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Pete, Auto Service Technician
Category: Ford
Satisfied Customers: 28197
Experience:  Over 17 years diagnosing and repairing automobiles various makes and models with some training and certifications.
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2005 f650 with cummins engine and allison1000 trans, has no

Customer Question

2005 f650 with cummins engine and allison1000 trans, has no tcc engagement most of the time,no dtc's,and the tcm is not commanding lock-up,all inputs look ok on the scanner
Submitted: 1 year ago.
Category: Ford
Expert:  Pete replied 1 year ago.

Hi my name is ***** ***** I will be happy to assist with this today.I apologize for any delay.

If the brake switch is sticking on this can cause the TCC fault here to where the computer will not command the TCC on.Even if the brake lights are operating properly on some models the switch uses a dual circuit which can if acting up disable the TCC from operating properly.

I have also seen issues with throttle position sensor signals causing faults like this as well needing replaced.

These should be checked to see if the fault can be located and repaired from there.

Thanks Pete

Customer: replied 1 year ago.
I'm sorry,my notes are mixed up vehicle is an 02 Freightliner MT-45 with cummins eng. and Allison 1000 trans, no commanded tcc with no dtc's
Expert:  Pete replied 1 year ago.

O.k.,this can still be the same issue here with a faulty brake switch/sensor signal to where it may be stuck engaged which will keep the TCC from operating.Same with the throttle position sensor if this is sending a false signal on the throttle position this can cause TCC disengagement or no engagement.These will have to be checked into to locate which is the cause here and repaired from there.

Thanks Pete

Customer: replied 1 year ago.
brake input on scanner is correct, tps signal is smooth and seems to be accurate
Expert:  Pete replied 1 year ago.

Are you able to obtain a cruising speed at all with the throttle when going down the road or are you needing to apply moderate throttle to keep the vehicle at a steady speed?

Customer: replied 1 year ago.
normal throttle
Expert:  Pete replied 1 year ago.

The only thing that makes sense here since all of the inputs are correct is an internal fault in the computer itself not sending a signal or commanding a signal to lock up the torque converter.Usually if it is a transmission fault you would see the commanded state turn on but in this case this isn't turning on and this sounds like the computer itself may be causing this.

Thanks Pete