P0172 Fuel Trim System Rich Bank - Isuzu 2000 Trooper Workshop Manual

Diagnostic Trouble Code (DTC) P0172 Fuel Trim System Rich Bank 1
Circuit Description
To provide the best possible combination of driveability,
fuel economy, and emission control, a "closed loop"
air/fuel metering system is used. While in "closed loop,"
the powertrain control module (PCM) monitors the Bank 1
heated oxygen sensors (HO2S) 1 and Bank 2 HO2S 1
signals and adjusts fuel delivery based upon the HO2S
signal voltages. A change made to fuel delivery will be
indicated by the long and short term fuel trim values which
can be monitored with a Tech 2. Ideal fuel trim values are
around 0%; if the HO2S signals are indicating a lean
condition the PCM will add fuel, resulting in fuel trim
values above 0%. If a rich condition is detected, the fuel
trim values will be below 0%, indicating that the PCM is
reducing the amount of fuel delivered. If an excessively
rich condition is detected on Bank 1, the PCM will set DTC
P0172.
The PCM's maximum authority to control long term fuel
trim allows a range between –15% (automatic
transmission) or –12 (manual transmission) and +20%.
The PCM's maximum authority to control short term fuel
trim allows a range between –11% and +20%. The PCM
monitors fuel trim under various engine speed/load fuel
trim cells before determining the status of the fuel trim
diagnostic.
Conditions for Setting the DTC
D No Tech 2 test is being run.
TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
D None of the following was set: EGR DTCs, HO2S
DTCs, (response, transition, open, low volts, no
activity), MAF DTCs, TPS DTCs, MAP DTCs, IAT
DTCs, canister purge DTCs, EVAP DTCs, injector
circuit DTCs, or misfire DTCs.
D Engine coolant temperature is between 25°C (77°F)
and 100°C (212°F).
D Intake air temperature is between –40°C (–40°F) and
120°C (248°F).
D Manifold absolute pressure is between 24 kPa and 99
kPa.
D Throttle angle is steady below 95%.
D Vehicle speed is below 136 km/h (85 mph).
D Engine speed is between 400 and 6,000 RPM.
D Barometric pressure is greater than 72.5 kPa.
D Mass air flow is between 2 g/second and 200 g/second.
D Ignition voltage is above 9.5 volts.
D Fuel system is in "closed loop."
D Canister purge duty cycle is greater than 0%, if "ON."
Action Taken When the DTC Sets
D The PCM will illuminate the malfunction indicator lamp
(MIL) after the second consecutive trip in which the
fault is detected.
D The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
6E–229
D06RY00171