2010 Cadillac CTS Sedan AWD V6-3.6L Page 1956
* Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 (LF1) (See: Powertrain Management/Computers and Control Systems/Oxygen
Sensor/Service and Repair)Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 (LLT) (See: Powertrain Management/Computers and
Control Systems/Oxygen Sensor/Service and Repair)
* Control Module References (See: Testing and Inspection/Programming and Relearning) for engine control module replacement, setup, and
programming
P2273
DTC P2271 or P2273 (w/LLT)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category.
DTC Descriptors
DTC P2271
- HO2S Signal Stuck Rich Bank 1 Sensor 2
DTC P2273
- HO2S Signal Stuck Rich Bank 2 Sensor 2
Circuit Description
The engine control module (ECM) supplies a voltage near 450 mV between the heated oxygen sensor (HO2S) high signal circuit and the low
reference circuit. The HO2S varies the voltage over a range from about 1,000 mV when the exhaust is rich, down through about 10 mV when the
exhaust is lean. The ECM monitors and stores the HO2S voltage information. The ECM evaluates the HO2S voltage samples in order to determine
the amount of time that the HO2S voltage was out of range. The ECM compares the stored HO2S voltage samples taken within each sample period
and determines if the majority of the samples are out of the operating range. The ECM test for the following conditions:
* The ECM monitors the HO2S voltage to determine if the signal voltage goes below a predetermined threshold within a certain amount of
time. If the ECM determines that the signal voltage remains above the threshold, the ECM will command the fuel system lean to determine if
the HO2S signal voltage can be forced below the threshold within a certain amount of time.
* The ECM monitors the HO2S voltage during fuel cut-off to determine if the signal voltage is greater than a predetermined threshold.
Conditions for Running the DTC
* Before the ECM can report DTC P2270 or P2272 failed, DTCs P0036, P0037, P0038, P0056, P0057, P0058, P013A, P013C, P013E, P0137,
P0138, P014A, P0140, P0141, P0157, P0158, P0160, P0161, P0443, P0458, P0459, P2097, P2099, P2178, P2180, P2188, and P2190 must
run and pass.
* DTC P0461, P0462, P0463, P2066, P2067, or P2068 is not set.
* The engine speed is greater than 240 RPM.
* The ignition voltage is greater than 10 volts.
* The HO2S 2 is at operating temperature for greater than 10 seconds.
* The long term fuel control is enabled.
* The mass air flow (MAF) signal is greater than 10 g/s.
* The MAF signal is between 6-33 g/s for greater than 3 seconds during the intrusive test.
* DTC P2271 and P2273 runs continuously once the conditions above are met for approximately 10 minutes, or 20 minutes if the fuel level is
less than 12 percent.
Conditions for Setting the DTC
The ECM detects that the HO2S 2 voltage is greater than 629 mV for greater than 100 seconds, then an intrusive test is performed. The ECM will
lean the fuel mixture -2 percent per second and then wait for 10 seconds at -15 percent. If the ECM detects that the HO2S voltage is still greater
than 629 mV, for 4 seconds or for a cumulative of 30 seconds the DTC sets.
Action Taken when the DTC Sets
DTCs P2271 and P2273 are Type B DTCs.
Conditions for Clearing the MIL/DTC
DTCs P2271 and P2273 are Type B DTCs.
