C280 immobiliser/starting problem

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Bearfacts

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:(Hi all

Originally posted a thread about my immobiliser problem on 3/9/2009. Car C280, registered early 1996 (could be 1995 model. After Scorpion alarm system was taken out on advice of auto electrician, car would still not start. Red LED on mirror diagnosed as problem (not lighting up when car locked). Mirror replaced and red LED now working but the one on the door handle only works intermittently, both green LEDs work ok. Car will still not start, engine turns over but will not fire. Desperate to know "proper" solution before taking out second mortgage to pay for further speculative diagnosis.
 

Dec

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Describe what exactly the Red and Green LEDs are doing ON THE MIRROR AND DOOR HANDLE when the car refuses to start.

As I understand it, there are 4 events when the mirror/door handle LED’s flash, I’m referring to cars with remote central locking with one button flip out key fob, powered by 2 X 3v batteries and associated with cars of around 1993 / 94 / 95 / 96.

1…When the car is locked with the flip out key, the Red LED will flash on the rear view mirror and the drivers door handle, the immobilizer is enabled, so car can’t be started.

2… When the car is unlocked with the flip out key,, the Green LED will flash on the rear view mirror and the drivers door handle, the immobilizer is disabled, so the car will start.

3…If you unlock or lock the car with the flip out key, and the Red and Green LED’s flash SIMULTANEOUSLY (for about 30 seconds) then the fob batteries will need replacing, however the car will still start, either during or after the Red and Green LED’s flash.

4…If you unlock the car and the Red and Green LED’s flash ALTERNATELY (when the key is turned to position 2) then the car won’t start because the immobilizer hasn’t been disabled, the engine will turnover, but it won’t start.

Dec
 
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Bearfacts

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Hi Dec

Thanks for your quick response. The answers to your questions are as follows;

1. Locking the car - red LED flashes on rear view mirror but not on door handle.

2. Unlocking the car - green LEDs flash both on the mirror and door handle.

Neither LEDs flash when turning the engine over. Semblance of it firing but cuts out.

NB The red LED on the door handle did flash on a couple of occasions when locking the car prior to replacing the mirror.

Wondering if there might be a connection problem?
 

Alex Crow

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why do you assume an immobiliser fault? could just as easily be the ovp relay.
 

Dec

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As said, might not be the immobelizer but the non working Red LED is suspicious, might be worth having a look at the door handle LEDs and spraying the connection with switch cleaner to see if you can get them to work every time the car is locked.
Easy enough job to do, just wiggle to remove after you have unscrewed the grub screw fully.

Dec
 

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Immobiliser Problem

Hi Dec

Thanks for the advice and accompanying photos. Have cleaned the connection as suggested but unfortunately no change. Looks as though I may have to pursue AP's suggestion re OVP module but not sufficiently competent to deal. Have you any other suggestions in the meantime?
 

Dec

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I was hoping that fixing the Red LED might have some bearing on the problem as I read that a defective led on the mirror and possibly door handle can cause your non starting problem.

Also, you aren’t getting the ALTERNATE Red and Green LEDs flashing which indicate that the immobelizer is disabled so the car should start.
This , I presume is why AP thinks it is some other fault like the OVP relay,(see small picture) so you better check that out, it has a fuse on top located under a large plastic cover, can’t advise you further as I don’t know enough about it or what exactly its purpose is.

Dec
JumpLeads.jpg
 
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C280 immobiliser problem

Hi Dec and AP

Sorry but since your replies of 28/9 & 2/10 I have been in hospital and have only just managed to get about. Discovered that the OVP fuse had blown and replaced it. Unfortunately insufficient power in the battery to turn the starter motor so have put it on charge. However on taking out the key I noticed the ignition and associated lights remained on and the only way they can be turned off is to take out the above mentioned fuse.
I'm more confused than ever, any more advice please.
 

Dec

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Not going to be much help on this, AP or others might be able to advise, in the mean time charge the battery and try again with the fuse, perhaps the charging of the battery has something to do with the dash lights coming on although that shouldn’t have happen with the key out of the ignition.

Hope you are fit again after your trip to hospital.

Dec
 
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Bearfacts

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Many thanks Dec for your best wishes. Yes, I will see if AP or others have any further advice
 

Arv

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I have a 1994 C280 also and I had not exactly same problem long time ago but problem with starting the car intermittently and as it happened, I had also installed after market alarm when I had bought the car.

I had to change the OVP which was malfunctioning and the wiring harness since the guy who had installed the alarm had tapped on to the harness at various points and it had damaged the harness. So, I ended up removing the alarm also and got a new harness.

May be your harness is also damaged because of the after market alarm installation and hence the instrument panel light problem and the car not starting. Have the harness checked.
Had costed me about $600 but it was almost 10 yrs ago, so probably it might be double by now considering all Mercedes parts prices at the dealer have doubled or tripled.

Hope this helps,
Arv.
 
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Bearfacts

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C280 immobiliser problem

Thanks Arv

Not sure if I should go down the harness replacement road just yet. Yes, the OVP relay could be faulty but I first need to establish whether the symptoms (ignition and associated lights remaining on when the key is withdrawn) suggest this is the case. What is the function of the OVP? Have already established that the central locking is inoperative with the fuse out, what else does it govern?
 
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Bearfacts

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Central locking now working ok but ignition light etc still illuminating with OVP relay fuse in situ and key withdrawn. Has anybody got an explanation?
 

Arv

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I think OVP (which is a relay) stands for Overload Voltage Protection. I wonder if you got a short somewhere in the harness after you removed the alarm which is causing the instrument cluster staying illuminated after the key is removed from the ignition.

Let us know what you find out or you have the problems fixed.

Good luck,
Arv.
 
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Bearfacts

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C280 Immobiliser Problem

:D Alexander Patient, Dec and Arv.
I'm mobile at last thanks to a friend's mechanic. OVP problem still outstanding despite exhaustive testing. However, been assured that running without the fuse is ok unless anybody has other views. Similarly red LED on door handle does not light up during locking procedure.
 

pwoods

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How do I bypass the factory starter disabler without am key?

My key came apart and the "mother board" was ruined. Is there a way that I can disable the immobiliser without my remote? I need my car to start!!!
 
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Dec

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Is there a chip glued inside the remote like the one in picture, at the RED arrow?

Dec

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pwoods

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No, everything is on the green circuit board- which is ruined! I was looking for a way to bypass the immobiliser without the remote if possible- Using the key only. I have tried everyhting I can think of. Tried locking the doors and unlocking the trunk as well (someone else''s suggestion)
 

Dec

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Got any pictures of the damage remote?
Does the car have an alarm fitted?
How is the remote ruined, in what way was it damaged, just how bad is the damaged remote, it may be repairable, can it be made to work OUTSIDE of it’s casing, see this example at timeline 6:08 seconds here… http://www.youtube.com/watch?v=lCqfivH9-Dg&feature=player_embedded
Repair or replacement of the remote is the best options, the immobiliser, as far as I know can’t be bypass.

Dec
 

pwoods

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it has broken connections - on the green circuit board. I am getting a replacement remote when I can, but I need a more immediate solution - because the mercedes dealer wants the vehicle there when the replacement key arrives, but until this is bypassed, I cannot drive it or move it since the car will not go into neutral without being started. I don't have pictures at the moment. Maybe when I get home.
 


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