Case IH 517651-16 - DEC – DEC: PTO rear two speed shaft size speed sensor data valid, above normal range - moderately severe.

The controller is receiving a valid frequency signal from the rear PTO shaft size speed sensor, but the reading is higher than the normal operating range for the physically installed shaft. When the frequency exceeds the expected threshold (often jumping erratically at higher RPMs), the controller assumes the PTO is slipping or reading incorrectly and will shut down the PTO to prevent damage.

• MAGNUM AFS Connect
• Magnum 215
• Magnum 235
• Magnum 245
• Magnum 255
• Magnum 275
• Magnum 305
• Magnum 335
• Magnum 340
• MX180
• MX200
• MX210
• MX215
• MX220
• MX230
• MX240
• MX245
• MX255
• MX270
• MX275
• MX285
• MX305
• Puma 180-260 CVX
• Puma

1. 1

   Verify tractor configuration to ensure it is actually equipped with a dual-speed PTO shaft size sensor (single-speed PTOs may have incorrectly configured controllers or phantom signals)

2. 2

   Inspect the dual-speed sensor connector (labeled 146M on the rear axle harness) for moisture intrusion or corrosion

3. 3

   Check the sensor gap and mounting on top of the transmission case, looking for loose bearings or an improperly seated O-ring that could cause the gear to move away from the sensor

4. 4

   Test wiring harness continuity from the PTO controller to the shaft size sensor, ensuring continuity to chassis ground and no short to battery voltage (Vbat)

5. 5

   Test the resistance of the shaft size sensor with a multimeter (expected value is approximately 3,000 ohms)

1. 1

   Access the Sensor

   Locate the PTO shaft size speed sensor on the rear transmission housing (typically near the PTO shaft output or top of the case near the remotes).

2. 2

   Disconnect and Inspect

   Unplug the sensor harness. Check the connector ends for damaged, bent, or dislocated pins. Dry out any moisture.

3. 3

   Test the Sensor

   Probe the sensor terminals. If the resistance is out of the 3 K ohm specification, or if it reads open/shorted, the sensor has failed internally and must be replaced.

4. 4

   Adjust or Replace

   If replacing the sensor, lubricate the new O-ring and seat it fully. Note: If the new sensor still reads erratically at high RPMs, adjust the sensor depth by modifying or removing the O-ring to correct factory machining tolerances in the transmission case.

5. 5

   Seal Unused Connectors

   If your machine is actually a single-speed PTO and the harness is just hanging open, install a sealing plug to prevent water from bridging the pins and sending false frequencies to the DEC.

6. 6

   Clear Codes

   Reconnect the harness, turn the key on, clear the DEC/TMF fault codes, and run the PTO up to 1000 RPM to verify the corner post/ICU speed display remains steady without shutting down.