Question on speed sensor & standard transmission

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chasmosis1

chasmosis1

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Obviously I'm new here, however I am far from new to the scene. I am actually in the process of installing an 04 Ram 5.7 into a Jeep YJ. I am going to build/modify the factory harness myself. I have already identified all of the needed pinouts with the FSM. I am using an AX15 connected through a 3.9 bellhousing. Question is whether I need the speed sensor signal for the PCM or is it strictly for shifting the trans? I would like to completely remove the C4 connector, but want to confirm that the speed sensor is unnecessary. I will either be using the AX15 speed sensor to send the signal to the factory electronic dash (using a 5v signal from the 5.7 PCM) or I will use a cable driven speedo. Programming is not an issue as I have the equipment and knowledge for that and will be shutting off the trans, rear O2's, & EGR. I am seeing nothing in the PCM that would require the signal, but I also know that today's programming only shows a limited portion of what the Dodge PCM is capable of.
 
I cant tell you for sure, but I can tell you my manual trans Hotwire harness does not even have the 4th ECU connector which, as I understand it, is the trans part of the harness.
 
I'm not sure as well, but I can tell you what I'm experiencing with my car. 5.7, Dakota ax15, no speed sensor, modified factory harness, hotwire PCM, bypassed clutch switch. When I shove in the clutch coming to a stop, the car will stall unless I blip the throttle, runs great otherwise. May be no clutch or speed signal, could be neither. I've just been driving it all summer that way, but over the winter I may add one or both to see if the problem goes away. I had a similar issue with my magnum swap car, and adding the speed sensor cured it.
 
Thanks for the input guys. This is exactly what I'm looking for. I have heard of issues with cars stalling when coming to a stop, but I also know, as co440da says, the C4 (green) plug is nonexistent on the standard shift vehicles. C4 is actually the transmission part of the PCM and that is where the 2 speed sensors from the trans connects to. However, after looking through the FSM as well as the harness that I started modifying this evening I am now seeing that the C1 (black) connector actually uses 2 speed signals that are coming from the Front wheel sensor(s) that I though we're just for ABS.......now I am thinking they are actually for this issue......cu440da are you still in the building stage or are you actually driving yours? Do you have a speed sensor connector on your Hotwire harness? If you do is it connected to anything? Is there any possibility you could look and see if there are any wires coming from the C1 (black) connector position 8 (top row 8th from the left) and/or position 13 (2nd row 3rd from the left) (looking at it while it is plugged in)? I really appreciate the help guys.......once I get this figured out I will be more than happy to pass on the information so that others can modify their own harnesses as well.
 
ralphie361 said:
When I shove in the clutch coming to a stop, the car will stall unless I blip the throttle, runs great otherwise.
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I was experiencing this as well. Did some googling and reading. Try taking your throttle body off and cleaning the bore spotless. Use brake cleaner, not throttle body cleaner. Mopar states that throttle body cleaner will destroy the electronics. My stalling stopped after I cleaned mine and it was caked thicker than it looked at first. It still idles low and recovers from time to time, but I have read that may be due to old plugs as well.
 
Chasmosis- I am driving it. There is no speed sensor of any kind in my harness. The only wires from the Hotwire harness hooked up to my transmission are for the reverse lockout solonoid.

I will check on those wires in the C1 plug tomorrow for you.

The front wheel speed sensors could be for the torque management and/or traction control circuits as well as the ABS. I can't think of what else would need that type of input.
 
cu440da said:
Chasmosis- I am driving it. There is no speed sensor of any kind in my harness. The only wires from the Hotwire harness hooked up to my transmission are for the reverse lockout solonoid.

I will check on those wires in the C1 plug tomorrow for you.

The front wheel speed sensors could be for the torque management and/or traction control circuits as well as the ABS. I can't think of what else would need that type of input.
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That makes sense! There are some settings that I can play with for TM in the PCM and I may do that if I find it necessary. I think I will just go without a VSS wire for now as I have other options available for my speedometer. I have C4 completely removed from the harness at this point, as well as everything that is unnecessary in C1 & C2. I am now working on C3 (white) which is actually a part of the harness they refer to as the "dash side harness" this is the one that apparently supplies power to the harness/PCM and will receive the fuse box & relays.

Thanks, Chas
 
cu440da said:
I was experiencing this as well. Did some googling and reading. Try taking your throttle body off and cleaning the bore spotless. Use brake cleaner, not throttle body cleaner. Mopar states that throttle body cleaner will destroy the electronics. My stalling stopped after I cleaned mine and it was caked thicker than it looked at first. It still idles low and recovers from time to time, but I have read that may be due to old plugs as well.
Click to expand...

I'll try that, I can't remember if I cleaned it or not, thanks!
 
cu440da said:
Chas,

There are no connections in my harness for 8 or 13.
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Thank you cu440da! That definitely tells me the PCM (at least yours from Hotwire) does not use the VSS signal. I appreciate it. I will keep this thread updated on what I find. I started a thread on FBBO also, but it yielded no usable replies.

Chas
 
In general, a speed sensor is part of the idle speed control. If the throttle is closed and speed is zero, the PCM regulates idle speed. Idle speed, is not adjusted when coasting, where speed is not zero. If the PCM thinks the speed is zero at coast, idle control cuts back on by pass air attempting to bring engine speed down, but results in stall when coming to stop, due to delay in control to raise speed again, from over speed cut.

If there is a TB bypass air adjustment, it can be set where the minimum idle speed is maintaned, when idle control is at minimum. That will avoid stalling, yet control idle speed for other loading conditions.
 
KitCarlson said:
In general, a speed sensor is part of the idle speed control. If the throttle is closed and speed is zero, the PCM regulates idle speed. Idle speed, is not adjusted when coasting, where speed is not zero. If the PCM thinks the speed is zero at coast, idle control cuts back on by pass air attempting to bring engine speed down, but results in stall when coming to stop, due to delay in control to raise speed again, from over speed cut.

If there is a TB bypass air adjustment, it can be set where the minimum idle speed is maintaned, when idle control is at minimum. That will avoid stalling, yet control idle speed for other loading conditions.
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KitCarlson thank you for your input. I am not against using a VSS signal, I am merely trying to figure out if one is necessary. From your reply it does sound as though it may not be necessary, it would make it simpler. My question now is whether the Jeep VSS signal http://www.rockauto.com/catalog/moreinfo.php?pk=40822&cc=1185207&jnid=409&jpid=0 would work, or if I can use the signal from the Ford 8.8 sensor http://www.rockauto.com/catalog/moreinfo.php?pk=1268469&cc=1354553&jnid=534&jpid=1 as I have changed the Dana 35 to the 8.8 already.
 
I can only guess based on limited information at hand. My guess is the pulse rate of the Jeep sensor will less than the ford. If I was there, I would make a simple circuit with pot and micro, to make test pulses. Then test, and see what is required.
 
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