Mazda CX 7. Manual - part 19

ON-BOARD DIAGNOSTIC [L3 WITH TC]

01-02–31

01-02

Diagnostic procedure

End Of Sie

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 heater 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

INSPECT FRONT HO2S CONNECTOR FOR 
POOR CONNECTION

• Turn the ignition switch 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 7.

No

Go to the next step.

4

INSPECT FRONT HO2S HEATER CONTROL 
CIRCUIT FOR SHORT TO POWER SUPPLY

• Turn the ignition switch to the ON position 

(Engine off).

• Measure the voltage between front HO2S 

terminal 2D (wiring harness-side) and body 
ground.

• Is the voltage B+?

Yes

Repair or replace the wiring harness for a possible short to 
power supply, then go to Step 7.

No

Go to the next step.

5

INSPECT FRONT HO2S HEATER

• Inspect the front HO2S heater.

(See01-40-37 HEATED OXYGEN SENSOR 
(HO2S) INSPECTION[L3 WITH TC].)

• Is there any malfunction?

Yes

Replace the front HO2S, then go to Step 7.
(See01-15-2 EXHAUST SYSTEM REMOVAL/
INSTALLATION[L3 WITH TC].)

No

Go to the next step.

6

INSPECT PCM CONNECTOR FOR POOR 
CONNECTION

• Turn the ignition switch 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 the next step.

No

Go to the next step.

7

VERIFY TROUBLESHOOTING OF DTC P0032 
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 for this 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.

8

VERIFY AFTER REPAIR PROCEDURE

• Perform the “AFTER REPAIR PROCEDURE”.

(See01-02-10 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

DTC troubleshooting completed.

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ON-BOARD DIAGNOSTIC [L3 WITH TC]

01-02–32

DTC P0037[L3 WITH TC]

id010239802200

Diagnostic procedure

DTC P0037

Rear HO2S heater circuit low input

DETECTION 

CONDITION

• The PCM monitors the rear HO2S heater output voltage. If the PCM turns the rear HO2S heater on or off 

but the rear HO2S heater circuit voltage remains low the PCM determines that the rear HO2S heater circuit 
has a malfunction.

Diagnostic support note

• This is a continuous monitor (HO2S heater).

• 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.

• DTCs are stored in the PCM memory.

POSSIBLE 

CAUSE

• Rear HO2S heater malfunction

• Connector or terminal malfunction

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

• Short to ground in the wiring harness between ignition switch and rear HO2S terminal C

• Open circuit in the wiring harness between rear HO2S terminal D and PCM terminal 2D

• Short to ground in the wiring harness between rear HO2S terminal D and PCM terminal 2D

• 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 heater 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.

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

3

3

4

6

5

REAR HO2S HEATER

2D

PCM

PCM

WIRING HARNESS-SIDE CONNECTOR

C

D

IGNITION SWITCH

REAR HO2S

WIRING HARNESS-SIDE CONNECTOR

A

B

C

D

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ON-BOARD DIAGNOSTIC [L3 WITH TC]

01-02–33

01-02

End Of Sie

3

INSPECT REAR HO2S CONNECTOR FOR 
POOR CONNECTION

• Turn the ignition switch off.

• Disconnect the rear 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.

4

INSPECT REAR HO2S HEATER POWER 
CIRCUIT FOR OPEN CIRCUIT OR SHORT TO 
GROUND

• Turn the ignition switch to the ON position 

(Engine off).

• Measure the voltage between rear HO2S 

terminal C (wiring harness-side) and body 
ground.

• Is the voltage B+?

Yes

Go to the next step.

No

Repair or replace the wiring harness for a possible open 
circuit or short to ground, then go to Step 9.

5

INSPECT REAR HO2S HEATER CONTROL 
CIRCUIT FOR SHORT TO GROUND

• Turn the ignition switch off.

• Inspect for continuity between rear HO2S 

terminal D (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 9.

No

Go to the next step.

6

INSPECT REAR HO2S HEATER

• Inspect the rear HO2S heater.

(See01-40-37 HEATED OXYGEN SENSOR 
(HO2S) INSPECTION[L3 WITH TC].)

• Is there any malfunction?

Yes

Replace the rear HO2S, then go to Step 9.
(See01-15-2 EXHAUST SYSTEM REMOVAL/
INSTALLATION[L3 WITH TC].)

No

Go to the next step.

7

INSPECT PCM CONNECTOR FOR POOR 
CONNECTION

• Turn the ignition switch 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 REAR HO2S HEATER CONTROL 
CIRCUIT FOR OPEN CIRCUIT

• Turn the ignition switch off.

• Inspect for continuity between rear HO2S 

terminal D (wiring harness-side) and PCM 
terminal 2D (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 the next step.

9

VERIFY TROUBLESHOOTING OF DTC P0037 
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 for this 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”.

(See01-02-10 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

DTC troubleshooting completed.

STEP

INSPECTION

ACTION

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ON-BOARD DIAGNOSTIC [L3 WITH TC]

01-02–34

DTC P0038[L3 WITH TC]

id010239802300

DTC P0038

Rear HO2S heater circuit high input

DETECTION 

CONDITION

• The PCM monitors the rear HO2S heater output voltage. If the PCM turns the rear HO2S heater off but the 

rear HO2S heater circuit voltage remains high the PCM determines that the rear HO2S heater circuit has a 
malfunction.

Diagnostic support note

• This is a continuous monitor (HO2S heater).

• 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.

• DTCs are stored in the PCM memory.

POSSIBLE 

CAUSE

• Rear HO2S heater malfunction

• Connector or terminal malfunction

• Short to power supply in the wiring harness between rear HO2S terminal D and PCM terminal 2D

• PCM malfunction

REAR HO2S HEATER

2D

PCM

PCM

WIRING HARNESS-SIDE CONNECTOR

C

D

IGNITION SWITCH

A

B

C

D

REAR HO2S

WIRING HARNESS-SIDE CONNECTOR

3

3

5

7

6

4

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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