Hi! Guys, ASR lights up shortly after W124 500E is started, but there is no abnormality, and everything is normal when driving at high speed at a constant speed. The only anomaly is that when you step on the accelerator when turning on a mountain road, you can flick the tail and there will be no ASR anti-skid warning light flashing to indicate intervention, and it is judged that the ASR function has been turned off. The ASR light will go out after restarting, but will light up again soon after driving, and the problem will happen repeatedly. The photo shows the fault code of the computer. May I have any repair suggestions?
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500E ASR lights up
- Thread starter Kensu
- Start date
That code has to do with the pressure switch in your ASR hydraulic unit, meaning that it isn't charging correctly. The reason for this is that the car has probably not been driven enough, and the brake fluid in the ASR pump unit has not been changed and bled.
Look at this thread: ABS/ASR Pressure Switch? | Brakes, Suspension and Steering
And look at this thread: ASR Light | Electrical, CAN and Wiring
Also, see this post for some diagnostic information and explanation.
This post from the @gsxr has the MB factory diagnostic instructions attached as PDFs.
I believe that you can probably remedy this by changing the fluid (brakes and ASR pump), and driving the car to ensure the fluid is circulated. It may resolve itself once you do this.
If not, then you will have to replace the entire ASR hydraulic pump assembly, as the switch is integrated with the pump unit.
Look at this thread: ABS/ASR Pressure Switch? | Brakes, Suspension and Steering
And look at this thread: ASR Light | Electrical, CAN and Wiring
Also, see this post for some diagnostic information and explanation.
This post from the @gsxr has the MB factory diagnostic instructions attached as PDFs.
I believe that you can probably remedy this by changing the fluid (brakes and ASR pump), and driving the car to ensure the fluid is circulated. It may resolve itself once you do this.
If not, then you will have to replace the entire ASR hydraulic pump assembly, as the switch is integrated with the pump unit.
Your ASR system is disabled when the light is on.
As Gerry said, the fault is internal to the ASR/ABS unit located behind the driver headlight. The pressure switch is not a separate item. However, first check the relays on top of the ASR unit - I don't know if this could affect the switch, but it would be easy to check before swapping the ASR unit.
BTW, where did you get the custom aluminium radiator?
As Gerry said, the fault is internal to the ASR/ABS unit located behind the driver headlight. The pressure switch is not a separate item. However, first check the relays on top of the ASR unit - I don't know if this could affect the switch, but it would be easy to check before swapping the ASR unit.
BTW, where did you get the custom aluminium radiator?
Thank you very much for your suggestion. I will try to change the brake oil first.
Thank you very much for your suggestion. I come from Taiwan, the aluminium radiator hand made in Taiwan.Your ASR system is disabled when the light is on.
As Gerry said, the fault is internal to the ASR/ABS unit located behind the driver headlight. The pressure switch is not a separate item. However, first check the relays on top of the ASR unit - I don't know if this could affect the switch, but it would be easy to check before swapping the ASR unit.
BTW, where did you get the custom aluminium radiator?
If you have a spare ASR pump (and realistically know that it works), I would recommend replacing the whole pump.
However, you can replace the switch, as it is physically removable and replaceable.
My reason for suggesting this was because a few years ago, I went through a period of not driving my E500 at all, literally for a number of months. When I did drive it, I had an issue where the ASR light went on, and I did not feel the pulsating (pressure building) of the ABS/ASR pump a few seconds after starting up the car, and the ASR system was not working.
This was because the brake fluid was stagnant in the system, uncirculated. Using the system allows the fluid to circulate and the problem eventually corrected itself. Our member @Klink told me the likely reason for the situation, and encouraged me to drive the car, and that it would likely work itself out, which it did.
Gerry, do you have a photo of where this switch is located on the ASR assembly? I'm not familiar with it, as I've never had one apart...
See this post from @Klink in one of the threads I linked to:
Arguing with "fixed" is usually a bad idea, but FYI, bubble formation isn't very likely. If that's a pattern you've seen more than once, it is possible that your ASR pre-charge pump (the one under the master cylinder) is inoperative. They can form a corrosion deposit and/or get debris in the pump gears that seizes them up. This is a more frequent occurrence on garage queens, and/or cars that are driven so gently that the ASR pressure reservoir doesn't get depleted enough to require a "recharge". It is usually discovered as a lurking time bomb on the technician that actually attempts a proper brake fluid change on an older car, which of course includes draining and refilling the pressure reservoir fluid circuit. You can usually fix the pumps with some careful disassembly and gentle cleaning. If that condition happens again, holler back here.
Also note this. If your battery is a little flat, the low voltage condition just as, and upon starting can leave traction controls inoperative. The control units will usually, but not always store voltage related fault codes in those cases. operation is usually restored by a key cycle. I don't think that's what is happening with you because you stated that you heard the pump running, and during those low voltage events, they usually remain off until the key is cycled.
OK, so the threads linked above generally recommend pressure bleeding the brake system (including port SP) and driving the car, to see if the issue goes away. That would definitely be worth trying, especially if @Kensu has not flushed the brake fluid in the past 2-3 years.
Otherwise, it sounds like the threads are indicating the issue could be the pre-charge pump located below the master cylinder, not pressurizing the ASR and possibly causing the A7/3s1 "sensor" issue.
Otherwise, it sounds like the threads are indicating the issue could be the pre-charge pump located below the master cylinder, not pressurizing the ASR and possibly causing the A7/3s1 "sensor" issue.
The switch is attached to the outside of the pressure reservoir of the ASR pump.Gerry, do you have a photo of where this switch is located on the ASR assembly? I'm not familiar with it, as I've never had one apart...
I have also heard that the charging pump under the master cylinder can get "stuck" (due to non-use) ... and gently tapping it with a hammer can "unstick" it, along with subsequent use and a brake fluid change.
For @gsrx and others
The A7/3s1 switch is inside ASR hydraulic unit between main block and cover block. To replace it you'll need to open the cover (hex bolts on top visible also in the pic and brake pipe connectors) and the plastic wiring box on fender side.
No spare part exists. So the best way the get one is to remove it from another ASR unit. On the other hand it's only on/off pressure switch for brake fluid that may have similar component somewhere in industry or enough similar to be able modify.
The A7/3s1 switch is inside ASR hydraulic unit between main block and cover block. To replace it you'll need to open the cover (hex bolts on top visible also in the pic and brake pipe connectors) and the plastic wiring box on fender side.
No spare part exists. So the best way the get one is to remove it from another ASR unit. On the other hand it's only on/off pressure switch for brake fluid that may have similar component somewhere in industry or enough similar to be able modify.
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002 431 20 12 (aka Bosch 0 265 202 005) is the correct unit for E500E.
002 431 44 12 (aka Bosch 0 265 202 012) is used in S-models (W140), not sure if compatible to E500E.
Thanks for your reply!
