P0145 02 Sensor Circuit Slow Response (Bank 1 Sensor 3)
OBD-II Trouble Code Technical Description
O2 Sensor Circuit Slow Response (Bank 1 Sensor 3)
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code, which means that it applies to all 1996-newer vehicles (Mitsubishi, Nissan, Volkswagen, Inifiniti, etc.). Although generic, the specific repair steps may vary depending on make/model.
If your OBD-II equipped vehicle has a stored P0145 code, it means that the powertrain control module (PCM) has detected a slow response time from a downstream (or post catalytic converter) oxygen (O2) sensor or circuit. Bank 1 denotes the bank of the engine that contains the number one cylinder and Sensor 3 indicates that the malfunction is related to the downstream sensor in a system equipped with only three sensors (as opposed to a four-sensor system).
O2 sensors are constructed using a zirconium dioxide sensing element which is protected by a vented steel housing. The sensing element is connected to wire leads in the O2 sensor wiring harness using platinum electrodes. The PCM is connected to the O2 sensor wiring harness using the controller area network (CAN). The PCM is supplied with data, pertaining to the percentage of oxygen particles in the engine exhaust as compared to the oxygen content of ambient air, by the O2 sensor.
Exhaust gases are pushed into the exhaust pipe and through the catalytic converter; afterward, they pass over the downstream O2 sensor. As exhaust flows through vent holes (in the steel housing) and across the sensing element, ambient air is drawn through the wire lead cavities and into a small chamber in the middle of the sensor. The ambient air (in the chamber) is heated by the exhaust, forcing the oxygen ions to produce (energy) voltage. Deviations between the number of oxygen molecules in ambient air (drawn into the O2 sensor) and the concentration of oxygen ions in the spent exhaust gases cause the voltage to change. These changes cause the oxygen ions inside the O2 sensor to jump between platinum layers very rapidly and repetitiously.
Voltage variations occur as the rushing oxygen ions jump between platinum layers. The PCM identifies these variations in voltage as changes in exhaust oxygen concentration. These changes indicate that the engine is either running lean (too little fuel) or rich (too much fuel). The voltage signal from the O2 sensor is low when more oxygen is present in the exhaust (lean condition) and high when less oxygen is present in the exhaust (rich condition). This data is used by the PCM primarily to monitor catalytic converter efficiency. If the downstream O2 sensor circuit fails to cycle as expected, over a set period of time and under certain programmed circumstances, a P0145 code will be stored and a malfunction indicator lamp may be illuminated.
Severity & Symptoms
Since a P0145 code means that the post catalytic converter O2 sensor has remained slow or unresponsive, it should be addressed at your earliest convenience.
Symptoms of a P0145 code may include:
Causes
Possible causes for this engine code include:
Diagnostic and Repair Procedures
A good starting point is always to check for technical service bulletins (TSB) for your particular vehicle. Your issue may be a known issue with a known fix put out by the manufacturer and can save you time and money during diagnosis.
A diagnostic scanner, digital volt ohmmeter (DVOM), and a reliable vehicle information source are tools that I would require when diagnosing a code P0145.
Misfire codes, throttle position sensor codes, manifold air pressure code, and mass air flow sensor codes must be diagnosed and repaired prior to attempting to diagnose a code P0145. If the engine is not running efficiently a successful diagnosis cannot be reached.
Most skilled technicians begin with a visual inspection of system wiring harnesses and connectors. I would focus on harnesses that are routed near hot exhaust pipes and manifolds, as well as those that are routed near sharp edges like the ones found on exhaust shields.
Retrieve all stored trouble codes and freeze frame data by connecting the scanner to the vehicle diagnostic port. Write this information down because it may be helpful if the P0145 proves to be intermittent. Clear the codes and see if the P0145 is reset.
If the P0145 is reset, start the engine and let it idle (with the transmission in neutral or park), after allowing it to reach normal operating temperature. Observe O2 sensor input data on the scanner data stream. By narrowing the data stream display to include only pertinent data you can get a more accurate data response. If the engine is running efficiently, downstream O2 sensor data should reach a mid-line and only fluctuate slightly. If there is little or no fluctuation, a P0145 will be stored.
To monitor live data from the O2 sensor, connect the DVOM test leads to the sensor ground and signal wires. The DVOM may also be used to check resistance of the O2 sensor in question, as well as voltage and ground signals. Disconnect related controllers prior to testing system circuit resistance with the DVOM.
Additional diagnostic notes:
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"Delete Error Code Permanently, Disable DTC Error Code Function for p0145 in the ECU"
In extreme cases, we even have the option to permanently remove the specific DTC p0145 and disable the function of the specific error code in the ECU. All other fault code functions will then continue to work to protect the engine. This is different from clearing an error code with a diagnostic device. We have the option to permanently remove the function of the specific error code, so that it never comes back. Also emergency running that occurs on the specific error code can be solved in most cases.
Of course we prefer to first try to solve the cause of the error code, but sometimes the only solution is to permanently disable the DTC function of p0145.
