DTC Advanced Diagnostics: P2097
DTC P2097:Post Catalyst Fuel Trim System Too Rich

General Description

The PCM monitors the offset of the air/fuel ratio (A/F) sensor (sensor 1) signal. The test is performed by monitoring the fuel trim control of the secondary heated oxygen sensor (secondary HO2S (sensor 2)). If there is an air/fuel ratio offset measured by the secondary HO2S (sensor 2), the secondary HO2S (sensor 2) fuel trim is used to correct this offset back to the commanded air/fuel ratio. If the offset is present for an extended time, the secondary HO2S (sensor 2) fuel trim is stored as the A/F sensor (sensor 1) offset adaptation. There are two ways that the A/F sensor (sensor 1) offset is adapted. If the secondary HO2S (sensor 2) fuel trim has a small deviation, then the A/F sensor (sensor 1) offset is adapted slowly. If the secondary HO2S (sensor 2) fuel trim has a large deviation, the A/F sensor (sensor 1) offset is adapted faster. If the adapted offset of the A/F sensor (sensor 1) sensor is too large, the PCM detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type
Execution
Multiple
Sequence
None
Duration
0.5 second or more
DTC Type
Two drive cycles, MIL on

Enable Conditions
Slow offset adaptation
Condition
Minimum
Maximum
Engine speed [Engine Speed]
1,400 rpm
3,000 rpm
Charging efficiency
20.3 % - 99.8 %
0 % - 69.8 %
Fuel feedback
Closed loop*
Other
Evaporative emission (EVAP) system monitor is not active
*: For at least 300 g (10.59 oz) of integrated amount of exhaust mass flow
[ ]: HDS Parameter

Fast offset adaptation
Condition
Minimum
Maximum
Engine coolant temperature [ECT Sensor 1]
104 °F (40 °C)
–
Engine speed [Engine Speed]**
1,000 rpm
–
Exhaust gas mass flow
25 kg/h (56 lbs/h)
200 kg/h (440 lbs/h)
Charging efficiency
13 % - 22 %
–
Fuel feedback
Closed loop
Other
No significant load changes
Other than during fuel cut-off operation
Misfire rate is not exceeding
EVAP system monitor is not active
**: For at least 80 g (2.83 oz) - 200 g (7.06 oz) of integrated amount of exhaust gas mass flow

Malfunction Threshold
Lambda offset is less than -0.05 but -0.1 or more and lambda offset change in non-fault direction for confirmation of fuel trim fault is less than 0.01.

Possible Cause
NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
A/F sensor (sensor 1) failure
Exhaust system leak

Confirmation Procedure
Operating Condition
1.
Start the engine. Hold the engine speed [Engine Speed] at 3,000 rpm without load (in neutral) until the radiator fan comes on, then let it idle.
2.
Drive the vehicle at constant speed with part load for a while.
Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.

Diagnosis Details
Conditions for setting the DTC
When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC and the freeze data are stored.

Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command.