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Ross, Diagnostic and repair technician
Category: Car
Satisfied Customers: 1180
Experience:  Licensed diagnostic and repair technician
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Mercedes vito 2009 was perfrect until last night when I started

Resolved Question:

mercedes vito 2009 was perfrect until last night when I started it the headlights are permantley on,no indicators no wipers no rear central locking dash lit up like a xmas tree when the ignition is off nearside rear tail light stays on.
Submitted: 1 year ago.
Category: Car
Expert:  Ross replied 1 year ago.
Hi my name is***** am a diagnostic technician and look forward to working with you.
Expert:  Ross replied 1 year ago.
Does the engine start, and if so does it return to normal or do the faults continue ? thanks, Ross.
Customer: replied 1 year ago.

Hi Ross The engine starts and runs perfect but the faults continue

Expert:  Ross replied 1 year ago.
Ok, the first step will be to carry out a re-set of all control systems, this may be a glitch so before going further we need to do a basic re-set by disconnecting the battery negative terminal for 30 seconds then re-connecting. Often this is a frozen controller rather than a fault. (ensure keys are NOT in the ignition while battery is reconnected)Please let me know if this cures the fault, if not I can move onto other options, thanks, Ross.
Customer: replied 1 year ago.


I tried disconnecting battery but faults are still there

Expert:  Ross replied 1 year ago.
Ok, this sounds like it could be a short between two circuits causing it to back feed. Ideally before going further the van needs to be put onto a diagnostic system to check the control units for faults, Although this could well be failure of the cabin control unit, there are other possibilities such a broken wire somewhere causing two circuits to back feed. This is often caused by melted wires so the faulty circuit needs to be tracked down using test equipment and the wiring examined. I strongly advise a fault code scan is carried out first as this will pinpoint a fault with the control unit before any time is spend tracing wiring.
Expert:  Ross replied 1 year ago.
I hope I’ve provided the information you were seeking. If you need more help, please use the reply tab to continue our conversation. If you do not require further assistance, kindly rate my service. Thank you, Ross.
Customer: replied 1 year ago.

Fault codes u0423 and p0087

Expert:  Ross replied 1 year ago.
Ok great, the P0087 is Low fuel rail pressure which would not be related to this problemThe code U0423 is invalid CAN Signal to the Instrument cluster, this makes perfect sense with the faults you have. There will be either a faulty control unit or wiring fault on the multiplex circuit which is a data network between controllers. I suspect this is a faulty instrument cluster or bad wiring between the cluster and other control unit (engine ECU)
Customer: replied 1 year ago.

ok thanks what can i do now?

Expert:  Ross replied 1 year ago.
My best advice would be to have your instrument cluster tested and repaired. Companies such as BBA Reman can test and repair the cluster within approx 1 week. The plus side of this is that you retain the current mileage and the repair carries a warranty, The instrument cluster on these models cannot simply be swapped for a second hand unit as they are coded to the ECU to prevent clocking.
Customer: replied 1 year ago.

I also have a sprinter so I have swapped clusters and the problems are still there I also put the cluster from the vito into the sprinter and it seems to be ok in the sprinter.

Expert:  Ross replied 1 year ago.
The sprinter cluster would not communicate due to different coding known as environment ID, they would need to be coded using main dealer diagnostics. If this still did not cure the fault then there is a wiring fault on the CAN circuit between cluster and ECU.
Customer: replied 1 year ago.

Hi Ross sorry for the delay.I have been told that it could be a faulty sam unit what do you think? I have removed the sam unit and it is dry so no water has got in it.But the night that the van went faulty it was really foggy and damp.Also one thing that I have noticed is that when the battery is just about flat the indicators and the central locking work but when I put it on charge they go faulty again.

Expert:  Ross replied 1 year ago.
This could be the SAM unit, Usually it is water ingress that causes the faults with these but it could be a random failure. What ever it is, it is the CAN network that has gone down. SAM Unit failure is common due to the water ingress, not so common for a random failure with no apparent reason but the fact you say things work with low battery voltage would actually point back to the SAM, this is not a software problem or frozen control unit I'm fairly sure about that, I think it has actually failed internally e.g a resistor or transistor is at fault. If possible I would be inclined to have the SAM unit tested/repaired or replaced with a known good one.
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