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Dodge Repair/Sensor Signal Modification: '03 Ram torque converter

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Trans Temp Signal
Trans Temp Signal  
QUESTION: I have a 2003 Dodge Ram 2500 with a 5.7 hemi and a 4 speed automatic (46RE)transmission. The torque convertor lockup will lockup in 3rd and 4th gears only - and also in 2nd gear manual select position when the transmission is overheated.  I would like to generate a false transmission high temperature signal to allow me to use 2nd gear with the convertor locked up when pulling my holiday trailer up hills. This would drop engine rpm by ~500 rpm and allow me to keep up with traffic on inclines.  I tried splicing into the violet wire on the transmission control module (Terminal 54, transmission temperature sensor signal)and installing a potentiometer on it.  This allows me to drop the voltage on this wire (right down to 0V, depending on how far the knob is rotated) and should trigger a high temperature signal at some voltage.  But it doesn't do anything that I can discern.  I have a voltmeter attached and can observe the normal voltage, which declines as the unit warms up from ~2.9 to ~1.1 V, and then the subsequent reductions when the potentiometer is activated.  Any suggestions?
Thanks, Martin

ANSWER: Hi Martin,
I am not an expert on the torque converter lock-up control programming. I wonder whether you will actually keep up with traffic better by operating at 500 rpm less. It may be that you can actually maintain a higher speed with the torque converter not locked up, albeit at a higher rpm. I picture the lockup as a feature that increases fuel economy but I am not sure that it will improve your speed going up hill if you use it then. You may simply have to accept the higher rpm under those conditions. I wish I could explain why you have not been successful in your effort as it looks plausible. But there may be more factors involved in achieving it.
Roland

PSK: See page 580 of the transmission chapter. It appears that the clutch control programming is quite detailed, and I would doubt that you can fake it out as you are attempting to do by altering just the temperature sensor reading.  

---------- FOLLOW-UP ----------

QUESTION: Thanks for your answer. What I want to find out is how do I get the computer to think there is a transmission high temperature condition.  If I can do this then the shop manual tells me that my vehicle will go into second gear torque convertor lockup, when I manually select 2nd gear.  (In Drive it will go into 3 lockup).  If I had a 5.9, 7.0 or diesel, it would be easy to get the torque convertor to lockup as there is a dedicated circuit going to the trans for this, however, with the onset of the 5.7 this was eliminated.  I thought I had it right, any suggestions...
Thanks again, Martin

Answer
Hi Martin,
Unfortunately the Chrysler service manual which we both have does indicate in the transmission wiring diagrams that there are differences between those various engine choices .
So my belief is that there is likely also a different tcm for those other engine models, and possibly also a different transmission as well. What you have tried appears to me to be a way of modifying the temperature sensor reading but that alone is not enough to produce the 2nd gear lock-up that you are seeking. If there is nothing wrong with your drivetrain but rather that you are seeking a choice that is not offered for the 5.7/46RE then you may have seek advice from Chrysler Corp. directly. I don't know if they offer such advice.
Roland

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Roland Finston

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Get a Free Fast answer to your repair question about a Chrysler/Dodge/Plymouth car, minivan, SUV, or truck. Problems with electronically controlled engines and transmissions as well as body wiring problems are my specialty. This free troubleshoot advice forum helps you diagnose faults, minimize repair costs or do-it-yourself.

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Degrees in Physics/bruised knuckles.

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