how to trick the PCM?????

Zookie400

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i tried the trailer OD 4 way flasher thing.....nothing.....what is supposed to happen? my truck is a 97.
 

94f450sd

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well?????anybody gonna answer the question?my 94 superduty and the 95 PSD both unlock the converter,turn off over drive and cruise when a brake,turn light is out.its a known fact that these trucks do this.i really dont care to argue about it i just want to know how to stop it so i can run all LEDS on my truck
 

stroker21

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well?????anybody gonna answer the question?my 94 superduty and the 95 PSD both unlock the converter,turn off over drive and cruise when a brake,turn light is out.its a known fact that these trucks do this.i really dont care to argue about it i just want to know how to stop it so i can run all LEDS on my truck

I don't hink anyone really knows what to do. You can be the first to experiment and then be educated and can tell everyone else that wants to do it how to. If people don't know that it does it, then they dang sure don't know how to fix it.
 

bushpilot

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seems to me if you know what CAUSES it then you fix isnt far off...
is it measured by resistance or current of the bulb...
 

94f450sd

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well the issue is i dont know much about electronics as in can i wire a resistor between the brake/turn wire and ground?that was my original question and still hasnt been answered.but the heck with it.really dont care about it anymore anyways.
 

stroker21

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What I would do then is take a OEM bulb and then measure the resistance across it. Then measure the resistance across the LED bulb if they are different then get a resistor to put in their. Make sure to get a good resistor. I don't see why this would not work.I guess I never got the original question. But this should work because the PCM will read the same resistance. But my bulbs have resitors already wired into the configuration.
 

bushpilot

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installing LED bulbs for the sake of installing 'em is DUMB IMO...
the idea of installing an LED bulb is to 1) obtain BRIGHTER light
and 2) reduce the current load on the electrical system.

additional benefits of GOOD led bulbs are longer life...(they arent
cheaper than conventional bulbs, thats for sure)

adding a RESISTOR to "fake" the pcm defeats one of the BIG benefits
of LED bulbs...installing LED's behind FACTORY lens' may NOT give you
better lighting (all angles should be taken into consideration when viewing
bulbs of ANY KIND).
 

Zookie400

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1- measuring the resistance of a col bulb wont do anything for you, because depending on the temp. of the element the resistance changes.

2-rather than trying to trick the pcm, wich could be done but will be way to complicated, KEEP IT SIMPLE. buy the led lights that are designed for applications like this.

i work for a freightliner dealer, and i dont have anything on the web to give you a link for but i know i have seen these in both the truck-lite book and the grote book. they are designed for vehicles that dont use a solid state blinker. all pcm issues set aside, if you put standard leds in your blinkers will go 50 flashes per second. they make leds that mock incandecents as far as resistance and amperage draw to eliminate this problem, and likely, your pcm issue.

my father had a 97 250 7.3 e4od, with a utility body that had one of these "special" leds on each side, and had no problems.
 

94f450sd

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heres the thing.its not a pickup its a tow truck so i have no "factory" lighting in the back.i already have LEDs under the bed.but i have 2 normal lights in my whelen lightbar.i want to get rid of those and get the LEDs that whelen made for this lightbar as i cant just stick any old LED up in there.

well thanx anyways ill just go back to the original idea of wireing in 2 regular bulbs under the truck and painting them black or something.
 

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