P0031 Code: HO2S Heater Control Circuit Low (Bank 1 Sensor 1)

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p0031 code displaying on an OBD-2 diagnostic tool

What Does the P0031 Code Mean?

The P0031 code means that the HO2S heater control circuit is low. The HO2S sensor has a built-in heating element and can be damaged if it gets too cold. The ECM monitors this circuit and when it drops below a certain voltage, it will cause your check engine light to come on and set off an OBDII code.

If you get an P0031 error code, then your first step should be to check the connections at both ends of the sensor plug. Make sure there are no broken wires or corrosion preventing good contact between them (you should also do this with all other OBDII sensors). 

What are the Common Symptoms of the P0031 Code?

The most common symptoms of this code are the check engine light being on, rough idling and acceleration, misfires and loss of power.

What are the Possible Causes of the P0031 Code?

The HO2S heater control circuit is monitored for voltage, resistance and intermittent operation.

Voltage: The HO2S heater control circuit voltage should be between 0.5 and 4.0 volts with the engine running. If it’s not, this could indicate a problem with your oxygen sensor or wiring harness.

Resistance: The HO2S heater control circuit resistance should be between 1 ohm and 4 ohms when measured across terminals 1 (cathode) and 2 (anode). If it isn’t within this range, there may be an issue with your oxygen sensor or wiring harnesses/connectors.* Intermittent Conditions: An intermittent condition exists when there are no continuous operating conditions within specifications listed above for three times longer than 10 seconds while driving at 45 mph (72 km/h) under moderate acceleration conditions without vacuum leak testing in place; or if you have tested all components involved in this test procedure without finding any defects then proceed to next step

How to Diagnose the P0031 Code?

The first step to diagnosing the P0031 code is to check for any other codes. If you don’t have any other ones, then it’s probably just this one.

Next, you’ll want to inspect your oxygen sensor and wiring connections. It’s possible that they could be loose or damaged in some way; make sure everything looks good before moving on!

You may also want to check your exhaust system for leaks or blockages; these could cause problems with airflow through the engine which could lead directly back here again as well (plus they’re just generally bad news). Finally–and most importantly–make sure there’s no problem with fuel pressure or delivery from either side of things: injectors won’t work properly if they’re getting too much pressure against them; likewise if there isn’t enough coming out at high speeds like when driving uphill at highway speeds where there isn’t enough air flowing through those pipes.

How to Fix the P0031 Code?

If you have a scanner, you can read the code and then clear it. If not, you can use a voltmeter to check the voltage of your sensor. If there is no output from either end of your sensor and it’s within range, then it’s likely bad and needs to be replaced. You can also test for continuity by checking between each terminal on the harness side of things; if there’s no connectivity between any two points then it could mean that something has failed inside or broken off inside that section of wiring (in which case replacing everything would be best).

If possible I would recommend replacing both sensors together since they’re unlikely to fail independently at different times unless something else happened like overheating due too much load being put on them (which should still show up via codes).