Well I'm stumped (electrical).

[OFC Ranger]

Recently my left rack sequential turn signal bar stopped working and I am getting a hyper flash arrow the dash on left blinker only. But here is why I am stumped;

- If I disconnect that light, I still get hyper flash arrows still.

- No factory bulbs are out

- If I swap the left light to the right side connector, it works no problem

- The running light function of the bar still works fine

- I double checked all rear tail light connections (the tapping point) for any bizarre break down and everything is still sealed tight

- Checked for any fault messages with obd scanner; nothing.

This setup worked fine for over a year until recently.

I am completely at a loss at this point.

Sponsored

 

[NotBudule]

Does it do it with both disconnected?

 

[Trigganometry]

I’m thinking you have a current draw on the hot line somewhere. It doesn’t have to be much ether. Like a wire has rubbed and the slightest amount of resistance from contact that is most likely intermittent is causing this from your description.

Deenergize the circuit in question and use an Ohm meter in resistance mode. Connect on leg to ground (preferably in circuit) and probe hot side along its entire length. Somewhere in that length you will probably find the culprit.

 

[OFC Ranger]

Does it do it with both disconnected?

Yes, this helped me rule out at least one source of the problem.

 

[JDowns]

Each of the vehicles four corner turn signals are on a separate BCM circuit(s) to regulate the flasher(s). Hyper-flashing is indicative of a non functioning bulb, and you have already determined that the bulbs work. Swapping to the opposite side isolates the problem to the other side (left).

Normally when replacing a bulb with an LED (not your instance) a resistor is required (not always a sure fix in warmer climates) so the BCM reads the correct current draw. So the BCM is not registering the correct current draw as indicated if you return to stock.

If the sequential turn signal does not utilize a constant current driver it may have gone into thermal runaway drawing too much current burning out the sense resistor that is part of the precision amplifier circuit that measures current across the resistor. Voltage is still going to the bulb, the circuit just thinks you have a burnt out bulb as it can no longer measure the current across the circuit causing the hyper-flash scenario. A DTC wouldn't be thrown in this instance since the hyper-flash is the default error code.

 

[Floyd]

without even reading carefully , I suggest checking all grounds.

 

[OFC Ranger]

Each of the vehicles four corner turn signals are on a separate BCM circuit(s) to regulate the flasher(s). Hyper-flashing is indicative of a non functioning bulb, and you have already determined that the bulbs work. Swapping to the opposite side isolates the problem to the other side (left).

Normally when replacing a bulb with an LED (not your instance) a resistor is required (not always a sure fix in warmer climates) so the BCM reads the correct current draw. So the BCM is not registering the correct current draw as indicated if you return to stock.

If the sequential turn signal does not utilize a constant current driver it may have gone into thermal runaway drawing too much current burning out the sense resistor that is part of the precision amplifier circuit that measures current across the resistor. Voltage is still going to the bulb, the circuit just thinks you have a burnt out bulb as it can no longer measure the current across the circuit causing the hyper-flash scenario. A DTC wouldn't be thrown in this instance since the hyper-flash is the default error code.

Is that sensory circuitry something I can access or some way I can test it?

 

[JDowns]

The current sensing circuit is part of the circuit board that makes up the BCM. In a broad view there will be a precision amplifier (PA), resistor (possibly a 1%) , and most likely an analog to digital converter (ADC), or scrap all that and use a resistor and an integrated circuit (IC). This reads the current across the resistor (typically called a shunt) gets amplified and converted from an analog to digital signal. That signal is then read by the BCM and probably compared for a value between less-than and/or greater-than. If the value is less-than the expected current it assumes a blown bulb and a hyper-flash situation is induced. A greater-than value probably disables the circuit.

Any part of that circuit could be damaged resulting in a null or zero current value.

My bet would be on the resistor if this is indeed the issue. I wouldn't expect the PCB design there to account for a fast large over draw of current since it was designed for a halogen bulb. It certainly has a ground to fault protection so that would rule out that scenario. It doesn't take a whole lot of extra current to blow those resistors. If the current were to gradually rise I would expect the BCM to disable the circuit. But if it was fast enough then the resistor would go before the BCM polling of the circuit could disable it.

This would be an example of a type of current sensing circuit using an integrated circuit and a shunt resistor (sensing resistor). See below.

If you pull to much current across the shunt resistor (Rshunt) it can blow. It may not have been designed to protect against thermal runaway in an led circuit. For the stock LED tail lamp assemblies there is most likely a constant current driver in the light housing itself.

This is why it's critical that if you tap into a circuit on the BCM that is driving an LED that you use some sort of constant current driver to protect the BCM against thermal runaway.

 

[OFC Ranger]

The current sensing circuit is part of the circuit board that makes up the BCM. In a broad view there will be a precision amplifier (PA), resistor (possibly a 1%) , and most likely an analog to digital converter (ADC), or scrap all that and use a resistor and an integrated circuit (IC). This reads the current across the resistor (typically called a shunt) gets amplified and converted from an analog to digital signal. That signal is then read by the BCM and probably compared for a value between less-than and/or greater-than. If the value is less-than the expected current it assumes a blown bulb and a hyper-flash situation is induced. A greater-than value probably disables the circuit.

Any part of that circuit could be damaged resulting in a null or zero current value.

My bet would be on the resistor if this is indeed the issue. I wouldn't expect the PCB design there to account for a fast large over draw of current since it was designed for a halogen bulb. It certainly has a ground to fault protection so that would rule out that scenario. It doesn't take a whole lot of extra current to blow those resistors. If the current were to gradually rise I would expect the BCM to disable the circuit. But if it was fast enough then the resistor would go before the BCM polling of the circuit could disable it.

This would be an example of a type of current sensing circuit using an integrated circuit and a shunt resistor (sensing resistor). See below.

If you pull to much current across the shunt resistor (Rshunt) it can blow. It may not have been designed to protect against thermal runaway in an led circuit. For the stock LED tail lamp assemblies there is most likely a constant current driver in the light housing itself.

This is why it's critical that if you tap into a circuit on the BCM that is driving an LED that you use some sort of constant current driver to protect the BCM against thermal runaway.

I have LED tail lights.

 

[JDowns]

Are they stock LED tail lights and turn signal lights?

Hyper flashing is indicative of a burned out bulb or too low a current draw.

Ground fault would just trip the e-fuse in the BCM, and would reset on a key on/off cycle.

I've seen your wiring, so I'm purposefully not going down the road of a hack job on the splice, and ruled that out from the get go.

The issue is in one of two areas IMO.

(1) Hardware issue on the BCM. I assume you tried a hard reset by disconnecting the battery and allowing any capacitive charge to dissipate. Be mindful of the reset procedure for the BMS.

(2) If stock LED tail lights possibly a fault there. You could swap LR if the pinout is the same.

Possible third issue, although unlikely since the lights worked for a long period of time before the fault. Are you sharing the ground? If so you may be adding resistance to the reference ground path. If the design is for low side current sensing you could be adding resistance to a signal ground.

 

[OFC Ranger]

Are they stock LED tail lights and turn signal lights?

Hyper flashing is indicative of a burned out bulb or too low a current draw.

Ground fault would just trip the e-fuse in the BCM, and would reset on a key on/off cycle.

I've seen your wiring, so I'm purposefully not going down the road of a hack job on the splice, and ruled that out from the get go.

The issue is in one of two areas IMO.

(1) Hardware issue on the BCM. I assume you tried a hard reset by disconnecting the battery and allowing any capacitive charge to dissipate. Be mindful of the reset procedure for the BMS.

(2) If stock LED tail lights possibly a fault there. You could swap LR if the pinout is the same.

Possible third issue, although unlikely since the lights worked for a long period of time before the fault. Are you sharing the ground? If so you may be adding resistance to the reference ground path. If the design is for low side current sensing you could be adding resistance to a signal ground.

1. I have not, so now I will.

2. Yes I do have a quick disconnect point that is sharing grounds now with the tail light. Let me isolate the tail light ground and see if that helps.

 

[OFC Ranger]

Are they stock LED tail lights and turn signal lights?

Hyper flashing is indicative of a burned out bulb or too low a current draw.

Ground fault would just trip the e-fuse in the BCM, and would reset on a key on/off cycle.

I've seen your wiring, so I'm purposefully not going down the road of a hack job on the splice, and ruled that out from the get go.

The issue is in one of two areas IMO.

(1) Hardware issue on the BCM. I assume you tried a hard reset by disconnecting the battery and allowing any capacitive charge to dissipate. Be mindful of the reset procedure for the BMS.

(2) If stock LED tail lights possibly a fault there. You could swap LR if the pinout is the same.

Possible third issue, although unlikely since the lights worked for a long period of time before the fault. Are you sharing the ground? If so you may be adding resistance to the reference ground path. If the design is for low side current sensing you could be adding resistance to a signal ground.

1. I disco'd the negative from the battery for well over 30 minutes while I worked on another project. Am I missing another step when you say be mindful of the reset?

2. Can you elaborate in reference to LR pinout?

3. Tried running the ground to its own point and as expected did not work.

I've pulled the left tail light again and double for any break down. I even went as far as to replace the ground and signal splice on the off chance it went bad. I use heat actived pre-solder splices so it was doubtful, but I did it anyhow.

I get the hyper arrow even with everything completely disconnected lol

 

[JDowns]

1. I disco'd the negative from the battery for well over 30 minutes while I worked on another project. Am I missing another step when you say be mindful of the reset?

After battery replacement, or in some cases after charging the battery with an external charger, the battery management system requires eight hours of vehicle sleep time to relearn the battery state of charge. During this time your vehicle must remain fully locked with the ignition switched off. Not sure if this applies to just disconnecting the battery or not. But something to be mindful of.

2. Can you elaborate in reference to LR pinout?

My thought was you could see if the problem is related to the electronics inside the light housing itself. You can't mount the lights opposite of course, but if the pinouts (wire positions) are the same you could at least swap locations and plug them in. If the hyper-flash switches sides then the problem is in the housing. But if the wiring on the plug (pinouts) is different it would suck to blow a light housing.

I've pulled the left tail light again and double for any break down. I even went as far as to replace the ground and signal splice on the off chance it went bad. I use heat actived pre-solder splices so it was doubtful, but I did it anyhow.

I get the hyper arrow even with everything completely disconnected lol

My gut tells me you damaged the BCM with the addition of the LED bar, which most likely doesn't have constant current protection. You could isolate this by using FORSCAN and disabling the hyperflash. If disabling via FORSCAN works at this point, all roads would point to a damaged BCM. That may stop the hyper-flash, but its anyones guess if anyting else was damaged that may cause longer term issues.[/QUOTE]

 

[OFC Ranger]

Well here is the other mystery... why does the stock tail light signal still work, but the after market signal does not? They both share the same power source, very weird. Both are extremely low voltage items.

And know its not the after market signal because as we discussed, swapping it use the other side of the truck it functions fine.

Very weird all around...

 

[JDowns]

I think you have to break this down into buckets to diagnose.

This get's convoluted trying to type out the scenario, but here's the ole college try.

You have two circuits, left and right, with four current draw sources.

1. Left stock light housing
2. Left after-market signal
3. Right stock light housing
4. Right after-market signal

With everything stock you get a hyper-flash which points to the BCM interpreting the circuit as being under drawn on current, ie. bad bulb or replacement bulb drawing less current than expected.

In one setup the after-market signal does not function but if you swap to the other it functions as expected but you still get hyper-flash in both scenarios.

It's possible that the after-market signal went into thermal runaway damaging a circuit on the BCM resulting in a loss of its ability to read the current on the line and enough damage was done that now it puts out less current than the other side. There is enough current available for the stock LED but not with the addition of the after market signal. The after-market signal may (most likely) have a higher current draw demand than the stock light housing.

Sponsored