Electrical ****-up, S204 2008 C220 - HELP!!

[Chrishazle]

As if this week had not been bad enough already with the SLK, this morning I went to start the c220 - which had a good drive on Tuesday and was fine - starter gave small hiccup but did nothing, luckily still enough to open the doors and release (but not raise) the boot. Thought bugger, flat battery, so put charger on it, for about 10 seconds it started charging at 14 amps then dropped to 10 amps and stayed there. OK, battery is probably original, 11 1/2 years old and died, so searched and found a suitable alternative at Halfords. 4 hours on the charger and car started fine, drove completely normally to Halfords. They tested my original battery in situ, their tester showed it just needed charging, but I decided to replace it anyway. They connected a small battery to the OBD port under the steering wheel then changed the battery, car started fine, job done, time to go home - except the gearstick would not move from P!! Halfords manager took over.

Also noted that PRND light in bottom of speedometer was not working, C-S button did nothing, autofold wing mirrors not working when car locked - but brake lights work when brake pedal pressed. 2 hours and a further battery change later, autofold now working having operated the mirrors from the door switch but otherwise no change. Using the emergency release switch under the gearshift gater released the gearstick so gears could be engaged, so Halfords manager said take it to garage, find and fix problem, we'll pay!! OK, headed home.

That's when I found (car in C mode) gear change was not working, either automatically or trying to use the tip feature by pushing the stick towards me, so had to drive home I guess in 2nd at 30-40mph, 3-4K RPM! Nowhere open, so will have to wait until Monday to get it to my local indie - fortunately just a mile away rather than about 8 miles of busy road to MB Ashford!

Is it likely to be the brake switch, the selector module or what? Is there anything else I can try, ATM it's our only car so we're stuck until it's fixed!!

 

[grober]

When you get multi-system failures after a battery change suspect blown fuses or fusible links
Help please Urgent?

 

[Chrishazle]

Halfords checked all the fuses they cold find (under bonnet box, rear OS) and said all were OK.

 

[ayvo]

isn't there one in the drivers side side panel too?

 

[Chrishazle]

Don't know, but I know a man who will, just can't get to him until Monday morning! Just as well herself is not too precious about getting to Mass tomorrow morning, but me running out of smokes (which I will do Monday) could pose a problem!

 

[grober]

Halfords checked all the fuses they cold find (under bonnet box, rear OS) and said all were OK.

Did they check the fusible links- see the link ?
https://fuse-box.info/mercedes-benz/mercedes-benz-c-class-w204-2008-2014-fuses-and-relay

 

[wongl]

They connected a small battery to the OBD port under the steering wheel then changed the battery, car started fine, job done, time to go home - except the gearstick would not move from P!! Halfords manager took over.

I have not seen this method of maintaining power to the car during the battery change (which I think is potentially risky should the positive terminal of the main battery cable accidentally touches the body while the main battery is being removed!). I would have simply connected a spare battery to the jump-starting points under the bonnet to ensure the power to the car is maintained via the same circuit as the main battery.

Hopefully, nothing is blown, and it is a simple case of resetting some stored error codes to restore the car back to normal operations.

Good luck, and hope to hear what the problem/solution is after you have the chance to visit your indie. You are local to Stevenson and not sure if they are open weekends these days?

 

[Mancstar]

Like Wongl mentioned never heard of this small battery plugged into the OCD dont think the OCD port is designed for this.
Anyhow hope you get the problem sorted and its dood that they will cover the cost.

Dont think I'd ever trust a Halfords kid to even clean my car!

 

[Chrishazle]

I did mention to the fitter that I'd previously (and on another car) used the under bonnet emergency +ve and top of the suspension to connect a second battery while changing the main one, he said it was not necessary as connecting to the OBD port kept the ECU's etc active and happy! We'll see tomorrow morning what Ben has to say when he connects his diagnostics to the car.

 

[Chrishazle]

This is what Ben found - and fixed. Took him 2 hours to trace the faults, as initially the OBD port was dead!

“Found no communication with entire car. Carried out can line check at OBD port, all OK. Carried out voltage and ground check at OBD port, pin 16 voltage feed missing. Carried out wiring check with tech data, found fuse blown, power returned, no communication to TCM only. Further checks found secondary power feed down, found and replaced, all functioning OK. Road tested OK, fault codes OK”. Threw him a bit of a curve ball, he plugged his code reader into the OBD port and got nothing, so had to go back to basics!

Halfords tomorrow get a bill (which I’ve already had to pay) for £174.

Moral : Do NOT connect a 12v battery to the OBD port!!

 

[Skd884]

This is what Ben found - and fixed. Took him 2 hours to trace the faults, as initially the OBD port was dead!

“Found no communication with entire car. Carried out can line check at OBD port, all OK. Carried out voltage and ground check at OBD port, pin 16 voltage feed missing. Carried out wiring check with tech data, found fuse blown, power returned, no communication to TCM only. Further checks found secondary power feed down, found and replaced, all functioning OK. Road tested OK, fault codes OK”. Threw him a bit of a curve ball, he plugged his code reader into the OBD port and got nothing, so had to go back to basics!

Halfords tomorrow get a bill (which I’ve already had to pay) for £174.

Moral : Do NOT connect a 12v battery to the OBD port!!

Your indie knows how to charge.

 

[grober]

Fuse 16@5amp in the underbonnet fuse box according to that link I posted.- so much for Halfords checking all the fuses! Glad you got it sorted.

 

[Chrishazle]

Your indie knows how to charge.

Somewhat cheaper than the other option - MB Ashford, who would be well over £100ph+VAT! Also he basically dropped what he planned to do this morning and spent 2 hours sorting my car, when he could have said "I've got other work on and can't look at it for .... days".

Do you know another specialist indie with full diagnostics as well as a lot of knowledge of MB cars who charges a lot less - I doubt it!

Thanks Grober, nice to get constructive help rather than keyboard warriors! I've forwarded your link to Ben for future reference - he does not do forums!

 

[grober]

There's also a link to the W203/W205 Fuses/Fusible-links on the same site.
https://fuse-box.info/mercedes-benz/mercedes-benz-c-class-w205-2015-2019-fuses-and-relay
https://fuse-box.info/mercedes-benz/mercedes-benz-c-class-w203-2000-2007-fuses-and-relay

 

[AMGeed]

Your indie knows how to charge.

For 2 hrs work, that is about right. £70 - 75 ph + VAT.
How much does your indy charge per hr?

 

[Chrishazle]

I emailed the link to the fusebox diagram to ben, interesting reply :

Good to hear, and thanks, we have access to main dealer wiring diagrams and fuse board layouts, the issue was the power feeds hadn't completely blown so was showing no voltage at DLC but some voltage else where, so we had to back check the wiring diagram for the second missing feed which had melted slightly but not blown, so caused a correct voltage until load dropped, weird really. Seems like the equipment they use potentially spikes the 12v circuits which have no direct feed back to battery.

It's better to just let the voltage die down after battery removal, and boot up on a new battery.