help alarm going off on my new S420

[benz_300se]

hello guys,

i just bought a new benz as was the replacement on for my old ( sold ) 93 300SE. it a 94 S420, white/black. anyway just bought it 3 days ago. i am having a f.. up problem with though. the lady i bought the car from it didnt have the remote key just the master key ( thats how i lock and unlock the car with the key in the key fob). so yeah anyway i went this morning to unlock the car an all in the sudden when i open the driver side door the alarm went off and crazy on it. i am like wht tha the hell .. so i jump out again and i try to lock and unlcok the car again by puting the key in the fob and see what it does. but nothing the alarm still going i try to start the car it wont let me to. my neighbors going crazy so i had to cut the horner( siren) on it and not just the headlight and tail lights flash when the alarm goes off. so yeah i been back and forth up and down for 2 hours and nothing i can not get my benz to start because of teh alarm. i tried that p[rocedure by puting the key in 1st position waiting 30 sec and so 2nd position 30 and waiting 90 sec and so and so... also i tried the neutral thing by pressing the brake and puting the car in neutral but nothing happened. also took fuse # 2 and # 15 out and also disconectyed the negative battery cable for a minute and still nothing nothing nothjing.. the only thing i hear is in the back seat righ side i hear like click clik relays and stuff. also when thealram goes off after 90 second the red dot flashes at the radio and also the central locking system button in the dash. can anyone please help me what to do...

thanks

[Mercedes Mechanix]

Originally Posted by benz_300se

hello guys,

i just bought a new benz as was the replacement on for my old ( sold ) 93 300SE. it a 94 S420, white/black. anyway just bought it 3 days ago. i am having a f.. up problem with though. the lady i bought the car from it didnt have the remote key just the master key ( thats how i lock and unlock the car with the key in the key fob). so yeah anyway i went this morning to unlock the car an all in the sudden when i open the driver side door the alarm went off and crazy on it. i am like wht tha the hell .. so i jump out again and i try to lock and unlcok the car again by puting the key in the fob and see what it does. but nothing the alarm still going i try to start the car it wont let me to. my neighbors going crazy so i had to cut the horner( siren) on it and not just the headlight and tail lights flash when the alarm goes off. so yeah i been back and forth up and down for 2 hours and nothing i can not get my benz to start because of teh alarm. i tried that p[rocedure by puting the key in 1st position waiting 30 sec and so 2nd position 30 and waiting 90 sec and so and so... also i tried the neutral thing by pressing the brake and puting the car in neutral but nothing happened. also took fuse # 2 and # 15 out and also disconectyed the negative battery cable for a minute and still nothing nothing nothjing.. the only thing i hear is in the back seat righ side i hear like click clik relays and stuff. also when thealram goes off after 90 second the red dot flashes at the radio and also the central locking system button in the dash. can anyone please help me what to do...

thanks

OK, the alarm system is enabled due to the door being opened without your security system being made valid/ ie: safe. Reason for your inability to start the engine is due to Relay 38 (immobilizer relay) not being satisfied. The Vacuum PSE (vacuum pump) for central locking is below the rear seat. The vacuum PSE also is the priority point for enabling the relay 38 (relay located passenger foot rest area... right bulkhead area behind the carpeted panel). This relay (R-38) supplies a ground to satisfy the starter/ignition system to allow the vehicle to be started. I suggest to first visit alldatadiy.com and get yourself a subscription for your S420 info as I have described. Recently assisted another owner regarding this same PSE and his K38 being the area of opportunity as well.

WILL NOT START, PLEASE HELP!
(description of Benz-World Post mentioned)

visit this post and review the diagrams...they also will assist with your vehicle and are valid for same.

You will require a small multimeter, screwdriver, small flashlight and notepad. The conductor connection points are also descriptive as you will note at the area just above the small terminal points (regarding the Central Locking vacuum pump or described as Vacuum PSE).

I would start by validating the K38 point (black with gray tracer as memory serves on terminal one of the PSE) as noted on dwg at noted post as well. Also to validate the remote contact status for the pump as well. When you review the aformentioned diagrams, the diagnostic path I am starting you on should become apparent. I will also PM you with more information on your security system and appropriate as designed protocol if you require same?

Following is descriptive data for below picture. Also a few connection diagrams of the vacuum PSE as discussed in previous post mentioned.

Figure 29/32/33
Component Name Starter lock-out relay module:
Component ID K38
Component ID Component Name
K38 Starter lock-out relay module
N42 Left SBE control module
N54 RCL control module

Robert

[benz_300se]

Originally Posted by Mercedes Mechanix

OK, the alarm system is enabled due to the door being opened without your security system being made valid/ ie:...

Robert

thank you for replying so what do i excatly have to do now cause i dont really get it . can you explain a little bit and also is there a way resteing the system without doing some modes to this relay k38?? let me know

thanks

[bobs]

This may sound kind of harsh, but Robert's instructions were quite clear. If you don't understand them, it might be wise to take the car in to a dealer and order a replacement key & fob and have them re-sync it for you. The key/remote will run you about $200 and they should charge you about .5 hours of shop time to re-sync it.

You will need to provide them with the VIN and proof of ownership. Keys will normally come back in a couple of days.

[z168]

wow - good info Robert

question : just for added knowledge, if I decide to jump the K38 relay, is this enough to bypass cutoff switch?