Attention: TDR Forum Junkies 
After reviewing around 1,000 posts on 5 different forums, I have come up dry on how to manually activate the high idle function on a Manual, 2003, HO truck. The stock “sensor driven” high idle is there, but no on has found a way to make it come on when desired. (It works automatically when the temperature is cold enough. ) One person has designed and demonstrated how to do it on a Gen 2 truck, but not on a 2003.
The Gen 2 solution was to lie to the ECM. There was only a two wire sensor in the Gen Two 24 valve trucks, providing intake air temperature to the ECM. Moparman73 designed a fix involving two switches and a splice into the existing wiring (see following url:
Mopar1973Man's Cummins Site • View topic - High idle feature... ). Two different resistors were chosen, whose values told the ECM that it was below 32 degrees, or below 13 degrees. When the ECM sees 32 degrees, it activates a 1,000 rpm high idle (not adjustable). When the ECM sees below 13 degrees, it also shuts down 3 cylinders, which provides even more heat production. Moparman73’s fix allowed him to use an in-cab switch selecting the two additional resistors instead of the actual sensor, a second in-cab switch allowed him to select which of the two resistors was inserted into the circuit.
Unfortunately, the 2003 truck added a manifold absolute sensor (MAP) in the same widget attached to the intake air box. There are now 4 wires instead of two. One of the wires provides 5 volts to both sensors. There is also a common ground to the two sensors. That leaves two wires, one providing the temperature signal to the ECM, and the other providing the intake air temperature to the ECM.
I have metered the wires with an accurate ohm meter. Neither sensor resistance is anywhere near the values quoted by Moparman73, so the actual values have changed. With no comparisons, I would just be guessing which wires were the ones driving intake air temperature.
Intend to purchase an intake box sensor tomorrow, and then do some extensive testing to find out just which two wires I need to use to try and lie to the 2003 ECM. I can see no reason why the technique which worked on the Gen 2 truck will not also work on the 2003.
I intend to cross post this on the four most popular Cummins/Dodge forums. Anyone providing hard information on the subject will have his data cross posted to the other forums. I know that “someone” out there has the missing bits of knowledge to allow us to do this. I am determined to get it done.
All the best,
Bill S.
The Gen 2 solution was to lie to the ECM. There was only a two wire sensor in the Gen Two 24 valve trucks, providing intake air temperature to the ECM. Moparman73 designed a fix involving two switches and a splice into the existing wiring (see following url:
Mopar1973Man's Cummins Site • View topic - High idle feature... ). Two different resistors were chosen, whose values told the ECM that it was below 32 degrees, or below 13 degrees. When the ECM sees 32 degrees, it activates a 1,000 rpm high idle (not adjustable). When the ECM sees below 13 degrees, it also shuts down 3 cylinders, which provides even more heat production. Moparman73’s fix allowed him to use an in-cab switch selecting the two additional resistors instead of the actual sensor, a second in-cab switch allowed him to select which of the two resistors was inserted into the circuit.
Unfortunately, the 2003 truck added a manifold absolute sensor (MAP) in the same widget attached to the intake air box. There are now 4 wires instead of two. One of the wires provides 5 volts to both sensors. There is also a common ground to the two sensors. That leaves two wires, one providing the temperature signal to the ECM, and the other providing the intake air temperature to the ECM.
I have metered the wires with an accurate ohm meter. Neither sensor resistance is anywhere near the values quoted by Moparman73, so the actual values have changed. With no comparisons, I would just be guessing which wires were the ones driving intake air temperature.
Intend to purchase an intake box sensor tomorrow, and then do some extensive testing to find out just which two wires I need to use to try and lie to the 2003 ECM. I can see no reason why the technique which worked on the Gen 2 truck will not also work on the 2003.
I intend to cross post this on the four most popular Cummins/Dodge forums. Anyone providing hard information on the subject will have his data cross posted to the other forums. I know that “someone” out there has the missing bits of knowledge to allow us to do this. I am determined to get it done.
All the best,
Bill S.
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