CEL light on- code P0170 - Mercedes-Benz Forum

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post #1 of 2 (permalink) Old 08-24-2004, 04:32 PM Thread Starter
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Date registered: Aug 2004
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CEL light on- code P0170

My check engine light comes on about an hour after I clear the computer. I have a cheap scanner which gives a code of P0170. Fuel trim Malfunction. I have new plugs and air filter, new oxygen sensors, and the car runs fine. No fuel leaking from pressure reg port. New fuel filter also. Car has platinum plugs. Any problems with Bosch Platinum Plugs??? All other I/M status go ready, but not before P0170. I have no way of reading adaptaion codes, doI??

Thanks, Fred
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post #2 of 2 (permalink) Old 11-22-2004, 10:38 PM
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RE: CEL light on- code P0170

This sounds like an air mass sensor.
Test the following circuits. 12 volt 5 volt and key on engine of signal voltage. If I remember correctly it is the pin 3 is gound, pin 2 is 12 volts, and pin 4 is 5 volt. key on engine off back probe pins until you find one between .9 volts dc to 1.? volts dc if it is greater than 1.3 this is definately your culprate. Be sure to check the mounting seal (just replace it) and the mounting bracket for cracks.

If air mass check out ok check for unmetered air, poor fuel prssure or volume (3.5 bar and 1 pint in 35 seconds roughly 3.9 bar if it is a compressor motor). If these items are ok pull the injectors, build pressure and manually energize them with a white towel behind the to check spray pattern.

p.s. if it is the air mass sensor clean and or replace air filter and check air box for warpage. Sand can damage the new one very quickly.
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