Mazda CX 7. Manual - part 71

ON-BOARD DIAGNOSTIC [L3 WITH TC]

01-02–239

01-02

DTC P2246[L3 WITH TC]

id010239813300

Diagnostic procedure

DTC P2246

Front HO2S sensor reference voltage circuit high input

DETECTION 

CONDITION

• The PCM monitors the front HO2S sensor reference voltage circuit voltage. If the voltage is above the 

threshold value while the engine is running, the PCM determines that the front HO2S sensor reference 
voltage circuit is high.

Diagnostic support note

• This is a continuous monitor (HO2S).

• The MIL illuminates if the PCM detects the above malfunctioning 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 conditions during the first drive 

cycle.

• FREEZE FRAME DATA is available.

• DTCs are stored in the PCM memory.

POSSIBLE 

CAUSE

• Front HO2S malfunction

• Connector or terminal malfunction

• Short to the power circuit between PCM terminal 2Y and front HO2S terminal 2C

• Open circuit between PCM terminal 2Y and front HO2S terminal 2C

• Open circuit between PCM terminal 2M and front HO2S terminal 2A

• PCM malfunction

STEP

INSPECTION

ACTION

1

VERIFY FREEZE FRAME DATA AND 
DIAGNOSTIC MONITORING TEST RESULTS 
HAVE BEEN RECORDED

• Have the 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 REPAIR INFORMATION 
AVAILABILITY

• Verify related Service Bulletins and/or on-line 

repair information availability.

• Is any related repair information available?

Yes

Perform the 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

IDENTIFY TRIGGER DTC FOR FREEZE FRAME 
DATA

• Is DTC P2246 on FREEZE FRAME DATA?

Yes

Go to the next step.

No

Go to troubleshooting for DTC on FREEZE FRAME DATA.
(See01-02-13 DTC TABLE[L3 WITH TC].)

FRONT HO2S 

PCM

WIRING HARNESS-SIDE CONNECTOR

1A

1B

1C

1D

2A

2B

2C

2D

FRONT HO2S

WIRING HARNESS-SIDE CONNECTOR

4

5

PCM

2C

2A

2Y

2M

7

4

6

7

8

8

2BE 2BA 2AW 2AS 2AO 2AK 2AG 2AC 2Y 2U 2Q 2M

2E

2A

2I

2BH 2BD 2AZ 2AV 2AR 2AN 2AJ 2AF 2AB 2X 2T 2P

2H

2D

2L

2BG 2BC 2AY 2AU 2AQ 2AM 2AI 2AE 2AA 2W 2S 2O

2G

2C

2K

2BF 2BB 2AX 2AT 2AP 2AL 2AH 2AD 2Z

2V 2R 2N

2F

2B

2J

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ON-BOARD DIAGNOSTIC [L3 WITH TC]

01-02–240

End Of Sie

4

INSPECT FRONT HO2S CONNECTOR FOR 
POOR CONNECTION

• Turn the ignition switch to off.

• Disconnect the front HO2S connector.

• Inspect for poor connection (such as damaged/ 

pulled-out pins, and corrosion).

• Is there any malfunction?

Yes

Repair or replace the terminal, then go to Step 9.

No

Go to the next step.

5

INSPECT FRONT HO2S REFERENCE VOLTAGE 
CIRCUIT FOR SHORT TO POWER AT FRONT 
HO2S

• Front HO2S connector disconnected.

• Turn the ignition switch to the ON position 

(engine off).

• Measure the voltage between front HO2S 

terminal 2C (part-side) and ground.

• Is the voltage above 5.0 V?

Yes

Replace the front HO2S, then go to Step 9.

No

Go to the next step.

6

INSPECT FRONT HO2S REFERENCE VOLTAGE 
CIRCUIT FOR SHORT TO POWER AT PCM - 
FRONT HO2S

• Front HO2S connector disconnected.

• Turn the ignition switch to the ON position 

(engine off).

• Measure the voltage between front HO2S 

terminal 2C (harness-side) and ground.

• Is the voltage above 5.0 V?

Yes

Repair or replace for a short to power, then go to Step 9.

No

Go to the next step.

7

INSPECT PCM CONNECTOR FOR POOR 
CONNECTION

• Turn the ignition switch to off.

• Disconnect the PCM connector.

• Inspect for poor connection (such as damaged/ 

pulled-out pins, and corrosion).

• Is there any malfunction?

Yes

Repair or replace the terminal, then go to Step 9.

No

Go to the next step.

8

INSPECT FRONT HO2S REFERENCE VOLTAGE 
CIRCUIT FOR OPEN AT PCM - FRONT HO2S

• Front HO2S and PCM connectors 

disconnected.

• Verify the continuity between following 

terminals at harness-side connectors.
— PCM terminal 2Y— front HO2S terminal 2C

— PCM terminal 2M— front HO2S terminal 2A

• Is there continuity?

Yes

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

No

Repair or replace for an open circuit, then go to the next 
step.

9

VERIFY TROUBLESHOOTING OF DTC P2246 
COMPLETED

• Make sure to reconnect all disconnected 

connectors.

• Clear the DTC from the PCM memory using 

the M-MDS.

• Perform the HO2S heater, HO2S and TWC 

Repair Verification Drive Mode.
(See01-02-10 OBD-II DRIVE MODE[L3 WITH 
TC].)

• Is the PENDING CODE same DTC present?

Yes

Replace the PCM, then go to the next step.
(See01-40-6 PCM REMOVAL/INSTALLATION[L3 WITH 
TC].)

No

Go to the next step.

10

VERIFY AFTER REPAIR PROCEDURE

• Perform the AFTER REPAIR PROCEDURE.

(See01-14-4 AFTER REPAIR 
PROCEDURE[L3 WITH TC].)

• Are any DTCs present?

Yes

Go to the applicable DTC inspection.
(See01-02-13 DTC TABLE[L3 WITH TC].)

No

Troubleshooting completed.

STEP

INSPECTION

ACTION

1871-1U-06B(01-02).fm  240 ページ  ２００６年３月１５日　水曜日　午前１０時３２分

ON-BOARD DIAGNOSTIC [L3 WITH TC]

01-02–241

01-02

DTC P2251[L3 WITH TC]

id010239813400

Diagnostic procedure

DTC P2251

Front HO2S negative current control circuit open

DETECTION 

CONDITION

• The PCM monitors the front HO2S negative current control circuit voltage. If the voltage does not change 

with the PCM control value while the engine is running, the PCM determines that the front HO2S negative 
current control circuit is open.

Diagnostic support note

• This is a continuous monitor (HO2S).

• The MIL illuminates if the PCM detects the above malfunctioning 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 conditions during the first drive 

cycle.

• FREEZE FRAME DATA is available.

• DTCs are stored in the PCM memory.

POSSIBLE 

CAUSE

• Front HO2S malfunction

• Connector or terminal malfunction

• Open circuit between PCM terminal 2AC and front HO2S terminal 1B

• Front HO2S heater cannot be controlled

• PCM malfunction

STEP

INSPECTION

ACTION

1

VERIFY FREEZE FRAME DATA AND 
DIAGNOSTIC MONITORING TEST RESULTS 
HAVE BEEN RECORDED

• Have the 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 REPAIR INFORMATION 
AVAILABILITY

• Verify related Service Bulletins and/or on-line 

repair information availability.

• Is any related repair information available?

Yes

Perform the 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.

FRONT HO2S 

PCM

WIRING HARNESS-SIDE CONNECTOR

1A

1B

1C

1D

2A

2B

2C

2D

FRONT HO2S

WIRING HARNESS-SIDE CONNECTOR

5

7

PCM

1B

1A

2AC

2AD

6

2Z

1C

6

6

5

5

2BE 2BA 2AW 2AS 2AO 2AK 2AG 2AC 2Y 2U 2Q 2M

2E

2A

2I

2BH 2BD 2AZ 2AV 2AR 2AN 2AJ 2AF 2AB 2X 2T 2P

2H

2D

2L

2BG 2BC 2AY 2AU 2AQ 2AM 2AI 2AE 2AA 2W 2S 2O

2G

2C

2K

2BF 2BB 2AX 2AT 2AP 2AL 2AH 2AD 2Z

2V 2R 2N

2F

2B

2J

1871-1U-06B(01-02).fm  241 ページ  ２００６年３月１５日　水曜日　午前１０時３２分

ON-BOARD DIAGNOSTIC [L3 WITH TC]

01-02–242

End Of Sie

WM: DTC P24XX

3

VERIFY RELATED PENDING CODE OR 
STORED DTC

• Turn the ignition switch to off, then ON position 

(Engine off).

• Verify the related PENDING CODE or stored 

DTCs using the M-MDS.

• Is the DTC P0030, P0031 or P0032 also 

present?

Yes

Go to appropriate DTC troubleshooting procedure.
(See01-02-13 DTC TABLE[L3 WITH TC].)

No

Go to the next step.

4

IDENTIFY TRIGGER DTC FOR FREEZE FRAME 
DATA

• Is DTC P2251 on FREEZE FRAME DATA?

Yes

Go to the next step.

No

Go to troubleshooting for DTC on FREEZE FRAME DATA.
(See01-02-13 DTC TABLE[L3 WITH TC].)

5

INSPECT FRONT HO2S CONNECTOR FOR 
POOR CONNECTION

• Turn the ignition switch to off.

• Disconnect the front HO2S connector.

• Inspect for poor connection (such as damaged/ 

pulled-out pins, and corrosion).

• Is there any malfunction?

Yes

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

No

Go to the next step.

6

INSPECT PCM CONNECTOR FOR POOR 
CONNECTION

• Turn the ignition switch to off.

• Disconnect the PCM connector.

• Inspect for poor connection (such as damaged/ 

pulled-out pins, and corrosion).

• Is there any malfunction?

Yes

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

No

Go to the next step.

7

INSPECT FRONT HO2S NEGATIVE CURRENT 
CONTROL CIRCUIT FOR OPEN AT PCM - 
FRONT HO2S

• The front HO2S and the PCM connectors 

disconnected.

• Verify the continuity between the PCM terminal 

2AC and the front HO2S terminal 1B at 
harness-side connectors.

• Is there continuity?

Yes

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

No

Repair or replace for open circuit, then go to the next step.

8

VERIFY TROUBLESHOOTING OF DTC P2251 
COMPLETED

• Make sure to reconnect all disconnected 

connectors.

• Clear the DTC from the PCM memory using 

the M-MDS.

• Perform the HO2S heater, HO2S and TWC 

Repair Verification Drive Mode.
(See01-02-10 OBD-II DRIVE MODE[L3 WITH 
TC].)

• Is the PENDING CODE same DTC present?

Yes

Replace the PCM, then go to the next step.
(See01-40-6 PCM REMOVAL/INSTALLATION[L3 WITH 
TC].)

No

Go to the next step.

9

VERIFY AFTER REPAIR PROCEDURE

• Perform the AFTER REPAIR PROCEDURE.

(See01-14-4 AFTER REPAIR 
PROCEDURE[L3 WITH TC].)

• Are any DTCs present?

Yes

Go to the applicable DTC inspection.
(See01-02-13 DTC TABLE[L3 WITH TC].)

No

Troubleshooting completed.

STEP

INSPECTION

ACTION

1871-1U-06B(01-02).fm  242 ページ  ２００６年３月１５日　水曜日　午前１０時３２分