Join Date: Oct 2017
Location: Sweden, South part
Vehicle: 2002 SLK 200K , Silver metallic (Special edition)
Other Toys: Notable earlier cars: MGB, Triumph Spitfire, Porsche 914 & 944, Jeep, Bv202 & 206 :-)
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You don't have the patience and vigilance of the ECU logging function, so it's pure luck (after all, stick to driving safely!) if you catch intermittent moments of being outside limits. The ECU has (likely, I don't KNOW for sure) an allowance regarding time and level of error before throwing codes. It may even collect towards an error, needing a few out-of-allowances values before triggering.
But generally, it can be one (or both) of either actual errors, due to metering problems (example: too little fuel, due to problems with injectors, presuure variations, delivery problems etc etc) OR problems with the monitoring devices (perhaps the lambda sensors AKA oxygen sensors) fooling the monitoring system.
The car is obviously thinking it gets too little fuel sometimes. :-)