2005 tn70a shuttle shift problems

[patti13]

My tractor just stopped going forward or backward in the middle of using it. The shifter will shift and it starts but won't move. The blinking code is 77. The wiring all looks good and seems to be getting volts in and out of shifter. At one point during testing the flashing codes went off and it was able to move but only for about 5 minutes. I jumped one wire that was inconsistent in volt readings and it made a loud noise like starting when started. Does anyone know the code or how to test for faulty wiring? Desperate....Patti
Also the dash indicator light that shows a gear with a circle around it and diaganal line through it is on???

 

[RickB]

Fault code 77; internal ECM supply voltage (8V) is too high.
Causes: Faulty ECM.
ECM connector 2, pin 35 is/was shorted by an external 12V source.
Internal circuit short to 12 volts

Tests: No HH menu test for this fault.

Effects: Trans is critically disabled, but can be re-enabled by cycling the ignition switch.

Probing around with jumper wires is a good way to fry the ECU (if it isn't already) and/or other components designed to operate with less than 12 volts input. Don't do it.
The transmission status indicator comes on when the ECU disables the transmission, either due to a power shutle system fault or operator presence not detected.

 

[patti13]

Fault code 77; internal ECM supply voltage (8V) is too high.
Causes: Faulty ECM.
ECM connector 2, pin 35 is/was shorted by an external 12V source.
Internal circuit short to 12 volts

Tests: No HH menu test for this fault.

Effects: Trans is critically disabled, but can be re-enabled by cycling the ignition switch.

Probing around with jumper wires is a good way to fry the ECU (if it isn't already) and/or other components designed to operate with less than 12 volts input. Don't do it.
The transmission status indicator comes on when the ECU disables the transmission, either due to a power shutle system fault or operator presence not detected.

Thank you Rick, I appreciate the help. When I get off the seat it does beep, but could it still have the operator presence undetected? Do you know why the code stopped and it worked for a little while? What would you try next? The shuttle system appears fine but how can I tell? Do you think any switches are bad? Thanks for your imput, Patti

 

[RickB]

Thank you Rick, I appreciate the help. When I get off the seat it does beep, but could it still have the operator presence undetected? Do you know why the code stopped and it worked for a little while? What would you try next? The shuttle system appears fine but how can I tell? Do you think any switches are bad? Thanks for your imput, Patti

It's normal to get an alarm if you leave the seat with the P-brake off, or with the PTO engaged. As for the fault 77, if it is not an active fault and the transmission operates normally, not much can be done except clearing stored faults with a diagnostic tool or laptop equipped with new Holland's ESTprogram. It will either come back, or it won't. There are often stored fault codes in ECU's that are no longer active faults and are non-recurring.

 

[patti13]

Is there any way to bi-pass the seat sensor? Is the seat sensor a normally closed or opened type switch? (can it be jumped to complete the circuit ? I need to determine if it is a faulty switch. If it can not be jumped, Is there another way to determine if the problem is in the seat sensor?) I tried ohming out the sensor both when I sat in the seat and when I was out of the seat and there was no resistance shown either way.

I think the shuttle shift works (because I am getting 12 volts on one connector at all times and 12 volts on another when in forward or reverse but not in neutral; two connectors are showing .9 volts and one showing 5 volts. The other wire is a ground) Does this seem correct? What should the proper voltage be on the five shuttle shift terminals ?

Is there a New Holland wiring diagram that I can download?

How do I test the switch that the pto lever engages? Could that switch be the problem?

Appreciate any help.....

 

[RickB]

The seat switch is normally open. When you sit in the seat, it closes. That circuit is not related to the 77 fault code. If you sit in the seat with the key on and move the PTO control, do you get a PTO dash icon and alarm, or just the icon? If you sit in the seat with the key on and park brake applied, is the P-brake dash icon lit? If you release the P-brake with the key on and seat occupied, does the P-brake dash icon go out and alarm sound, or does the dash light just go out? The seat switch circuit can be totally inoperative, and what happens is you have no PTO icon and you have to use the clutch pedal to get the tractor to move. You can shuttle directly from F to R or R to F, but if you hesitate in N, you will have to cycle the clutch pedal to initiate movement.

 

[patti13]

The PTO icon comes on when you sit in the seat, key on, and the lever is engaged AND it beeps. \
The parking brake on while sitting in the seat, key on, has no icon ever and it only beeps once in a while when you move the lever (but not all the time).
What does this mean? Are we on to something? Thank you, Patti

 

[RickB]

Seems as if the seat switch circuit is open and the P-brake circuit has problems as well. Could be the bulb for the p-brake dash icon is blown, but I wouldn't bet on it. None of this should affect the tractor's movement if you are using the clutch pedal as if it were a gear drive tractor. Are you still having shuttle issues, too? Is the 77 fault code back?

 

[patti13]

YES the shuttle shift will NOT make the tractor move, AND it does not move as a manual clutch either. The 77 code only went off that one time for 5 minutes and has been on ever since. Is there something special I should do to operate the tractor with out using the shuttle shift? What do you mean specifically when you say 'cycle the clutch?' It will not move regardless of what gear it is in, or position of shuttle shift or if the clutch is in or out. If the seat is 'open' is that a problem? I'm checking the parking bulb now. Thanks.

 

[RickB]

You probably need a powershuttle computer. When it is replaced, the clutches will need to be calibrated. You may as well get a dealer involved that has the proper tools and service information.