P0172high severityPowertrain
System Too Rich Bank 1
on 2002 Toyota 4Runner 3.4L V6 · RWD
What this code means
The long-term fuel trim for Bank 1 has exceeded the negative limit, indicating the engine is running rich. The PCM is subtracting fuel to compensate.
Symptoms
- Check Engine Light
- Black exhaust smoke
- Poor fuel economy
- Rough idle
- Fuel smell
- Fouled spark plugs
Common causes
- Leaking fuel injector
- High fuel pressure
- Faulty O2 sensor reading lean
- Stuck-open EVAP purge valve
- Saturated charcoal canister
- Faulty MAF sensor (underreporting)
Diagnostic steps
- Check fuel trim values
- Test fuel pressure
- Check for leaking injectors (fuel pressure drop test)
- Inspect EVAP purge valve
- Test MAF sensor
- Inspect spark plugs
Repair notes
Check fuel injectors for leaks. Test fuel pressure regulator. Inspect EVAP system.
Other Powertrain codes on this vehicle
P0001
Fuel Volume Regulator Control Circuit/Open
P0002
Fuel Volume Regulator Control Circuit Range/Performance
P0003
Fuel Volume Regulator Control Circuit Low
P0004
Fuel Volume Regulator Control Circuit High
P0010
Intake Camshaft Position Actuator Circuit/Open Bank 1
P0011
Intake Camshaft Position Timing Over-Advanced Bank 1
P0012
Intake Camshaft Position Timing Over-Retarded Bank 1
P0013
Exhaust Camshaft Position Actuator Circuit/Open Bank 1
P0014
Exhaust Camshaft Position Timing Over-Advanced Bank 1
P0015
Exhaust Camshaft Position Timing Over-Retarded Bank 1