-
Hi Guest !
Welcome to the 500Eboard forum.
Since its founding in late 2008, 500Eboard has become the leading resource on the Internet for all things related to the Mercedes-Benz 500E and E500. In recent years, we have also expanded to include the 400E and E420 models, which are directly related to the 500E/E500.
We invite you to browse and take advantage of the information and resources here on the site. If you find helpful information, please register for full membership, and you'll find even more resources available. Feel free to ask questions, and make liberal use of the "Search" function to find answers.
We hope you will become an active contributor to the community!
Sincerely,
500Eboard Management
ASR light
- Thread starter aldedmon
- Start date
if the line is leaking , it can't hold pressure....if it can't hold pressure, it can't charge the ASR pump...so my ASR light would come on
I drove my E500 on Sunday after (and I am ashamed to admit this) not driving it since I think October or November 2022. Of course, the ASR light went on after the ASR pump cycled itself for the two or three minute period (I could hear/feel it humming while it was cycling).
I have not yet replaced the brake fluid (it has been some years since I last changed it) and I believe that old brake fluid is clogging the pre-charge pump.
In any case, when this happens, I am often able to clear the issue (the stuck pre-charge pump) by flooring the accelerator during the first couple of minutes while the ASR pump is cycling, before shuts off and activates the ASR light in the cluster.
By doing this, ASR is activated (the triangle in the center of the speedo lights up) and this forces fluid to circulate through the system and into the pre-charge pump and ASR pump. And then (particularly the next time you start the car, resetting the full cycle) it acts normally.
It's a Band-Aid fix for the problem, until a) new fresh clean fluid is replaced in the system, which should help "unstick" the ASR pump and allow a proper charging cycle; and/or b) the pre-charge pump is removed and cleaned (which is a difficult job due to its location under the master cylinder and booster area).
So, I'm going to change fluid and see if that solves the problem of properly lubricating the system. If not, then I will have to remove and rebuild the pre-charge pump. I have the parts and new tubing for it in hand.
To reiterate, if you have this issue, and want to try to resolve it, try forcing the ASR system to activate BEFORE the ASR pump stops cycling and lights up the ASR lamp. But only floor it with a warmed-up car.
Funnily enough, the last time I drove my SL500 was probably around the same time. It developed a surging/rough idle after engine warm-up and i've been too busy to look into it. Ordered up some new rotors, caps, and insulator shields which should be here later in the week and solve that issue (
I drove my E500 on Sunday after (and I am ashamed to admit this) not driving it since I think October or November 2022. Of course, the ASR light went on after the ASR pump cycled itself for the two or three minute period (I could hear/feel it humming while it was cycling).
I have not yet replaced the brake fluid (it has been some years since I last changed it) and I believe that old brake fluid is clogging the pre-charge pump.
In any case, when this happens, I am often able to clear the issue (the stuck pre-charge pump) by flooring the accelerator during the first couple of minutes while the ASR pump is cycling, before shuts off and activates the ASR light in the cluster.
By doing this, ASR is activated (the triangle in the center of the speedo lights up) and this forces fluid to circulate through the system and into the pre-charge pump and ASR pump. And then (particularly the next time you start the car, resetting the full cycle) it acts normally.
Its a Band-Aid fix for the problem, until a) new fresh clean fluid is replaced in the system, which should help unstick the ASR pump and allow a proper charging cycle; and/or b) the pre-charge pump is removed and cleaned (which is a difficult job due to its location under the master cylinder and booster area).
So, Im going to change fluid and see if that solves the problem of properly lubricating the system. If not, then I will have to remove and rebuild the pre-charge pump. I have the parts and new tubing for it in hand.
To reiterate, if you have this issue, and want to try to resolve it, try forcing the ASR system to activate BEFORE the ASR pump stops cycling and lights up the ASR lamp. But only floor it with a warmed-up car.
).Looking forward to trying out this band-aid afterwards.
I've been reading through this thread because I have the same issue with my '95 e320 Cabriolet. The ASR light comes on 2-3 minutes after car is started, code #21, and no check engine light. Given that a couple of years have passed, did you fully resolve your issue? If so, what was the solution? I'm hoping it only took changing the fluid! Thanks.
I drove my E500 on Sunday after (and I am ashamed to admit this) not driving it since I think October or November 2022. Of course, the ASR light went on after the ASR pump cycled itself for the two or three minute period (I could hear/feel it humming while it was cycling).
I have not yet replaced the brake fluid (it has been some years since I last changed it) and I believe that old brake fluid is clogging the pre-charge pump.
In any case, when this happens, I am often able to clear the issue (the stuck pre-charge pump) by flooring the accelerator during the first couple of minutes while the ASR pump is cycling, before shuts off and activates the ASR light in the cluster.
By doing this, ASR is activated (the triangle in the center of the speedo lights up) and this forces fluid to circulate through the system and into the pre-charge pump and ASR pump. And then (particularly the next time you start the car, resetting the full cycle) it acts normally.
It's a Band-Aid fix for the problem, until a) new fresh clean fluid is replaced in the system, which should help "unstick" the ASR pump and allow a proper charging cycle; and/or b) the pre-charge pump is removed and cleaned (which is a difficult job due to its location under the master cylinder and booster area).
So, I'm going to change fluid and see if that solves the problem of properly lubricating the system. If not, then I will have to remove and rebuild the pre-charge pump. I have the parts and new tubing for it in hand.
To reiterate, if you have this issue, and want to try to resolve it, try forcing the ASR system to activate BEFORE the ASR pump stops cycling and lights up the ASR lamp. But only floor it with a warmed-up car.
Code #21 from which module (which diagnostic pin)?
Use this PDF document to decode the codes on your M104 engine. If you don't have SDS with HHT-Win, you at least need a handheld blink code reader.
Code #21 on the 16-pin analog blink/flash code reader.
Not sure what you mean. Is this the built-in LED & button on the passenger side near the strut tower area?
Yes.
OK. As described in the document linked above, that is only showing you codes from the Diagnostic Module.
DM Code #21 = "Purge switchover valve, open/short circuit"
You need a handheld blink code reader to check codes on the EA/CC/ISC (E-GAS) module, pin/socket #14. There are not many codes related to ASR though. This could be tough to diagnose on your M104 car. The V8 models have a separate ASR module which will generate ASR-specific codes, but you don't have that on the cabriolet.
Yes, it is difficult to diagnose in my car, but my symptoms are the same as what Gerry described in post #11 and what I've seen elsewhere. I'd like to hear if he has resolved the problem and what the solution was, which is why I asked the question.
Understood. Can you hear the ASR charge pump audibly run for ~3 minutes, then the ASR light turns on right when the pump turns off?
Difficult to tell in the garage with the engine running. I have not tried flooring the car as gerryvz mentioned.
There are a few things you can do to "un-stick" this aux pump.
1) Change your brake fluid, including the ASR pump (do this first, per the forum's HOW-TO on brake fluid change)
2) Exercise your ASR by forcing it to activate via flooring the gas pedal to turn the yellow light on
3) If these don't work after several drives, then you would need to remove the pump and either clean it, or replace it. Generally you should be able to remove and disassemble the pump to clean it. It is not easy to get to.
Generally #1 above, followed by #2, should do the trick.
To prevent the issue from recurring, make sure you drive your car at least once a month so that the pump is activated at startup and the fluid is circulated properly.
1) Change your brake fluid, including the ASR pump (do this first, per the forum's HOW-TO on brake fluid change)
2) Exercise your ASR by forcing it to activate via flooring the gas pedal to turn the yellow light on
3) If these don't work after several drives, then you would need to remove the pump and either clean it, or replace it. Generally you should be able to remove and disassemble the pump to clean it. It is not easy to get to.
Generally #1 above, followed by #2, should do the trick.
To prevent the issue from recurring, make sure you drive your car at least once a month so that the pump is activated at startup and the fluid is circulated properly.
Thanks, Gerry. I don't drive it a lot, and the steps you note are my game plan. In the end, did #1 and #2 work for you, or did you have to clean or replace the pump?
Note there are 2 different pumps involved. First is the "precharge" low-pressure pump located below the brake fluid reservoir. This provides fluid to the ASR unit itself. The other is a high-pressure pump internal to the ASR unit itself. On the M104 cars, you may not be able to tell which one is causing the fault.
Regardless, try Gerry's recommendations above and see what happens. Make sure when replacing the brake fluid that you use a pressure bleeder, required for models with ASR, and bleed the ASR unit as well per the FSM instructions.
Regardless, try Gerry's recommendations above and see what happens. Make sure when replacing the brake fluid that you use a pressure bleeder, required for models with ASR, and bleed the ASR unit as well per the FSM instructions.
Thanks! Yes, I'm aware of the things you noted, but only due to having done a lot of research on this irritating ASR light issue.Note there are 2 different pumps involved. First is the "precharge" low-pressure pump located below the brake fluid reservoir. This provides fluid to the ASR unit itself. The other is a high-pressure pump internal to the ASR unit itself. On the M104 cars, you may not be able to tell which one is causing the fault.
Regardless, try Gerry's recommendations above and see what happens. Make sure when replacing the brake fluid that you use a pressure bleeder, required for models with ASR, and bleed the ASR unit as well per the FSM instructions.
Yes, actually just activating the ASR a few times to circulate the fluid and "shock" the pump into action worked. But I'd recommend changing the brake fluid first. It has certain lubricating properties and should (in combination with step 2) ensure that you won't have problems in the future.
Great! I'll be sure to change the fluid first. Thanks for your feedback, hopefully it works!
Yes, I'll warm up the car first by driving a bit. Anytime I drive it, if I turn off the engine and restart, the ASR light comes on again in 2-3 minutes.
You can tell if the pre-charge pump (under the master cylinder) is not working a couple of ways.
First, with the car cold, and a normally working pump, you will feel a small vibration a few seconds after you start up the car -- perhaps as you move it into Drive and then start moving. There is a small vibration through the brake pedal that you'll feel, and it lasts about half a second. If you are not feeling this vibration, then the system is not charging itself.
Second, you can literally hear the pre-charge pump running when you are inside the car, when idling, with the engine running. It is a faint hum, but you CAN hear it. And then if the pump is not working/charging, it will shut itself off after a couple of minutes, and then the ASR light will come on. You should be able to hear this pump running.
If the first (vibration) thing doesn't happen, then the second thing (pump running then timing itself out, then ASR lamp on) will happen.
Brake fluid change HOW-TO is here:
First, with the car cold, and a normally working pump, you will feel a small vibration a few seconds after you start up the car -- perhaps as you move it into Drive and then start moving. There is a small vibration through the brake pedal that you'll feel, and it lasts about half a second. If you are not feeling this vibration, then the system is not charging itself.
Second, you can literally hear the pre-charge pump running when you are inside the car, when idling, with the engine running. It is a faint hum, but you CAN hear it. And then if the pump is not working/charging, it will shut itself off after a couple of minutes, and then the ASR light will come on. You should be able to hear this pump running.
If the first (vibration) thing doesn't happen, then the second thing (pump running then timing itself out, then ASR lamp on) will happen.
Brake fluid change HOW-TO is here:
Thanks so much, Gerry!You can tell if the pre-charge pump (under the master cylinder) is not working a couple of ways.
First, with the car cold, and a normally working pump, you will feel a small vibration a few seconds after you start up the car -- perhaps as you move it into Drive and then start moving. There is a small vibration through the brake pedal that you'll feel, and it lasts about half a second. If you are not feeling this vibration, then the system is not charging itself.
Second, you can literally hear the pre-charge pump running when you are inside the car, when idling, with the engine running. It is a faint hum, but you CAN hear it. And then if the pump is not working/charging, it will shut itself off after a couple of minutes, and then the ASR light will come on. You should be able to hear this pump running.
If the first (vibration) thing doesn't happen, then the second thing (pump running then timing itself out, then ASR lamp on) will happen.
Brake fluid change HOW-TO is here:
I can't hear the pump when I start the car, but after 2:58, the ASR light comes on, and I feel a slight vibration in the car/brake pedal. I presume this is when the pump shuts off. This seems consistent with what you're describing. I'll be changing the brake fluid in the next couple of days. Fingers crossed.You can tell if the pre-charge pump (under the master cylinder) is not working a couple of ways.
First, with the car cold, and a normally working pump, you will feel a small vibration a few seconds after you start up the car -- perhaps as you move it into Drive and then start moving. There is a small vibration through the brake pedal that you'll feel, and it lasts about half a second. If you are not feeling this vibration, then the system is not charging itself.
Second, you can literally hear the pre-charge pump running when you are inside the car, when idling, with the engine running. It is a faint hum, but you CAN hear it. And then if the pump is not working/charging, it will shut itself off after a couple of minutes, and then the ASR light will come on. You should be able to hear this pump running.
If the first (vibration) thing doesn't happen, then the second thing (pump running then timing itself out, then ASR lamp on) will happen.
Brake fluid change HOW-TO is here:
I returned at 1:15 AM this morning from a trip to Austin TX, and parked my E500 in the middle of our driveway. Had to move it a few minutes ago so my wife could get her Lexus out of the garage. Just starting the car, putting it into reverse about 15-20 feet, backing up the car, I felt the "vibration" in the brake pedal that I mentioned while starting to back up. So it should happen literally within 10 seconds of starting the car up.
The vibration you describe is different. The vibration I am talking about always happens within 10 seconds of starting the car, no matter if you are moving forward or backward. If you don't have that, then your pre-charge pump isn't activating - likely it is stuck.
Hopefully others here have also observed this vibration just after startup.
The vibration you describe is different. The vibration I am talking about always happens within 10 seconds of starting the car, no matter if you are moving forward or backward. If you don't have that, then your pre-charge pump isn't activating - likely it is stuck.
Hopefully others here have also observed this vibration just after startup.
I will see if I feel the vibration immediately after startup. If I don't feel it at startup, but do feel a vibration at the 2:58 mark, as mentioned, doesn't that mean the pump is shutting off at that time? Therefore, it would have been activated before that time but not working. If this is the case, then I would use the procedure you mentioned previously to unstick it - change the fluid and floor the car while driving before the ASR light comes on. Correct?
The pump is shutting off at the 3 minute mark yes, if the ASR light is coming on. Vibration at the 3-min mark, or no.
The pump is set to begin running immediately at startup. Every startup. If it is stuck or burned out (inop), then yes it will try to run, and then shut itself off (time out) at the 3 minute mark, then throw the ASR lamp. Should do this same behavior every time you start the car if it is not working.
When my pump was stuck, I found that I could hear a "hum" during this 3-minute period when the pump was trying to run. With a properly operating pump, you don't hear this hum because it immediately pre-charges the system (hence the vibration that you feel within a few seconds of starting the car) and thus doesn't need to run any longer after pre-charging.
And yes, you want to try to activate the ASR (I found that near-flooring it while making a right turn, say at a stop sign) is enough to briefly activate the ASR and hopefully unstick the pump. Yes, try to do this before the 3-minute mark. Don't go crazy, use moderation as you don't want to harm anything with a cold engine. Perhaps drive the car, let the ASR light go on, warm it up a bit. Then go into a store or somewhere for 10-15 minutes, then do your ASR activation when leaving. That way the car is warmed up. You may need to try this activation several times in succession -- I mean drive cycles where the car is turned off, then restarted.
I have also found that with a properly operating system, it will stay pressurized for the rest of the day, and will only de-pressurize itself (and thus start the process all over again, evidenced by the vibration at the 5-10 second mark after starting) only after sitting for many hours, or overnight.
The pump is set to begin running immediately at startup. Every startup. If it is stuck or burned out (inop), then yes it will try to run, and then shut itself off (time out) at the 3 minute mark, then throw the ASR lamp. Should do this same behavior every time you start the car if it is not working.
When my pump was stuck, I found that I could hear a "hum" during this 3-minute period when the pump was trying to run. With a properly operating pump, you don't hear this hum because it immediately pre-charges the system (hence the vibration that you feel within a few seconds of starting the car) and thus doesn't need to run any longer after pre-charging.
And yes, you want to try to activate the ASR (I found that near-flooring it while making a right turn, say at a stop sign) is enough to briefly activate the ASR and hopefully unstick the pump. Yes, try to do this before the 3-minute mark. Don't go crazy, use moderation as you don't want to harm anything with a cold engine. Perhaps drive the car, let the ASR light go on, warm it up a bit. Then go into a store or somewhere for 10-15 minutes, then do your ASR activation when leaving. That way the car is warmed up. You may need to try this activation several times in succession -- I mean drive cycles where the car is turned off, then restarted.
I have also found that with a properly operating system, it will stay pressurized for the rest of the day, and will only de-pressurize itself (and thus start the process all over again, evidenced by the vibration at the 5-10 second mark after starting) only after sitting for many hours, or overnight.
Thanks for your feedback, but I'm a little confused now.
I do not hear the pump running/hum before the ASR light at 3 minutes and I do not feel the vibration at startup. I do feel the vibration at the time the ASR light comes on at 3 min.
Given this, is this still the same procedure I should follow, which if successful, results in clearing out the pump and enabling the vibration at startup and no ASR light? Or does my issue seem different than yours was? I hope I'm being clear. Thanks.
I don't know. I have explained everything I know and have experienced in multiple posts to the finest detail that I know how.
I guess I would enlist the expertise of @gsxr going forward on this, because everything that I know, literally, is in the many above posts that I have made on the topic.
Sorry, but I just have nothing more to say/add on the topic. It's all here.
I guess I would enlist the expertise of @gsxr going forward on this, because everything that I know, literally, is in the many above posts that I have made on the topic.
Sorry, but I just have nothing more to say/add on the topic. It's all here.
Wish I could help, but I only know the M119 ASR systems, where the ASR computer module has a plethora of specific fault codes to identify the failing component(s).
On the M104 in question, I'm not sure what to do besides what Gerry already outlined above.
On the M104 in question, I'm not sure what to do besides what Gerry already outlined above.
The difference between our cases seems to be that before you did the brake fluid flush, your pump was making a humming noise before the ASR light came on, and mine is not. I'm not sure how to interpret this.
