Engine Management – V6 – Diagnostics
Page 6C1-2–174
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1
Using Tech 2, clear the DTCs.
2
Switch off the ignition for 30 seconds.
3
Start the engine.
4
Operate the vehicle within the conditions for
running the DTC.
Does DTC P2096 or P2098 fail this ignition cycle?
—
Go to Step 2
Go to Step 20
20
Using Tech 2, select the DTC display function.
Does Tech 2 display any DTCs?
—
Go to the
appropriate DTC
Table in this
Section System
OK
When all diagnosis and repairs are completed, clear all DTCs and verify correct operation
7.47 DTC P2097 or P2099
DTC Descriptors
This diagnostic procedure supports the following DTCs:
•
DTC P2097 Post Catalyst O2 Sensor Fuel Trim Above Upper Limit (Bank 1)
•
DTC P2099 Post Catalyst O2 Sensor Fuel Trim Above Upper Limit (Bank 2)
Circuit Description
The wide band heated oxygen sensor 1 measures the amount of oxygen in the exhaust system and provides more
information than the switching style HO2S2. The wide band sensor consists of an oxygen sensing cell, an oxygen
pumping cell, and a heater. The exhaust gas sample passes through a diffusion gap between the sensing cell and the
pumping cell. The engine control module (ECM) supplies a voltage to the HO2S and uses this voltage as a reference to
the amount of oxygen in the exhaust system. An electronic circuit within the ECM controls the pump current through the
oxygen pumping cell, maintaining a constant voltage in the oxygen sensing cell. The ECM monitors the voltage variation
in the sensing cell and attempts to keep the voltage constant by increasing or decreasing the amount of current flow, or
oxygen ion flow, to the pumping cell. By measuring the amount of current required to maintain the voltage in the sensing
cell, the ECM can determine the concentration of oxygen in the exhaust. The HO2S voltage is displayed as a lambda
value. A lambda value of 1 is equal to a stoichiometric air fuel ratio of 14.7:1. Under normal operating conditions, the
lambda value will remain around 1. When the fuel system is lean, the oxygen level will be high and the lambda signal
will be high or more than 1. When the fuel system is rich, the oxygen level will be low, and the lambda signal will be low
or less than 1. The ECM uses this information to maintain the correct air / fuel ratio.
Fuel trim biasing is used by the ECM to keep the post catalyst HO2S voltage within a range of 580 – 665 mV as
possible. This allows optimal catalyst efficiency under light load conditions, such as at idle or a steady cruise. The ECM
constantly monitors how lean or rich the fuel trim bias is commanded. If the ECM detects that the fuel trim bias is
commanded rich for more than a calibrated amount, DTC P2097 or P2099 sets.
Conditions for Running the DTC
•
Before the ECM can report DTC P2096 or P2098 failed, DTCs P0030, P0031, P0032, P0041, P0050, P0051,
P0052, P0101, P0131, P0132, P0135, P0137, P0138, P0140, P0141, P0151, P0152, P0155, P0157, P0158,
P0160, P0161, P2231, P2234, P2237, P2240, P2243, P2247, P2251, P2254, P2270, P2271, P2273, P2626, and
P2629 must run and pass.
•
The engine is operating for more than 2 seconds.
•
The post catalyst fuel trim control is enabled.
•
The front and rear HO2S are in Closed Loop.
•
DTCs P2097 and P2099 run continuously once the above conditions are met for more than 40 seconds.
Conditions for Setting the DTC
The post catalyst fuel trim correction factor is biased rich by more than –3 percent of the HO2S lambda value for more
than 4 seconds.