Attention: TDR Forum Junkies I finally finished building the circuitry and just need to finish up the cosmetics. Everything works just as I wanted it to. Special thanks go to Gizmo 007 and his post here Gizmo's Schematic
I expanded on the design and also added a cool down timer into it. My setup is activated by momentary switches, requires the emergency brake to be on, and depressing the brake will shut off the circuit.
There are few important things that I found out while building this and hooking it up.
1) The ECM should never see more than 3. 5 volts coming from the TPS wire. Normal idle voltage is 0. 46 volts. It took 0. 65 volts to make 900RPM and only 1. 05 volts to reach 2000RPM. A voltage regulator is highly recommended to keep from exceeding this voltage and to stop voltage fluctuations.
2) The ECM WILL FREAK OUT if it does not see AT LEAST 0. 4 volts coming from the TPS wire at ALL TIMES. I found that if I had the potentiometer turned all the way down upon activating the high idle circuit the engine would sometimes go to max RPM. If I started the circuit with the pot turned up high enough to supply at least 0. 4 volts and then turned it ll the way down and then back up the idle would not go up even though the ECM was being supplied 1+ volts.
I solved this problem by adding two 10k ohm trimmers in parallel after the voltage regulator. One trimmer controls the minimum voltage and the other the max voltage. These trimmers must be diode protected from each other so that they don't use each others sinks. I set mine up so that the minimum RPM is 900 and max is 1800.
3) If you use the emergency break switch be aware it is a GROUND SWITCH. It allows 5V from the instrument panel light to go to ground. This 5V source NEEDS to be DIODE PROTECTED. I used the EB switch as my sole ground for my circuit.
4) Fuse #9 is what needs to see 12V in order to keep the truck running with the key off. Even though it is a 10 amp fuse, it is actually powering a relay and only pulls milliamps worth of current.
I had thought about including a schematic of my circuit but I made it a little complex and if not copied exactly would cause some problems. I am by no means an expert in circuitry but I do have some training. I still managed to blow one fuse, one diode and had to rewire three connections. Here is a pic of the black box. There are 16 wires coming out of it. It is mounted on top of the underhood fuse box to keep the TPS wires as short as possible without having too much heat.
I expanded on the design and also added a cool down timer into it. My setup is activated by momentary switches, requires the emergency brake to be on, and depressing the brake will shut off the circuit.
There are few important things that I found out while building this and hooking it up.
1) The ECM should never see more than 3. 5 volts coming from the TPS wire. Normal idle voltage is 0. 46 volts. It took 0. 65 volts to make 900RPM and only 1. 05 volts to reach 2000RPM. A voltage regulator is highly recommended to keep from exceeding this voltage and to stop voltage fluctuations.
2) The ECM WILL FREAK OUT if it does not see AT LEAST 0. 4 volts coming from the TPS wire at ALL TIMES. I found that if I had the potentiometer turned all the way down upon activating the high idle circuit the engine would sometimes go to max RPM. If I started the circuit with the pot turned up high enough to supply at least 0. 4 volts and then turned it ll the way down and then back up the idle would not go up even though the ECM was being supplied 1+ volts.
I solved this problem by adding two 10k ohm trimmers in parallel after the voltage regulator. One trimmer controls the minimum voltage and the other the max voltage. These trimmers must be diode protected from each other so that they don't use each others sinks. I set mine up so that the minimum RPM is 900 and max is 1800.
3) If you use the emergency break switch be aware it is a GROUND SWITCH. It allows 5V from the instrument panel light to go to ground. This 5V source NEEDS to be DIODE PROTECTED. I used the EB switch as my sole ground for my circuit.
4) Fuse #9 is what needs to see 12V in order to keep the truck running with the key off. Even though it is a 10 amp fuse, it is actually powering a relay and only pulls milliamps worth of current.
I had thought about including a schematic of my circuit but I made it a little complex and if not copied exactly would cause some problems. I am by no means an expert in circuitry but I do have some training. I still managed to blow one fuse, one diode and had to rewire three connections. Here is a pic of the black box. There are 16 wires coming out of it. It is mounted on top of the underhood fuse box to keep the TPS wires as short as possible without having too much heat.
Last edited:
