Mercedes ML Diesel Low Exhaust Pressure Warning

A 'particulate filter exhaust pressure too low' error on your Mercedes ML certainly rings a bell. Given the symptoms – warning light, power loss, smoke, and strong exhaust smell – a faulty exhaust back pressure sensor is a very plausible culprit. However, before condemning the sensor outright, it would be prudent to verify the integrity of the exhaust system itself. Are there any signs of physical damage, such as cracks or leaks, particularly around the particulate filter? A blockage in the exhaust system downstream of the sensor could also conceivably cause a low pressure reading upstream. What diagnostic steps have you taken beyond reading the error code?

Good point. I visually inspected the exhaust system and didn't see any obvious cracks or leaks. I didn't think about a blockage. How would I check for a blockage, and is there anything else that can cause a 'low pressure' reading besides a bad sensor or a blockage?

Detecting a blockage in the exhaust system, particularly within the particulate filter, can be challenging without specialized equipment. Differential pressure testing, comparing pressure readings before and after the filter, is a common method. However, given your described symptoms and the error code, replacing the exhaust back pressure sensor is a reasonable first step. If the issue persists after sensor replacement, further diagnostics by a qualified technician would be advisable, potentially including an examination of the particulate filter's condition. Ignoring this issue could lead to further damage to the exhaust system and potentially impact emission control components.

Thanks, that's helpful. I replaced the exhaust back pressure sensor, cleared the code, and it seems to have fixed the problem. Runs like a champ again. The sensor cost me 245€. Appreciate the advice.