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P0620 - Error Code - Mercedes E220 W212 Saloon

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10K views 6 replies 2 participants last post by  SanFrenchysco  
#1 ·
Hi All,

I am having a major issue with my car at present. It is firing the P0620 code intermittently now for the past few days. Over the last year I have replaced the alternator and battery as these were the initial points of failure. The car has had 2 alternators before the mechanic realized that it might be something else causing the issue.

I have my own code reader and get the P0620 code only - no other codes. When the fault appears the battery indication light comes on the dashboard and the stereo switches off (I'm assuming to conserve power). If I use my code reader to clear the code the stereo will come back on and everything is fine.

The problem I have is that this code may not appear again for another 2 months but when it does I'm generally on a long run to the airport or a meeting etc and unless I pull in every 20 seconds to reset the code the car just dies completely.

I really need to figure out what else could be causing this error.
I've been told that the PCM / ECM could be the cause but wondered should there be something else I could look at before going down this (expensive) route.

I've talked with 2 Mercedes specialists and they say that unless the code is being fired constantly to fault find then there isn't much they can do.

All help would be appeciated.

Thanks
 
#2 ·
What's the P0620 (Gen control circuit fault) code pointing you to on your W212??

I take it you have a smart alternator on your MY... One that's 100% controlled by the ECM to charge or discharge the main AGM while cruising on the Fwy to "save fuel" and pump in 90Amps@ 14.9VDC (1,300Watts!!) during decelerations.

While using OBD2 scanner, have you scanned through the 30+ extended PID'S to see what else is going down on your CAN bus? (basic scanners are mostly limited to basic engine & emissions).

With the details you've provided, I'd guess one of your 2 batteries could have reached its end of life or one of the 1/2 dozen micro-relay contact is going intermittent on you - Take a long hard look at available TSB's to help funnel the troubleshooting for faster closure.

Also there is a magic dashboard hidden menu that can display battery info while driving instead of using OBD2 "live data" scanner.

Changing alternator twice seems like a questionable way to through money at problems with limited results.

Could be a simple fuse or a bad link in front/rear SAM - An extended scan will give you a whole lot more visibility.
Good luck.

Sent from my Galaxy Tab 2 using Tapatalk
 
#3 ·
Hi

At the minute, there are no codes. My scanner is quite basic but I'm not getting much help from the two techs I've spoken to. It seems they are not interested in diagnosing such a fault. For the two alternators, these were done by the original mechanic and one warranted the other so no cost to me.

I have replaced the main battery not long ago so it's unlikely to be this. I have thought about the second battery but have not looked for it yet. I believe it's under my dashboard on the model I have.

My next step is to get detailed codes read like you said and take it from there.

Thanks for your input, it's greatly appreciated.
 
#5 ·
Just looking into this, it seems I have a permanent DTC of PP0562. Does anyone know the procedure for clearing this fault code?

I'd like to start fresh with diagnosing this intermittent fault.

I took the car for a drive and all seems well. No other codes fired apart from the permanent PP0562.

Also, I highly recommend the Carly app for detailed diagnostics. It was amazing the amount of extra information it provided.
Right down to one of my heated seats malfunctioning and records of when bulbs were blown or replaced.
It even told me about the rear trunk bulb that was not working.

Thanks for any assistance.