Mercedes Benz

P2257 Relay for air pump : Short circuit to ground (P2257) Possible cause: ­ M33 (electric air pump) Affected functions: ­ Engine diagnosis ­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­ Test 1: Check component M33 (electric air pump). 1. Check component M33 (electric air pump). Test 1.1: Check component M33 (electric air pump) by means of actuation. Test 1.2: Check power supply of component M33 (electric air pump). Test 1.3: Check component K40/4kO (Air pump or reserve relay). 1.1. Check component M33 (electric air pump) by means of actuation. Test prerequisite ­ ­ Engine at idle Actuate component M33 (electric air pump).(Move on to actuation with button F2) Warning!Communication with ECU required. 1.2. Check power supply of component M33 (electric air pump). Test prerequisite ­ Actuation is not OK. Test sequence ­ Switch off ignition. ­ (M33) Measure direct voltage with multimeter between 2 and 1 (M33) ­ Switch on ignition. ­ Actuate with key F2. Speci...