ASR light

[aldedmon]

I’m trying to narrow down the issue with my ASR light coming on. I’ve done most of the usual checks and was hoping someone with technical expertise could solve my issue. I’ve discovered that the light comes on exactly 2:58 seconds after I start the car. I can just start it first thing in the morning or restart it at anytime . I can drive it or it be sitting still. Like clock work the light comes on in 2:58 secs. Any ideas? By the way the car still seems to have full function. It only rarely goes into limp home mode but that’s after the ASR light has been in for a while...

 

[gsxr]

What codes appear on the E-GAS and ASR modules? Do you have spares of either module that you can swap in for testing?

 

[aldedmon]

Have constructed a decoder (ring) . No spares either . I’m On the look out for reasonably priced ones that I can swapped to check


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[aldedmon]

Also, no CEL noted


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[gsxr]

Pick up a spare E-GAS and ASR module from a 400E / E420 with ASR. These are usually available at a reasonable price via eBay. The ASR module part number will be identical; the E-GAS will not be identical but it will work fine.

No CEL is expected; the CEL only shows emissions related faults (USA-only thing). CEL doesn't care if there is limp mode or not.

 

[gerryvz]

I just listed appropriate ASR and E-GAS modules for sale last night, here on the forum, that are applicable to the E500E. I'll be happy to make you a deal on both together, and you save a bit of shipping cost as well.

Cheers,
Gerry

 

[Efraim]

Does the ASR pressure pump run when starting engine and stops simultaneusly ASR light on?

https://www.500eboard.com/forums/showthread.php?t=11361&p=145064#post145064

 

[Klink]

That is probably due to the high-pressure pump being unable to pressurize the pressure reservoir. THAT condition is usually caused by an in operative primer pump. The primer pump is located below the master cylinder. They get stuck due to corrosion formation in the pump wheels, and/or simple lack of use. If you never drive the car aggressively, the pressure reservoir never get to drain down enough to require a recharge, then the day it does, or the day you change brake fluid and open the bleeder “SP” the system is unable to replenish itself. Sometimes, you can start the car reach down there with an appropriately shaped piece of wood, etc. and just smack the thing a few times and it may start to run.
If not, you can disassemble the pump end of it easily, remove any accumulated corrosion gently, make sure the wheels turn easily, and you are probably good to go. I’ve had excellent luck getting many of them to run again.

 

[emerydc8]

I’m trying to narrow down the issue with my ASR light coming on. I’ve done most of the usual checks and was hoping someone with technical expertise could solve my issue. I’ve discovered that the light comes on exactly 2:58 seconds after I start the car. I can just start it first thing in the morning or restart it at anytime . I can drive it or it be sitting still. Like clock work the light comes on in 2:58 secs. Any ideas? By the way the car still seems to have full function. It only rarely goes into limp home mode but that’s after the ASR light has been in for a while...

Had the exact thing happen to me. You could hear the pump stop a few minutes after starting the car, like clockwork, and the ASR light would illuminate. Over a period of a few years, the pump completely stopped running and now causes the ASR light to illuminate constantly. I pulled the bulb out and looked at it as my own auto-antislip-delete feature. I might take Klink's advice and tear into it someday but it's pretty low on my to-do list.

 

[Klink]

Had the exact thing happen to me. You could hear the pump stop a few minutes after starting the car, like clockwork, and the ASR light would illuminate. Over a period of a few years, the pump completely stopped running and now causes the ASR light to illuminate constantly. I pulled the bulb out and looked at it as my own auto-antislip-delete feature. I might take Klink's advice and tear into it someday but it's pretty low on my to-do list.

If you overworked and killed the HP pump, you may have killed your ABS too...

 

[gerryvz]

Two weekends ago, I drove from my home up to the Wilmington, DE area to survey a yacht that we are looking at purchasing. It was about 1.5 hours up there, and 1.5 hours back. The E500 operated perfectly the entire way, at all kinds of speeds on rural Maryland Eastern Shore and Delaware highways.

On Sunday, I drove from my home up to Gettysburg, PA to visit a museum. Again, a round trip of almost exactly 200 miles, and about 1.5 hours' drive each way on mostly Maryland freeways and highways, and a little bit on Pennsylvania roads.

Getting ready to head out to Gettysburg, I pulled my E500 out of the garage onto the driveway for a couple of minutes to let it idle, and gather my phone, wallet and a winter coat to throw in the rear seat. When I came back out to the car after a few minutes, the ASR light was on - no ABS light or CEL. I turned the car off and then back on again, and the ASR light was extinguished, but I could hear the ASR pump loudly running. After about 3 minutes, it abruptly shut off, and the ASR lamp lit up again.

Knowing what this was (the ASR system failing to develop proper pressure), I went ahead and drove the car on the trip, with zero issues. There was no limp-home mode, Check Engine light, or other issue. Just the lit ASR light.

It is most likely that the pre-charge pump for the ASR is inoperative, due to being "stuck".

Pulling codes from the car showed a Code #21 in the ASR system, as noted by others.

I am going to do a diagnosis on this, with several steps:

1) I am going to gently tap the main ASR pump, and also the pre-charge pump (located under the brake master cylinder), to see if a "stuck" pre-charge pump is the culprit;

2) I am going to do a "quick change" of the brake fluid in the main ASR pump, through the "SP" bleeder valve, to see if old/bad brake fluid is the culprit;

3) I am going to remove the pre-charge pump, disassemble it, and clean it. I believe this is the step that will actually successfully remedy the issue at hand.

When I do step 3, I will create a HOW-TO on this procedure. It is obvious from the number of threads on the forum, that this issue with the ASR system not properly charging upon engine startup, is more than an occasional/rare issue.

Cheers,
Gerry

 

[gerryvz]

Little update on this. I drove the car about 35 miles today -- first time since parking it after the trip up to Gettysburg.

When I started the car, I pulled it out of the garage into the driveway. Using a hammer and a long, thick metal screwdriver, I did some tapping on both the main ABS/ASR pump, and the pre-charge pump underneath the master cylinder.

Neither action did any good -- the pump ran and they cycled off, with the ASR lamp turning on.

Got to my destination, and parked and did my errand. In the parking lot I was in, there was a Shell station, so I decided to fill up my gas tank, as I was down to just over 1/4 tank. The pump ran during the time I crossed the parking lot, and then I shut it off when I pulled up to the gas pump.

After filling up, I started the car and headed the 15-17 miles back home. The pump did not run after doing the normal immediate cycle thing, and the ASR light never came on the entire trip home. Near my house, I did a couple of "quick starts" to activate the ASR system (light up the triangle in the speedo) to help circulate some of the fluid in the pre-charge pump, though this is not going to be much of a long-term fix.

Next stop will be to do a "quick bleed" of the ASR/ABS pump through the SP valve; hopefully the increased lubricity of some new brake fluid will free things up in the pre-charge pump.

However, unfortunately, I think that a full removal, disassembly, cleaning and then re-assembly/installation of the pre-charge pump, and then a full brake bleed, will be in order to remedy what is looking to be a gummed-up interior of the pre-charge pump gears.

This will entail a brand-new HOW-TO, which I know will be of use to some folks here in the future who also have the ASR light come on and the main pump cycling.

The main thing with this is that the pre-charge pump is a SERIOUS PITA to get at due to its location underneath the brake master cylinder. However, I believe that there is JUST enough room to get it out. It is held in a metal bracket, and has two brake-line connections, and an electrical connection, so not that complex in terms of connections. However, given the two brake line connections, plenty of rags and padding will be required UNDERNEATH the pre-charge pump to catch and soak up any brake fluid that is spilled when removing the connections. So, I think a HOW-TO will be coming in the near future on this.

Checking my records, my brake fluid was last changed in April, 2016, which was nearly 11,000 miles ago. So it is in STRONG need of replacement. Sigh.

 

[gerryvz]

On last week's parts order, I threw on two meters of the braided rubber brake hose that goes to the charging pump from the brake master cylinder. It's a short hose (given physical proximity), but it's good to have some extra in case it is needed.

The part number for this hose is 009 997 38 82, and it is sold by the meter.

This is all part of the preparation for the removal and cleaning of the ASR charging pump.

Diagram per ISPPI is below, showing this hose (#68) and the charging pump (#50).

 

[gerryvz]

Here are a couple of views of the ASR "pre-charge" pump -- located directly under the master brake cylinder.

 

[emerydc8]

However, unfortunately, I think that a full removal, disassembly, cleaning and then re-assembly/installation of the pre-charge pump, and then a full brake bleed, will be in order to remedy what is looking to be a gummed-up interior of the pre-charge pump gears.

This will entail a brand-new HOW-TO, which I know will be of use to some folks here in the future who also have the ASR light come on and the main pump cycling.

Good! We'll wait for you on this! Too many things to screw up.

In the mean time, I'll order the hose.

 

[emerydc8]

.

The main thing with this is that the pre-charge pump is a SERIOUS PITA to get at due to its location underneath the brake master cylinder. However, I believe that there is JUST enough room to get it out. It is held in a metal bracket, and has two brake-line connections, and an electrical connection, so not that complex in terms of connections.

Do you think the master cylinder might have to come out to get to it? If so, I see a seal in your diagram (part #11) that might be good to have on hand.

Sealing Ring - 1954-2025 Mercedes-Benz (001-431-33-60) | Get Mercedes Parts

1954-2025 Mercedes-Benz Sealing Ring 001-431-33-60

www.getmercedesparts.com

[EDIT] Now I remember why I was avoiding this charge pump issue for years, aside from not really wanting ASR anyway. I had a stripped ASR bleeder valve (pic) and I wasn't sure if it might break off in the ASR module as I attempted to remove it with a bolt extractor. I just hit the bleeder valve with PB-Blaster and ordered a new valve, but I'm not sure it's the right part. I couldn't find the ASR bleeder valve in the EPC, so I assumed it was the same as for the brake calipers (000 421 27 65). Anyone know?

 

[gsxr]

The ASR bleeder has an 11mm hex, the calipers have a 9mm hex. But I don't know if the thread & length are the same or not.

Anyone have a loose ASR pump that could remove the bleeder screw and at least check length / diameter? I don't have a loose one.

 

[gerryvz]

I think I have a spare pump in my basement - I'll try to put my hands on it and measure.

@emerydc8 -- in that pictured situation, I would just take a pair of Vise-Grips and clamp them on, to loosen that bleeder screw. I would not mess with wrenches/sockets and the like. The only thing you can really do with that is to use a pair of Vise-Grips on it. And look perhaps for a spare bleeder valve on an ASR car in the wrecking yards (or just grab the entire pump). They are commonly found on ASR-equipped W124 models, as well as W140s of the 1992-1995 era.

 

[gerryvz]

Do you think the master cylinder might have to come out to get to it? If so, I see a seal in your diagram (part #11) that might be good to have on hand.

It would certainly make things easier to remove the master cylinder, and I have seen some instructions that say to do this. In the factory service manual (42-0818), for the W124 it doesn't explicitly say to do this, but for the W140, it very definitely DOES say to remove the master cylinder.

I am going to see if I am able to do this without removing the master cylinder, but I am not very hopeful that I will be able to do this. There are two connections (the rubber braided brake line, and the hard metal brake line that goes directly to the ASR/ABS pump), and the pre-charge pump is held into its bracket by what looks to be a 5 or 6mm hex bolt, and a 9mm or 10mm nut on the other side. Particularly this nut, is going to require some wobbly sockets and extensions to access, as it is very far under the master cylinder.

 

[emerydc8]

It would certainly make things easier to remove the master cylinder, and I have seen some instructions that say to do this. In the factory service manual (42-0818), for the W124 it doesn't explicitly say to do this, but for the W140, it very definitely DOES say to remove the master cylinder.

I am going to see if I am able to do this without removing the master cylinder, but I am not very hopeful that I will be able to do this. There are two connections (the rubber braided brake line, and the hard metal brake line that goes directly to the ASR/ABS pump), and the pre-charge pump is held into its bracket by what looks to be a 5 or 6mm hex bolt, and a 9mm or 10mm nut on the other side. Particularly this nut, is going to require some wobbly sockets and extensions to access, as it is very far under the master cylinder.

My concern was that the bleeder valve would break off in there and create a mess. That's why I wanted to have another valve on standby. I haven't seen many 90s-vintage Mercedes in the wrecking yard here in Arizona.

I looked at those bolts holding the charge pump on. You're right--it's going to take some wobbly sockets and extension for sure. And with my luck, the connector for the hard line going to the pump will strip. I hit them all with PB-Blaster last night. Will wait for your HOW-TO whenever you get to it.

 

[gerryvz]

My concern was that the bleeder valve would break off in there and create a mess. That's why I wanted to have another valve on standby. I haven't seen many 90s-vintage Mercedes in the wrecking yard here in Arizona.

I looked at those bolts holding the charge pump on. You're right--it's going to take some wobbly sockets and extension for sure. And with my luck, the connector for the hard line going to the pump will strip. I hit them all with PB-Blaster last night. Will wait for your HOW-TO whenever you get to it.

I'm off to Disney World for this coming week, but I also have the following week (week of 21-Feb) off -- likely I will do the job during that week. Looking forward to two full weeks off of work !!

 

[SL500_WPB]

I'm off to Disney World for this coming week, but I also have the following week (week of 21-Feb) off -- likely I will do the job during that week. Looking forward to two full weeks off of work !!

Bumping an old thread but wanted to know if you ever got around to pulling off and cleaning the ASR precharge pump? I've got a 1994 SL500 with the same issue and trying to gather as much info as I can before diving into the job. Same symptoms, same issue, same pump location.

 

[gerryvz]

Bumping an old thread but wanted to know if you ever got around to pulling off and cleaning the ASR precharge pump? I've got a 1994 SL500 with the same issue and trying to gather as much info as I can before diving into the job. Same symptoms, same issue, same pump location.

I didn't, because the condition cleared itself up. But I need to. I purchased new hose to attach to the pump from MB.

 

[GRAEME JOHNSON]

I have a 1990 R129 SL that spends a lot of time standing and I have this pre charge pump issue as well
so this would be of great interest to me as well ! . I know this is 500e board and not R129 board but I
think this how to and the correct bleading procedure would help a lot of members
Graeme Johnson

 

[SL500_WPB]

I have a 1990 R129 SL that spends a lot of time standing and I have this pre charge pump issue as well
so this would be of great interest to me as well ! . I know this is 500e board and not R129 board but I
think this how to and the correct bleading procedure would help a lot of members
Graeme Johnson

Surprised there isn't one out there yet between this site and BenzWorld. Luckily there's no limp home mode, but it does bother me to have the light on.

Anyway.. thinking I'm going to approach the problem in this sequence:

1. Give a couple love taps to the main ABS/ASR Unit and the Precharge Pump. Probably won't do anything but can't hurt.
2. Try purging out some fluid from the ABS/ASR Unit using the "SP" bleeder valve. Maybe there's just some air in there causing the issue?
3. Full brake fluid flush including the ABS Unit (car was purchased recently, can't find a record of the last time it was changed). Good instructions on Post #9 here.
4. Take off the precharge pump, give it a good clean, reinstall. Few pics of the process were posted here.

 

[French02chris]

Funny enough, my ASR light came up ( as the same time as my brake pads light...LOL....totally coincidence)

I pulled the code and got 21 on pin 6 ( ABS/ASR hydraulic unit, pressure switch (A7/3s1), charge )

Does anyone know the part number of the ASR charge pump ( I am currently visiting my grandmother at the hospital, and don't have hours to look thru google!!! so thank you for your help)

 

[gsxr]

That code is for the pressure switch (A7/3s1), not the pump. I don't think the switch can be replaced, it's internal to the ASR unit.

 

[French02chris]

That code is for the pressure switch (A7/3s1), not the pump. I don't think the switch can be replaced, it's internal to the ASR unit.

View attachment 151786 View attachment 151787

so you don't think that it is related to the "pre charge" pump.....I was wondering if it just needed to be cleaned or purge?
anyhow. any idea on the part number of that "pre charge" pump ( located under the master brake cylinder) ??

 

[gsxr]

so you don't think that it is related to the "pre charge" pump.....I was wondering if it just needed to be cleaned or purge?

I don't think so. The precharge pump (M15) has a separate fault code, #24, and you said you had code 21.

anyhow. any idea on the part number of that "pre charge" pump ( located under the master brake cylinder) ??

Sure, the precharge pump is p/n A0004300432, only $1700 MSRP if you want to give it a try!

 

[French02chris]

I don't think so. The precharge pump (M15) has a separate fault code, #24, and you said you had code 21.



Sure, the precharge pump is p/n A0004300432, only $1700 MSRP if you want to give it a try!

thanks.....so I will be looking to buy an used (working) ABS/ASR pump on Ebay (0024312012)....lol

 

[gsxr]

0024312012 is for 6-cylinder 124's... what year/model do you have?

 

[French02chris]

0024312012 is for 6-cylinder 124's... what year/model do you have?

nope...this is definitely what I have in my car.....for at least the last 6 years that i have owned it...LOL

 

[French02chris]

0024312012 is for 6-cylinder 124's... what year/model do you have?

1993 400E with ASR

 

[SL500_WPB]

so you don't think that it is related to the "pre charge" pump.....I was wondering if it just needed to be cleaned or purge?
anyhow. any idea on the part number of that "pre charge" pump ( located under the master brake cylinder) ??

What symptoms are you having relating to the ASR light?

 

[French02chris]

What symptoms are you having relating to the ASR light?

none...only the light is on.
so i pulled the code and got code 21 on pin 6

 

[SL500_WPB]

Hm, i'd probably agree with gsxr then... if you aren't experiencing symptoms described in posts #1, 7, and 8 then it seems unlikely to be related the charging pump.

 

[French02chris]

Hm, i'd probably agree with gsxr then... if you aren't experiencing symptoms described in posts #1, 7, and 8 then it seems unlikely to be related the charging pump.

well....I have no driving symptoms...However, light comes on about 2 minutes or so after starting the car.
I can hear the ABS unit turning off when I start the car, and then turns off about 2 minutes ( and light comes on).
So basically the same as post 1 and 7 and 8

 

[gsxr]

1993 400E with ASR

Oh weird. Apparently the 034/036 were produced with the 002-431-20-12 module, but the EPC does not show that supercession... it only shows 002-431-45-12!

Meanwhile, on some other models, it does show #20 superceding to #45.

Only ~$12k if you want a new one.

Brake Pressure Regulator 002-431-45-12-38 | MB OEM Parts

002-431-45-12-38 - Brake Pressure Regulator

www.mboemparts.com

 

[French02chris]

Oh weird. Apparently the 034/036 were produced with the 002-431-20-12 module, but the EPC does not show that supercession... it only shows 002-431-45-12!

Meanwhile, on some other models, it does show #20 superceding to #45.

Only ~$12k if you want a new one.

Brake Pressure Regulator 002-431-45-12-38 | MB OEM Parts

002-431-45-12-38 - Brake Pressure Regulator

www.mboemparts.com

View attachment 151798 View attachment 151797

I already bought an used one on Ebay....

 

[French02chris]

I didn't, because the condition cleared itself up. But I need to. I purchased new hose to attach to the pump from MB.

Ok...so i have a question or two
my ASR light has been on for a week now .( code 21 on Pin 6)
I can hear the ABS unit working, and when it gets quiet ( about 2 or 3 minutes after the engine is running), the ASR light comes ON.
ABS light in NOT on.....driving is the same ( no loss of power)

Questions :
- Should I try to clean the charge pump ?
-Should I try to replace the ASR computer/unit?
-Should I try to replace the 2 relays on the ABS pump?
-Should i let it be?? ( how long was your issue before it cleared by "itself"?)

Thank you

 

[gsxr]

Ok...so i have a question or two
my ASR light has been on for a week now .( code 21 on Pin 6)
I can hear the ABS unit working, and when it gets quiet ( about 2 or 3 minutes after the engine is running), the ASR light comes ON.
ABS light in NOT on.....driving is the same ( no loss of power)

See post 9 and 10 above.

Questions :
- Should I try to clean the charge pump ?
-Should I try to replace the ASR computer/unit?
-Should I try to replace the 2 relays on the ABS pump?
-Should i let it be?? ( how long was your issue before it cleared by "itself"?)

Why not install the used unit from eBay?

 

[French02chris]

Why not install the used unit from eBay?

because for that, I would have to bring it to the mechanic...
For the other things, I just a 2 minutes thing ( replacing relays, replacing ASR computer...etc..etc)

 

[French02chris]

Well....
Actually had to drive the car to the mechanic today..
I noticed that the brake fluid reservoir was under minimum... So I added some, and it started to leak under the front left wheel.. It stopped leaking when it was under the minimum line... Drove & braked fine all the way to the mechanic... When I arrived at the mechanic, the brake fluid was still at the same (low) level..

 

[gsxr]

I noticed that the brake fluid reservoir was under minimum... So I added some, and it started to leak under the front left wheel.. It stopped leaking when it was under the minimum line... Drove & braked fine all the way to the mechanic... When I arrived at the mechanic, the brake fluid was still at the same (low) level..

That isn't good. Pull the driver fender liner out and see what's leaking. Could be a rotted line between the ASR pump and the accumulator located in the driver fender. You must fix this first... also might be the root cause of your code 21, but I'm not certain. See post #6 here.

 

[French02chris]

That isn't good. Pull the driver fender liner out and see what's leaking. Could be a rotted line between the ASR pump and the accumulator located in the driver fender. You must fix this first... also might be the root cause of your code 21, but I'm not certain. See post #6 here.

As I wrote.. I dropped the car at the mechanic.. Will know in a day or so

 

[French02chris]

That isn't good. Pull the driver fender liner out and see what's leaking. Could be a rotted line between the ASR pump and the accumulator located in the driver fender. You must fix this first... also might be the root cause of your code 21, but I'm not certain. See post #6 here.

I actually told them to look at the accumulator

 

[gsxr]

AH, got it, didn't realize it was there for an overnight stay.

Let us know what they find out!

 

[French02chris]

AH, got it, didn't realize it was there for an overnight stay.

Let us know what they find out!

it's overnight stay because of family health issues ( i can't stay at the mechanic all day)....

 

[Efraim]

@French02chris, perhaps these will help you:
500E - ASR lights up | Electrical, CAN and Wiring
What does one make of these codes? | De-Coding

 

[French02chris]

AH, got it, didn't realize it was there for an overnight stay.

Let us know what they find out!

Got some news from the mechanic....
The accumulator lines under the wheel well are completely rusted and leaking!!!! so , they have to build a line line...and get an used accumulator with bracket ( via Ebay...)
SO, it will probably take an extra week...
the leaking line is probably why the precharge pump could not charge the ASR pump!!!!