Mazda CX-7 2007 Workshop Manual page 263

DTC P2178 Fuel system too rich at off idle
• Misfire
• Front HO2S deterioration
• Front HO2S heater malfunction
• MAF sensor malfunction
• Pressure regulator malfunction
• Fuel pressure sensor malfunction
• Relief valve (built-in fuel delivery pipe) malfunction
• Spill valve control solenoid valve (built-in high pressure fuel pump) malfunction
• High pressure fuel pump malfunction
POSSIBLE
• Fuel pump malfunction
CAUSE
• EGR valve improper operation
• Variable swirl control improper operation
• Purge solenoid valve improper operation
• Purge solenoid valve malfunction (stuck open)
• Purge solenoid hoses improper connection
• PCV valve malfunction
• Variable valve timing control system improper operation
• PCM malfunction
Diagnostic procedure
STEP
1 VERIFY FREEZE FRAME DATA AND
DIAGNOSTIC MONITORING TEST RESULTS
HAVE BEEN RECORDED
• Have the FREEZE FRAME DATA and
DIAGNOSTIC MONITORING TEST RESULTS
(Fuel system related) been recorded?
2 VERIFY RELATED REPAIR INFORMATION
AVAILABILITY
• Verify related Service Bulletins and/or on-line
repair information availability.
• Is any related repair information available?
3 VERIFY RELATED PENDING CODE OR
STORED DTCS
• Turn the ignition switch to off, then to the ON
position (Engine off).
• Verify related pending code or stored DTCs.
• Are other DTCs present?
4 IDENTIFY TRIGGER DTC FOR FREEZE FRAME
DATA
• Is DTC P2178 on FREEZE FRAME DATA?
5 VERIFY CURRENT INPUT SIGNAL STATUS
(IGNITION SWITCH TO THE ON POSITION/
IDLE)
• Access the APP1, APP2, ECT, MAF, TP and
VSS PIDs using the M-MDS.
• Is there any signal that is far out of specification
when the ignition switch is at the ON position
and the engine runs?
6 VERIFY CURRENT INPUT SIGNAL STATUS
UNDER TROUBLE CONDITION
• Inspect the same PIDs as Step 5 while
simulating FREEZE FRAME DATA condition.
• Is there any signal which causes drastic
changes?
7 VERIFY CURRENT INPUT SIGNAL STATUS OF
FRONT HO2S
• Access the O2S11 for P2177 PID using the M-
MDS.
• Check the PID under following accelerator
pedal condition in NEUTRAL.
• Is the PID reading normal?
— –0.1— 0.1 A when idle
— More than 0.25 mA just after release of
accelerator pedal (lean condition)
ON-BOARD DIAGNOSTIC [L3 WITH TC]
INSPECTION
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.
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.
Yes If misfire the DTC is present, go to Step 8.
If other DTCs is present, go to the applicable DTC
inspection.
(See01-02-13 DTC TABLE[L3 WITH TC].)
No If driveability concern is present, go to Step 8.
If not, go to the next step.
Yes Go to the next step.
No Go to troubleshooting procedures for DTC on FREEZE
FRAME DATA.
Yes Inspect the sensor and excessive resistance in related
wiring harnesses.
Repair if necessary.
Then go to Step 19.
No Go to the next step.
Yes Inspect the sensor and related wiring harnesses, repair or
replace it.
Then go to Step 19.
No Go to the next step.
Yes Go to the next step.
No Visually inspect for any gas leakage between the exhaust
manifold and the front HO2S.
Then go to Step 19.
ACTION
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