Lost: Transmission Control Module 2003 AT

[ContraAl]

I'm trying to figure out how the PCM reads the vehicle speed on a 2003 LE Automatic. The shop manual shows it for a manual trans but nothing for the automatic.

Usually there is an White/Orange speed sensor wire that sends the signal from the speed sensor or TCM to the PCM.

Problem 1.. There is no TCM in the standard location on my 2003 LE automatic.

Problem 2.. There is no White/Orange wire in any harness at the PCM.

Question... Does anyone know how the PCM reads the vehicle speed or the color of the wire?

Yes, I have checked the Mopar 2003 and 2003 shop manuals. I also picked up the new Chilton manual.

[MX-5]

Page 8W-31-3 of the 2003 manual shows the speed sensor circuit.

Pin 32 of connector #4 at the PCM recieves the signal on a Light Green with White stripe wire.

From page 8E-7:

The PCM monitors gear ratio changes by monitoring
the Input and Output Speed Sensors. The Input,
or Turbine Speed Sensor sends an electrical signal to
the PCM that represents input shaft rpm. The Output
Speed Sensor provides the PCM with output
shaft speed information.
By comparing the two inputs, the PCM can determine
transaxle gear ratio.


That wasn't too hard. What are you trying to do?

[ContraAl]

This was the original question..

But I just read a little tidbit that would have halped long ago..

From page 8E-7:

The PCM is an engine and transmission controller
module all in one, if the vehicle is equipped with an
automatic transmission.


See my GPS is running in portable mode, which sucks. So I've been trying to find a white/orange wire. Well since it doesn't exist where people keep saying it is. I decided to go hunt down the TCM and see if I could tag it there. Well I looked again and it wasn't there.. But it all makes sense now..

Since the PCM compares the input and output signal to determine speed. How accurate would just tagging the output signal be? If the output signal (LG/W) and the vehicle speed (WH/O) are different or are they pretty close to the same signal?

[MX-5]

See....

It was the manual/auto trans that caused the confusion.
It wasn't until you specified the auto trans that I noticed the differences in the wiring.

That wire and PCM input to pin 13 is for the manual trans only.

This is also the same mess that makes my sporty shift-mod not available for the 2003 PT.

The output speed sensor should be a simple AC square wave. The voltage should be a constant 5vdc and the pulse width will decrease with increase in speed.