Yaw sensor

I have ABS & PSM faults that will not clear. When reading the codes I get a 4440 code, it says �Steering Angle Sensor�. It shows an angle of 720 degrees and the angle does not change when the steering wheel is rotated. I have replaced the steering angle sensor but no difference in the code and the angle reading (720 deg). I am trying to check the wiring. The wiring diagram shows that the 4z wires from the steering angle sensor go to �AY Sensor (under right side of seat)� , the PSM control unit in the trunk and the MFI & DI Control Unit (Behind left rear seat well). They are listed as pins 36 (CAN HI) & 37 (CAN LO). Does anyone know where the AY sensor is located? Is it in the seat? I did not see anything under the seat except the Immobilizer

I checked the wiring and the “AY Sensor” appears to be the yaw sensor that is located in front of the shifter to the right of the drivers seat. The wiring matches for the number of wires and the color coding of the wires. Does anyone know of a procedure to test the yaw sensor and the steering angle sensor with them disconnected from the car’s wiring harness?

Quotes source post: 18598483

PM me your address, I'll pull the one out of my car and send it to you if you want. Since @De Jeeper is going to help me get the .1 NON PSM ABS system going in mine, I don't need it anymore.

AY sensor is the lateral(=y) acceleration (=a) sensor, not yaw sensor. The yaw rate sensor is integrated in the PSM sensor housing, it sits right below the cylindrical shape of its housing. No way to test it separately you need a diagnostic tool. This is for Bosch 5.2 based PSM (up to MY 2000 I believe): MY 2001 onwards used BOSCH 5.7 ABS/PSM and the yaw sensor looks like this Steering angle sensor I am not sure about but I honestly doubt it can be tested standalone using a dvm.

Mark the wiring diagram show 4 wires to the Steering Angle Sensor..2 for power/ground and 2 for CAN -high/low gry/brn = ground and goes to pin 21 of the PSM module gry/red= power and goes to pin 39 of the PSM module gry/wht= CAN high and goes to pin 40 of the PSM module blu/wht= CAN low and goes to pin 24 of the PSM module.. You could test for power and ground at the Steering Angle Sensor with key ON, but there is no way easily to test CAN high/low at the Sensor You can test for continuity for pin 21,39,40,and 24 from PSM module to steering angle sensor to verify complete circuit...( key off / dissconnected) NOTE ::the AY Sensor is "T'ed" into this circuit so dissconnect it also so as to not effect your measurements..

I have done some further research. The wiring diagram shows the power ( GRY/RED; U+ Sensors, pin 39 of the PSM Controller) and ground (GRY/BRN, pin 21 of the PSM Controller). So I will be checking for 5.0 V on the power conductor to the steering angle sensor and the yaw sensor under the center console. I will report findings tomorrow. It looks like the output of the steering angle sensor goes top the CAN BUS. HI and LO at t4he MFI & DI Control Unit in the back shelf (Pins 36 & 37) so I will check for continuity of those wires also.

Jason, Thanks for the offer. I will let you know if I need that part. Mark

Thanks Skip for this info. I will check this tomorrow. IS the AY sensor the sensor under the center console?

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Yes it is ....

I have 12V going to the steering angle and yaw sensors on the Gray/Red wire. I have continuity on all three of the other wires from the steering angle sensor to the CAN BUS connections at the ECU, Instrument cluster and the PSM control unit. I also have continuity from the Gray/Brown wire to Ground. I disconnected the plugs at all three control units to eliminate the possibility of feedback thru the control units. All I can figure is the replacement steering angle sensor (used) was bad also. Is it possible to test the steering angle sensor by providing power to it and checking for square wave signals on the CAN HI and CAN LO outputs with an Oscilloscope? Thanks for all your help. Mark

Plot thickens. Looks like the PSM/ABS controller has been changed. I was making a closer inspection and I see blue paint writing on it like it was marked by a Salvage yard. The BOSCH number on it is 0 285 850 041. I don’t see a Porsche number.

Do u have to learn or reset the steering angle sensor with a pwis?

[QUOTE=168Sierra;18599331]Plot thickens. Looks like the PSM/ABS controller has been changed. I was making a closer inspection and I see blue paint writing on it like it was marked by a Salvage yard. The BOSCH number on it is 0 285 850 041. I don�t see a Porsche number.[/n] I�ve got this exact problem. I even replaced my ABS/PSM unit. I don�t think that�s the problem though - because when I did the replacement, everything worked fine (I got the unit from specialized German on eBay). It wasn�t until I took the car for an alignment that the problem started. I believe that they reset the steering wheel after alignment because it wasn�t straight. This lead to the steering angle sensor fault�

I had the car aligned and they used their Snap On Scanner to tryn to align the steering sensor. It showed the steering angle at 720 degrees and the reading would not change when they turned the wheel. I replaced the steering angle sensor and they tried to align it again. The results were the same. I did check all the wiring and it is all good. I could not read any outputs by hooking my oscilloscope to the outputs of the sensor (3 different sensors) but I may not have hooked it up correctly. I will take it to a shop tomorrow that has a PIWIS and have them try to calibrate it. I have had this problem since i first powered up the car. I bought it as a roller and put an engine in it this fall. Been trying to get rid of the nABS/PSM fault lights ever since. Thanks for the suggestions.and offers of parts (Jason and Skip). Mark

Do you have actual problems with the ABS/PSM, or just the lights? Mine seems to function normally besides for the lights coming on (they�re off at start up and come on in approximately 6 miles - every time).

The Steering Angle Sensors are very very reliable, I have never had to replace one. I have calibrated hundreds of them with PIWIS after alignment that were off by a few * ... It should never read 720* unless at full lock turn? or damaged ? It will read 0* when straight ahead then + or - from 0* when turned ... I don't know if it can be damaged by "over rotating" .. like a clock spring can be damaged by over rotating.. I have never damaged one or had one damaged..... I have never tried to fix one without a PIWIS, it may be a simple coding issue of the PSM module...All modules have to be coded using PIWIS..

I think it is much more likely that the garage's scan tool could not read the steering angle sensor and showed 720 as some kind of default or error message.

I took it to an Indie shop this morning that has PIWIS. They were able to calibrate the steering angle sensor and that solved my problem. Evidently many scan tools cannot recalibrate the steering angle sensor. A code is required to enter into PIWIS prior to recalibration. The yaw sensor is powered by the same circuit that powers the steering angle sensor but it does not output to the CAN Bus like the steering angle sensor does

Very glad you got the issue sorted.....another case where PIWIS is absolutely needed... I miss not having a PIWIS at my disposal...I would have one and use it for EVERYTHING if it were not so very very expensive and only afforadable to someone who uses it everyday for a living..

HI, I see you all have some excellent thoughts here and I am wondering if any one has any thoughts on how to assist in my PSM issue. I have a 981 Boxster with pdk, 3.8, tractive suspension setup. Withe the PSM switched off it keeps coming on and my brakes are cooked after only 3 or 4 laps. I am wondering if it would be possible to add a 718 gt4 PSM sensor module and the wiring to a center consul switch to completely disable PSM. Any thoughts much appreciated.

Not familiar with the 981 (this is the 996 sub section after all) but if anything you would need the software that iis implemented on the gt4. The sensor module as well as the hydraulic module with its attached ecu most probably is the same between the two anyway. The brake intervention you are experiencing is to help traction out of corners. A limited slip differential (does the gt4 have one?) would lessen corner-inside wheel spin and reduce the necessity for the above intervention (going by the acronym ABD, automatic brake differential, another of those BOSCH acronyms translated from German into pigeon English that don't bring across what the german naming did...) thus saving your rear brakes. Pulling the PSM fuse will disable it but most probably you will loose ABS as well as the electronic brake force distribution (EBD) between front and rear axle, in other words your rear axle will get too high a brake pressure and you'll probably spin at the slightest attempt to brake into a corner. I would expect that if you switch PSM off by means of a long press on the appropriate button, you'll disable ABD whilst keeping ABS and EBD and will no longer cook your rear brakes. At the cost of corner inside wheel spinning whithout getting out of that corner any quicker, that is. You might want to consider the brake intervention as a hint that you should wait a little longer before stepping on the gas when exiting such a corner. It will make you driving smoother, lessen wear on brakes and(/or) tyres and will not make you any slower.

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Hi I have a PSM ABS light problem on my 1999 C4. My diagnostics says it�s a steering angle sensor but I can read it real time and changes as I turn the wheel. Would you recommend I still take it to a PiWiS guy and have it reset? Thanks!

What does it read with the wheel straight? If its not real close to 0 then yes u will need a piwis to reset it. Or u can disco the stearing shaft and rotate it to 0, pull the steering wheel to straighten it up and put it all back together. Kinda a pita but u cam do it with out special computer tools.

Quotes source post: 19612563

I couldnt zero my steering even with the Dynamteric system I bought so i cheated. I borrowed a mates Snap On system that read the angle real time. I disconnected the steering column and with the wheels inline, the angle sensor at zero I reconnected the column and moved the steering wheel to suit. Still have the ABS light on. Turning my attention to the Yaw Sensor but I can�t find it. Any idea where it would be on a 1999 C4?

Yaw sensor is in front of the shifter under the console/dash area. If the codes implicate the steering angle sensor, why do you suspect the yaw sensor? What codes do you have?

Quotes source post: 19613440

Hi, I just have the steering angle sensor fault. But I did start the car up without the PSM plugged in so thought I�d check all connectors associated with the PSM system. just spent 4 years renovating it and must have had brain fade when I put it all back together.