jk952

The engine check light came on, checked the codes at a service shop last week and it showed something like " throttle position sensors incomprehensible", he reset it and it was fine for several days. Just came on again sometime while driving on a highway, (2013 GLK 350) runs fine before and with the light on.
Any thoughts on cause, your input would be appreciated?
Jack

bop11

Sounds like an intermittent sensor. Did you have some water ingress recently? Since this is a "fly by wire" vehicle, I would look at having the sensor replaced.

jk952

Thanks for the response. In the meantime I removed and reconnected the two connectors at the top front of the air system, presumably air temp, and flow. After a couple of short trips the light went out. I live in the snow belt so moisture can be a problem. When I get my code reader will check again and hopefully know what device was the problem.
Cheers...

ZZGlk

The throttle position sensor is just a variable resistor that changes value based on throttle position. When a bad spot develops on the resistor, the input to the ECM will go full scale or to zero, which will read as "incomprehensile" or out of range. On my diagram, it shows as located behind the accelerator pedal. It's probable that this will be an intermittent problem unless the resistor goes completely open. Could also be bad wiring connection to the sensor. If the resistor only has a small bad spot, the car will run normally, but you will get the error any time the reading goes from normal to out of range. Once the sensor gets a bad spot it will grow, so best just replace it. You should be able to troubleshoot it with an ohmmeter to confirm its the sensor and not the wiring.