The P155.R2 code relates to the heated oxygen sensors that your vehicle relies on to get your engine to operating temperature quickly so as not to stay in open-loop operation too long. The P0155 code occurs when the Power Control Module (PCM) tests the upstream heated oxygen sensor’s circuit on Bank 2, or one side of a V-configured engine like a V6 or a V8, and detects a short in the circuit or too much resistance in the heater circuit. The codes P0161 and P0167 relate to the other two sensors located on the Bank 2 side of the engine and exhaust system.
As we mentioned, the PCM performs tests on the heated oxygen sensors to prevent your engine from operating in open-loop mode for too long. Open-loop mode is found in fuel-injected motors, which makes up the majority of all motors today, and means that the engine is operating independently of any oxygen or air-to-fuel sensors and makes no adjustments to that mixture. The heated oxygen sensors are needed to ensure that the engine can have a reliable sensor to listen to and start adjusting the air and fuel ratio accordingly. This then lands the motor in closed-loop mode. Nevertheless, there are many cases when a particular sensor isn’t working that the ECM will infer a signal in order to keep the vehicle operational. This would then store a substituted value in the freeze frame data that wouldn’t change and could be picked up with a scanner later.
More About The P0155 And Related Codes
The P155.R2 code appears when the PCM performs a circuit test on the front end of the Bank 2 system and runs into any circuit issues or excessive resistance problems with the oxygen sensor. What this means is that it will take longer for the motor to enter the closed-loop mode. As the O2 heater reaches operating temperature, the oxygen sensor responds by adjusting according to the oxygen content of the exhaust surrounding the sensor. The PCM tracks how long this time takes for the oxygen sensor to begin switching, and if it determines that it is taking too long, it will trigger the P0155 code.
