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#1
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98 C280 odd ABS/ASR
Hi folks
Here's an oddity that's happened twice in the last few days: My BAS/ASR and ABS lights came on...after some brake pulsing (on a completely dry road) so I figure that's either a sensor or brake switch, no biggie But then inside 1 - 2 minutes the check engine comes on, which is odd. I put the OBD reader on it says there's a P0700 (transmission related) fault, which I clear. Later in the day the ABS lights go out, on their own. The next night the whole thing replays itself, a few brake pulses and then the BAS/ASR and ABS lights come on, 60 seconds later the check engine light returns... What would be the common problem that would activate both these seemingly unrelated warnings? Thanks |
#2
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Were the brakes pulsing when the pedal was pressed or just driving down the road not on the brakes?
If pulsing when pressed, I think a wheel speed sensor is having an issue. Sometimes metal filings, rust gets on the sensor / tone wheel making the computer think the wheel speed is lower than normal triggering the ABS. One way to zero into this is to add a set of lights to the ABS coils and see what one is actuating or even better use a 4 channel oscilloscope and watch the wheel speed sensors. It would be tempting to unplug any BAS sensors that are not related to ABS function and see if the problem continues. I just got a 99 C230 parts car that has 2 sensors on the brake booster ( diaphragm position and vacuum reading I think. ) and a small computer under the master cylinder. |
#3
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Hi and thx
When pressed. My real q is why would the CE light come on? |
#4
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I'm not sure, you need the Mercedes description of the code.
Also, Mercedes stacks grounds on a common bolt / stud. If the point corrodes, circuits start to seek ground from each other causing all sorts of odd behavior. I have a 97 E320 parts car that exhibits left fog light on , high beam indicator on , I message on the dash I can't recall and a trans that is in limp mode. Once, all of this went away at once the the trans shifted normally. I haven't looked very hard for the problem but I bet is is a common ground opening up |
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