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No speedo, traction and abs light on

6K views 4 replies 3 participants last post by  mrboca 
#1 ·
Hello all,

My E320 w210 merc had the speedo stop working. The traction and abs lights came on and I took it to my mechanic.
He initially found some wiring damage due to the insulation falling off and a small amount of burning took place. They removed the harness and had it repaired by the auto-elec. The wires damaged were the start wire and reverse wire.
Refitted harness and no joy. No comms with ECU possible - even had 2 mercedes scan tools and no comms. ABS and Traction lights on and still no speedo.

The Ecu was sent away for testing and no fault was found. Refitted and misfire was detected. All speed sensors test ok and all wiring test ok also.
My Auto-Elec sent the Ecu and the Traction control module back to the Electronics specialist.
This is where it gets interesting.
The message to the repairer mentioned the misfire only - not the lack of speedo. Ecu was 'repaired' and no fault with TC module.
At this point we all thought the problem would be solved. Refitted the module and misfire was gone and speedo returned!!

The repairer denies any speedo related faults were repairedas his repair imfo was for misfire only. - I believe they somehow disturbed poor contacts and created the misfire - but will move on!

One day it lasted. Exclaimation light flicked on a road test. Then the ABS and Traction lights came back - Not at the same time - not sure which one was first and Speedo back to zero.

This is becoming a drama. The so called expert in the electronics place - says the Traction control module as nothing to do with the speedo. However I have seen on your forums that it is critical.
Why did the speedo come back for a day after they 'tested' and repaired the modules? Where do I go from here?

Any help or guidance would be greatly appreciated.
 
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#5 ·
OK, now we know that the car is a 1996, NOT a 1995, the car has 4 x speed sensors, (one for each wheel) regardless of ASR/ No ASR.

The wheel sensors are connected to ASR/ETC (depending on the option), and the speed info is passed to the ECU which feeds the Instrument cluster.

If your ABS/TC warning displays are intermittent) comes and goes when driving) I would check the charging system (alternator) and watch the battery voltage while driving. If the battery voltage goes low enough due to heavy electrical load, the ASR/ETC module shuts off, so no speed info is passed to the ECU.
 
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