Parktronic Sensor Replacement ML (W164)

[firstML]

Hi

I am a new member having recently bought a ML320 CDi (W164).
All is good but the front left parking sensors do not work, hopefully someone can help!!
The lights go on with the ignition but do not respond to close objects, the local dealer checked for faults and they show as working but give no reading when anything approaches so I was advised to change all 3.
To save a bit of money I bought some after market replacements, part numbers match and they fit ok but the once fitted the display constantly reads as full lights as if something is close to the sensor. The 3 original sensors on the other side, which were fine, initially read correctly but will not then switch off after the object is removed.
I checked the electrical resistance on the pins and found that they the new sensors were considerably different to the originals, at the top end 1340 against 1650.
Can anyone advise, I am told they are compatible and part number matches but do all 6 front sensors need to be the same resistance or should that not make any difference?
Any other advice would be appreciated?

 

[whitenemesis]

Local dealer used STAR/Xentry to diagnose the faults?

Sensors tend to work or not. If they fail the system shuts down front and or rear sections.

After IGN on self-test does the display show just red sections or does it shut down and the Switch in the console show red?

 

[firstML]

Thanks for coming back to me.

I'm not sure what system they used to test. It plugged in under the steering column and showed each sensor and the distance to the nearest obstacle. The 3 that were not working showed as active and distance at 225mm even when something was close.

With the new sensors in the display shows full orange and red lights as if close to objects. The other, previously working side, still with original sensors is fine but after reading an object moving closer the lights stay in that position even when the object is removed. So new sensors with different resistance reading are not feeding back correctly and messing the others up as well.