21 XLT, new to me, rear park aid warning, hyperflash on left turn, but right side blinks too.

[TomHanx]

Have you checked the wiring harness connectors that feed the lights by pulling the connectors apart and checking for corrosion or damaged connections? Follow the wiring harness from the taillights towards the front of the truck. Pull each connector and examine carefully for issues. You mentioned that you couldn't get the one connector apart. That one may have corrosion in it as others have had water enter that connector and cause corrosion. Look in the taillight connectors for evidence of water entry and corrosion. I would still check the grounds with an ohmmeter as an open ground could cause current back-feeding between the lighting circuits that share a common ground.

The one I couldn't get appart was under the drivers' seat, on the frame rail. The tail lights look sealed, no signs of water. The connectors on them are both clean. There's a couple others under the rear end that I pulled apart, all looked good.

I'm intrigued by airline tech's post yesterday, where he mentioned seeing the pulse from the park assist sensors, in the tail lights. I'm wondering if that is what's causing the strobe effect that is only visible until I shift out of park. Once I shift past reverse, the park aid warning pops up on screen, I assume that turns the sensors off, at which point the strobe effect in the taillights also stops. (still flashing on the right side though, when using left signal. Were you able to see the video I uploaded? It's not showing up for me. So where's the commonality between turn signals, rear park lights, and rear park sensors? Sure looks like connector C422.....the one I couldn't get apart of course! It looks clean, it just felt like the plastic tab was gonna break off, so called it a night, and haven't had the chance to try again yet. Thursday I'm hoping.

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[RangerBill]

The one I couldn't get appart was under the drivers' seat, on the frame rail. The tail lights look sealed, no signs of water. The connectors on them are both clean. There's a couple others under the rear end that I pulled apart, all looked good.

I'm intrigued by airline tech's post yesterday, where he mentioned seeing the pulse from the park assist sensors, in the tail lights. I'm wondering if that is what's causing the strobe effect that is only visible until I shift out of park. Once I shift past reverse, the park aid warning pops up on screen, I assume that turns the sensors off, at which point the strobe effect in the taillights also stops. (still flashing on the right side though, when using left signal. Were you able to see the video I uploaded? It's not showing up for me. So where's the commonality between turn signals, rear park lights, and rear park sensors? Sure looks like connector C422.....the one I couldn't get apart of course! It looks clean, it just felt like the plastic tab was gonna break off, so called it a night, and haven't had the chance to try again yet. Thursday I'm hoping.

C422 is the connector that others have had water and corrosion inside. It has contacts for the taillights and the rear parking sensors. Find a way to get it apart to check inside for corrosion or pins that are not fully inserted in the connector shell. The shop manual shows it under the bed of the truck along the left frame rail.

 

[airline tech]

Ok I had to verify what I was thinking, and since I do not stare at these lights I wanted to confirm.

Light Operation:

So, you have the LH Turn (Power) shorting over to the Brake Light (Power)

This issue may come from either C422 or C405

Using C408 as an example, release and pull the lever to disconnect the connector.

C405

Ref: Rear Park Aid

Ref: TRM Feed for the Trailer Connector.

Note: The TRM normal function is to use a Can Bus signal from the BCM for which lights to apply and it combines the Stop & Turn (Trailer Only)
Note: C405 LH Stop & Turn = Pin 1 and note that Pin 2 = Pwr Feed for the Rear Park Sensors.

I am thinking that if Pin 1 is touching Pin 2, it will generate a Brake Light signal with the Turns, and the park sensors are being grounded by the TRM instead of powering them and may be back feeding the regular taillight circuit.

You may try disconnecting C405 and see if that cures the Turn Signal Issue.
Note the Rear Sensors will be inop / power cut and also note that when you disconnect the taillights (like you did) it is normal for the hyper flash.

So, you either have a burned overheated contact in a connector or (the turn & brake) light power feed wires are touching somewhere in the harness.

 

[airline tech]

Sound Ref: For the Park Sensors -they are powered anytime the key is (ON)

 

[TomHanx]

Sound Ref: For the Park Sensors -they are powered anytime the key is (ON)

I found the problem! One of you guys had it right all along. It's the C422 connector.

I only had a few minutes before the rain started, but I pulled C405, and at first it seemed like things were working correctly. Then suddenly they weren't. So I crawled under to look at C422 again, and see if I could get it open. I did get the lever to release, and probably a tablespoon of water poured out....but I still couldn't actually pull the connector apart. But..... here's the good news.... I had to run back to town to pick up dinner, and during that time, I got no hyperflashes, and 2 of the 3 times I put the truck in reverse, the park aid actually worked! One time still gave me the dash error. I checked that tail lights both places I stopped, and they appear to be working normally. I still want to get that connector apart, and probably replaced, but I'm 99% sure the water trapped inside is the cause of everything.

Thank you guys for all the help! I'll followup if there's anything else worth sharing.

 

[TomHanx]

And unrelated to the issues, my first "mods" showed up in the mail. Those orange lights on the front fenders bothered me way too much. Cheap and easy fix, makes such a big difference imo. Also grabbed a shock for the tailgate. I don't have any other plans, except for a tonneau cover.

 

[RangerBill]

I found the problem! One of you guys had it right all along. It's the C422 connector.

I only had a few minutes before the rain started, but I pulled C405, and at first it seemed like things were working correctly. Then suddenly they weren't. So I crawled under to look at C422 again, and see if I could get it open. I did get the lever to release, and probably a tablespoon of water poured out....but I still couldn't actually pull the connector apart. But..... here's the good news.... I had to run back to town to pick up dinner, and during that time, I got no hyperflashes, and 2 of the 3 times I put the truck in reverse, the park aid actually worked! One time still gave me the dash error. I checked that tail lights both places I stopped, and they appear to be working normally. I still want to get that connector apart, and probably replaced, but I'm 99% sure the water trapped inside is the cause of everything.

Thank you guys for all the help! I'll followup if there's anything else worth sharing.

I would get the connector apart and dried out as soon as possible to limit the amount of corrosion the water will cause. Also clean up both male and female connector ends and maybe put some silicon dielectric grease on the pins and seal to help prevent future water damage.

 

[TomHanx]

I would get the connector apart and dried out as soon as possible to limit the amount of corrosion the water will cause. Also clean up both male and female connector ends and maybe put some silicon dielectric grease on the pins and seal to help prevent future water damage.

Dielectric was my plan. I'm hoping the water was recent, likely when they washed and detailed the truck. Thursday is still my next real opportunity, and the forecast looks dry! Thanks again for all your help!

 

[seasprite]

Dielectric was my plan. I'm hoping the water was recent, likely when they washed and detailed the truck. Thursday is still my next real opportunity, and the forecast looks dry! Thanks again for all your help!

DeoxIT D5

This stuff is supposed to be great at breaking up the green crusties on contact pins.

I know the youtube mechanics rave about it.
Ivan off of Pine Hollow Auto diag.
Eric off of South main auto.

These guys are up in the rust belt with you, so I'm sure they have plenty of practice dealing with the corrosion issues that your dealing with.

 

[airline tech]

C408 as an example - I do not recall there being a secondary lock, once the lever is pulled back it should pull apart.

 

[TomHanx]

C408 as an example - I do not recall there being a secondary lock, once the lever is pulled back it should pull apart.

I did get it apart this morning. I think the minor corrosion inside just made it difficult to pull apart....and I really didn't want to break something, so I was being too gentle. I left it apart to dry all day, but it did still give me a park aid warning on my way home tonight. I've got a can of CRC electrical cleaner, and some dielectric grease. Gonna clean it up real good tomorrow, and see what happens.

 

[airline tech]

Closely inspect Pins: 3-4-6-8 & 10, pay close attention to 6 & 8 as those are the Power & Ground feeds.
If issue continues - do the same for C405 and each of the 4 sensors.
You should also inspect for a pushed back contact pin and the cavities for anything that looks like it's dark colored (burned) from overheat.

As it appears the detail shop (MAY) have pressure washed the underbody and drove water into the connectors, you may have water or corrosion in one of the other connectors in that downstream circuit.
Just be gentle with the sensor connectors - so you do not dislodge the sensor from the plastic retainers.

 

[TomHanx]

As it appears the detail shop (MAY) have pressure washed the underbody and drove water into the connectors, you may have water or corrosion in one of the other connectors in that downstream circuit.

That's what I was thinking. It makes sense. And visually, the corrosion on the pins didn't look all that bad at first glance. A fair amount of that green copper patina, but nothing looks burnt or damaged. I've got all day today to get it cleaned up...but we got our first frost this morning, and I am in no hurry to go outside lol.

 

[TomHanx]

Update: I went to clean it up yesterday, and when I pulled it apart, a couple more drops of water came out. Guess it didn't get all the way dry being left hanging open all day the day before. I left it hanging, with a fan blowing on it all afternoon yesterday. Ended up not cleaning and applying dielectric yet, figured I'd check again on Sat. to see if any more moisture comes out.

Everything was working 100% today. All rear lights, and park aid worked everytime I shifted out of park. Never got the warning. Hopefully that means it's finally completely dry. If it looks dry when I pull it apart tomorrow, I'm gonna clean it up and grease it, and hopefully consider it a done deal.

 

[TomHanx]

Before and after cleaning with the CRC electric cleaner. It was all just surface, and really minor. I packed it full of dielectric, and hopefully never have to worry about it again!!!

Thanks again to everyone that helped, would've taken me a lot longer on my own!

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