Down Stream Fuel System 1/2 Rich

Test 1 - 4:

Test 5 - 6:

SYMPTOM
P0172-DOWN STREAM FUEL SYSTEM 1/2 RICH

WHEN MONITORED
With the engine running in closed loop mode, the ambient/battery temperature above (-7° C) 20° F and altitude below 8500 ft.

SET CONDITION
If the PCM multiplies short term compensation by long term adaptive as well as a purge fuel multiplier and the result is below a certain value for 30 seconds over two trips, a freeze frame is stored, the MIL illuminates and a trouble code is stored.

POSSIBLE CAUSES
- Good trip equal to zero
- Exhaust leak
- engine mechanical problem
- O2 sensor
- O2 signal circuit
- O2 return circuit
- Fuel contamination