Case IH 158 – TMF (Tractor Management Frame / Transmission Management Function) or Armrest Controller: PTO remote fender switch open circuit

Case IH tractors utilize a double-redundant safety circuit for the rear fender PTO switches. When the switch is in the 'OFF' position, one set of contacts is closed while the other is open. When switched to 'ON,' the circuits reverse. If the controller detects that both circuits are open simultaneously, it cannot determine the state of the switch. For safety, it logs fault code 158 and disables the PTO.

• Magnum
• Magnum Series
• Maxxum Series
• Puma Series
• MX Series
• MXM Series
• TG Series
• JXU Series

1. 1

   Verify Tractor Configuration: If your tractor does not have fender PTO switches, the controller may have lost its configuration. A technician will need to use the CNH Electronic Service Tool (EST) to configure the controller.

2. 2

   Visual Inspection: Check the rear fender PTO switches to ensure they are not physically broken, packed with mud/debris, or stuck in a depressed state.

3. 3

   Wiring and Connector Check: Look under the fender to see if the wiring harness has been snagged by a tire or debris. Ensure the connector is fully plugged into the switch.

4. 4

   Continuity Test: Remove the switch and test it with a multimeter. Because it is a double-redundant switch, you should never see an 'open' reading on both circuits at the same time. If you do, the internal contacts have failed.

1. 1

   Park the tractor on a level surface, turn off the engine, and remove the key.

2. 2

   Locate the remote PTO switch on the rear fender that is triggering the fault.

3. 3

   Reach behind the fender panel and disconnect the wiring harness connector from the switch.

4. 4

   Inspect the harness connector for corrosion, moisture, or pushed-out pins.

   Clean with electrical contact cleaner if necessary. If the wires are torn, splice and repair the harness.

5. 5

   If the wiring is intact but the switch failed the continuity test, remove the retaining clips or screws holding the switch into the fender housing.

6. 6

   Push the old switch out and snap the new OEM replacement switch into place.

7. 7

   Reconnect the wiring harness until the locking tab clicks.

8. 8

   Start the tractor and test the PTO engagement.

   The code should move from 'Active' to 'Stored/Inactive.' Test the PTO engagement from both the cab armrest and the new fender switch to verify proper operation.