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Old 11-01-2017, 02:18 PM
dlicheri dlicheri is offline
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Default Mercedes 190D 2.5 ABS constantly light on

The ABS light on my 1992 mercedes 190D stays constantly on from when I turn the key. I start the car normally and light never goes out.

Everything seems to work correctly, however, I have not had a chance or opportunity to test the ABS system. I have replaced the following :

1. OVP relay
2. ABS ECU

I have cleaned terminals on relays located on ABC pump. Battery is fine and charges correctly. I have measured voltage while alternator is running and it is 14.2 volts.

I have read through the various forums and infer from some of the issues that have been reported, that if the light never goes off it can only be the ECU, OVP relay or relays that are on pump.

Does anyone have any info on how the system works and what phases it goes through on power up to full operation?

thanks in advance ...
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Old 11-01-2017, 05:59 PM
bembo449 bembo449 is offline
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going to be an ABS sensor on the hub surely ? or a reluctor ring ( if they had them )
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Old 11-01-2017, 07:24 PM
umblecumbuz umblecumbuz is offline
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Here's a strange thing. Apart from reading fault codes to help eliminate your ABS light, this might just help:

My ABS light would not clear, no matter what I tried. My scanner showed other faults which I cleared, and the only one that kept recurring - apart from the persistent ABS light - was a gearbox code. The gearbox fault was a spin-off from the ABS system, so that didn't concern me too much.

But, to get to the point, in desperation I unplugged the Maf while the engine was running and the ABS light vanished. I reconnected the Maf, cleared the gearbox code, and all has been well since.

Don't ask me why this fixed the fault, because I don't understand it. I pass this little gem on in case it helps someone else.

Umble
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Old 11-01-2017, 08:03 PM
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Cole@MBS Cole@MBS is offline
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Pull the RPM sensors of the hubs and make sure there not filled with swafe, seen that before.......
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Old 11-01-2017, 11:23 PM
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The abs light should go out when the car is started. It does a self check at 3mph, only then will it trigger a sensor fault. If it stays on when the engine is started, you need to get it on an Bosch abs tester.
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Old 12-01-2017, 07:01 AM
dlicheri dlicheri is offline
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Quote:
Originally Posted by star View Post
The abs light should go out when the car is started. It does a self check at 3mph, only then will it trigger a sensor fault. If it stays on when the engine is started, you need to get it on an Bosch abs tester.
I was told that was the case, abs test happens when wheel start to spin. If light remains on it is something else. Doesanyoneknow what sort of tests it goes through on power up ?

Is there a abs manual available anywhere? What would be good is some sort of diagram showing you how it all fits together. Is there anything else I can try ?

Finally, I live in southgat north London. Is there a borsch abs tester in my area?

Thanks in advance.
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Old 12-01-2017, 08:52 AM
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Check the relays under cover on pump. We have tester but there might be someone closer.
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Old 12-01-2017, 10:03 AM
dlicheri dlicheri is offline
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If the speed sensors are open or short circuit / disconnected would that cause abs light to stay on permanently?

thx in advance ...
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Old 12-01-2017, 12:52 PM
dlicheri dlicheri is offline
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I have now tested the following :

1. OVP relay (metered at pins and tried with power to solenoid)
2. ABS ECU (tried replacement)
3. metered speed sensors and they show a resistance of 1K Ohm
4. tested relays on ABS pump (as in 1)

Puzzled !
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Old 12-01-2017, 02:41 PM
umblecumbuz umblecumbuz is offline
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Looks like you didn't get live readings from the speed sensors.
Doing this would certainly help to eliminate them as a possible cause.

Umble
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