Removing and installing/replacing oxygen monitoring sensor for cylinders 4-6 (S55 engine)

Special tools required: 

• 11 7 020

Installation note: 

The threads of new monitoring oxygen sensors are already coated with NEVER SEEZ compound.

If a lambda monitoring sensor is to be reused, apply a thin and even coating of Never Seez Compound to the thread only.

The part of the lambda monitoring sensor which projects into the exhaust system branch (sensor ceramics) must not be cleaned and not  coated with lubricant.

Necessary preliminary work: 

• Remove REAR ENGINE GUARD .
• Remove STIFFENING PLATE .

Removal: 

Unlock and disconnect blue plug connection of monitoring oxygen sensor, cylinder 4-6 (1).

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Release cable strap (1).

Release clamp (2).

Guide out the thermal protection (3) in direction of arrow  and set it aside.

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Slacken nut (1).

Thread out the bolt (2) and remove it.

Loosen screws (3).

Feed out holder (4) and remove.

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Release oxygen monitoring sensor (1) with special tool 11 7 020.

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Installation: 

Pull in monitoring oxygen sensor (1) and install.

Tighten down oxygen monitor sensor (1) with special tool 11 7 020.

Tightening torque 11 78 1AZ .

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Insert and install the thermal protection (3) in the direction of the arrow  .

Fasten cable strap (1).

Parts:  Cable strap

Secure clamp (2).

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Feed in holder (4) and install.

Tighten down screws (3).

Tightening torque 28 00 1AZ .

Thread in bolt (2) and install.

Tighten nut (1).

Tightening torque 18 20 1AZ .

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Connect and lock blue plug connection of monitoring oxygen sensor, cylinder 4-6 (1).

Plug connection (1) must audibly snap into place.

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Required follow-up work: 

• Install STIFFENING PLATE .
• Install REAR ENGINE GUARD .