C5 X7 same abs sensor fault twice a year

[torneol]

Hello!

I have C5 X7 and some problems with abs sensor in front LH wheel. Sensor have been change several times (past year three times). Bearing is changed too, because it was wearn out.

Is there any theory why same sensor keep getting faulty all the time? Year ago it takes 4000 km and two month. This time it was 15000 km and about eight month. If it is bearing issue, it should illuminate when wheel is running? If it is cable issue, it should be on always and new sensor would not help about it, right? However, when problems start, this say "bling blong" every time, when I open the doors with remote. Meaning that when bsi / bsm wake up?

Could it be bsm box fault?

[admiral51]

The only thing i can think of is that it maybe the ABS ring at fault.
How it is fitted i have no idea but for new sensors to go so quickly on the same axle makes me think it is not BSM/BSI fault but then i have been wrong before on many many times

Colin

[GiveMeABreak]

We'll need the exact fault codes to help - without that it will be guessing. The ABS / ESP system self-checks on start up, so if there is a fault, that is when it will tell you on the inside of the vehicle via the warning. If it is a permanent fault logged, then it will remain until the fault is rectified.

The opening of the door using the remote wakes up the RCD circuit in preparation for the vehicle starting - so suspension ECU is woken up to start checking height level etc., but although the ESP ECU is linked to the suspension ECU (BHI) I couldn't say for sure whether this is also on the RCD circuit - which may be the reason why the warning is coming up on opening.

[torneol]

The only thing i can think of is that it maybe the ABS ring at fault.
How it is fitted i have no idea but for new sensors to go so quickly on the same axle makes me think it is not BSM/BSI fault but then i have been wrong before on many many times

Colin

There is no abs ring in that contruction. It is electromagnetic system, there is some magnets inside at wheelbearing.

[GiveMeABreak]

They still have a magnetic ring attached to the hubs at the rear and for the front wheels, they are integral to the front wheel bearings.

[torneol]

I have no other faultcode, what iCarsoft gives me. There is no actually code, error is mentioned like "Permanent fault, front LH abs sensor signal fault. Incoherent..." I dont remember it exactly.

Last time and time before, it was same problem. Even with Lexia at workshop. Same as today.

[torneol]

Behaviour of the fault has always be the same. First when it appears, fault is intermittent. When I read that code and erase it, it will appear again in short period of time (for ex. in few weeks). Then it seems to be permanent.

[GiveMeABreak]

There are 2 main fault codes with the front LH wheel speed sensor. One is C1320 which relates to Open Circuit, but as you've mentioned 'Coherence' it's likely the second one C1321:

Fault Code:	C1321
Description of Fault:	Front LH wheel speed sensor signal fault: Coherence. Error in the values coming from the wheel speed sensor. The time of appearance of the fault code is 20s to 80s depending the driving conditions. The vehicle speed higher than 20 km/h. Possibility 1: Wheel speed sensor fault Possibility 2: Electromagnetic interference Possibility 3: The width of the signal sent by the wheel speed sensor is incorrect
Conditions for Fault to clear:	Receiving of valid data.
Downgrade Modes whilst Fault is active:	Immediate cutting of all the speed control functions The electronic brakeforce distribution function is in down-grade mode The "electric parking brake" functions are in manual mode* Deactivation of the hill start assistance* Switching on of the warning lamp and/or warning message* Electric parking brake automatic functions deactivation warning lamp* Service ABS ESP/traction control
Symptoms:	Lighting of the ABS and ESP warning lamps If 3 sensors are faulty: The vehicle speed is no longer displayed on the instrument panel.
Suspect Areas:	Front left wheel speed sensor Connectors Electrical harness

* According to Equipment Fitted

[Hell Razor5543]

I recall dealing with Savoy Garage about something unrelated, and he mentioned they had had the devil of a time tracking down an ABS fault (on a Xsara Picasso). It turned out that one of the magnetic rings had a hairline crack that was almost impossible to see, but was enough to cause the ABS system to throw a wobblie!

[GiveMeABreak]

There are 48 pairs of magnetic poles on these and they are extremely sensitive. They can be damaged by tools knocking them, or being dropped or when the hubs are replaced for example. If the data being sent is out of limits, it will be enough to create a fault.

Another issue can be where the tyres are changed for a different size and the ESP computer is not configured correctly (evolute of the tyre) the frame transmits the invalid value.

[admiral51]

Are the front wheel bearings the same across all models of C5 X7 ?
Just thinking that although OP states the bearing has been replaced has it been replaced with the correct one for the vehicle.
My only other thought is that the sensor securing position is not aligned correctly or maybe not holding the sensor securely so allows it to move?
I know random thoughts

Colin

[torneol]

Thanks for everybody about good thoughts! I wait for tomorrow, if the fault may appear again. If so, maybe next fix is the bearing change, once again.

Maybe electrical harness have to check, too.

[GiveMeABreak]

Are the front wheel bearings the same across all models of C5 X7 ?
Just thinking that although OP states the bearing has been replaced has it been replaced with the correct one for the vehicle.
My only other thought is that the sensor securing position is not aligned correctly or maybe not holding the sensor securely so allows it to move?
I know random thoughts

Colin

Yes Colin the front hubs (specifically) are the same across all the C5 X7 range.