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International Automotive Technicians Network
Ignition Coil Current Waveform Oscillations
Posted to Technical Theory Forum on 5/26/2014 14 Replies

Hello fello techs, the vehicle in question here is a 2007 Mercedes B170. The customers complaint was check engine light and low poor up hills. I took the vechile for a test drive and could not feel any misfires, rough running or lack of power. A diagnostic scan relived a P0303 cylinder 3 misfire in pending codes through OBD2 protocol. The ignition coil is a 3 wire what looks like a waste spark system 1 power supply, 1 ground and 1 sqaure wave trigger. I dont have a coil wand thing for my pico, so i deciede to scope the current waveforms. First i scoped the coil for cylinders 1 and 2 [coil current cylinder 1 and 2] and compared it to the coil for cylinders 3 and 4 [ignition coil cylinder 3 and 4 old]. Amperage looks good on both waveforms the only difference i see is the oscillatons at the turn off point could anybody explain to why there is oscillation there and what the mean. I had a spare coil for one of these motor of a 2005 A140 so i tryed it and this is what i got [ignition coil cylinder 3 and 4 new] the oscillation are now smaller ???

Michael Haimes
Home Tune
Auckland, Auckland, New Zealand

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