Posted on Renntech but STILL having PSM issues
05-19-2011, 08:17 PM
#1
Rennlist Member
Thread Starter
Posted on Renntech but STILL having PSM issues
I thought I'd cast a wider net to the braintrust on rennlist as well. here is what I posted on Renntech. Any guidance will be appreciated.
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I have been chasing this issue for a while now, trying to figure out what the hell is the cause. I'm trying to go about it methodically partly because there's so much stuff tied into the PSM/ABS system.
I'm getting PSM activation/intervention when the car is turning left on an off/on ramp or a curve at speed. The speed itself isn't really at play (doesn't happen when making a left turn on the street, for example) but almost always activates on the higher speeds of a highway curve (whether the surface is at an incline up/down or level).
So far, we've checked the tires, ABS speed sensor, steering angle, yaw sensor, brake switches.
I had a ABS/PSM light as well, but that turned out to be the brake switch which is now fixed, yet the PSM problem persists. The steering wheel angle was reset and calibrated. The yaw sensor shows readings that are not out of range.
I cleaned the MAF and seems to be fine (It was fine beforehand but just in case, I cleaned it). I also got a new Battery just in case.
What else could it be? Help would be appreciated.
It only happens when car is turning to the left. Normal operation to the right. Is there something I can buy that logs the driving conditions and record PSM activation? maybe it's a particular speed that needs to be reached, a particular steering angle or yaw combination? What other sensors are on-board that affect this?
-----------
I have been chasing this issue for a while now, trying to figure out what the hell is the cause. I'm trying to go about it methodically partly because there's so much stuff tied into the PSM/ABS system.
I'm getting PSM activation/intervention when the car is turning left on an off/on ramp or a curve at speed. The speed itself isn't really at play (doesn't happen when making a left turn on the street, for example) but almost always activates on the higher speeds of a highway curve (whether the surface is at an incline up/down or level).
So far, we've checked the tires, ABS speed sensor, steering angle, yaw sensor, brake switches.
I had a ABS/PSM light as well, but that turned out to be the brake switch which is now fixed, yet the PSM problem persists. The steering wheel angle was reset and calibrated. The yaw sensor shows readings that are not out of range.
I cleaned the MAF and seems to be fine (It was fine beforehand but just in case, I cleaned it). I also got a new Battery just in case.
What else could it be? Help would be appreciated.
It only happens when car is turning to the left. Normal operation to the right. Is there something I can buy that logs the driving conditions and record PSM activation? maybe it's a particular speed that needs to be reached, a particular steering angle or yaw combination? What other sensors are on-board that affect this?
05-19-2011, 11:24 PM
#4
Rennlist Member
Thread Starter
Indie tech said the alignment was ok, but I haven't taken it to the alignment shop which I guess I should to make double sure.
I will say that I don't notice any drifting, the car tracks straight and I don't feel a noticable change in the way the car turns, or any skittishness under braking.
I will say that I don't notice any drifting, the car tracks straight and I don't feel a noticable change in the way the car turns, or any skittishness under braking.
05-19-2011, 11:25 PM
#5
Rennlist Member
Thread Starter
05-19-2011, 11:26 PM
#6
Rennlist Member
I vote intermittent loss of wheel speed sensor signal do to more than "normal" suspension compression from higher Gs causing short/open in connector/wiring or change in gap between sensor and ring while turning at speed.
Here is why:
I had the same type of problem with my Mercedes ML350.
I would get abs/traction control/&? (can't remember the 3rd symbol) fail light on the dash during sharp turn to the left or when the steering wheel was hard left. Most of the time the lights would go out soon after traveling in a straight line for a short distance.
It kept happening when backing into my driveway.
Once the right rear brake activated momentarily (microsecondarily?) before the nanny lights came on. It was at lower speed but enough to nudge me into fixing it before it erroneously leaped into action flipping me on my noggin on the highway while trying to save me.
The above started after I had to remove the front wheel carriers from the car. Last touched first suspect??
(As an aside if you want to have an interesting experience that requires a 20 ton press, some heat and most of your "working" vocabulary - twice, replace original lower ball joints on a Mercedes SUV. They are glued in?!? The replacements require a special 3/4" drive pin wrench and 6' extension to generate the 250ftlbs to pull into place... that is the second time use of "working" vocabulary)
Among the assorted bits that I had to remove were the wheel speed sensors that were semi-rusted in place. I was able to remove them without breaking the plastic housings but evidently damaged the wires causing an intermittent short/open connection on one.
When I put a DVM on them and twisted the sensor around the digital meter would show a reaction that would never settle down to show open or short but obviously a reaction on the left one. So I replaced both front sensors and no problem for 5 weeks now.
YMMV
Here is why:
I had the same type of problem with my Mercedes ML350.
I would get abs/traction control/&? (can't remember the 3rd symbol) fail light on the dash during sharp turn to the left or when the steering wheel was hard left. Most of the time the lights would go out soon after traveling in a straight line for a short distance.
It kept happening when backing into my driveway.
Once the right rear brake activated momentarily (microsecondarily?) before the nanny lights came on. It was at lower speed but enough to nudge me into fixing it before it erroneously leaped into action flipping me on my noggin on the highway while trying to save me.
The above started after I had to remove the front wheel carriers from the car. Last touched first suspect??
(As an aside if you want to have an interesting experience that requires a 20 ton press, some heat and most of your "working" vocabulary - twice, replace original lower ball joints on a Mercedes SUV. They are glued in?!? The replacements require a special 3/4" drive pin wrench and 6' extension to generate the 250ftlbs to pull into place... that is the second time use of "working" vocabulary)
Among the assorted bits that I had to remove were the wheel speed sensors that were semi-rusted in place. I was able to remove them without breaking the plastic housings but evidently damaged the wires causing an intermittent short/open connection on one.
When I put a DVM on them and twisted the sensor around the digital meter would show a reaction that would never settle down to show open or short but obviously a reaction on the left one. So I replaced both front sensors and no problem for 5 weeks now.
YMMV
Last edited by fpb111; 05-20-2011 at 04:42 PM.
06-05-2011, 11:04 PM
#7
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Hello folks...,
Just out of curiosity....
What is exactly the recalibration of the steering wheel angle sensor and how the dealer did it...they need any special tool or just with the computer...like a reset...
How long does it take for the calibration of the wheel steering angle.
I will have to go to the stealership for the calibration....
Thanks
Robert
Just out of curiosity....
What is exactly the recalibration of the steering wheel angle sensor and how the dealer did it...they need any special tool or just with the computer...like a reset...
How long does it take for the calibration of the wheel steering angle.
I will have to go to the stealership for the calibration....
Thanks
Robert
