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Just joined today have been a Mechanic for 40 years Cars mostly.I work at a independent shop in Dearborn Mich. I have 93 7.3 ( Not a Power stroke) that is from another shop. The trans does not shift, If the shifter is pulled it down in low and accelerate then move shifter into drive it will shift one time. The tach does not work, I put in a new RPM sensor (the original one was open) I believe the tach is bad. I do have a RPM signal.
I have a digital signal (PSOM) coming out of the cluster but I'm not sure it's normal. top and bottom are sloped equaly and it's peak to peak is 4 volts when in gear. seems to me it should be a normal square wave with a positive to ground toggle.
Also I am unable to pull codes from the TCM. The power and grounds are all good and the STI and STO wire continuity is good.I suspect the TCM is bad. Can use some help...Carl
 

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A common problem with these is the EEC power relay failing. This prevents the TCM from powering up. Your symptoms exactly match that of a bad power relay.

On the TCM connector check pins 37 & 57 for +12 volts. I'll bet it isn't there, indicating the TCM isn't powered.
 
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