2010 Cadillac CTS Sedan AWD V6-3.6L Page 1110
Typical Scan Tool Data
Circuit Description
The heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding
air with the oxygen content of the exhaust stream. When the engine is started, the control module operates in an Open Loop mode, ignoring the
HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference, or bias voltage of about 450
mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above
and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control
module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a
rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.
The heating elements inside each HO2S heat the sensor to bring the sensor up to operating conditions faster. This allows the system to enter Closed
Loop earlier and the control module to calculate the air-to-fuel ratio sooner.
Conditions for Running the DTCs
P0137 and P0157
* DTC P0036, P0037, P0038, P0056, P0057, P0058, P0116, P0117, P0118, P0119, or P0128 is not set.
* The engine speed is greater than 240 RPM.
* The ignition voltage is greater than 10 volts.
* The engine coolant temperature is colder than 40掳C (104掳F) at start-up and the engine coolant temperature was warmer than 60掳C (140掳F)
when the ignition was turned OFF last ignition cycle.
* The calculated exhaust temperature at the HO2S 2 is warmer than 700掳C (1,292掳F) and the HO2S 2 is warmed up for greater than 90
seconds.
* The calculated exhaust temperature is colder than 800掳C (1472掳F) 5 seconds after engine start.
* DTCs P0137 and P0157 run continuously once the above conditions are met.
P0138, P0140, P0158, and P0160
* The engine speed is greater than 240 RPM.
* The ignition voltage is greater than 10 volts.
* The HO2S 2 heater duty cycle is stable and the HO2S 2 is warmed up for greater than 90 seconds.
* The calculated exhaust temperature is colder than 800掳C (1472掳F).
* DTCs P0138 and P0158 run continuously once the above conditions are met for greater than 5 seconds.
* DTCs P0140 and P0160 run continuously once the above conditions are met for greater than 60 seconds.
Conditions for Setting the DTC
P0137 or P0157
The ECM detects that a secondary HO2S signal voltage is less than 60 mV for greater than 1 seconds of for a cumulative of 10 seconds.
P0138 or P0158
The ECM detects that the HO2S signal voltage is greater than 1,150 mV for greater than 1 seconds or for a cumulative of 10 seconds.
P0140 or P0160
* The ECM detects that the HO2S 2 signal voltage is between 401-519 mV.
* The ECM detects that the measured internal resistance of the HO2S 2 is greater than 40,000 ohms, when the calculated exhaust temperature
is warmer than 500掳C (932掳F).
