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Mazda CX-9 Grand Touring. Manual - part 240



Measure the resistance between the
following terminals:



PCM terminal 2Y (wiring
harness-side) and front HO2S
(RH) terminal B (wiring harness-
side)



PCM terminal 2BG (wiring
harness-side) and rear HO2S
(RH) terminal B (wiring harness-
side)



PCM terminal 2U (wiring
harness-side) and front HO2S
(LH) terminal B (wiring harness-
side)



PCM terminal 2BC (wiring
harness-side) and rear HO2S
(LH) terminal B (wiring harness-
side)



PCM terminal 2AL (wiring
harness-side) and HO2S terminal
D (wiring harness-side)



Are the resistances less than 5 ohms?

are in the proper location.

Repair or replace suspected part, Then go to

Step 17.

INSPECT HO2S CONTROL CIRCUIT IN
WIRING HARNESS



Turn the ignition switch off.



Disconnect the HO2S connector.



Perform the KOEO self-test.



Measure the voltage between: HO2S
connector terminal C and D on the
wiring harness side.



Is the voltage more than 10 V?

Yes Go to the next step.

Repair or replace suspected part, Then go to the

next step.

INSPECT HO2S HEATER FOR SHORT
IN WIRING HARNESS



Turn the ignition switch off.



Disconnect the HO2S connector.



Disconnect the PCM connector.



Measure the resistance between the
following terminals:

Yes Go to the next step.

2008 Mazda CX-9 Grand Touring

2008 ENGINE PERFORMANCE On-Board Diagnostic (MZI-3.7) - Mazda CX-9

Microsoft

Sunday, November 15, 2009 10:08:35 AM

Page 93



HO2S terminal A (wiring
harness-side) and battery negative
terminal



HO2S terminal A (wiring
harness-side) and HO2S terminal
C (wiring harness-side)



HO2S terminal A (wiring
harness-side) and HO2S terminal
D (wiring harness-side)



HO2S terminal A (wiring
harness-side) and HO2S terminal
B (wiring harness-side)



Are the resistances more than 10
kilohms?

Repair or replace suspected part, Then go to

Step 17.

INSPECT HO2S HEATER CIRCUIT FOR
OPEN CIRCUIT IN WIRING HARNESS



Measure the resistance:



For DTC P0133 measure
resistance between PCM terminal
2J and front HO2S (RH) terminal
A



For DTC P0153 measure
resistance between PCM terminal
2AS and rear HO2S (RH)
terminal A



For DTC P0139 measure
resistance between PCM terminal
2E and front HO2S (LH) terminal
A



For DTC P0159 measure
resistance between PCM terminal
2AO and rear HO2S (LH)
terminal A



Is the resistance less than 5 ohms?

Yes Go to the next step.

Repair or replace suspected part, Then go to the

next step.

INSPECT INTERNAL RESISTANCE OF
HO2S HEATER



Measure the resistance between the
suspect HO2S terminal A and C at
component side.



Is the resistance between 3-30 ohms?

Yes Go to the next step.

Install a new HO2S. Then go to Step 17.

INSPECT HO2S HEATER CIRCUIT FOR
INTERNAL SHORT TO SIGRTN OR

Yes Go to the next step.

2008 Mazda CX-9 Grand Touring

2008 ENGINE PERFORMANCE On-Board Diagnostic (MZI-3.7) - Mazda CX-9

Microsoft

Sunday, November 15, 2009 10:08:35 AM

Page 94

GROUND



Measure the resistance between:



HO2S terminal A and D at
component side



HO2S terminal A at component
side and battery negative terminal



Is the resistance more than 10 kilohms?

Replace the HO2S.

(See FRONT HEATED OXYGEN SENSOR

(HO2S) REMOVAL/INSTALLATION

[MZI-3.7] .)

(See REAR HEATED OXYGEN SENSOR

(HO2S) REMOVAL/INSTALLATION

[MZI-3.7] .)

Then go to Step 17.

INSPECT HO2S



For DTC P0133 Inspect the front HO2S
(RH)



For DTC P0139 Inspect the rear HO2S
(RH)



For DTC P0153 Inspect the front HO2S
(LH)



For DTC P0159 Inspect the rear HO2S
(LH)

(See FRONT HEATED OXYGEN
SENSOR (HO2S) INSPECTION
[MZI-3.7] .)

(See REAR HEATED OXYGEN
SENSOR (HO2S) INSPECTION
[MZI-3.7] .)



Is there any malfunction?

Yes

Replace the HO2S.
(See FRONT HEATED OXYGEN SENSOR
(HO2S) REMOVAL/INSTALLATION
[MZI-3.7] .)
(See REAR HEATED OXYGEN SENSOR
(HO2S) REMOVAL/INSTALLATION
[MZI-3.7] .)
Then go to Step 17.

Go to the next step.

INSPECT FOR CORRECT PCM
OPERATION



Disconnect all the PCM connectors.



Visually inspect for:



Pushed out pins



Corrosion



Connect all the PCM connectors and
verify that they seat correctly.



Retrieve DTCs using the M-MDS.



Is the PENDING CODE for this DTC
present?

Yes Go to the next step.

The system is correctly. Go to the next step.

VERIFY TROUBLESHOOTING OF
MISFIRE DTC HAS BEEN COMPLETED

2008 Mazda CX-9 Grand Touring

2008 ENGINE PERFORMANCE On-Board Diagnostic (MZI-3.7) - Mazda CX-9

Microsoft

Sunday, November 15, 2009 10:08:35 AM

Page 95

DTC P0135, P0141, P0155, P0161 [MZI-3.7]

DTC P0135, P0141, P0155, P0161 (MZI-3.7) DETECTION CONDITIONS AND POSSIBLE CAUSES



Verify that all disconnected connectors
are reconnected.



Turn the ignition switch to the ON
position (Engine off).



Clear the DTC from the PCM memory
using the M-MDS.



Retrieve DTCs using the M-MDS.



Is the PENDING CODE for this DTC
present?

Yes

Replace PCM, then go to the next step. (See
PCM REMOVAL/INSTALLATION [MZI-
3.7] .)

Go to the next step.

VERIFY AFTER REPAIR PROCEDURE



Perform "AFTER REPAIR
PROCEDURE". (See AFTER
REPAIR PROCEDURE [MZI-3.7].)



Are any DTC present?

Yes

Go to the applicable DTC inspection. (See
DTC TABLE [MZI-3.7].)

Troubleshooting completed.

DTC P0135

P0135: Front HO2S heater (RH) circuit

DTC P0141

P0141: Rear HO2S heater (RH) circuit

DTC P0155

P0155: Front HO2S heater (LH) circuit

DTC P0161

P0161: Rear HO2S heater (LH) circuit

DETECTION

CONDITION



During testing the heated oxygen sensor heaters are checked for open and short
circuits and excessive current draw.



The test fails when the current draw exceeds a calibrated limit or an open or
short circuit is detected.

POSSIBLE CAUSE



Short to ground between HO2S terminal A and HO2S terminal C



Short to ground between HO2S terminal A and HO2S terminal D



Short to ground between HO2S terminal A and HO2S terminal B



Water in the wiring harness connector



Open circuit between PCM terminal 2J and front HO2S (RH) terminal A



Open circuit between PCM terminal 2AS and rear HO2S (RH) terminal A



Open circuit between PCM terminal 2E and front HO2S (LH) terminal A



Open circuit between PCM terminal 2AO and rear HO2S (LH) terminal A



Low battery voltage



Corrosion or incorrect harness connections



HO2S heater malfunction

2008 Mazda CX-9 Grand Touring

2008 ENGINE PERFORMANCE On-Board Diagnostic (MZI-3.7) - Mazda CX-9

Microsoft

Sunday, November 15, 2009 10:08:35 AM

Page 96

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