Parking Sensor Fault

[zatta]

Was wondering if anybody else has had a similar issue and would possibly know how to solve. I am getting an open to ground code for the rear mid left parking sensor and after replacing the sensor, taking the bumper off, and inspecting the wires I did not notice anything that seemed off. Unfortunately due to this code it immediately comes back after clearing and turns all park assist off including the backup camera. Anybody have any suggestions?
Below is the picture of the fault code.



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[Ur20v]

Looks like April 30th was an eventful day.

Check the connectors on all your rear sensors? A little spray contact cleaner can't hurt.

[zatta]

Looks like April 30th was an eventful day.

Check the connectors on all your rear sensors? A little spray contact cleaner can't hurt.

Yeah this is an old picture but it’s been going on for that long unfortunately, just recently decided to try to dive in and possibly figure it out.


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[tag62221]

Would it be possible to switch connectors with one that's working? That seems like the quickest way to check continuity on the signal wires from the bad pod. If may just be your sensor has failed internally. If you've got a volt meter, you can check for voltage on the car side of the connector, compare with other connectors, etc. Good luck with the fix. Maddening it turns the camera off! Why??

[Smac770]

Is this a B8.0 or B8.5 vehicle? The parking sensors are connected to different control modules.

[ILVTRANCE]

WOW this literally just happened to me today. I couldn't clear it initially. Shut car off then came back an hour later and then was able to clear it. so bizarre. 2014 SQ5 P+

[zatta]

Is this a B8.0 or B8.5 vehicle? The parking sensors are connected to different control modules.

8.5, I don’t think I have the different control module


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[Smac770]

Each sensor has three pins, 12v, ground, and signal. The 12v and ground are common connections to all the sensors. The DTC gives the impression the error is with the signal line from the center left sensor G204. The J519 does not see any voltage signal coming in, so it assumes the line is broken or shorted to ground.

First thing to do would be to swap the center left and center right sensors. If the error stays G204, it's not the sensor. If the error moves to G205, it's the sensor. If the error goes away, it might have been a poor terminal connection and just playing with the plugs was sufficient.

If it says G204, then the question becomes is the issue the wire from the G204 plug to the J519, or with power to the G204 plug. If the sensor is unpowered, it's not going to work. Test the voltage between pins 1 and 3 on the G204 plug (pin 2 is the signal line). I don't know if it will be 5V or 12V, and I don't know if it's always on or if the J519 only supplies power when the functionality is utilized (put the car in reverse). I'd just use VCDS and turn on one of the sensor output tests. But the expectation is to get the same reading between 1 and 3 on the G204 plug as you measure on the G205 plug.

If the plug is supplying the appropriate voltage across pins 1 to 3, then the issue likely moves to a wire issue with pin 2.

G204 plug pin 2 >> plug T16v pin 13 >> J519 plug T32b pin 12
G205 plug pin 2 >> plug T16v pin 12 >> J519 plug T32b pin 15

The rear bumper harness connects to the interior harness at plug "T16v", a 16-pin plug. I'd swap the pins on the rear bumper harness plug (not the interior harness plug) positions 13 and 12. If the issue stays G204, it's in the interior harness going to the J519. But if it moves to G205, it's with the G204 signal line in the rear bumper harness.

There are a ridiculous number of rear bumper harnesses, depending on standard or s-line or SQ and with or without side assist radars, as well as with or without parking sensors. An example: https://www.ebay.com/itm/364069620913

You see the big rubber grommet in the middle, which is going to be mounted on the body somewhere under there. The sealed cable with the white stripe goes to the outside with all the device connections. The exposed wires loosely wrapped goes to the inside, the brown 16-pin plug being the T16v. Where you'll find that in the vehicle, no idea. But you see it's not far on the inside from wherever the grommet is mounted to the body.

If swapping the pins 12 and 13 on the brown plug, the issue remains reported for G204, then the issue is likely with the interior harness or the J519 itself. Put everything back to normal (always put everything back to normal after a test, or you'll lose track of what's what) and then go swap the pins 12 and 15 in the T32b plug on the J519. The J519 is under the dash, behind the headlamp switch. Getting to it sucks. Dealing with that plug will suck more. The T32b one is the black one; the gray one is T32a.

If 12 and 15 on T32b are swapped and the issue is still reported for G204, it must be the J519 itself.

So that's your process. Is it the sensor, is it power to the sensor plug, is it the signal line in the bumper harness, is it the signal line in the interior harness, is it the J519 itself.

[zatta]

Each sensor has three pins, 12v, ground, and signal. The 12v and ground are common connections to all the sensors. The DTC gives the impression the error is with the signal line from the center left sensor G204. The J519 does not see any voltage signal coming in, so it assumes the line is broken or shorted to ground.

First thing to do would be to swap the center left and center right sensors. If the error stays G204, it's not the sensor. If the error moves to G205, it's the sensor. If the error goes away, it might have been a poor terminal connection and just playing with the plugs was sufficient.

If it says G204, then the question becomes is the issue the wire from the G204 plug to the J519, or with power to the G204 plug. If the sensor is unpowered, it's not going to work. Test the voltage between pins 1 and 3 on the G204 plug (pin 2 is the signal line). I don't know if it will be 5V or 12V, and I don't know if it's always on or if the J519 only supplies power when the functionality is utilized (put the car in reverse). I'd just use VCDS and turn on one of the sensor output tests. But the expectation is to get the same reading between 1 and 3 on the G204 plug as you measure on the G205 plug.

If the plug is supplying the appropriate voltage across pins 1 to 3, then the issue likely moves to a wire issue with pin 2.

G204 plug pin 2 >> plug T16v pin 13 >> J519 plug T32b pin 12
G205 plug pin 2 >> plug T16v pin 12 >> J519 plug T32b pin 15

The rear bumper harness connects to the interior harness at plug "T16v", a 16-pin plug. I'd swap the pins on the rear bumper harness plug (not the interior harness plug) positions 13 and 12. If the issue stays G204, it's in the interior harness going to the J519. But if it moves to G205, it's with the G204 signal line in the rear bumper harness.

There are a ridiculous number of rear bumper harnesses, depending on standard or s-line or SQ and with or without side assist radars, as well as with or without parking sensors. An example: https://www.ebay.com/itm/364069620913

You see the big rubber grommet in the middle, which is going to be mounted on the body somewhere under there. The sealed cable with the white stripe goes to the outside with all the device connections. The exposed wires loosely wrapped goes to the inside, the brown 16-pin plug being the T16v. Where you'll find that in the vehicle, no idea. But you see it's not far on the inside from wherever the grommet is mounted to the body.

If swapping the pins 12 and 13 on the brown plug, the issue remains reported for G204, then the issue is likely with the interior harness or the J519 itself. Put everything back to normal (always put everything back to normal after a test, or you'll lose track of what's what) and then go swap the pins 12 and 15 in the T32b plug on the J519. The J519 is under the dash, behind the headlamp switch. Getting to it sucks. Dealing with that plug will suck more. The T32b one is the black one; the gray one is T32a.

If 12 and 15 on T32b are swapped and the issue is still reported for G204, it must be the J519 itself.

So that's your process. Is it the sensor, is it power to the sensor plug, is it the signal line in the bumper harness, is it the signal line in the interior harness, is it the J519 itself.

Thank you, this is great information. I did manage to follow (what I presume) is the ground wire all the way to where they are crimped together, and had no issues there. And checked the wire as much as I could without taking apart the wiring loom and I saw no issues. I also already tried buying a new sensor, did not seem to solve the issue either. I don’t know when I’ll have time to do a more thorough diagnosis but I appreciate the info!


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[Smac770]

Yeah, it's not about the "ground line" (pin 3) per se. The errors says to me the control module is seeing nothing on the signal line, that's pin 2.

[zatta]

Yeah, it's not about the "ground line" (pin 3) per se. The errors says to me the control module is seeing nothing on the signal line, that's pin 2.

Good to know, wish I was looking for this when I took the bumper off


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