SL/R230: Key FOB no longer turns in ignition, nor unlocks
Thread Starter
Super Member
Joined: Sep 2021
Posts: 537
Likes: 115
From: Ann Arbor, MI
2004 SL600
Key FOB no longer turns in ignition, nor unlocks
To again chase down why the rear battery drains so quickly, I pulled all fuses out of the three SAM/Fuse blocks, disconnected the rear-prefuse block, added fuses to the BCM and documented everything for an upcoming thread here. I did not open the front pre-fuse block this time due to the effort.
Put it all back together, battery drain is the same, BUT now neither key-fob turns in the ignition. Also does not lock or unlock anything. I pulled out the metal key, but it does not seem to fit in the ignition. I can use it to lock and unlock the glove compartment and then hear the rear bins lock too.
Dash lights when I open the door, both batteries are fully charged.
So a couple questions:
Q1 - Is there a way to turn on the ignition with just the metal key? If yes, where and how?
Q2 - Other than the front prefuse block, are they any other fuses for the EIS? (I checked F8 "Central Gateway").
Q3 - Did I overlook something else?
Without ignition turned on, my scanner will not connect to diagnose this further.
In the meantime, I will figure out how to test for power to the EIS.
BTW - From swapping engines to disassembling the ABS to chasing down battery drain, perhaps even rebuilding the trans soon, it is all part of my learning more about the car, especially during winter in Michigan. I plan to document much of what I learn, although unlikely to hit the 10,000 posts I have on various GM cars.
Thanks. Look forward to any suggestions and learning every more.
Put it all back together, battery drain is the same, BUT now neither key-fob turns in the ignition. Also does not lock or unlock anything. I pulled out the metal key, but it does not seem to fit in the ignition. I can use it to lock and unlock the glove compartment and then hear the rear bins lock too.
Dash lights when I open the door, both batteries are fully charged.
So a couple questions:
Q1 - Is there a way to turn on the ignition with just the metal key? If yes, where and how?
Q2 - Other than the front prefuse block, are they any other fuses for the EIS? (I checked F8 "Central Gateway").
Q3 - Did I overlook something else?
Without ignition turned on, my scanner will not connect to diagnose this further.
In the meantime, I will figure out how to test for power to the EIS.
BTW - From swapping engines to disassembling the ABS to chasing down battery drain, perhaps even rebuilding the trans soon, it is all part of my learning more about the car, especially during winter in Michigan. I plan to document much of what I learn, although unlikely to hit the 10,000 posts I have on various GM cars.
Thanks. Look forward to any suggestions and learning every more.
Last edited by mrvedit; Jan 6, 2025 at 04:41 PM.
Super Member
Joined: Sep 2018
Posts: 746
Likes: 184
From: Melbourne, Australia
2005 SL 500 R230
It does sound like the EIS has lost power. They are known for bad connections or cold solder joints.
2) Check the 7.5A fuse in the rear prefuse block (F33) near the rear battery. That's power to the EIS. If that's OK then start tracing it through to the EIS.
1) The blade in the fob does not operate the ignition key - you will need to find the issue with the EIS.
3) Did you forget to reconnect the rear prefuse block F33?
Go back over what you have done or forgotten to do - sounds like something simple.
HTH
2) Check the 7.5A fuse in the rear prefuse block (F33) near the rear battery. That's power to the EIS. If that's OK then start tracing it through to the EIS.
1) The blade in the fob does not operate the ignition key - you will need to find the issue with the EIS.
3) Did you forget to reconnect the rear prefuse block F33?
Go back over what you have done or forgotten to do - sounds like something simple.
HTH
Thread Starter
Super Member
Joined: Sep 2021
Posts: 537
Likes: 115
From: Ann Arbor, MI
2004 SL600
Thanks for informing me that the EIS power starts with the rear 7.5A fuse. I just checked it visually and it seems OK. Yes, I reconnected the rear prefuse block F33 which then made the trunk lights work, the vacuum pump turn on and such.
Didn't have time today to start tracing voltages. Today was the 50th anniversary of the day my wife and I met at the Univ of Mich. Visited the German dept where we met and her apartment to which I followed her that first day for lunch. Married almost 48 years.
Didn't have time today to start tracing voltages. Today was the 50th anniversary of the day my wife and I met at the Univ of Mich. Visited the German dept where we met and her apartment to which I followed her that first day for lunch. Married almost 48 years.
Thread Starter
Super Member
Joined: Sep 2021
Posts: 537
Likes: 115
From: Ann Arbor, MI
2004 SL600
Tom, you nailed it. I didn't have the 7.5A fuse in the rear seated correctly. The key now turns in the ignition.
Still surprised MB doesn't allow the metal key to start the car in case the FOB is destroyed, e.g. crushed.
I just tried an unprogrammed MB key and it won't turn in the ignition; I thought it might turn on the ignition but then refuse to start the engine.
Still surprised MB doesn't allow the metal key to start the car in case the FOB is destroyed, e.g. crushed.
I just tried an unprogrammed MB key and it won't turn in the ignition; I thought it might turn on the ignition but then refuse to start the engine.
Thread Starter
Super Member
Joined: Sep 2021
Posts: 537
Likes: 115
From: Ann Arbor, MI
2004 SL600
Super Member
Joined: Sep 2018
Posts: 746
Likes: 184
From: Melbourne, Australia
2005 SL 500 R230
Petty sure it works thus: there is an RFID tag in the fob that allows you to turn the key and start the car even if the battery in the fob is flat. Without the right RFID tag the EIS will not unlock. If you look at all modern cars there is no way to insert a blade into a lock, other than the door lock, so blades in ignition are obsolete.
Our keys are pretty tough and durable things, I'd rather have the big chunky plastic key than a flimsy old blade.
Our keys are pretty tough and durable things, I'd rather have the big chunky plastic key than a flimsy old blade.
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Thread Starter
Super Member
Joined: Sep 2021
Posts: 537
Likes: 115
From: Ann Arbor, MI
2004 SL600
OK, it must have been some specific brand cars from the late '80s or '90s which had a start button but could be started with a metal key.
I learned more from everyone and thanks to Tom have my car working again.
Thanks.
I learned more from everyone and thanks to Tom have my car working again.
Thanks.
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