Mercedes Benz GL (incl. GLS) Fault Codes

About the GL (incl. GLS)

The GL-Class first made its debut as a full-sized luxury SUV in 2006. There have been two further generations to hit the market since then, with the latest being released in 2020.

The three generations have been given the model designation of X164, X166, and X167 respectively. The model was renamed as the GLS when it received a facelift in 2016.

It sits above the Mercedes GLE, formerly known as the M-Class, in terms of sizing. This is a part of the GL-Class’ status as the flagship SUV model offered by Mercedes. Competition from outside of the company comes from rivals like the Audi Q7, BMW X5, and even the Land Rover Range Rover Sport.

The GL models are outfitted with a range of fairly high-performance modern engines. This does have its pros when it comes to performance, but also cons.

One of these cons happens to be fault code P0172 being the most commonly searched code for the model.

This code indicates that there is too much fuel in the air-fuel mixture. Unfortunately, the cause of the problem can be very hard to pinpoint, especially with such complex engines. However, owners have reported that poor maintenance can be one of the leading causes.

This can include issues like a faulty or dirty MAF sensor, as well as a faulty air filter. In some cases, defective fuel injectors can be the cause.

As if to illustrate how complex these engines can be, the second most common code is P0171, which represents that the engine is running too lean. Again, the code does not really help find the cause, but the MAF sensor is a good place to start again.

Both of these codes are limited to the first bank of the engine, which means GL models with V8s will only be affected on the one side, which can indicate it is not an upstream issue like the MAF sensor.