This relates back to a thread from a couple of weeks ago that has probably expired by now. Original problem was loss of power on a Merc C200 CDi - this was intermittent and (obviously) didn't display itself when the car went for its scheduled service. I finally got around to reading the codes when the engine management light came on - results are P0299 (Turbo underboost) and P2A00 (O2 sensor circuit range). I *think* that what is happening is that the car doesn't like the O2 sensor and accordingly is running the engine in emergency mode - this would account for the loss of power and rpm restriction. I *assume* that the turbo message is caused by the engine running in emergency mode - though this may be wrong. So, if the real cause is flagged up by the P2A00 message, ie an O2 sensor fault, how to find / fix it?
Mercedes loss of power
Jul 29, 2008
6 Replies
Could this be a broken lambda sensor or spark plug/glow plug problems. Could also be an air leak ... so I read which causes this fault to come up. Someone with way more experience than me will be along to shoot my theory down :)
Air leak sounds possible to me -- assuming there's a MAF sensor in there somewhere. Air leaks out beyond the turbo, causing the turbo pressure to be low. Less air getting in to the cylinder than expected would result in the mixture being too rich and the O2 sensor reading an unexpected value for the amount of air assumed to be in the cylinder.
Or it could be something else entirely.
Have you changed the MAF? They cause most of the problems in MB CDis, as they will incorrectly report the airflow.
You'd probably hear an air leak beyond the turbo - suggest trying
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for more help
Now fixed - it was indeed a leaking hose. Thanks for all the suggestions
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