Ford repair professionals: Ford Focus Heated Oxygen (HO2S) Sensor?

Heated Oxygen (HO2S) Sensor
OPERATION
REMOVAL & INSTALLATION

Details are as follows :----

Operation

The catalyst efficiency monitor uses pre and post-catalyst heated oxygen sensors (HO2S) to infer the hydrocarbon (HC) efficiency based on the oxygen storage capacity of the catalyst. Under normal, closed-loop fuel conditions, high efficiency catalysts have significant oxygen storage. This makes the switching frequency of the post-catalyst HO2S (B) very slow and reduces the amplitude of those switches as compared to the switching frequency and amplitude of the pre-catalyst HO2S (A). As catalyst efficiency deteriorates due to thermal and chemical deterioration, its ability to store oxygen declines. The post-catalyst HO2S (B) signal begins to switch more rapidly with increasing amplitude, approaching the switching frequency and amplitude of the pre-catalyst HO2S (A).

Removal & Installation

With Secondary Air System

Disconnect the battery ground cable.

Disconnect the electrical connector and detach the wiring retainer.

Fig. Disconnect the electrical connector and detach the wiring retainer

Remove the evaporative emissions (EVAP) canister purge valve heat shield.

Remove the four bolts and position the exhaust manifold heat shield aside.

NOTE
If necessary, lubricate the heated oxygen sensor (HO2S) with penetrating and lock lubricant to assist in removal.

Using a 22 mm crows foot wrench, remove the HO2S.

Fig. Removing the heated oxygen sensor

Installation is the reverse of the removal procedure.

NOTE
Make sure that the electrical connector locking tab is engaged.

CAUTION
Make sure that the sensor wiring is secured with all retainers and routed away from hot surfaces and sharp edges.

NOTE
Make sure to apply anti-seize lubricant to the threads of the sensors before installation.

Without Secondary Air System

Disconnect the battery ground cable.

Raise and support the vehicle on a hoist.

Unsnap the electrical connector heat shield.

Disconnect the electrical connector and detach the wiring retainer.

NOTE
If necessary, lubricate the heated oxygen sensor (HO2S) with penetrating and lock lubricant to assist in removal.

Fig. Disconnect the electrical connector and detach the wiring retainer

Using a 22 mm crows foot wrench, remove the HO2S.

Fig. Removing the heated oxygen sensor

Installation is the reverse of the removal procedure.

NOTE
Make sure that the electrical connector locking tab is engaged.

CAUTION
Make sure that the sensor wiring is secured with all retainers and routed away from hot surfaces and sharp edges.

NOTE
Make sure to apply anti-seize lubricant to the threads of the sensors before installation.