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Mazda CX-9 Grand Touring. Manual - part 243

DTC P0171, P0174 [MZI-3.7]

DTC P0171, P0174 (MZI-3.7) DETECTION CONDITIONS AND POSSIBLE CAUSES



Disconnect the fuel supply line at the
fuel rail.



Disconnect the fuel supply line at the
fuel pump.



Check the fuel supply line for
restriction.



Apply 21-34 kPa {2142-3467 mmHg,
84.34-136.4 inHg} air pressure to the
fuel supply line.



Does air flow freely through the line?

NOTE:



Observe the Warnings, Cautions, and
Notes.

Yes

Replace the fuel pump module. Then go to the
next step.

Repair the cause of the restriction. Then go to

the next step.

VERIFY TROUBLESHOOTING OF DTC
P0148 HAS BEEN COMPLETED



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.



Start the engine and run it at idle.



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 P0171

P0171: System too lean (RH)

DTC P0174

P0174: System too lean (LH)

DETECTION



P0171 indicates that the fuel/air ratio is too lean (RH).



P0174 indicates that the fuel/air ratio is too lean (LH).

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 105

DIAGNOSTIC PROCEDURE

DTC P0171, P0174 (MZI-3.7) DIAGNOSTIC PROCEDURE

CONDITION



The adaptive fuel strategy continuously monitors the fuel delivery hardware.
The test fails when the adaptive fuel tables reach a rich calibrated limit.

POSSIBLE CAUSE

Fuel System:



Damaged or leaking fuel pulse damper



Fuel filter plugged or dirty



Damaged or worn fuel pump



Leaking fuel pump check valve



Leaking/contaminated fuel injectors



Low fuel pressure or running out of fuel



Purge solenoid valve is leaking when the canister is clean



Fuel supply line restricted



Fuel rail pressure sensor bias

Exhaust System:



Exhaust leaks in the exhaust manifold gasket or mating gaskets before or
near the HO2S

Intake Air System:



Air leaks after the MAF sensor



Vacuum leaks



PCV system is leaking or the valve is stuck open



Improperly seated engine oil dipstick



Damaged or contaminated MAF sensor

STEP

INSPECTION

ACTION

VERIFY FREEZE FRAME DATA HAS BEEN
RECORDED



Has FREEZE FRAME DATA been
recorded?

Yes Go to the next step.

Record FREEZE FRAME DATA on the

repair order, then go to the next step.

VERIFY RELATED REPAIR INFORMATION
AVAILABILITY



Verify related Service Bulletins and/or on-

Yes

Perform repair or diagnosis according to
the available Service Bulletins.



If the vehicle is not repaired, go to

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 106

line repair information availability.



Is any related Service Bulletins available?

the next step.

Go to the next step.

VERIFY RELATED PENDING CODE OR
STORED DTCS



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



Verify related PENDING CODE or stored
DTCs.



Are any DTCs present other than the
following:



P0171, P0174, P2195 or P2197?

Yes

Go to the appropriate DTC
troubleshooting procedures. (See DTC
TABLE [MZI-3.7].)

Go to the next step.

PERFORM VISUAL INSPECTION ON
INTAKEAIR SYSTEM AND ALL VACUUM
HOSES



Turn the ignition switch off.



Check the intake air system for leaks,
obstructions, and damage.



Inspect the entire length of all the vacuum
hoses for:



Proper connections



Damage or cracks



Damaged or cracked vacuum vacuum
hose joint



Verify the integrity of the positive crankcase
ventilation system.



Verify that the PCV valve part number is
correct.



Is a concern present?

Yes Repair if necessary. Then go to Step 7.

Go to the next step.

INSPECT FOR PRESENCE OF VACUUM
LEAK

NOTE:



Fuel trim values at idle are more sensitive
to a vacuum leak. The vacuum leak
(unmetered air) represents a larger portion
of the total air flow at idle than at part
throttle.



The BARO PID is not a commended PID to
monitor when diagnosing a vacuum leak.
BARO is calculated during high engine
load, when the vacuum leak represents a

Yes No vacuum leak is present. Go to Step 8.

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 107



Turn the ignition switch to the ON position
(Engine running)



Access the PCM and monitor the ECT, CHT
and IAT PIDs.



Access the PCM and monitor the LONGFT1,
SHRTFT1, LONGFT2 and SHRTFT2 PIDs.



Allow the engine to stabilize at the
temperature necessary to recreate the
concern.



Add and record the LONGFT PID value to
the SHRTFT PID value for each bank,
correction at idle.



Increase the engine speed to 2,500 rpm for 10
s. Record the LONGFT1, SHRTFT1,
LONGFT2, and system SHRTFT2 PID
values.



Add and record the LONGFT PID value to
the SHRTFT PID value for each bank,
correction at 2,500 rpm.



Is the total fuel correction value difference
between idle and 2,500 rpm less than 15%?

small portion of the total air flow



When calculating the total fuel correction
in the following steps, if LONGFT1 equals
+13% and SHRTFT1 equals +23%, the total
fuel correction for bank 1 equals +36%. If
LONGFT2 equals +24% and SHRTFT2
equals -3% the total fuel correction for
bank 2 equals+21%.



If the freeze frame ECT PID is available,
stabilize the engine at the temperature
recorded by the freeze frame ECT PID. If
the freeze frame ECT PID is not available,
maintain the engine coolant temperature
between 82-101°C {180-215°F} and the
intake air temperature at less than 46°C
{115°F}.

Go to the next step.

LOCATE VACUUM LEAK

CAUTION:



Do not clamp or pinch a hard plastic hose.
Use a vacuum cap or equivalent to restrict
the hose.

Yes

Repair if necessary. Then 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 108

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