How I installed Tow/Haul without BCM
01-26-2016, 06:52 PM
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How I installed Tow/Haul without BCM I have had a few people ask how I did my tow haul and figured I would put it up for those that were interested. This is completely stand alone meaning NO BCM needed. Its also a good way to tell in the relay failed to latch (causing tow haul to not engage) because if it does then the led wont turn on.
Material used:
1- Pac Tr7
1- 2002 Blazer center console Tow/Haul button and harness
1- 390 Ohms 5% resistor
1- Led, I used a smd 5050 bright white
1- Diode
Misc. wire, shrink wrap, solders terminals.
The first thing I did was add a pin to the PCM harness on pin 71 in the blue connector
Then I flashed the PCM using HP tuners. Open your flash with the VCM editor the go to trans tab . Click the Auto Shift Propertied and go to Perf Option. Select One switch. Now flash it to the PCM.
I then went to work on adding a button to my s10 so I could test new shift points. The first thing I did was add a 4th wire the pig tail as the stock one only has 3.
I then disassembled the button. I did this for 3 reasons. The first was to clean the contacts seeing as I cannot seem to find a source to buy a new one. The second was to change the light bulb for a led and the third was to change what pins the light used.
You can see here it uses pin B and A
I had some of these led lights left over from my first gen s10 so I used it for the led and soldered a resistor to it. Then I tucked it in and soldered it moving it from pins B and A to Pins A and C. By doing this it gives me room for two separate circuits B and D now for negative only. This is the trigger for the PCM to activate Tow/Haul and activates the negative input trigger on the TR-7.
As you can see it lights up bright enough to see in the day but not too bright to blind me at night.
The relay will need to be programmed to select option 3 to set it as a latch option. This will let you turn it on and off with the button and it will automatically shut it off with the ignition. Just like stock. I added a died to the line going to the PCM because in the paperwork for the TR7 it says that positive and negative out put share a circuit and I'm paranoid it'll short out and fry my PCM.
Sorry Im not an artist. This is how I wired it.
and this is my toy.....
Material used:
1- Pac Tr7
1- 2002 Blazer center console Tow/Haul button and harness
1- 390 Ohms 5% resistor
1- Led, I used a smd 5050 bright white
1- Diode
Misc. wire, shrink wrap, solders terminals.
The first thing I did was add a pin to the PCM harness on pin 71 in the blue connector
Then I flashed the PCM using HP tuners. Open your flash with the VCM editor the go to trans tab . Click the Auto Shift Propertied and go to Perf Option. Select One switch. Now flash it to the PCM.
I then went to work on adding a button to my s10 so I could test new shift points. The first thing I did was add a 4th wire the pig tail as the stock one only has 3.
I then disassembled the button. I did this for 3 reasons. The first was to clean the contacts seeing as I cannot seem to find a source to buy a new one. The second was to change the light bulb for a led and the third was to change what pins the light used.
You can see here it uses pin B and A
I had some of these led lights left over from my first gen s10 so I used it for the led and soldered a resistor to it. Then I tucked it in and soldered it moving it from pins B and A to Pins A and C. By doing this it gives me room for two separate circuits B and D now for negative only. This is the trigger for the PCM to activate Tow/Haul and activates the negative input trigger on the TR-7.
As you can see it lights up bright enough to see in the day but not too bright to blind me at night.
The relay will need to be programmed to select option 3 to set it as a latch option. This will let you turn it on and off with the button and it will automatically shut it off with the ignition. Just like stock. I added a died to the line going to the PCM because in the paperwork for the TR7 it says that positive and negative out put share a circuit and I'm paranoid it'll short out and fry my PCM.
Sorry Im not an artist. This is how I wired it.
and this is my toy.....
Last edited by Brandenhs; 01-27-2016 at 05:43 AM. Reason: wrong wiring diagram
