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LED Tail Light w/ Brake Light - Low Voltage PSB/ABS Failure


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Looking for help in resolving a low voltage situation with my 2002 996 C4 Cab. I installed a pair of LED smoke clear tail lights and I immediately received a PSB/ABS failure message on the dash. I also have the LED brake lights, btw. The overall swap out would have been fairly easy, but in the process I uncovered that the stock tail light harness bulb socket prongs had broken and caused a short. So, after a bit of debugging I was finally able to get beyond that issue. Also, had the usual blinker cadence issue, so I installed resistors and have the blinkers back to the proper cadence.

I stopped into my local Porsche shop here in Scottsdale (Beck's European) and he was able to confirm that I have a low voltage situation, due to the LED tail lights. My conundrum is, where would I need to put another resistor to solve the current issue? The tech at the shop could see the voltage, when the brake pedal was depressed, was below 12v, so the computer is triggering a brake switch error and then putting the PBS/ABS into a failure state.

Would really appreciate any help and guidance on this. Seems I do need to add a resistor(s), but not sure if I need one on each tail light and if so, what wires would the resistor go between?

Anybody work through this issue before?

Thanks in advance...

G

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Hi,

You can resolve the problem by buying a load equalizer from ex.Autozone for about $10. You get two of them and you don't have to cut the wires to do the job. They also come with simple instructions.

If you have stock tail lights and add an LED 3rd brake light, you have no issues. Also no issues, when you have a stock 3rd brake light and add LED tail lights. You only have issues when all your brake lights are LED

KL

Looking for help in resolving a low voltage situation with my 2002 996 C4 Cab. I installed a pair of LED smoke clear tail lights and I immediately received a PSB/ABS failure message on the dash. I also have the LED brake lights, btw. The overall swap out would have been fairly easy, but in the process I uncovered that the stock tail light harness bulb socket prongs had broken and caused a short. So, after a bit of debugging I was finally able to get beyond that issue. Also, had the usual blinker cadence issue, so I installed resistors and have the blinkers back to the proper cadence.

I stopped into my local Porsche shop here in Scottsdale (Beck's European) and he was able to confirm that I have a low voltage situation, due to the LED tail lights. My conundrum is, where would I need to put another resistor to solve the current issue? The tech at the shop could see the voltage, when the brake pedal was depressed, was below 12v, so the computer is triggering a brake switch error and then putting the PBS/ABS into a failure state.

Would really appreciate any help and guidance on this. Seems I do need to add a resistor(s), but not sure if I need one on each tail light and if so, what wires would the resistor go between?

Anybody work through this issue before?

Thanks in advance...

G

post-18320-1263924534_thumb.jpg

Edited by kristian
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Looking for help in resolving a low voltage situation with my 2002 996 C4 Cab. I installed a pair of LED smoke clear tail lights and I immediately received a PSB/ABS failure message on the dash. I also have the LED brake lights, btw. The overall swap out would have been fairly easy, but in the process I uncovered that the stock tail light harness bulb socket prongs had broken and caused a short. So, after a bit of debugging I was finally able to get beyond that issue. Also, had the usual blinker cadence issue, so I installed resistors and have the blinkers back to the proper cadence.

I stopped into my local Porsche shop here in Scottsdale (Beck's European) and he was able to confirm that I have a low voltage situation, due to the LED tail lights. My conundrum is, where would I need to put another resistor to solve the current issue? The tech at the shop could see the voltage, when the brake pedal was depressed, was below 12v, so the computer is triggering a brake switch error and then putting the PBS/ABS into a failure state.

Would really appreciate any help and guidance on this. Seems I do need to add a resistor(s), but not sure if I need one on each tail light and if so, what wires would the resistor go between?

Anybody work through this issue before?

Thanks in advance...

G

Apparently you haven't yet noticed but your CC is also disabled.

In my RX300 I went in and modified the current flow sensing aspects of the bulb failure detection controller so it was satisfied with the lower (~10:1) LED current flow.

For my '01 C4 I simply added a relay and a 50 watt incandescent bulb in the LED high mount circuit behind the high mount itself. The NC contacts of the relay connect the bulb into the circuit, satisfying the CC bulb "keep-alive" current flow requirement. When a full 12 volts is applied (the brake lights are on) the relay pick sup and takes the 50 watt incandescent out of the circuit.

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Here's the wiring instructions.

KL

Looking for help in resolving a low voltage situation with my 2002 996 C4 Cab. I installed a pair of LED smoke clear tail lights and I immediately received a PSB/ABS failure message on the dash. I also have the LED brake lights, btw. The overall swap out would have been fairly easy, but in the process I uncovered that the stock tail light harness bulb socket prongs had broken and caused a short. So, after a bit of debugging I was finally able to get beyond that issue. Also, had the usual blinker cadence issue, so I installed resistors and have the blinkers back to the proper cadence.

I stopped into my local Porsche shop here in Scottsdale (Beck's European) and he was able to confirm that I have a low voltage situation, due to the LED tail lights. My conundrum is, where would I need to put another resistor to solve the current issue? The tech at the shop could see the voltage, when the brake pedal was depressed, was below 12v, so the computer is triggering a brake switch error and then putting the PBS/ABS into a failure state.

Would really appreciate any help and guidance on this. Seems I do need to add a resistor(s), but not sure if I need one on each tail light and if so, what wires would the resistor go between?

Anybody work through this issue before?

Thanks in advance...

G

Apparently you haven't yet noticed but your CC is also disabled.

In my RX300 I went in and modified the current flow sensing aspects of the bulb failure detection controller so it was satisfied with the lower (~10:1) LED current flow.

For my '01 C4 I simply added a relay and a 50 watt incandescent bulb in the LED high mount circuit behind the high mount itself. The NC contacts of the relay connect the bulb into the circuit, satisfying the CC bulb "keep-alive" current flow requirement. When a full 12 volts is applied (the brake lights are on) the relay pick sup and takes the 50 watt incandescent out of the circuit.

post-18320-1263924704_thumb.jpg

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