5

INSPECT REAR HO2S HEATER CONTROL 
CIRCUIT FOR SHORT TO POWER

• Turn ignition key to ON (Engine OFF).

• Measure voltage between rear 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.

6

VERIFY TROUBLESHOOTING OF DTC P0038 
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.

7

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 P0101

MAF sensor inconsistent with TP sensor (lower than expected) or engine speed (greater than 
expected)

DETECTION 

CONDITION

• The PCM compares actual input signal from MAF sensor with expected input signal from MAF sensor 

(calculated by input voltage from throttle position sensor or engine speed).
— If mass intake air flow amount is below 5.0 g/sec. {0.66 lb/min.} for 5 s and throttle opening angle is 

above 50% with engine running, the PCM determines that detected mass intake air flow amount is too 
low. 

— If mass intake air flow amount is above 96.0 g/sec. {12.7 lb/min.} for 5 s and engine speed is below 

2,000 rpm with engine running, the PCM determines that detected mass intake air flow amount is too 
high.

Diagnostic support note

• This is a continuous monitor (CCM).

• 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 during first drive cycle.

• FREEZE FRAME DATA is available.

• DTC is stored in the PCM memory.

POSSIBLE 

CAUSE

• MAF sensor malfunction

• TP sensor malfunction

• Electrical corrosion in MAF signal circuit

• Electrical corrosion in MAF RETURN circuit

• Voltage drops in MAF signal circuit

• Voltage drops in ground circuit

STEP

INSPECTION

ACTION

1

VERIFY FREEZE FRAME DATA HAS BEEN 
RECORDED

• Has FREEZE FRAME DATA been recorded?

Yes Go to next step.

No

Record FREEZE FRAME DATA on repair order, then go to 
next step.

2

VERIFY RELATED SERVICE INFORMATION 
AVAILABILITY

• Check for related Service Information 

availability.

• Is any related Service Information available?

Yes Perform repair or diagnosis according to available Service 

Information.

• If vehicle is not repaired, go to next step.

No

Go to next step.