P0051 - Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 2 Sensor 1)

Description and meaning of DTC p0051

This diagnostic trouble code (DTC) is a generic powertrain code, which means that it applies to OBD-II equipped vehicles, including but not limited to Toyota, VW, Ford, Dodge, Honda, Chevrolet, Hyundai, Audi, Nissan, etc. Specific repair steps may vary depending on the model. A P0051 DTC trouble code refers to the O2 sensor (oxygen sensor)located on Bank 2 in frontof the catalytic converter. There is also an oxygen sensor behind the converterwhich is Sensor #2. Bank #2 is the side of the engine that does not contain cylinder #1. This O2 sensor #1 may also be refered to as an air/fuel ratio sensor sinceon some vehicles it is. It detects the amount of oxygen in the exhaust gas comparedto the outside air and then vehicle's computer adjusts the air/fuel ratio goinginto the engine. The sensor is less effective when the exhaust gas temperatureis low, so it includes a heater which is activated to help get better readingsfrom the A/F O2 sensor. Essentially this P0051 code means that the resistanceof the heater circuit is lower than normal. In most cases, that resistance levelmust fall below 0. 8 A to trigger the DTC code. Note, this code is very similar in nature to P0031, P0032,and P0052

p0051 diagnostic trouble code symptoms

Most likely you'll not notice any symptoms other than the MIL (malfunctionindicator lamp, a. k. a. the check engine light) will illuminate.

DTC p0051 - possible causes

A P0051 DTC trouble code may be caused by one or more of the following:A short in the heater circuit in the sensorA failed O2 sensor heaterWiring/connectors broken/frayed leading to sensor and/or relayFailed PCM/ECM

How to fix OBD-II diagnostic trouble code p0051

To fix a P0051 DTC code, you'll need to do a proper diagnosis. To do that,you'll want to inspect the wiring and connectors leading to the sensor. Alsoif equipped with a heater relay and fuse, you'll want to check those as well. Use a digital volt ohm meter to:check for 12 volts at the heater circuit feed (hint: unplug the sensor andcheck at the wiring connector to do this measurement)check the ground circuit for continuitymeasure the resistance of the heater circuit (done on the sensor itself)measure the resistance and voltage of the wiringRefer to a service manual for the correct specifications (volts, ohms) foryour vehicle. On some Toyota vehicles this code is triggered when the resistanceof the heater circuit is below 0. 8 A. With that said, a common fix for this DTC is to replace the air/fuel (O2 oxygen)sensor #1 on bank 2 (the side of the engine that doesn't contain cylinder #1). Please keep in mind that OEM (original equipment) replacement sensors are recommended(from the dealer). Aftermarket sensors can be less reliable and of poorer quality(not always, but more often). There's also a chance that replacement parts forthe P0051 code may also fall under a federal emissions warranty (check withyour dealer to see if it's covered).

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