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Having an engine misfire and engine light with code “Actuation of Ignition coil 4 has a short circuit to positive”.
I noticed oil in two spark plug cavities and I decided to change the valve cover seals. Post cleaning, I checked all the coils and spark plugs and all of them look okay. I cleared the error and checked again but error still there with engine vibrations eventually giving check engine lights. Switched coils and plugs with no luck. Checked 12v and ground wires and they are good. 12v wire controlled by ignition relay for all cylinders as expected. Control signal not showing any shorts within 12v or ground. To further check what going on, I took ignition coil 4 out without removing wires and installed a spark plug with its body grounded with car. Upon starting the engine I noticed a weak spark in the beginning and then no more. Repeated the same procedure swapping with new ignition coil and same behaviour. To me it seems to be an ecu related issue, perhaps driver is gone bad for this cylinder. Since I am not sure, Any advice to debug would be highly appreciated,
Having an engine misfire and engine light with code “Actuation of Ignition coil 4 has a short circuit to positive”.
I noticed oil in two spark plug cavities and I decided to change the valve cover seals. Post cleaning, I checked all the coils and spark plugs and all of them look okay. I cleared the error and checked again but error still there with engine vibrations eventually giving check engine lights. Switched coils and plugs with no luck. Checked 12v and ground wires and they are good. 12v wire controlled by ignition relay for all cylinders as expected. Control signal not showing any shorts within 12v or ground. To further check what going on, I took ignition coil 4 out without removing wires and installed a spark plug with its body grounded with car. Upon starting the engine I noticed a weak spark in the beginning and then no more. Repeated the same procedure swapping with new ignition coil and same behaviour. To me it seems to be an ecu related issue, perhaps driver is gone bad for this cylinder. Since I am not sure, Any advice to debug would be highly appreciated,
I am afraid you've come to the right conclusion for your bad ECU.
You've swapped everything around and misfire has not moved...
-- Check for "oil in harness" at ECU connectors.
-- Compare wiring resistance with an ohmmeter.
The error code is about short to positive which really means: GND side is missing!
As far as I know... the ignition circuit output MOSFET transistors drive the GND side of each individual coil while all of them are supplied by the shared +12V.
Your only luck would be a bad connection along the way to your Cyl.4 else get your ECU swapped or refurbished.
Happy holiday's
Last edited by CaliBenzDriver; Dec 31, 2024 at 01:10 PM.
Thanks for your help. There is no oil in the harness. Regarding wiring for all four cylinders, ground is common, 12v is also common but controlled by ignition relay. Control signal is coming from ECU that should ideally supply the mosfet/BJT to drive current into primary. Checking the ignition coil, I was surprised to see that it’s control signal pin and 12v pin show a resistance of 1.2 ohms which would indicate a short but this is the case for all ignition coils including the brand new coil I measured. I plotted voltage/current characteristic between control pin and 12v pin using a power supply and the curve is same in both directions showing same and very low resistance. My hunch is that even if Merc has used 3pin ignition coil’ the actual driver for primary coil is perhaps inside ecu only. I could not find the circuit diagram of this coil (Beru A000 150 25 80) to confirm.
Thanks for your help. There is no oil in the harness, Will try to check the wiring resistance for control signal but I don't have a circuit diagram for ecu and connector. Is there a way to get it ?
Also, if I swap with a secondhand ecu, would it be plug n play or I need to get it codified ?
You can quickly get your diagram in the next 5mn by signing up for alldata dot com.
Yes, ECU will need to be coded with your car data to work with your own specifics.
While you're around there unplug related injector for good measure. So it won't wash down cylinder walls and melt the cat.
I side with refurbed ECU because a used one has every chance to be nearly as good as your failed unit... fortunately/unfortunately are not solderless!
> FORWARD....:
What killed that rugged MOSFET is a good question.
They don't just quit or get tired!
- I side with a high-voltage spike in the primary coil circuit.
- or a low impedance in the primary windings causing a short with higher currents.
--> Conclusion: buy a fresh set of coils and keep your plugs gapped down to limit voltage spikes !
Last edited by CaliBenzDriver; Dec 31, 2024 at 01:31 PM.
W212 e200, is your engine M271.8xx EVO 1.8L turbocharged ?
If so..............
Do not get fooled by 3 wires COP, that COP is oldie dumb COP which the actual high power driver is inside the ECU .
It will fail eventually, the driver inside the ECU.
Read here to post number 6 https://mbworld.org/forums/e-class-w...ml#post8479202
or, read from the start to better understand how I was fooled thinking that this 3 wire COP is a smart COP with built-in driver like my M276.8 4 wire COP.
Good luck....
Last edited by S-Prihadi; Jan 1, 2025 at 05:38 AM.
W212 e200, is your engine M271.8xx EVO 1.8L turbocharged ?
If so..............
Do not get fooled by 3 wires COP, that COP is oldie dumb COP which the actual high power driver is inside the ECU .
It will fail eventually, the driver inside the ECU.
Read here to post number 6 https://mbworld.org/forums/e-class-w...ml#post8479202
or, read from the start to better understand how I was fooled thinking that this 3 wire COP is a smart COP with built-in driver like my M276.8 4 wire COP.
Good luck....
Many Thanks for your reply, highly appreciate your help and specially the comments on "oldie dumb COP" ha ha ha !! This re-confirms my suspicion, and V/I characteristics showing very low and constant impedance. I was indeed measuring the primary coil all the time and wondering where is the MOSFET !!
Since yesterday, I managed to do further diagnostics and my wire harness till ECM is perfect.
With nothing else to doubt, I opened the ECM module and found that a capacitor has leaked, and this leakage is perhaps causing ignition controller IC to malfunction. This ignition controller is both driving IGBTs to power Ignition coils and take a feedback from output of IGBT to confirm that the signal is pulled to gnd and later pulled back to 12V to have proper ignition cycles in each cylinder. Apparently, 3 cylinders are working fine and only 1 is failing. I am planning to replace the capacitor, de-solder, clean and re-solder the IC again and try my luck on the weekend !
Wondering if anyone knows about this controller IC and if it would need a code to be flashed to work properly ? Thanks in advance for any comments or help !
Ignition control IC shorted by electrolyte leak from capacitor
that chip itself does not require programming. It's a logic driver. cleanup time!
The area were capacitor has leaked may need a good cleaning to undo shorted paths way.
If you spot a charcoaled area: multilayers circuits are hardly-repearable.
Seems you have a fair chance at making this work right.
🤞
Many Thanks for your reply, It's great if no programming needed for this chip, I will go in two steps, First is to try cleaclean and re-use the same chip, Second is to replace with a new chip ... lets see
unfortunately, I have to wait a few days till the SMD caps I ordered arrive back o me... This chip was not available locally, I will need some research to find a source. Will post my update in a few days
You're doing good work man. I would have definitely replaced the whole module and called it a day. But we need information like this out there for when there are no more working modules available... :S
Does anyone have a Mercedes document that explains how misfires are actually detected?
You're doing good work man. I would have definitely replaced the whole module and called it a day. But we need information like this out there for when there are no more working modules available... :S
Does anyone have a Mercedes document that explains how misfires are actually detected?
Misfires are detected by flywheel RPM variations.
The ECU is a timing computer that expect clock ticks on-time from the high resolution CKP pulses.
It runs firmware code to match all the various engine conditions. When non-contributing cylinders are spotted, the ECU can decide to stop injecting fuel to prevent scoring walls.
Our best effort is to help make timings more reliable for maximum performance.
Weak chain tensioners are serious offenders that detune the engines with... jittery cam timings.
Cancel variations and witness how much ECU thrive with more stability:
ALT LIN!
vulnerable ignition chips
Last edited by CaliBenzDriver; Jan 2, 2025 at 12:00 AM.
Japanese cars oldie ones keep ECM inside car cabin, in my hot country 20+ years is easy life for them.
Come MB with ECM inside engine bay and on top of engine, many ME9.7 for M272 in my country and the SIM271 for E200/C200 M271.x engine suffered ECM failure under 12 years.
Engine bay temperature at 85C or higher is common for Jakarta based car with creeping traffic jam.
SIM271 with its COP power driver circuit inside the ECM generate more heat and I guess ripple current too = adding fire to misery
.
Both M272 engines I have opened the car hood, has got repaired or replacement ECM .
One belongs to Tesna a member here, 2010 model ( I recall ) year E300 with M272 and a 2009 M272 on S-Class S350 of a friend..... these are ME9.7 ECM.
If one is good with multilayer board soldering and can get access to genuine high temperature automotive capacitors as used on our ECM,
replacing them capacitors on a schedule basis say per 4,000 engine hours .....could do good if one is to keep the car say 20 years.
My engine now at approx 43,000KM, with average speed I know been like 21 KM/H as average, in theory I am at 2,047 running hours.
Albeit my ECM is newer MED 17.7 without the hot COP power circuit inside but at the COP itself, if I can ensure a good workmanship,
by 80,000KM is the expected 4,000 hours running and replacing my capacitors would be good.
MED17.7 ECM has temperature sensor built in and can be seen using Xentry. Its alway 80ish Celsius
Indeed a very valid point there for hot temperatures, engine bays are easily 85C... I have ordered following replacement and hope it should last longer !NICHICON-SMD Aluminium Electrolytic Capacitor rated to work for 7000 hours @ 105°c Capacitor
Sweet, I hope the capacitor juice corossion has not entered middle layer of the PCB, assuming the PCB is a multilayered one.
Update us on your progress yah.
Today's update : Post Through cleaning, I felt no need to de-solder and solder the ignition chip again. Sharing the picture for reference
Post Thorough cleaning with generous use of IPA My replacement CAPs still in Transit, hence I tested the board with a higher voltage temporary capacitor .... Good news, it worked !! Simplified Schema of Ignition Circuit
Before I close the thread, let me thank fellow colleagues CaliBenzDriver & S-Prihadi who have shared valuable hints and suggestions that helped me progress and fix my issue ... Cheers !
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