Technical Description of OBD-II Trouble Code
Malfunction in the O2 Sensor Heater Circuit (Bank 1 Sensor 3)
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to vehicles equipped with OBD-II. Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
O2 (Oxygen) sensors are equipped with a heating element that enables them to quickly reach their operating temperature. This helps in reducing emissions by allowing the engine to enter closed loop faster and maintain closed loop at idle.
The heater circuit receives a 12 V battery feed from the PCM or ignition circuit (depending on the model) and a ground. The PCM (powertrain control module) monitors the time it takes for the sensors to become active after engine start-up. If the o2 sensors take too long to reach their operating temperature, this P0147 code may be triggered.
Symptoms
For this specific o2 sensor, there may not be any noticeable symptoms other than:
Causes
Possible causes of a P0147 code include:
Possible Solutions
Disconnect the Bank 1, 3 sensor. With KOEO (key on engine off), use a voltmeter to check for the presence of battery voltage at the o2 sensor connector (PCM side). (You can also use a test light for this. Connect it to ground and touch the lead to the heater circuit supply. The light should illuminate with KOEO) Battery voltage should be present.
a. If voltage is present, also check the ground side of the heater element to ensure a good ground is present. If it is, check for any faulty connections and then replace the o2 sensor. If a good ground is not present, there may be an open in the ground circuit that needs to be repaired. Look for any contact between the wiring harness and exhaust components or any broken/missing connectors, etc.
b. If battery voltage is not present with KOEO, check for a blown fuse that supplies the heater elements. You may need to refer to a wiring diagram for this. If the fuse is blown, you’ll need to check for a short to ground on the battery supply circuit before replacing the fuse. If no short is found and replacing the fuse restores battery voltage at the o2 sensor connector, then the o2 sensor may have internally shorted, causing the fuse to blow. Replace the o2 sensor and recheck. (NOTE: It is possible for an o2 sensor’s heater circuit to be open or shorted and still function properly).
c. If there is no battery voltage present with KOEO and there are no blown fuses supplying the heater circuit, then check for an open in the supply circuit. You can do this by measuring the circuit’s resistance with the o2 sensor and PCM unplugged. Repair any open circuit and recheck.
