P0056 on Ford Focus III. Causes, how to remove

Regardless of engine size on Ford Focus 3 cars, error P0056 can occur at mileage over 100-120,000 km. Let’s find out together what the error code means, whether you can drive, how to reset it, and what to change.

Causes of error P0056 on Ford Focus III

A quick search for decoding error code 0056 will show us that we are dealing with a faulty oxygen sensor 2 bank 1. This means that the lambda probe, installed after the catalyst, has given up its life. Not everything is so clear-cut. Error P0056 Heated Oxygen Sensor Control Circuit B1S2 means that we should pay attention to the lambda sensor heating circuit.

Briefly about what this circuit and the second oxygen sensor itself does. The Ford Focus 3 has heated zirconium-oxide oxygen sensors. The heating is necessary for the sensor to start working from the moment the engine is started. 

Since the zirconium capsule begins to give readings only after warming up to 300 °C, the sensor is built into a ceramic heating element, which heats it to the desired temperature immediately after starting the engine.

If the first oxygen sensor, which is installed before the catalyst, is responsible for correcting the proportions of the fuel-air mixture, the second sensor is only needed to monitor the condition of the catalyst. It is used to check the ƛ parameter, i.e. the content of excess oxygen in the exhaust gases after the catalytic converter.

Can I drive my Focus with the error P0056

Based on this, it can be assumed that the second sensor readings are only diagnostic and do not affect the function of the engine. The Check Engine alarm may illuminate and the OBD II scanner will generate error P0056, but it will not affect the engine performance.

To definitively verify that the lambda sensor itself is working and only its heater is out of order, you can do a quick check.

How to check the oxygen sensor Focus 3 quickly

The resistance rating of the oxygen sensor heater element is 10-15 Ω, depending on the sensor model. There are two wires of the same color or gray and white wires connected to the heater. The resistance should be measured on them. It is not necessary to remove the sensor.

Take a multimeter, switch it to resistance measurement mode and measure it on a cold engine. If the resistance is close to the rating (about 10 Ω), the heater is working. Now check the power at the heater element. 

After the ignition is turned on, 12 V should be supplied to one of the heater contacts. If there is no power, look for an open or short circuit in the oxygen sensor supply circuit, a broken wire, or a broken insulation.

To check the functionality of the zirconium element itself, it is enough to measure the voltage on the warmed up sensor. It can be removed from the car, heated in any way (carefully with a gas burner, for example). When heated, the sensor voltage should be about 0.8-0.9 V. When it cools down, the sensor generates voltage in the range of 0.1-0.2 V.

Conclusions. Error P0056 can be caused by:

1. Broken power supply circuit of the second oxygen sensor.
2. Breakage of one of the heater element wires.
3. Heater failure.
4. Malfunction of an electronic engine control unit.

How to reset error P0056 on Ford Focus III

If we are convinced that the sensor or its heating element is inoperative, the lambda sensor must be replaced. However, there are several ways to fool the control unit and temporarily reset the error before buying a new sensor. 

Knowing that the resistance of the heating element is 10 ohm, you can install a load resistance of the same rating in parallel to the heater. ECU will not notice the breakage, and the sensor itself will start working in normal mode after the engine warms up naturally. Alternatively, you can install a 12-volt lamp of about 20 watts instead of the resistor, the effect will be the same.

What is the best oxygen sensor for Ford Focus 3?

Depending on the engine model, either two catalysts or one may be installed at the exhaust manifold outlet. However, this does not affect the lambda probe model. The native oxygen sensor for Ford Focus has the FORD part number 1327549. Its price is about 100 USD. Not too democratic price, so we will look for analogues. And there are enough of them:

When selecting the sensor, you need to consider the wire length, since the front sensor has a slightly shorter wire length. As a rule, universal oxygen sensors come with a wire length of about 600 mm, which is enough to install both before and after the catalytic converter.

It is easy to change the sensor with a 22 mm socket. It is better to pick up a cut socket, so it will be easier to cope with the wires going to the sensor. One more thing – the original sensor has heat protection on the wires, so it is better to move them to the new sensor before installing. 

Do not use silicone sealant because the zirconium sensor is just as afraid of its vapors as it is of ethylated gasoline.

After installing a new oxygen sensor, the error P0056 will disappear after 20-30 km, or it can be reset with the scanner immediately after replacement.