P0172

[P0172] The scan tool indicates Diagnostic Trouble Code (DTC) P0172: The fuel system is too rich.

Description
By monitoring the Long Term Fuel Trim, long term malfunctions in the fuel system will be detected.
If a malfunction has been detected during two consecutive trips, the MIL will come on and DTC P0171 and/or P0172 will be stored.

NOTE: If some of the DTCs listed below are stored at the same time as DTC P0171 and/or P0172 troubleshoot those DTCs first, then troubleshoot DTC P0171 and/or P0172.

P0107, P0105, P1128, P1129: MAP Sensor
P0135: Primary HO2S Heater (Sensor 1)
P0137, P0138: Secondary HO2S (Sensor 2)
P0141: Secondary HO2S Heater (Sensor 2)
P1259: VTEC System

Possible Cause
- Fuel Pressure Regulator clogged, stuck closed
- Fuel Return Pipe clogged
- Fuel Injector leaking
- Gasoline doesn't meet Owner's Manual spec.
- Primary HO2S (Sensor 1) deteriorated Valve Clearance