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

[TomHanx]

I've done some searching and reading other posts here, and there's 1 in particular that might get me headed in the right direction. I know about Forscan, and I'm going to get it, I just don't currently have a windows laptop.

Truck only has the rear park aid sensors. Anytime you put it in reverse, the backup camera comes on, but there's a picture of a truck with a red ! on it. It also sometimes does a hyperflash on the dash, only for left signals. I went and bought bulbs, only to discover there are no bulbs in the rear end. When using the left signal, the outer red portion of the right side tail light also blinks, but it's not a clean blink... it's almost strobe like. It's too late tonight, but I'll get a video tomorrow evening. The left license plate bulb was also burned out.

I'm an electrician by trade, and with everything being on the left side, it screams bad ground, damaged wiring, or something loose. A quick visual from the connectors under the drivers side, to the rear end, I didn't see anything obvious. Maybe somebody here has had a similar issue, knows where to look. I assume forscan will show me exactly what sensors/circuits are affected, which would likely lead me to finding the cause.

Thanks for letting me join. This is my first modern vehicle. Drove my last one for 20yrs! Already found some threads here that helped me figure out some stuff with the SYNC screen. I'm sure I've still got a lot to learn about this truck.

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[RangerBill]

I've done some searching and reading other posts here, and there's 1 in particular that might get me headed in the right direction. I know about Forscan, and I'm going to get it, I just don't currently have a windows laptop.

Truck only has the rear park aid sensors. Anytime you put it in reverse, the backup camera comes on, but there's a picture of a truck with a red ! on it. It also sometimes does a hyperflash on the dash, only for left signals. I went and bought bulbs, only to discover there are no bulbs in the rear end. When using the left signal, the outer red portion of the right side tail light also blinks, but it's not a clean blink... it's almost strobe like. It's too late tonight, but I'll get a video tomorrow evening. The left license plate bulb was also burned out.

I'm an electrician by trade, and with everything being on the left side, it screams bad ground, damaged wiring, or something loose. A quick visual from the connectors under the drivers side, to the rear end, I didn't see anything obvious. Maybe somebody here has had a similar issue, knows where to look. I assume forscan will show me exactly what sensors/circuits are affected, which would likely lead me to finding the cause.

Thanks for letting me join. This is my first modern vehicle. Drove my last one for 20yrs! Already found some threads here that helped me figure out some stuff with the SYNC screen. I'm sure I've still got a lot to learn about this truck.

Here is a wiring diagram for the taillights. There is a ground splice S405 is used for both taillights and license plate bulbs (shown on another diagram. I would concentrate on the left turn signal problem first, and when that is solved, the other issues will probably be solved.

 

[airline tech]

You have a deeper issue than a bad ground, you have a short.
If the RH Taillight is lighting up (which lights?) when the LH Turn is (On)
Plus, the additional issue of the (rear cam) working but the BLIS module is shorted, the rear cam ties into the BLIS for (Cross-Traffic)
The Rear (4ea) sensors on the bumper are (parking aid)

I would check both the (LH and RH) Lamp Assemblies for water, they are known to get water into them and short out the BLIS Modules.
You may isolate it down by disconnecting the LH Lamp Assembly and see if you still have the RH flashing issue.
Take it a step further and pull the (BLIS - SODL) module out and disconnect it, plug the tail lamp back in and see if the RH still flashes

I have a hunch you have a bad LH assembly or module or a wiring issue feeding it and either the Ground - Stop Lamp or BLIS Power Feeds are feeding over to the RH Assembly.
LH Turn power touching another circuit and back feeding the RH Side.

With GRD (G123) being shared with the Rear Lamps and BLIS, as well as the Side Mirrors, CHMSL and Rear Defog grid - I suspect power is shorting to the Ground and back feeding the circuit to power some lighting on the RR Light.

Look for any evidence of wire splice or taps, where the previous owner had tapped the circuit for extra lighting.

We can dig deeper into the circuit if needed, but I suspect the issue is in the LH Light Assembly and I would start there.
Note: The wiring diagram above does not show the BLIS circuit.
When you start the truck - does the BLIS indicator (Lights) flash on for a few seconds then go out?
These are on the mirrors, and this is the BLIS (self-test) of the circuit.
I have a hunch these are not working either.



The Module that mounts here is the BLIS Module (SODL) & (SODR)
Side obstacle detection (L & R) they are the same part number however are programmed specific to each side, so if replaced they must be programmed with Forscan

I will also point out - so you are not shocked - these are EXPENSIVE

 

[DukeCanBuildit]

Does your truck have a topper/canopy?

Sorry to hear of your troubles. It must be frustrating. Airline Tech mentioned looking for splices or taps. That made me immediately think of how exposed and vulnerable the wires are for the third brake light on my truck’s topper. Installers often tap into the taillight to power these.

Other possible culprits are non-OEM things like bed lighting and extra backup or signal lights.

 

[TomHanx]

Here is a wiring diagram for the taillights. There is a ground splice S405 is used for both taillights and license plate bulbs (shown on another diagram. I would concentrate on the left turn signal problem first, and when that is solved, the other issues will probably be solved.

You have a deeper issue than a bad ground, you have a short.
If the RH Taillight is lighting up (which lights?) when the LH Turn is (On)
Plus, the additional issue of the (rear cam) working but the BLIS module is shorted, the rear cam ties into the BLIS for (Cross-Traffic)
The Rear (4ea) sensors on the bumper are (parking aid)

I would check both the (LH and RH) Lamp Assemblies for water, they are known to get water into them and short out the BLIS Modules.
You may isolate it down by disconnecting the LH Lamp Assembly and see if you still have the RH flashing issue.
Take it a step further and pull the (BLIS - SODL) module out and disconnect it, plug the tail lamp back in and see if the RH still flashes

I have a hunch you have a bad LH assembly or module or a wiring issue feeding it and either the Ground - Stop Lamp or BLIS Power Feeds are feeding over to the RH Assembly.
LH Turn power touching another circuit and back feeding the RH Side.

With GRD (G123) being shared with the Rear Lamps and BLIS, as well as the Side Mirrors, CHMSL and Rear Defog grid - I suspect power is shorting to the Ground and back feeding the circuit to power some lighting on the RR Light.

Look for any evidence of wire splice or taps, where the previous owner had tapped the circuit for extra lighting.

We can dig deeper into the circuit if needed, but I suspect the issue is in the LH Light Assembly and I would start there.
Note: The wiring diagram above does not show the BLIS circuit.
When you start the truck - does the BLIS indicator (Lights) flash on for a few seconds then go out?
These are on the mirrors, and this is the BLIS (self-test) of the circuit.
I have a hunch these are not working either.



The Module that mounts here is the BLIS Module (SODL) & (SODR)
Side obstacle detection (L & R) they are the same part number however are programmed specific to each side, so if replaced they must be programmed with Forscan

I will also point out - so you are not shocked - these are EXPENSIVE

Thanks for the reply. It was your posts in another thread that I thought would be helpful.

The "BLIS" seems to be working fine. The lights in the mirrors do light up on start, and they do function while driving. There is no obvious signs of water being in either side assembly, and def. no water currently. In my initial investigating, I saw no evidence of wires being spliced anywhere, everything appears to be factory condition. I never thought to disconnect the whole assembly and test, I will do that later today.

Thank you for the info and suggestions. Will followup this evening.

 

[TomHanx]

Does your truck have a topper/canopy?

Sorry to hear of your troubles. It must be frustrating. Airline Tech mentioned looking for splices or taps. That made me immediately think of how exposed and vulnerable the wires are for the third brake light on my truck’s topper. Installers often tap into the taillight to power these.

Other possible culprits are non-OEM things like bed lighting and extra backup or signal lights.

It does not have a cap, but the bed is in pristine condition, so maybe it did before I bought it? I didn't see any obvious signs of a previous splice anywhere, but I'll keep looking. Thanks for the tip.

 

[airline tech]

Pull and Inspect C422 - Pay attention to Pins 6 & 7.

I am focused on the Glow you are getting on the RR.
Since it appears its not the BLIS, we need to shift focus to the Park Aid Sensors

With the truck running all 4 sensors should be operating, use your phone and record video sound and pass the phone near all 4 sensors. You should hear all 4 pulsing.

If we look at C422 and note that
Pin 6 = the Grd Return for all 4 park aid sensors
Pin 7 = The RR Turn Power Feed
Pin 30 = The LR Turn Power Feed

Pin 20 = Ground for Both Taillight Assemblies

I am thinking (What If) Pins 6 & 7 are touching, it may produce a pulse on the RR light assembly and since they both have a shared ground (Pin 20 = G123) then when the LH Turn signal is used its picking up a voltage anomaly on the ground circuit that should not be present, and produces the hyper flash.

So, if I am correct the feedback pulse of the park Sensors if feeding through to the RR Turn circuit.

You may try, getting the symptom of the RR Pulsing Light and match it to the recording (sound) and see if they possibly sync up. (Sound vs Light Pulse)

This is just an observation of the pinouts and proximity of the pins, it may not be it, but worth a check.

 

[TomHanx]

Pull and Inspect C422 - Pay attention to Pins 6 & 7.

I am focused on the Glow you are getting on the RR.
Since it appears its not the BLIS, we need to shift focus to the Park Aid Sensors

With the truck running all 4 sensors should be operating, use your phone and record video sound and pass the phone near all 4 sensors. You should hear all 4 pulsing.

If we look at C422 and note that
Pin 6 = the Grd Return for all 4 park aid sensors
Pin 7 = The RR Turn Power Feed
Pin 30 = The LR Turn Power Feed

Pin 20 = Ground for Both Taillight Assemblies

I am thinking (What If) Pins 6 & 7 are touching, it may produce a pulse on the RR light assembly and since they both have a shared ground (Pin 20 = G123) then when the LH Turn signal is used its picking up a voltage anomaly on the ground circuit that should not be present, and produces the hyper flash.

So, if I am correct the feedback pulse of the park Sensors if feeding through to the RR Turn circuit.

You may try, getting the symptom of the RR Pulsing Light and match it to the recording (sound) and see if they possibly sync up. (Sound vs Light Pulse)

This is just an observation of the pinouts and proximity of the pins, it may not be it, but worth a check.

My day didn't go as planned (other problems), so I didn't get to do anything with the truck today. When I drove it earlier, it was not doing the hyperflash, it's definitely intermittant. Still giving the rear park assist warning on dash when shifting out of park. I'll check the sensors tomorrow as you suggested. This might be a stupid question, but how do you get that connector apart? I tried the other day, and felt like I was going to break it, so I stopped.

 

[TomHanx]

Pull and Inspect C422 - Pay attention to Pins 6 & 7.

I am focused on the Glow you are getting on the RR.
Since it appears its not the BLIS, we need to shift focus to the Park Aid Sensors

With the truck running all 4 sensors should be operating, use your phone and record video sound and pass the phone near all 4 sensors. You should hear all 4 pulsing.

If we look at C422 and note that
Pin 6 = the Grd Return for all 4 park aid sensors
Pin 7 = The RR Turn Power Feed
Pin 30 = The LR Turn Power Feed

Pin 20 = Ground for Both Taillight Assemblies

I am thinking (What If) Pins 6 & 7 are touching, it may produce a pulse on the RR light assembly and since they both have a shared ground (Pin 20 = G123) then when the LH Turn signal is used its picking up a voltage anomaly on the ground circuit that should not be present, and produces the hyper flash.

So, if I am correct the feedback pulse of the park Sensors if feeding through to the RR Turn circuit.

You may try, getting the symptom of the RR Pulsing Light and match it to the recording (sound) and see if they possibly sync up. (Sound vs Light Pulse)

This is just an observation of the pinouts and proximity of the pins, it may not be it, but worth a check.

Same story, different day. Didn't have much time before dark. I tried recording the sensors in the bumper like you said, but I didn't hear anything from any of them. But this afternoon, for the first time, I did not get the park aid warning on the dash. But now tonight it's doing it again. And the tail light issue seems to come and go too. Sometimes the outer portion on both sides flashes, sometimes it looks like a strobe, other times it's a normal looking flashing. I feel like Forscan would probably make this a lot easier to troubleshoot.

 

[TomHanx]

And obviously I screwed something up with the video. Wrong format maybe? Idk. I'm exhausted, and apparently just too dumb to do anything right lately. Just trying to get things done before winter gets here, and I'm losing that battle.

 

[TomHanx]

And obviously I screwed something up with the video. Wrong format maybe? Idk. I'm exhausted, and apparently just too dumb to do anything right lately. Just trying to get things done before winter gets here, and I'm losing that battle.

 

[RangerBill]

Same story, different day. Didn't have much time before dark. I tried recording the sensors in the bumper like you said, but I didn't hear anything from any of them. But this afternoon, for the first time, I did not get the park aid warning on the dash. But now tonight it's doing it again. And the tail light issue seems to come and go too. Sometimes the outer portion on both sides flashes, sometimes it looks like a strobe, other times it's a normal looking flashing. I feel like Forscan would probably make this a lot easier to troubleshoot.

If you have a meter, check for a good ground connection (on ohms scale) to chassis at each taillight connector (pin 1) using the schematic diagram that I posted above.

 

[airline tech]

I will have to revisit the diagram again to isolate it - but the center (rectangle) is the turn signal - so the LH turn is
Bleeding over to either Park or Stop on the RH side, note the RH side turn is not pulsing but park or brake lights are.
And when the LH side is plugged in, the turn plus park or brake lights are flashing.
It’s not a ground issue, the LH turn power feed is touching the park or brake light circuit.

 

[TomHanx]

I will have to revisit the diagram again to isolate it - but the center (rectangle) is the turn signal - so the LH turn is
Bleeding over to either Park or Stop on the RH side, note the RH side turn is not pulsing but park or brake lights are.
And when the LH side is plugged in, the turn plus park or brake lights are flashing.
It’s not a ground issue, the LH turn power feed is touching the park or brake light circuit.

That was my initial thought as well, but I didn't see any wiring that looked like it had been damaged or spliced into. The electrician in me is thinking that the rear park assist must be related, but maybe it's not? I'm hoping to have some time on Thursday to really trace out the wiring, and look for any signs of damage, corrosion, etc.

 

[RangerBill]

That was my initial thought as well, but I didn't see any wiring that looked like it had been damaged or spliced into. The electrician in me is thinking that the rear park assist must be related, but maybe it's not? I'm hoping to have some time on Thursday to really trace out the wiring, and look for any signs of damage, corrosion, etc.

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.

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