DTC P0172

BHE010200100W21

DTC P0172

System too rich

DETECTION CONDITION

• The PCM monitors the short term fuel trim (SHRTFT) and long term fuel trim (LONGFT) when under closed loop fuel control. If the fuel trim is less than the specification, the PCM determines that the system is too rich.

Diagnostic support note

• This is a continuous monitor (Fuel system).
• 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.
• The DTC is stored in the PCM memory.

POSSIBLE CAUSE

• Front HO2S malfunction
• Fuel line pressure malfunction
• Fuel pump unit malfunction
• Purge solenoid valve malfunction
• Fuel pump speed control malfunction
• PCM malfunction

Diagnostic procedure

STEP

INSPECTION

ACTION

1

VERIFY FREEZE FRAME DATA HAS BEEN RECORDED

• Has FREEZE FRAME DATA been recorded?
Yes
Go to the next step.
No
Record the FREEZE FRAME DATA on the repair order, then go to the next step.
2

VERIFY RELATED REPAIR INFORMATION AVAILABILITY

• Verify related service repair information availability.
• Is any related repair information available?
Yes
Perform 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

VERIFY RELATED PENDING CODE OR STORED DTC

• Turn the ignition switch off, then to the ON position (Engine off).
• Verify the related PENDING CODE or stored DTCs.
• Are other DTCs present?
Yes
• If misfire DTC is present, go to Step 8.
• If other DTC is present, go to the appropriate DTC inspection.
(See DTC TABLE.)
No
• If drive ability concern is present, go to Step 8.
• If other, go to the next step.
4

IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA

• Is DTC P0172 on FREEZE FRAME DATA?
Yes
Go to the next step.
No
Go to the FREEZE FRAME DATA DTC inspection.
(See DTC TABLE.)
5

VERIFY CURRENT INPUT SIGNAL STATUS

• Connect the WDS or equivalent to the DLC-2.
• Verify the following PIDs.
– APP
– ECT
– MAF
– TP
– VSS
• Are the PIDs normal?
Yes
Go to the next step.
No
Inspect the malfunctioning part according to the inspection results.
Then go to Step 11.
6

VERIFY CURRENT INPUT SIGNAL STATUS UNDER FREEZE FRAME DATA CONDITION

• Connect the WDS or equivalent to the DLC-2.
• Verify the following PIDs under the FREEZE FRAME DATA condition.
– APP
– ECT
– MAF
– TP
– VSS
• Are the PIDs normal?
Yes
Go to the next step.
No
Inspect the malfunctioning part according to the inspection results.
Then go to Step 11.
7

VERIFY CURRENT INPUT SIGNAL STATUS OF FRONT HO2S

• Connect the WDS or equivalent to the DLC-2.
• Start the engine and warm it up completely.
• Access the O2S11 PID.
• Read the O2S11 PID under following accelerator pedal condition (in PARK or NEUTRAL).
– Less than 1 mA when accelerator pedal is suddenly depressed (rich condition).
– More than 1 mA just after release of accelerator pedal (lean condition)
• Is the PID normal?
Yes
Go to the next step.
No
Replace the front HO2S, then go to Step 11.
8

INSPECT FUEL LINE PRESSURE

• Perform the "FUEL LINE PRESSURE INSPECTION".
• Is there any malfunction?
Yes
Replace the fuel pump unit, then go to Step 11.
No
Go to the next step.
9

INSPECT LONG TERM FUEL TRIM

• Connect the WDS or equivalent to the DLC-2.
• Access the LONGFT1 PID.
• Compare the LONGFT1 PID with recorded FREEZE FRAME DATA at Step 1.
• Is the LONGFT1 PID above FREEZE FRAME DATA?
Yes
Inspect the purge solenoid valve.
• If there is any malfunction, replace the purge solenoid valve.
Then go to Step 11.
No
Go to the next step.
10

INSPECT FUEL PUMP SPEED CONTROL OPERATION

• Perform the "Fuel Pump Speed Control Operation Inspection".
• Is there any malfunction?
Yes
Repair or replace the malfunctioning part according to the inspection results.
Then go to the next step.
No
Go to the next step.
11

VERIFY TROUBLESHOOTING OF DTC P0172 COMPLETED

• Make sure to reconnect all disconnected connectors.
• Clear the DTC from the PCM memory using the WDS or equivalent.
• Perform the "DRIVE MODE 1".
• Is the PENDING CODE same as the DTC present?
Yes
Replace the PCM, then go to the next step.
No
Go to the next step.
12

VERIFY AFTER REPAIR PROCEDURE

• Perform the "AFTER REPAIR PROCEDURE".
• Are any DTCs present?
Yes
Go to the applicable DTC inspection.
(See DTC TABLE.)
No
DTC troubleshooting completed.