Borris1954
Active Member
- Joined
- Feb 4, 2013
- Messages
- 415
- Location
- South Bucks
- Car
- S204 C 250 CGI BlueEFFICIENCY, R170 SLK 230, B 180d AMG Line
This is a plea for a sanity check by someone with more experience than me in successfully tracking down the cause of False Alarms in my 2011 SLK 200.
I bought the car at the end of last year and have steadily been working through a number of issues but this one is driving me nuts. As purchased the car reported on my first XENTRY scan:
U114000 Communication with the tow-away protection sensor has a malfunction.
U116900 Communication with interior protection sensor 1 has a malfunction.
This was eventually traced to a break in the LIN bus wire to the sensor mounted in the storage lid of the centre console due to the frequent opening and closing of this compartment. This was fixed and the faults cleared (using XENTRY). All seemed well for a few days and then whilst working on something else I saw that I now had multiple stored occurrences of:
B1A4849 Interior protection sensor 1 has a malfunction. There is an internal electrical fault.
If I cleared the fault and alarmed the car it would sometimes stay away for days and other times return within hours. I thought it’s time for a replacement sensor at which point I found that my original sensor part number A 207 820 28 10 (white with two connection ports) had been superseded by A2319052600 (Black with a single port). Hedging my bets I managed to buy a used of each type from eBay to try. The upshot was that the identical part number part produced the identical behaviour with the internal fault appearing at random intervals. I then discovered that once this fault has occurred the internal protection remains disabled until the alarm is next armed – not ideal security but understandable.
So I tried the newer black sensor which was blemish free in terms of faults but got a big black mark for randomly raising false alarms. Checking the Alarm Source recorded in the rear SAM always showed the trigger as the Internal Protection Sensor. Was it a faulty sensor or something else? The obvious something else was a rodent “visitor” in the car but there were no obvious signs and my traps all remained empty. The car was on a kept battery tender so I hoped that eliminated varying battery voltage as the cause. Testing went on for a while (weeks!) before I bit the bullet and bought a brand new sensor module at vast expense from MB after assuming mine must be faulty. The result was no change whatsoever so I had I just been unlucky in getting a new faulty part from MB. Finally getting desperate and assuming that the law of averages must work in my favour eventually I sourced two more used sensor modules one of each type. Believe it or not each behaved exactly the same as it predecessor i.e. random B1A4849 codes for the white and random Alarm activations (and no faults) for the black.
Rightly or wrongly it therefore appears to me that:
Next steps?
Well firstly any suggestions on next steps and things I have missed are most welcome. But as I have now studied the WIS document (AD80.50-P-5000CW) “Anti-theft alarm (ATA [EDW]) Diagnosis troubleshooting” it seems it could possibly be related to the security of the compartment lid in which the sensor is fitted (mine is very slightly loose at the hinge end) or maybe even the contents of the storage compartment itself (particularly anything metal). To be continued…
Thanks for reading this War & Peace of a post and all suggestions welcome.
I bought the car at the end of last year and have steadily been working through a number of issues but this one is driving me nuts. As purchased the car reported on my first XENTRY scan:
U114000 Communication with the tow-away protection sensor has a malfunction.
U116900 Communication with interior protection sensor 1 has a malfunction.
This was eventually traced to a break in the LIN bus wire to the sensor mounted in the storage lid of the centre console due to the frequent opening and closing of this compartment. This was fixed and the faults cleared (using XENTRY). All seemed well for a few days and then whilst working on something else I saw that I now had multiple stored occurrences of:
B1A4849 Interior protection sensor 1 has a malfunction. There is an internal electrical fault.
If I cleared the fault and alarmed the car it would sometimes stay away for days and other times return within hours. I thought it’s time for a replacement sensor at which point I found that my original sensor part number A 207 820 28 10 (white with two connection ports) had been superseded by A2319052600 (Black with a single port). Hedging my bets I managed to buy a used of each type from eBay to try. The upshot was that the identical part number part produced the identical behaviour with the internal fault appearing at random intervals. I then discovered that once this fault has occurred the internal protection remains disabled until the alarm is next armed – not ideal security but understandable.
So I tried the newer black sensor which was blemish free in terms of faults but got a big black mark for randomly raising false alarms. Checking the Alarm Source recorded in the rear SAM always showed the trigger as the Internal Protection Sensor. Was it a faulty sensor or something else? The obvious something else was a rodent “visitor” in the car but there were no obvious signs and my traps all remained empty. The car was on a kept battery tender so I hoped that eliminated varying battery voltage as the cause. Testing went on for a while (weeks!) before I bit the bullet and bought a brand new sensor module at vast expense from MB after assuming mine must be faulty. The result was no change whatsoever so I had I just been unlucky in getting a new faulty part from MB. Finally getting desperate and assuming that the law of averages must work in my favour eventually I sourced two more used sensor modules one of each type. Believe it or not each behaved exactly the same as it predecessor i.e. random B1A4849 codes for the white and random Alarm activations (and no faults) for the black.
Rightly or wrongly it therefore appears to me that:
- The white sensors were possibly superseded because as they aged they exhibited this failure mode (which many people without suitable code reader would never even notice)
- All my black sensors are working fine and I have some other environmental issue triggering them.
- Least likely to me is that whatever is causing my random alarms in the black units somehow raises that fault code instead in the white ones. I just struggle to buy that.
Next steps?
Well firstly any suggestions on next steps and things I have missed are most welcome. But as I have now studied the WIS document (AD80.50-P-5000CW) “Anti-theft alarm (ATA [EDW]) Diagnosis troubleshooting” it seems it could possibly be related to the security of the compartment lid in which the sensor is fitted (mine is very slightly loose at the hinge end) or maybe even the contents of the storage compartment itself (particularly anything metal). To be continued…
Thanks for reading this War & Peace of a post and all suggestions welcome.
