1992 maxima ABS low speed actuation

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  #1  
Old 09-14-05, 09:38 PM
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1992 maxima ABS low speed actuation

Hi. Happy to be a member of this group.

I'll be starting to diagnose a problem where the ABS always actuates when almost stopped. Braking system is otherwise OK except for slight rotor warpage. Any hints would be appreciated.

Thanks.
 
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  #2  
Old 09-15-05, 05:51 PM
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I'm not much of a Nissan tech, but it sounds to me like you have a wheel speed sensor dropping to zero before the others, which inturn is enabling the ABS. The way we diagnose this on the GM vehicles, is to connect a scan tool and road test the vehicle while monitoring the ABS wheel speed data on the scan tool, while coming to a stop. More than likely, you will need to do the same; the dealer has the scan tool and may charge you 0.5 hours at the most for the diagnosis.
 
  #3  
Old 09-15-05, 06:05 PM
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Re: Re: Nissan ABS excessive actuation

Dear Mr Dummas:

Thanks for your reply. I had come to the same conclusion concerning sensor dropout, which may be due to increased gap between a sensor and the slotted ring which it reads. It could be due to corrosion of the slotted ring. The service manual does not state if the sensor is a magnetically biased pickup or a modulated carrier type, but excessive gap for the former type sounds like a plausible cause.

Being involved in electronics work, I presume this can be checked by spinning each wheel manually while observing the sensor waveform with an oscilloscope. Please let me know if you have any comments about this approach. I would rather undertake the repair myself.

Take care.

Bernie Katz
 
  #4  
Old 09-15-05, 06:50 PM
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I'm not too familiar with the wheel speed sensors on the Nissan's, but GM's are integral to the wheel bearing. If in fact your's has a reluctor ring and a separate pick-up, I would first do a visual inspection and clean the tip of the pick-up off. After the clean up, go drive it and see what happens. As far as checking the AC voltage while spinning the wheel, that is an important step in diagnosing wheel speed sensors. I always use a DVOM myself to measure the AC voltage, but I'm sure you can use an oscilloscope with good results as well.
 
  #5  
Old 09-15-05, 07:05 PM
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Re: Re: Re: Nissan ABS excessive actuation

Dear Mr. Dummas:

Thanks again for the reply. I'll take a look at the sensor tips. Nissan also uses reluctor rings which are part of the wheel hub assembly, as you state GM does.

Since the problem began suddenly, I'm beginning to think a sensor might have come loose to an extent. Since the problem only happens just before stopping, there must be enough AC voltage induced in the sensor at higher speeds to keep the ABS controller satisfied that lockup has not occured. So, increased sensor gap, corrosion (same effect) or magnetic (?) junk on the sensor face may be the reason. This weekend will tell.

Take care, and the help is much appreciated.

Bernie Katz
 
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