c5 traction activating unnecessarily and magnasteer fault

[68sstt]

I had a replacement rack and power steer pump fitted in my c5 RHD aussie converted car and since then the maganasteer does't seem to work. It is always hard but was light for the first 10 miles only. the steering wasn't centred after the rack replacement and was 360 degrees out and was throwing dtc c1283 but this was solved by straightening the wheel. the other fault is that when the car is accelerated up to 70 mph the traction cuts in and the throttle control cuts out, when this happens the screen says "traction sys active". I have had a scan tool on and there are no codes throwing and the wheel speeds seem normal. Can anyone tell me if there are any other things that could cause the trac to activate that I can test.

Thanks in advance

 

[Toms007]

Well, first off lets get you properly welcomed! Now for the problem you are experiencing....I really can't help you much, but I do know that there are sensors that must be sending the wrong info. There is a sensor at the base of the steering column that might be out of whack to might be causing some of your issues.

I'm no mechanic, so take what I say with a grain of salt. GMJunkie should check in here and should be able to give you some guidance. Anyone else help out the newcomer?

 

[Hib Halverson]

What size tires are on this car?

 

[68sstt]

What size tires are on this car?

275/35 18 rear and 245/45 17 front and the wheel speeds are the same side to side and only 1 to 2 kph different at 100kph(60mph)

 

[c4c5specialist]

HI there,

I would be looking VERY CLOSELY at the installation of the steering wheel position sensor and appropriate wiring.

The C1283 has everything to do with that sensor AND the Magnasteer function.

That would be your first course of action.

Allthebest, c4c5

 

[Hib Halverson]

Did the C1283 not reset once it was cleared?

If so, I'm puzzled by the errant TCS activation. Does traction control activate any time the speed gets over 70 mph?

 

[c4c5specialist]

HI there,
No but if the steering wheel position sensor was not centered correctly, meaning 2.5 volts on signal A and signal B, then the EBTCM will think there is a need for active handling control and activate.

The sensation is similar to TCS activating.

Allthebest, c4c5

 

[68sstt]

HI there,
No but if the steering wheel position sensor was not centered correctly, meaning 2.5 volts on signal A and signal B, then the EBTCM will think there is a need for active handling control and activate.

The sensation is similar to TCS activating.

Allthebest, c4c5

I did reset the steer wheel and steer position voltage was about 2.46 or there abouts when pointing straight i am unsure what you mean with signal A and B though I only saw 1 steer position data in the abs screen on my modis. I read somewhere that 2.5 should be straight ahead and any slight offset will be automatically calibrated when the car is in the straight position over so many (30?) mph for a certain period of time, this is why I assumed that being 2.46 would not be a problem. after I reset the wheel the fault code has not logged again and no other codes come up either. Thanks for helping with this problem as you guys can appreciate its hard to get any help in aussie because not too many people know these cars that well.

 

[68sstt]

Did the C1283 not reset once it was cleared?

If so, I'm puzzled by the errant TCS activation. Does traction control activate any time the speed gets over 70 mph?

The traction activates every time you get to 110kph (70mph) and the car bogs down,this has only happened since the rack has been changed and the fault code no longer comes up since turning the wheel 360 degrees

 

[68sstt]

The company that supplies the rack here got me to do some tests for the maganasteer because of the rhd conversion, he suggested to apply 12v to the magnasteer and check if the steering felt lighter at idle which I couldnt feel any difference even applying reverse polarity felt the same, this would suggest that the mechanical side of the steer might not be functioning properly but I wonder if this would cause the trac to cut in?

 

[c4c5specialist]

If the traction control system does activate, you will see a message.

So that way you KNOW the system is seeing different tire rotations.

Allthebest, c4c5

 

[68sstt]

If the traction control system does activate, you will see a message.

So that way you KNOW the system is seeing different tire rotations.

Allthebest, c4c5

The message on the display centre that comes up is "traction sys active" if this is a message that comes up when the car sees diffrent wheel speeds, do you know what the allowable difference is at 70mph. I remember looking at the wheel speeds and they were around about 2 or 3 kmph different from front to rear but side to side they were the same, I will drive the car again today to verify this.

 

[c4c5specialist]

Ok, so that means that the module DOES see a rear wheel speed that is MORE than the fronts.

Your next course of action is to make sure that there isnt a signal thats dropping out.

Tech 2 data is the accurate way to continue diagnosis.

Allthebest, c4c5

 

[68sstt]

Ok, so that means that the module DOES see a rear wheel speed that is MORE than the fronts.

Your next course of action is to make sure that there isnt a signal thats dropping out.

Tech 2 data is the accurate way to continue diagnosis.

Allthebest, c4c5

unfortunately the closest tech 2 with american software is 1250 miles away so unless a drive brisbane is comming up I need to try and diagnose with my snap on modis.
I took another drive 5 mins ago and noticed that a parameter called rough road (g) was hovering between 0 and 20 and shot to 99 when trac activated, I am waiting to hear from snap on to find out what tthis parameter is.
I think this could be the key?

 

[68sstt]

unfortunately the closest tech 2 with american software is 1250 miles away so unless a drive brisbane is comming up I need to try and diagnose with my snap on modis.
I took another drive 5 mins ago and noticed that a parameter called rough road (g) was hovering between 0 and 20 and shot to 99 when trac activated, I am waiting to hear from snap on to find out what tthis parameter is.
I think this could be the key?

I just took it for another drive and logged some parameters
the wheel speeds when the trac cut in were

lhf 106 kph
rhf 106 kph
lhr 113 kph
rhr 112 kph

rough road sensor 99g

rough road sensor just before trac activating was 13g max at 107kph

just trying to work out if the rough road sensor is the lateral accelerometer

 

[68sstt]

took the car for numerous drives down my street and logged the abs module

every time the trac activated the rough road signal jumped sraight up to 99g
often from about 20g or less but the wheel speeds all remain constant at
about 6 or 7 kph faster on the rear than the fronts.

I think that this rough road signal is something to do with the engine knock as described by the local snap on tech.

I removed the lateral g sensor and this is not changing the values on the rough road sensor .

Maybe the yaw sensor might have something to do with this rough road signal.

It just seems to coincidntal that this value shoots straight up to 99 exactly when the trac activates.

 

[c4c5specialist]

HI there,
First, your variations in speed is what is causing it to activate.

I am curious if this control module is the correct one for the vehicle.

The rough road parameter is simply a signal sent to the PCM for misfire diagnostics and has NOTHING to do with traction control activation.

My suggestion, is to obtain correct size tires and install. I know they are not off by much, but that is all I can suggest.

Make sure you do not have stainless steel brake lines or anything that could interupt your sensor signal.

Allthebest, c4c5

 

[68sstt]

HI there,
First, your variations in speed is what is causing it to activate.

I am curious if this control module is the correct one for the vehicle.

The rough road parameter is simply a signal sent to the PCM for misfire diagnostics and has NOTHING to do with traction control activation.

My suggestion, is to obtain correct size tires and install. I know they are not off by much, but that is all I can suggest.

Make sure you do not have stainless steel brake lines or anything that could interupt your sensor signal.

Allthebest, c4c5

Thanks c4c5 , the snap on dealer says the same about the engine misfire being related to the rough road signal maybe its just a coincidence that this spikes at the same time.
Also why would that parameter show up in the abs/traction parameters if this has nothing do with these systems.

I looked at the tire size plaque and the rear tires have the incorrect profile
the plaque says the car should have p275/40 zr18 and the car at the moment has p275/35 zr18 which should have a smaller rolling diameter.
if iwere to put larger profile tires on the rear this should make the rear speeds show slower than previous on the rear sensors.
This should fix the problem fingers crossed.

thanks

 

[68sstt]

I just read in another post that from factory the rolling diameter of the standard tires has a diffrence of 2.5% and the traction cuts in when it sees a difference of 5% front to rear wheel speeds. so if ihave 6kph over 110 that equates to at least 5%.

So ill try changing some tires to see if that fixes the fault

 

[68sstt]

c4c5 thanks for your help I took the car for another drive and let the front tires down to 15psi and the difference in speed at 100kph was only 4kph and the trac didn't cut in all the way to 120kph.
problem fixed

Now to put 2 new tires on the rear with the right profile and send the rack back to get fixed.