Ignition switch relay stopped working

[oli3000]

My ignition switch control relay, 4H0909131, does not work anymore. I put the key up against the designated area on the dash but the car wont turn on. Start button works fine. Key works fine unlocking.

Could it be a fuse? Can the relay be replaced without coding or is it protected? I have brand new battery in the key fob just in case. Maybe there's some reset procedure?

VCDS does throw an error about the MMI screen as it was replaced with android touchscreen. But I am told this has never affected any others.
02259 - Information Display and Control Head (Front) (J685) 004 - No Signal/Communication


ignition switch relay2.jpg

ignition switch relay1.jpg

[Alabama]

My ignition switch control relay, 4H0909131, does not work anymore. I put the key up against the designated area on the dash but the car wont turn on. Start button works fine. Key works fine unlocking.

Could it be a fuse? Can the relay be replaced without coding or is it protected? I have brand new battery in the key fob just in case. Maybe there's some reset procedure?

I'm probably not understanding the issue. In my owner's manual (C7 S6) replacing the battery in the key fob does not then require any reset procedure. There is a fuse for "convenience key" located in the luggage compartment for my vehicle. You may wish to check your owner's manual. If the key fob unlocks the car and the start button starts the car, then what else are you trying to do with the key fob?

[oli3000]

I'm probably not understanding the issue. In my owner's manual (C7 S6) replacing the battery in the key fob does not then require any reset procedure. There is a fuse for "convenience key" located in the luggage compartment for my vehicle. You may wish to check your owner's manual. If the key fob unlocks the car and the start button starts the car, then what else are you trying to do with the key fob?

When the key fob is put against the designated area on the dash the ignition on the car is turned on. Like pressing the Start button.

It's a fail safe that if the car doesn't recognize the key, or the battery on the fob is dead, then you can still switch ignition on by putting the key onto the designated area. This is what is broken for me.

[Alabama]

When the key fob is put against the designated area on the dash the ignition on the car is turned on. Like pressing the Start button.

It's a fail safe that if the car doesn't recognize the key, or the battery on the fob is dead, then you can still switch ignition on by putting the key onto the designated area. This is what is broken for me.

Interesting. My car does not function in that way. The "designated area" is only intended to be used if the battery in the key fob is dead. The car can scan for the key fob, but I still have to push the "start engine stop" button to start the car. Someone else will have to help.

[qcrazy]

Interesting. My car does not function in that way. The "designated area" is only intended to be used if the battery in the key fob is dead. The car can scan for the key fob, but I still have to push the "start engine stop" button to start the car.

^ This

[gk1]

Interesting that it does not throw a code specifically for that module.

In the service manual it is described specifically as "Anti-Theft Immobilizer Reader Coil -D2-"

It does indeed have a fuse location ST2 Fuse 4 on panel C, brown, LHD. So it is the passenger's side fuse panel. It is a 5A fuse.

If that is not the issue I'm sorry, I don't know if it has to be coded to be replaced. Although I'm doubtful since it apparently does not even throw a code when it fails indicating to me it does not have much built in intelligence like other control modules.

IMO for around $100US it would be worth it to me to try just swapping it if the fuse is not the issue.

[Alabama]

Interesting that it does not throw a code specifically for that module.

In the service manual it is described specifically as "Anti-Theft Immobilizer Reader Coil -D2-"

It does indeed have a fuse location ST2 Fuse 4 on panel C, brown, LHD. So it is the passenger's side fuse panel. It is a 5A fuse.

Wow, am I confused. For my car, the fuse you reference is named "electrical ignition lock". But why would that system throw a code? The car starts when OP pushes the 'start engine stop" button. Would not the procedure to test just the "reader coil" be to remove the battery from the fob, then hold the fob to the reader coil, then push the "start engine stop" button and see if the car starts? OP seems to want the car to start itself whenever the key fob is held to the reader coil. Does your S6 behave in that fashion?

[Audisthesia]

Wow, am I confused. For my car, the fuse you reference is named "electrical ignition lock". But why would that system throw a code? The car starts when OP pushes the 'start engine stop" button. Would not the procedure to test just the "reader coil" be to remove the battery from the fob, then hold the fob to the reader coil, then push the "start engine stop" button and see if the car starts? OP seems to want the car to start itself whenever the key fob is held to the reader coil. Does your S6 behave in that fashion?

Just throwing my worthless 2 cents in here.... 2018 S6 NAR... If i hold my fob up to the indicated area on the dash, I still have to press the start/stop button and press the brake pedal to start the engine. Simply holding the fob to the dash DOES NOT start the engine.

[gk1]

Wow, am I confused. For my car, the fuse you reference is named "electrical ignition lock". But why would that system throw a code? The car starts when OP pushes the 'start engine stop" button. Would not the procedure to test just the "reader coil" be to remove the battery from the fob, then hold the fob to the reader coil, then push the "start engine stop" button and see if the car starts? OP seems to want the car to start itself whenever the key fob is held to the reader coil. Does your S6 behave in that fashion?

Yeah, you are probably right...removing the fob battery is a good test....my assumption was something was perhaps "lost in translation" with the OP being from Finland.
The service manual does specify a fuse for that item so figured I would offer that up as something to check.
For me if you take the fob battery out (or have it far enough away) and try to start the car, the car gives you the message to place the fob near the reader coil. When you do that the car turns on to accessory mode. You are right it does not start the engine, but does basically get ready to start and you have to put your foot on the brake and press the start button again to get the engine started. Kind of of makes sense why it is described as "anti-Theft Immobilizer Reader Coil" then.
I assumed that the OP was not getting the accessory "on" like I'm describing, but re-reading perhaps I misunderstood and he is looking for it to start the engine which, as pointed out, is incorrect.

[TexasDfwS4]

Battery in backwards????

[Alabama]

my assumption was something was perhaps "lost in translation" with the OP being from Finland.
For me if you take the fob battery out (or have it far enough away) and try to start the car, the car gives you the message to place the fob near the reader coil. When you do that the car turns on to accessory mode. You are right it does not start the engine, but does basically get ready to start and you have to put your foot on the brake and press the start button again to get the engine started. Kind of of makes sense why it is described as "anti-Theft Immobilizer Reader Coil" then.
I assumed that the OP was not getting the accessory "on" like I'm describing, but re-reading perhaps I misunderstood and he is looking for it to start the engine which, as pointed out, is incorrect.

OK, maybe the idea is that holding the key fob by the reader will automatically start the ignition (accessory mode) but not the engine, equivalent to pushing the "start engine stop" button while NOT pressing the brake pedal, and that is what is not working. I'm pretty sure in my car if I hold the key fob by the reader coil the ignition is not activated. I can't find any reference to this in my owner's manual. I'll have to give it a try.

[Alabama]

Yeah, you are probably right...removing the fob battery is a good test....my assumption was something was perhaps "lost in translation" with the OP being from Finland.

If qcrazy can do experiments, then so can I! First I tried holding my key fob with battery intact against the reader coil for over 10 seconds. Nothing happened, no warning message, no ignition on, no engine start. Then I moved far away from the car, removed the battery from the key fob, and returned to the car. When I pushed the "start engine stop" button (foot off brake), a warning message immediately appeared in the display telling me to hold the key fob near the reader coil. I then held the key fob without battery near the reader coil for over 10 seconds but did not push the "start engine stop" button. Again, nothing happened, no ignition on (i.e., no accessory mode), no engine start. I then continued to hold the key fob (without battery) near the reader coil and pushed the "start engine stop" button (foot off brake). The ignition came on (accessory mode), dash lights came on, and the MMI started up. The engine stayed off (as expected). My conclusion at least for my car: the reader coil is only intended to compensate for when the key fob battery is dead and the key fob cannot broadcast whatever code is needed to turn off the immobilizer system. Other than that, starting the car still requires pushing the "start engine stop" button with or without foot on brake depending on goal.
Of course, I've got all OEM, stock equipment for this part of the car. Aren't there aftermarket remote start devices? I don't think that's what OP is referring to though. Totally off topic, I vaguely recall being told by native Swedish speakers that Finnish is a tough language even for them to understand, so "lost in translation" may be very likely!

[gk1]

If qcrazy can do experiments, then so can I! First I tried holding my key fob with battery intact against the reader coil for over 10 seconds. Nothing happened, no warning message, no ignition on, no engine start. Then I moved far away from the car, removed the battery from the key fob, and returned to the car. When I pushed the "start engine stop" button (foot off brake), a warning message immediately appeared in the display telling me to hold the key fob near the reader coil. I then held the key fob without battery near the reader coil for over 10 seconds but did not push the "start engine stop" button. Again, nothing happened, no ignition on (i.e., no accessory mode), no engine start. I then continued to hold the key fob (without battery) near the reader coil and pushed the "start engine stop" button (foot off brake). The ignition came on (accessory mode), dash lights came on, and the MMI started up. The engine stayed off (as expected). My conclusion at least for my car: the reader coil is only intended to compensate for when the key fob battery is dead and the key fob cannot broadcast whatever code is needed to turn off the immobilizer system. Other than that, starting the car still requires pushing the "start engine stop" button with or without foot on brake depending on goal.
Of course, I've got all OEM, stock equipment for this part of the car. Aren't there aftermarket remote start devices? I don't think that's what OP is referring to though. Totally off topic, I vaguely recall being told by native Swedish speakers that Finnish is a tough language even for them to understand, so "lost in translation" may be very likely!

Interesting, can I ask you to try one more test?

I think this is a correct statement "the reader coil is only intended to compensate for when the key fob battery is dead and the key fob cannot broadcast whatever code is needed to turn off the immobilizer system.", but I am curious if when the fob battery is in place it works as it does in mine and turns on the accessories when held near the reader coil after a failed start attempt.


Put the key away from the car (with battery in), doesn't even really have to be far just not inside the vehicle.
Push the start button with your foot on the brake as if trying to start it.
(You should get the warning asking you to put the key in the spot.)
Put the key in the spot and see if it activates accessories. (You have to be pretty quick, after the warning disappears it seems to no longer work.)

Danka.

P.S. the reason I notice this is sometimes I have the key in my pants pocket when working on my car and lean in with my hand on the brake and push the start button to start the engine, and it fails because that is far enough away amazingly, but then if I dig the key out and put it near the reader the accessories come on. I still then obviously have to push the brake and start button to start the engine.

[Alabama]

Interesting, can I ask you to try one more test?

INCONCEIVABLE!! So OP may be right after all. Here are my further experiments. First, battery in key fob, but key fob placed away from car. Foot off brake, press and release "start engine stop" button. In a few seconds, message appears on display to place key fob near reader coil. I placed the key fob near the reader coil, foot still off brake and no further pressing of the "start engine stop" button. In a second or two the ignition turns on (accessory mode) but the engine does not start. That's what gk1 reported; my car has the same behavior. For the second experiment I placed key fob away from car again, pressed and released "start engine stop" button, this time with foot on brake. Again in a few seconds the message appears on display to place key fob near reader coil. I placed the key fob near the reader coil, kept my foot on the brake, but no further pressing of the "start engine stop" button. This time in a second or two the ignition turned on AND the engine started. So, I had to press the "start engine stop" button first to activate the message about putting the key fob close to the reader coil, but did not have to press it again to start the engine, just place the key fob near the reader coil. Maybe the system has some form of memory that the "start engine stop" button had already been pressed. However, I still don't understand OP's issue. If the key fob is broadcasting and within range, the normal behavior is that the display message won't appear and the reader coil does not get activated.
Cooling mod issues are child's play compared with these locksmithing challenges!

[qcrazy]

Good stuff!

[oli3000]

Wow you guys have been busy. Sorry for not being more active, got busy with baby stuff and now had a few hours to look into this again.

In my first post when I said ignition on I meant accessory on only, not engine on.

And for the life of me I truly believed that before when I put the key onto the "coil" the accessory would come on.

Today I went out and did what was suggested by someone or a couple of you to remove the battery from the fob to test, super thanks btw!! I removed the battery from the fob, pressed start button and car said key not recognized, I then put the fob onto the coil and voila, accessory on. So nothing is broken. Just my memory.

Case closed. User error. it would seem the coil or ignition switch relay seems to only be "activate" when the key is not recognized, at other times it sits dormant.

[Alabama]

So nothing is broken. Just my memory. Case closed.

Great news. That's what we non-engineers go for. Maybe no multi-colored graphs with varieties of data points, but at least a definitive answer and "case closed"!