ABS coming on all the time

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brickbox
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ABS coming on all the time

Postby brickbox » Tue Jul 26, 2022 9:32 pm

I’m having this issue now for the past 2 drive cycles where the abs actuator is constantly cycling irrespective of what speeds I’m driving - incidentally I didn’t drive past 50mph on both drives. So I’m not sure what it would do at highway speeds. Any time I hit the brakes it feels like ABS is kicking in, which is disconcerting.

I noticed over the past month I would get abs to actuate the first time I hit the brakes, but now it’s all the time even after I’ve driven 20-25 mins with multiple brake actuations. I could be going 45mph and tap on the brakes, abs gets activated. This is all in clear weather conditions. No ABS light on the dash. Turning off VSC doesn’t result in any difference. Reservoir is just below the max line. Tires are all set to the same pressure +/- 1 psi.

How do I trouble shoot this issue?? Any help would be greatly appreciated.


grm3
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Re: ABS coming on all the time

Postby grm3 » Wed Jul 27, 2022 7:06 am

I recall having a similar problem a while back. Looking at my old post, it seems to have resolved itself before I was able to get it to my mechanic.
topic12091.html#p72271

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VStar650CL
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Re: ABS coming on all the time

Postby VStar650CL » Wed Jul 27, 2022 7:06 am

The ABS should have codes in it. Could be a wheel sensor, but could also be the Steering Angle Sensor (SAS), they're a frequent-failure item on R51's. If that is the issue, check prices on a whole combination switch instead of just the sensor. The price for those sensors alone is semi-insane and a whole switch assembly is usually cheaper. If you don't have an ABS-capable scanner, the ones at the parts stores are almost always ABS-capable.

TooMuchControl
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Re: ABS coming on all the time

Postby TooMuchControl » Wed Jul 27, 2022 4:24 pm

is it anything like what this Nissan had a problem with?

Nissan Pathfinder: Traction Control Kicks On When Turning A Corner

https://www.youtube.com/watch?v=Hc8X7eE ... oRepairLLC

If not, then wheel sensor is my bet on this.
Scan tool hooked up while driving will determine which wheel is "slower/faster" than the others.

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VStar650CL
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Re: ABS coming on all the time

Postby VStar650CL » Wed Jul 27, 2022 8:40 pm

That's funny as hell. I fixed one exactly like that some years back. What the guy in the vid didn't catch is that the white ring is an insert, held in by pawls on the OE part. Harry Usedcar probably lost it on the floor of the vehicle and either didn't realize it or was too lazy to wonder what it was and take the combo switch off again. On the one I did, the lady's son did the work and the engagement ring turned up underneath the driver's seat.
:lol:

brickbox
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Re: ABS coming on all the time

Postby brickbox » Thu Jul 28, 2022 5:01 am

TooMuchControl wrote:
Wed Jul 27, 2022 4:24 pm
is it anything like what this Nissan had a problem with?

Nissan Pathfinder: Traction Control Kicks On When Turning A Corner

https://www.youtube.com/watch?v=Hc8X7eE ... oRepairLLC

If not, then wheel sensor is my bet on this.
Scan tool hooked up while driving will determine which wheel is "slower/faster" than the others.

Thank you sharing that video. Looks like his vehicle only did it while turning. I don’t ever get any lights on the dash to come on (well my CEL is on for P0442) - but brake, VSC, slip lights are all off. I check yesterday, I can get the abs to actuate whether I’m driving straight or making a turn. In fact, I was on a back road going about 60mph and had to slow down because someone popped in front of me, i could feel ABS kick on then too.

Is there a recommended scan tool that’s not obscenely expensive which can be used for checking the wheel speed sensors/ABS codes? My current basic OBD 2 reader doesn’t have that capability

brickbox
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Re: ABS coming on all the time

Postby brickbox » Thu Jul 28, 2022 5:06 am

VStar650CL wrote:
Wed Jul 27, 2022 7:06 am
The ABS should have codes in it. Could be a wheel sensor, but could also be the Steering Angle Sensor (SAS), they're a frequent-failure item on R51's. If that is the issue, check prices on a whole combination switch instead of just the sensor. The price for those sensors alone is semi-insane and a whole switch assembly is usually cheaper. If you don't have an ABS-capable scanner, the ones at the parts stores are almost always ABS-capable.
Would the ABS have codes stored even if the slip, brake and/or VSC lights never came on? Would you have a a reasonably priced recommendation for an ABS capable scanner?
I’ll start checking out the price for the switch assembly.

On a separate note, how hard is it to replace wheel speed sensors if that’s what the problem ends up being? Should these be Nissan OEM or aftermarket Beck Arnley from RockAuto will do?

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VStar650CL
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Re: ABS coming on all the time

Postby VStar650CL » Thu Jul 28, 2022 5:35 am

brickbox wrote:
Thu Jul 28, 2022 5:06 am
Would the ABS have codes stored even if the slip, brake and/or VSC lights never came on? Would you have a a reasonably priced recommendation for an ABS capable scanner?
If the SAS is "falsing" a few milliseconds at a time then there may not be any codes in it, because the ABS doesn't realize anything is wrong. That's actually pretty common when SAS's first begin to fail. Less commonly, a miscalibrated or failing G-sensor could cause similar issues with no ABS lights. On the other hand, Bosch ABS's are very picky about wheel sensors and usually a single missed-tooth on a reluctor will throw a code and turn on the ABS lamp. So anything is possible, but a wheel sensor would be at the bottom of my checklist.
brickbox wrote:
Thu Jul 28, 2022 5:06 am
On a separate note, how hard is it to replace wheel speed sensors if that’s what the problem ends up being? Should these be Nissan OEM or aftermarket Beck Arnley from RockAuto will do?
Aftermarket sensors generally do fine. Make sure you check the wheel bearings and clear any magnetic trash off the reluctor before you summarily replace it. Things can be wrong that aren't the sensor's fault.

brickbox
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Re: ABS coming on all the time

Postby brickbox » Thu Jul 28, 2022 8:21 am

VStar650CL wrote:
Thu Jul 28, 2022 5:35 am
If the SAS is "falsing" a few milliseconds at a time then there may not be any codes in it, because the ABS doesn't realize anything is wrong. That's actually pretty common when SAS's first begin to fail. Less commonly, a miscalibrated or failing G-sensor could cause similar issues with no ABS lights. On the other hand, Bosch ABS's are very picky about wheel sensors and usually a single missed-tooth on a reluctor will throw a code and turn on the ABS lamp. So anything is possible, but a wheel sensor would be at the bottom of my checklist.
Gotcha, thanks for laying that out logically. Any advise on how to check for the SAS outside of taking it to a shop with a fancy scanner?
I’ve had a failing ABS wheel speed sensor on a previous vehicle, but that one would only occur when I was at really low speeds (like 20mph or so). This one has me baffled.

Is driving the Pathy like this acceptable? Or should I pull the ABS fuse in the interim as I go about trouble shooting?

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VStar650CL
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Re: ABS coming on all the time

Postby VStar650CL » Thu Jul 28, 2022 8:44 am

brickbox wrote:
Thu Jul 28, 2022 8:21 am
Gotcha, thanks for laying that out logically. Any advise on how to check for the SAS outside of taking it to a shop with a fancy scanner?
I’ve had a failing ABS wheel speed sensor on a previous vehicle, but that one would only occur when I was at really low speeds (like 20mph or so). This one has me baffled.
You're most welcome. With a falsing SAS, sometimes even a scanner won't catch it. I had a Juke some years back that every couple of miles would tap the right rear actuator for no apparent reason. Just one tap, then it was fine again. Graphing the wheel sensors and SAS told us nothing, The only way we caught it was to put the C3+ in log mode and trigger it on the actuator signal with a 20% pre-trigger applied, then expanded the output with Flying Graph, which has finer resolution than the C3+ graph. We saw a single glitched reading with a duration under 10 milliseconds, but that was enough to make the ABS react. However, as I mentioned earlier, the Bosch 7S000 sensors on the R51 (as well as Titans/Xterras/Frontiers) do fail. I wouldn't call it an "everyday" failure rate, but frequent enough to call it a "known issue". The ABS looks at the G-sensor in a more leisurely manner unless the steering and wheels indicate possible yaw, so you can eliminate that for sure just by scanning and exercising it like the guy in the vid. If that checks out and there are no wheel codes, you can be pretty certain your SAS is glitchy.
brickbox wrote:
Thu Jul 28, 2022 8:21 am
Is driving the Pathy like this acceptable? Or should I pull the ABS fuse in the interim as I go about trouble shooting?
It's probably fine to drive it as long as the glitching isn't causing uncontrollability issues. Pulling the fuse is fine provided it doesn't make the engine or tranny go limp. It might, that behavior varies from model to model.

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ShipFixer
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Re: ABS coming on all the time

Postby ShipFixer » Sat Jul 30, 2022 11:56 am

This is probably not your cause, but...I once had this issue because Sears installed one slightly smaller tire in a new set of four. Didn't notice for a couple months until ABS noticed the speed difference between the two rear wheels downhill coming out of the mountains at highway speeds and started freaking out. I assumed it was a brake issue until I looked really closely at the tires.

brickbox
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Re: ABS coming on all the time

Postby brickbox » Mon Aug 01, 2022 5:03 pm

VStar650CL wrote:
Thu Jul 28, 2022 8:44 am
brickbox wrote:
Thu Jul 28, 2022 8:21 am
Gotcha, thanks for laying that out logically. Any advise on how to check for the SAS outside of taking it to a shop with a fancy scanner?
I’ve had a failing ABS wheel speed sensor on a previous vehicle, but that one would only occur when I was at really low speeds (like 20mph or so). This one has me baffled.
You're most welcome. With a falsing SAS, sometimes even a scanner won't catch it. I had a Juke some years back that every couple of miles would tap the right rear actuator for no apparent reason. Just one tap, then it was fine again. Graphing the wheel sensors and SAS told us nothing, The only way we caught it was to put the C3+ in log mode and trigger it on the actuator signal with a 20% pre-trigger applied, then expanded the output with Flying Graph, which has finer resolution than the C3+ graph. We saw a single glitched reading with a duration under 10 milliseconds, but that was enough to make the ABS react. However, as I mentioned earlier, the Bosch 7S000 sensors on the R51 (as well as Titans/Xterras/Frontiers) do fail. I wouldn't call it an "everyday" failure rate, but frequent enough to call it a "known issue". The ABS looks at the G-sensor in a more leisurely manner unless the steering and wheels indicate possible yaw, so you can eliminate that for sure just by scanning and exercising it like the guy in the vid. If that checks out and there are no wheel codes, you can be pretty certain your SAS is glitchy.
brickbox wrote:
Thu Jul 28, 2022 8:21 am
Is driving the Pathy like this acceptable? Or should I pull the ABS fuse in the interim as I go about trouble shooting?
It's probably fine to drive it as long as the glitching isn't causing uncontrollability issues. Pulling the fuse is fine provided it doesn't make the engine or tranny go limp. It might, that behavior varies from model to model.
So I ended up purchasing Bluedriver and it shows no ABS codes. The local advance auto didn’t have a code reader capable of reading ABS….

With that being said now, would you have any advise on the next step for troubleshooting?

Edit: Bluedriver is fancier than my $15 basic scanner. Will the Bluedriver allow me to scan the SAS?
Last edited by brickbox on Mon Aug 01, 2022 5:08 pm, edited 1 time in total.

brickbox
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Re: ABS coming on all the time

Postby brickbox » Mon Aug 01, 2022 5:07 pm

ShipFixer wrote:
Sat Jul 30, 2022 11:56 am
This is probably not your cause, but...I once had this issue because Sears installed one slightly smaller tire in a new set of four. Didn't notice for a couple months until ABS noticed the speed difference between the two rear wheels downhill coming out of the mountains at highway speeds and started freaking out. I assumed it was a brake issue until I looked really closely at the tires.
That is a good point. I went and looked at the tires as they came with the Pathy when I bought it a couple years ago. They are all the same, 265/65/17.
Bummer, because I was hoping it would be something simple. Tire pressures are all within 1-2 psi of each other.

brickbox
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Re: ABS coming on all the time

Postby brickbox » Sat Aug 06, 2022 7:29 pm

So I was able to drive around a little more earlier today. I can hear it actuating around even while I’m driving. If I tap my brakes irrespective of driving straight or through a corner, it causes the ABS to come on.

I pulled out the ABS fuse and sure enough no ABS kicking on (but it also makes me lose the speedometer in addition to 4WD and causes slip, VSC, ABS and brakes lights all come on).

Using my blue driver, here are the codes that I got:
1. U1000 (this one popped up for Meter/MA, intelligent key - as current, transmission - as current, AWD/4WD)
2. P1808 (under AWD/4WD. Description is vehicle speed sensor - ABS)
3. P1815 (as current under transmission. Description is manual mode switch/circuit)
4. P0615 (as current under transmission. Description is starter relay).

Any suggestions on how to get started on diagnosing the U1000 and P1808 outside of giving up and simply starting to replace the wheel speed sensors.

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VStar650CL
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Re: ABS coming on all the time

Postby VStar650CL » Sun Aug 07, 2022 6:53 am

The ABS has multiple power sources, two fusible links in addition to the 10A fuse in the IPDM, so you may not actually have killed the unit but only disabled its communication. U1000's often show up as "current" until they're cleared even if the problem no longer exists, so there's a good chance all those codes cropped up when you had the fuse pulled. Try clearing them and see what (if anything) comes back.


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