SOLVED: Troubleshooting 2013 rear park assist

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DaveO9

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Short story: I have always gotten a "service park assist message" since I've owned the rig (sept this year) but after replacing sensors, and more recently, taking the bumper off a second time and inspecting the wiring harness, it seems to be working as it should. Perhaps I will just live with the message that comes on every time after 1-2 minutes of driving. Or perhaps I should replace the harness. Or something else.

Longer story: When I bought the rig in Sept, the message was on permanently - it would show upon startup and it didn't work at all. I replaced the sensors with eBay aftermarket ones. (China, of course). It didn't really change anything, would still get a message upon startup. If I cleared it before I went into reverse it would occasionally work, but most of the time, no. Also if I cleared it before going into reverse, it would show up again after 1-2 minutes of driving forward.

Now I have a Tech2. I found that I was getting three DTCs - one each for sensors 2,3, and 4, but NOT sensor 1. The message was "Parking Aid Rear Sensor 2 Circuit Short to Battery" That led me to believe there was a short somewhere in the harness between sensor 1 and 2. Took the bumper off and pulled the wires out of the loom in that area and did some un-taping. Didn't see any obvious damage. Put everything back together and now it seems to be working, I just keep getting the message. Exact scenario of what happens now: at startup, no message; put in reverse, a single beep saying system is active; get close to an obstruction in reverse - many beeps; drive normally for 1-2 minutes - message appears. Once message appears, the light comes on in the button used to disable the system. Pushing the button causes the light to blink several times but not turn off. Here's the weird part, on that same ignition cycle, I can go into reverse again, the light on the button turns off and the system works normallly. Even though I never turned the engine off.

So, as I see it, I can live with the message, or I can try and replace the harness. Another option may to do some further diagnosis on my old sensors and possibly go back to them. Problem is, one of them got ran over so I at least would have to replace that one with an OEM. :)
 
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DaveO9

DaveO9

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It would seem that you have an issue in the wiring harness.
That's what I thought too, but new harness didn't solve it. I still get a "short to battery" message for sensors 2,3,4, but not 1. I may go back to my old sensors for a next step. I only have three, but I can at least see if replacing one removes a code. If that doesn't solve it, my guess is either the module or the wiring between the module and the back bumper. Or I could just live with the message for a while. It's annoying, but hte system seems to be working fine.
 

Joseph Garcia

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That's what I thought too, but new harness didn't solve it. I still get a "short to battery" message for sensors 2,3,4, but not 1. I may go back to my old sensors for a next step. I only have three, but I can at least see if replacing one removes a code. If that doesn't solve it, my guess is either the module or the wiring between the module and the back bumper. Or I could just live with the message for a while. It's annoying, but hte system seems to be working fine.
I believe that you previously stated that you tried swapping another existing sensor to position #1 and it still generated the message. Is that correct?
 
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DaveO9

DaveO9

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I believe that you previously stated that you tried swapping another existing sensor to position #1 and it still generated the message. Is that correct?
No, I haven't done that. I haven't done any sensor swapping yet. But I did do some additional testing this weekend. I believe all four sensors are working fine. I had engine running, trans in reverse, wheels blocked/park brake on and could get all four to trigger by lowering a piece of cardboard in front of them. Even though I'm getting a DTC for three of the four sensors, I'm feeling pretty good that the problem is not with the sensors themselves or the harness in the bumper. I neglected to mention in my previous posts that I'm also getting some other DTCs on the tech 2, seemingly not related to the parking assist issue, but now I'm wondering if they are related. I'm doing another post momentarily about the DTCs.
 

Joseph Garcia

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No, I haven't done that. I haven't done any sensor swapping yet. But I did do some additional testing this weekend. I believe all four sensors are working fine. I had engine running, trans in reverse, wheels blocked/park brake on and could get all four to trigger by lowering a piece of cardboard in front of them. Even though I'm getting a DTC for three of the four sensors, I'm feeling pretty good that the problem is not with the sensors themselves or the harness in the bumper. I neglected to mention in my previous posts that I'm also getting some other DTCs on the tech 2, seemingly not related to the parking assist issue, but now I'm wondering if they are related. I'm doing another post momentarily about the DTCs.
Good to read that all 4 of your sensors are functioning properly in detecting material in front of them. Yes, please post the other codes, as the relationships between controllers can have an impact on other ones.
 
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DaveO9

DaveO9

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I bought this rig in Sept of last year and I finally have gotten rid of the ever-present "Service Park Assist" DIC message. The problem and solution were simple: one of the four original sensors was bad, and a simple replacement with an OEM sensor solved the problem. Unfortunately, I made it much more complicated than that.

Lessons Learned -
1. With that message, you MUST dig deeper and figure out what the problem is before replacing parts. I didn't have a Tech 2 when I first started, so I bought four new sensors and replaced them all. That partially worked. The system actually worked like it was supposed to, but the message was still there. It had to be cleared every time after the vehicle was put into reverse. After a few months of that, I bought the Tech 2, which is where this thread started. The messages I was getting from the Tech 2 made it sound like there was a short in the wiring, so I replaced the harness in the bumper, but I SHOULD have started swapping out the new sensors for the originals to see if that would change the codes on the Tech 2. If I had done that, I would have seen that the bad OEM sensor would have given a code on the Tech 2 that said that specific sensor had a fault or open. Leads me to Lesson 2.....
2. Do NOT replace the OEM sensors with the 4 for $50 sensors from eBay. They are junk. The reason I got tricked is 3 out of the 4 gave error messages on the tech 2. I'm guessing the module is not seeing exactly the right voltage back when it does a diagnostic test. I replaced 2,3, and 4 that were giving the message with the originals, and, after trial and error to find the bad original, message is gone and system works as expected. #1 is still the eBay junk sensor (for some reason that one doesn't give an error, but I don't trust it to last, and it's unpainted black), but I will be replacing it with a used OEM from eBay. I think I can find the correct color, too.
3. You do NOT need to pull the bumper cover to replace the sensors. I did that the first few times I messed with these, but you can get to them without doing so, even with a trailer hitch. Just fish your hand up there, push the two tabs out from center, and push out the sensor with thumb on other hand. Piece of cake to replace them now.

Anyhow, pleased to have a working park assist system, and to now have a code-free DIC display. Thought I'd share.
 

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