The heated oxygen sensor (HO2S) bank 2 sensor 2 is threaded into the cylinder 2, 4, 6 exhaust pipe behind the pre-converter (cylinders 2, 4, 6 are closest to front of vehicle). The sensor is an electrical source that responds to oxygen content out of the catalytic converter. When the sensor reaches approximately 316°C (600°F), it produces a voltage based on the difference in oxygen between the atmosphere and exhaust gas. The ECM sends a bias voltage (425-460 mV) on the signal line, which is pulled up through high resistance. When the HO2S bank 2 sensor 2 is cold, it produces no voltage and has extremely high internal resistance. The internal resistance of the sensor is much greater than the resistance of the bias pull-up resistor. However, when the sensor heats up, it produces voltage that overrides the bias voltage. This voltage is read by the ECM to determine the efficiency of the catalytic converter. Under normal conditions, low sensor voltage means high oxygen content/lean air-fuel mixture and vice versa. Normal sensor readings at steady cruise with a properly functioning catalytic converter will be around 500-800 mV. If the ECM does not see the expected response ( the signal switching above or below a threshold for a certain length of time) from the HO2S bank 2 sensor 2, the ECM will command a rich and lean status to force a response. DTC P0159 sets when the HO2S bank 2 sensor 2 does not react for a certain length of time.
DTC Parameters
DTC P0156 will set if HO2S bank 2 sensor 2 voltage is less than 40 mV when:
| • | Condition exists for longer than 1 minute and 40 seconds. |
| • | Engine is running. |
| • | HO2S bank 2 sensor 2 in closed loop. |
| • | Calculated converter temperature less than 940°C (1724°F). |
| • | Commanded air/fuel ratio is 14.7 to 1. |
| • | Battery voltage greater than 11.0 volts. |
DTC P0159 diagnostic runs continuously once the above conditions have been met.
P0159 is a (type B) DTC.
Diagnostic Aids
Important: An intermittent open in the signal wire or ground wire will not set this DTC.
Important: Do not apply grease or any material in the HO2S bank 2 sensor 2 harness connector or alter the wiring in any way. The wires carry air reference to the sensor used to determine the difference in oxygen between the exhaust gas and atmosphere.
The most probable cause for DTC P0159 is contamination of the HO2S bank 2 sensor 2. Source the cause of contamination (i.e. oil, fuel, coolant, or carbon) and correct the contamination condition. Then replace HO2S bank 2 sensor 2.
