2008 Mercedes-Benz P0325: What It Means & Is It Safe to Drive?
P0325 on the 2008 Mercedes-Benz: Knock Sensor 1 Circuit Malfunction (Bank 1). Here's what it means, what usually causes it, what repairs typically cost, and whether it's safe to keep driving.
What this code means
The PCM isn't receiving a valid signal from knock sensor 1. Without knock feedback, the PCM retards ignition timing as a safety measure, reducing power and economy.
Common causes on the 2008 Mercedes-Benz
- Failed knock sensor
- Corroded or broken wiring/connector at the sensor
- Actual engine knock from carbon buildup or low-octane fuel
Symptoms
- Check Engine Light
- Reduced power and fuel economy (PCM retards timing)
- Possible audible knock or ping under load
Typical fixes
- Replace knock sensor
- Repair wiring and connector
- Use correct octane fuel and address carbon buildup
Repair cost range
For a 2008 Mercedes-Benz, repairs for P0325 typically fall between $150 and $500, depending on the root cause and labor rates in your area.
Known issues on Mercedes-Benz
Mercedes P0325 on M272 3.5L V6 is important in context of the balance shaft gear failure—a worn balance shaft causes mechanical vibration that the knock sensor may misinterpret, or conversely, sensor damage from severe vibration can set P0325. On M274 2.0T turbocharged engines, the knock sensor harness routes near the turbo exhaust housing; heat damage to the insulation is a common P0325 cause. On AMG-variant engines using higher compression ratios, a non-functional knock sensor is a serious protection issue; do not drive extended distances with active P0325.
Most commonly affected models