Troubleshooting
DTC P0172 SYSTEM TOO RICH (FUEL TRIM) (BANK 1)CIRCUIT DESCRIPTION
DTC Detecting Condition:
Fuel trim is related to the feedback compensation value, not to the basic injection time. Fuel trim includes short-term fuel trim and long-term fuel trim.
Short-term fuel trim is the short-term fuel compensation used to maintain the air-fuel ratio at its ideal theoretical value. The signal from the heated oxygen sensor indicates whether the air-fuel ratio is RICH or LEAN compared to the ideal theoretical value, triggering a reduction in fuel volume if the air-fuel ratio is RICH and an increase in fuel volume if it is LEAN.
Long-term fuel trim is overall fuel compensation carried out in long-term to compensate for continual deviation of the short-term fuel trim from the central value, which is due to individual engine differences, wear overtime and changes in the using environment.
If both the short-term fuel trim and long-term fuel trim are LEAN or RICH beyond a certain value, it is detected as a malfunction and the MIL lights up.
Wiring Diagram:
Step 1 - 6:
Step 7 - 9:
Step 9 (continued):
Step 10 - 11:
Step 12 - 13:
Step 14 - 21:
INSPECTION PROCEDURE
HINT: Read freeze frame data using the hand-held tester or the OBD II scan tool, as freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, this is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.
CONFIRMATION DRIVING PATTERN
1. Connect the hand-held tester to the DLC3. (*1)
2. Switch the hand-held tester from the normal mode to the check mode. (*1)
3. Start the engine and warm it up with all the accessory switches OFF. (*2)
4. Drive the vehicle at 60 - 120 km/h (38-75 mph) and engine speed at 1,400 - 3,200 rpm for 3 - 5 min. (*3)
HINT: If a malfunction exists, the MIL will light up during step (*3).
NOTE: If the conditions in this test are not strictly followed, detection of the malfunction will not be possible.
If you do not have a hand-held tester, turn the ignition switch OFF after performing steps (*2) and (*3), then perform steps (*2) and (*3) again.
CHECK FOR INTERMITTENT PROBLEMS
Hand-held tester only:
By putting the vehicle's ECM in the check mode, the 1 trip detection logic is possible instead of the 2 trip detection logic and the sensitivity to detect open circuits is increased. This makes it easier to detect intermittent problems.
1. Clear the DTCs.
2. Set the check mode.
3. Perform a simulation test.
4. Check the connector and terminal.
5. Handle the connector.