Flashing OD, Several Error Codes - HELP!

[Mutchinator]

2001 Ford Explorer Sport 145k Miles

My Check Engine Light began intermittently turning on a few weeks ago; until it remained on constantly. Then two weeks ago my Overdrive Light began flashing at times - when this occurs the engine seemed to either not shift into the next gear or not shift down to the previous one. Also, when it begins flashing the only was to alleviate the problem is to turn the truck off and on again. I believe it occurs when the engine tries to shift down from OD or 4th gear - but have not been able to totally guarantee this is the case. Also, shifting seems very fast/hard (i.e. tranny is shifting very early all the way up) during non-OD-Flashing times.

I took to a garage and there were about 10 Engine Error codes - very suspicous of a possible computer problem I was told. The Neutral Safety Switch was replaced (it was obviously bad), but the problem remained. So, we found a used ECU/ECM (computer) and replaced the existing - same problem. Two errors which stick out are the Neutral Safety Switch Error and Turbine Speed Sensor.

The strange thing found was the TRANSRANGE voltages being measured through the Garage Diagnostics System:

Park = .01V, R = 1.66V, N = 1.66V, D=1.66V, 1=.01V, 2=.01V

These exact same values were measured with BOTH Neutral Safety Switch's and through BOTH ECM's. This seems incredibly strange...

Any ideas? The garage owner does not want to rib apart the transmission at this point as this seems to point to an electrical problem - I give him credit for not raking me over the coals just yet.

Any help would be greatly appreciated - I can drive, but find myself often pulling to the side of the road in order to restart/reset the truck.

One last interesting note, the garage happened to have a 2000 Ford Taurus with tranny problems which was showing the EXACT same TransRange Voltages.

 

[Glacier991]

Generally when error codes pop up, you start by fixing all the engine codes. One by one.... often it may be something there that is causing your trans complaints.

It would be helpful to know all your codes.

As for the trasnmission range sensor (I think you are calling this the neutral safety switch - it also serves that function) the range of correct values using the Rotunda Transmission Tester is:

Position Resistance Voltage

PARK 3770-4607 3.97-4.85
REVERSE 1304-1593 3.24-3.96
NEUTRAL 660-807 2.55-3.11
OD 361-442 1.88-2.30
D/2 190-232 1.23-1.51

If you are just using a DVOM, the proedure is to put the transmission in D, and measure voltage (car not running but ignition ON) between pin 6 and 7 - the middle pins farthest from the clip on the connector... it should be between 4.75 and 5.25 volts. If not.... then we suspect a harness issue.

I cannot explain your readings, are you getting a solid VREF voltage?

Your mechanic is an honest one it sounds. I would inspect all the harnesses and make sure you are getting a good ground and a good solid VREF voltage.

Get me all the codes, I can be a better help.

Your rough shifts are probably the computer going into "limp" mode (FMEM it is called). It bumps up pressures so you can at least "limp" somewhere.

 

[Mutchinator]

Thank you much for the quick response. I will obtain all of the error codes and post tomorrow - one quick note, though. A DVOM was not used, it was actually the readings through the Diagnostic System (I am sure I am not using the correct term, but it is the same device used to obtain the error codes). I actually am hoping to measure the Voltages from the Range Sensor directly to see what it is putting out.

Also, when the "failure" occurs I can still drive although the car is either revving too much (i.e. 5k RPM at 60MPH) or working hard to get up to speed.