M.O.T Failure Problem

[the prince]

I've taken my 2001 W208 CLK 230k for MOT today and it has failed on emissions too high and a dash bulb (Main beam 'tell-tale' not working. Engine management light has been on since i bought the car, but as i bought it with a full mot, done on the day i bought i thought everything should have been ok. Hmmm.

So i'm not too concerned with the dashboard light being out, only a bulb (hopefully), but the emissions issue is proving to be a problem. At the advice of the tester I took my car to an auto electric centre and they attempted to hook it up to STAR, but this is where the plot thickens. They initially tried to hook up using the 31 pin socket in the aircon unit housing, but no signal. So they then tried on the 16 pin socket under the hand brake handle, but again no signal. The laptop kept saying turn on ignition, but it was already switched on. I was told that the car is not allowing STAR to connect and it was suggested that there could be a fault with the ignition switch or a blown fuse or wiring / circuit failure. All things considered, i'm in the dark about what if's and maybe's could be causing this. They told me that they'd used their STAR system three times in the last week and an 05 SLK was sat repaired in their parking lot.

I seem to remember when I took the car to a Mercedes Dealer that they said something similar, and muttered that maybe their system doesn't link up to vehicles this old!

Either way am I going to be unable to find out what is causing the high emissions and fix the fault unless i can access the STAR system?

Help desperately needed. Two weeks left for MOT. Really cheesed off. Car has only done 500 miles since last test.

 

[grober]

Basically the obd2 or diagnostic port needs to provide a 12v power outlet socket to "handshake" with any diagnostic scanner that's plugged in. That's why its telling you to switch on the ignition. The 12volt is obviously absent. I suggest you try probing the 12v outlet on the each diagnostic plug for a low or total lack of voltage on ignition switch on. You then need to go backwards in the car electrical circuits to determine why. There may be fuses or a faulty relay involved. With a bit of luck if you sort the 12v diagnostic outlet supply then your scanner will be able to give you a readout of fault codes.

OBDII Pin Connections MERC(38Pin)
4,5 Ground 1
7 K Line 4
15 L Line 15
16 +12v Positive 3

so test pin 16 on the obd2 connector or pin 3 on the 38pin connector for 12volts wrt earth

http://pinoutsguide.com/CarElectronics/mercedes_38pin_pinout.shtml

http://www.mbcluster.com/Media_Diagnostics/ODBII Master Pinout.jpg

and background
http://www.mbcluster.com/Media_Diagnostics.htm

 

[BlackC55]

You need to see what the issue is with a Star. Everything else will be a guess.

The diag socket needs to be tested firstly. A decent MB specialist will be able to do this using wiring diagrams and a meter.

Don't worry too much. Its all fixable.

I expect the engine light is a faulty llambda sensor or similar.

 

[grober]

The box that's marked aircon is in fact the main fuse box. Check the fuses in particular the 7.5 fuse

 

[the prince]

Both posts very much appreciated. I will try testing the ports myself initially. The auto electric place i went to is supposed to be good with Mercedes and were recommended by someone from Mercedes Dealers as a cheaper STAR option. As said i went today and they told me they can test it and look for where the faults lie. No sure of costs as they offered a £180 + VAT fault find and fix or £45 per hour + VAT hourly rate. But then when they were unable to even connect to STAR the charges became slightly vague No cheap way around it really. Seeing as the CO2 levels for MOT should be below 0.30 and they are at 11.1, there is something not quite right!

The bloke told me that his laptop was picking up a voltage read from the battery on link up, but no further info was manageable.

I guess it's got to be left in someone else's hands for a change.

 

[the prince]

Cheers Grober. I'm used to general mechanics and electronics, but these Mercedes are something else. I've already managed to replace the roof module, remove an old tracker device, fix the dash clocks, heater resistor, and boot release etc etc, but i'm stuck when it comes to Diagnostics. As you will see from my Tag, most of my cars are ancient so it's undo/tighten up and you're on your way again. I must admit I've had this car for 12 months and done less than 500 miles in it, so I've not had the best of it yet. As for fuse boxes i've not even been in one yet. Cheers for pic and tips. Very much appreciated.

 

[the prince]

I eventually took it to an alternative Auto Electrician N. Grayson - Heeley, Sheffield. He new what he was doing fortunately and had it done within the day. It was the pre-cat Lambda Sensor and Mass Air Flow Meter. I got a bit anxious with the costs, but it worked out cheaper than Mercedes by some measure. Grayson's charged me 2 hours labour, which seemed fair, so all in at £380 (parts £265 + labour £115). Mercedes wanted £255 for Lambda and £315 for MAF, plus whatever their diagnostic and fitting would have come to. Obviously Grayson's didn't use Mercedes parts at that price, but they are Siemens which should be of good quality. Not got back in for re-test yet, but the emissions were tested at Grayson's below the test limits, so should go through this time.

So as advised a good auto electrician with STAR is crucial, and especially one you think you can trust. I won't ever use the other one again (name withheld).

 

[brucemillar]

OP. What was stopping STAR communicating with the car?

 

[the prince]

OP. What was stopping STAR communicating with the car?

Nothing. The 'so called - self proclaimed' Mercedes specialist auto electrician, were either incompetent or trying it on. They told me neither port was functioning, but the second auto electrician, said no fault with the ports at all. Worrying if i'd have left the car with the first place and said, get on with it.