ABS problems

[sidneyhop]

I recently bought a 98 with 85,000 miles and it has ABS problems that Id like to get sorted out. While test driving it I noticed the light was on on the dash and when testing them they didnt engage when stopping suddenly. This appears to me to be a legitimate ABS problem and not just bad sensor. What generally causes the ABS system to fail? Where should I first start to trouble shoot to fix this problem? Any help would be greatly appreciated!

 

[99xlsdude]

If ABS lite on, regular brakes continue to operate normally but ABS is disabled. Check fluid level first.

Had same problem (99 XLS 4WD V6 OHV). Was rear speed sensor - located on top of rear axle housing (center of vehicle). This is most likely the cause. Part is less than $20at AutoZone ($35 at dealer).

I went to dealer and it cost around $170 -- $90 diagnosis, $35 part, and $45 labor. Should have just changed this part (w/new O-ring) myself and if it didn't work then go to dealer. It is held on by one bolt, has one electrical connector.

 

[sidneyhop]

Great! Thanks for the tip.

Stupid question but does the ABS have a separate fluid reservoir or just the reg brake fluid reservoir? I know the brake res is at the correct fluid level as I checked that before I bought the vehicle. If its the same then Ill swing by and get the rear sensor.

If indeed this is the problem and the ABS is fixed by switching out the sensor will the warning light automatically go out or will I have to reset it?

 

[99xlsdude]

Same reservoir.

Not sure about the light - maybe someone else can help with that. (dealer did my repair).

For CEL, disconnecting the negative battery terminal for 10 minutes or so resets the CE light. Probably the same for ABS.

 

[gijoecam]

If the sensor was the problem and you then replace it, the system function will be restored and the light will go out.

It's worth a shot... the sensor seems to be a problem about 1/4 of the time around here. It's about a $15 part, and is simple to replace.

The only way to accurately diagnose the problem is to pay a dealership (or independent shop with the proper diagnostic equipment to retrieve the ABS codes. (Hint: AutoZone won't be able to do it)

Good luck!

 

[sidneyhop]

thanks guys! Replaced the speed sensor for the ABS (important because when I first asked for the part they almost gave me the speed sensor that fits into the trany) and the light immediately went out when I turned on the engine. Tested the ABS system and everything works perfectly now.

 

[DeRocha]

thanks guys! Replaced the speed sensor for the ABS (important because when I first asked for the part they almost gave me the speed sensor that fits into the trany) and the light immediately went out when I turned on the engine. Tested the ABS system and everything works perfectly now.

How did the old speed sensor Look? Did it have gunk stuck to it? Every time you restart the engine the ABS system runs through a diagnostic check and will clear the ABS warning light if everything is good. If the system detects a problem while driving the ABS warning light will come on (which indicates ABS is completely disabled) until you shut the engine off and restart it (at which point it would run through its diagnostic check).

 

[sidneyhop]

How did the old speed sensor Look? Did it have gunk stuck to it? Every time you restart the engine the ABS system runs through a diagnostic check and will clear the ABS warning light if everything is good. If the system detects a problem while driving the ABS warning light will come on (which indicates ABS is completely disabled) until you shut the engine off and restart it (at which point it would run through its diagnostic check).

Yep...it had greyish gunky chunks on it. Thought about cleaning it off and re inserting it but figured prob best to just switch it out.

That brings up another question. Should the diff fluid be grey like that? Last time I did any rear end work I thought I remembered it being redish like tranny fluid. Hope its not grey from ground down metal from the gears!! I dont have any symptoms of rear end problems but maybe time for a flush.

 

[DeRocha]

Yep...it had greyish gunky chunks on it. Thought about cleaning it off and re inserting it but figured prob best to just switch it out.

That brings up another question. Should the diff fluid be grey like that? Last time I did any rear end work I thought I remembered it being redish like tranny fluid. Hope its not grey from ground down metal from the gears!! I dont have any symptoms of rear end problems but maybe time for a flush.

The sensor is magnetic and senses the highs and lows of the teeth on the ABS tone ring (installed on the Ring gear withing the diff). Over time metal particles from wear and tear can collect on the sensor effectively blinding it. When this occurs the sensor can no longer sense the highs and lows and reports and error to the ABS computer. The diff fluid should be slightly grey. All the gear oil I have used is dark yellowish in color. The grey could be from an additive or friction modifier, and I sure partly from bearing and or R&P wear.