werner_held1
GLS Oxygen Sensor Problems
Summary of the thread
A 2016 Mercedes GLS diesel is experiencing an oxygen sensor heater failure, leading to a check engine light and increased fuel consumption. The suspected causes include a bad cable or plug, but other possibilities like a defective relay or compromised wiring harness are also considered. Testing the sensor's heater element resistance and checking the air-fuel ratio are suggested diagnostic steps. Due to the sensor's challenging location, professional repair is recommended to ensure proper diagnosis and resolution.
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4 comment(s)
werner_held1 (community.author)
Thanks for the quick reply. I haven't checked the heater element resistance yet. Where is the oxygen sensor located in the GLS? Is it easy to reach the cable and plug?
rainersturm10
The sensor's location is challenging. Access isn't great, requiring dexterity and specialized tools. I'd recommend taking it to a qualified workshop. The cost might seem high, but a misdiagnosis or improper repair could be worse. My repair cost around 95€. The peace of mind from professional work was worth it. They fixed the problem.
werner_held1 (community.author)
Thanks for the advice. I'll take it to a workshop. It sounds like too much trouble to do myself. Thanks again.
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MERCEDES
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GLS
rainersturm10
This sounds familiar. My GLS had the same symptoms: oxygen sensor heater malfunction, check engine light, and increased fuel consumption. Have you tested the sensor, specifically the heater element's resistance? Check the air-fuel ratio; deviations may provide insight into the sensor's operation. The problem might not be the sensor itself, but other components. Consider a defective relay or a compromised section of the wiring harness.