Massey Ferguson 00.1.38 – Dash: Signal Voltage From Engine Speed Sensor Issue Dyna 4, Dyna 6 (Dash)

The control module is detecting an abnormal, missing, or out-of-range electrical signal voltage coming from the inductive engine speed sensor. Without a reliable engine speed signal, the transmission controller and dash cannot properly manage shifting or display RPMs.

• 5710SL
• 5711SL
• 5712SL
• 5713SL
• T4
• 4700 Series
• 4707
• 4708
• 4709
• 4710
• 5400 Series
• 5600 Series
• 5608–5613
• 5700SL Series
• 6400 Series
• 6600 Series
• 6700S Series
• 7600 Series
• 7614–7626
• 7700 Series
• 7714–7726S
• 5710
• 6465
• 6475
• 6480

1. 1

   Visual Inspection: Check the 2-pin connector and pins for corrosion, moisture, or physical damage.

2. 2

   Wiring Harness Test: Check the harness for continuity, proper insulation, and ensure there are no short-circuits to ground or power.

3. 3

   Resistance Test: With the engine stopped, the sensor disconnected, and at ambient room temperature, measure the resistance across the two pins. A healthy inductive speed sensor should read 450 Ohms +/- 20 Ohms.

4. 4

   Voltage Output Test: Back-probe the sensor while the engine is cranking/running (gear is turning). The sensor should output an alternating voltage (AC).

5. 5

   Air Gap Check: Verify that the sensor hasn't backed out, which would increase the air gap and weaken the signal.

1. 1

   Prepare tractor for repair

   Turn off the tractor, apply the parking brake, and disconnect the battery.

2. 2

   Disconnect sensor

   Locate the engine speed sensor and unplug its 2-pin electrical connector.

3. 3

   Remove faulty sensor

   Loosen the counter-nut (lock nut) and unscrew the faulty sensor from the housing.

4. 4

   Prepare new sensor

   Apply a small amount of thread sealant (OEM recommends Loctite 5922) to the threads of the new sensor.

5. 5

   Install new sensor

   Screw the new sensor in fully until it gently bottoms out against the internal gear.

6. 6

   Set the air gap

   Carefully unscrew the sensor by exactly 3/4 of a turn.

7. 7

   Secure the sensor

   Hold the sensor in this position and tighten the counter-nut to approximately 6 Nm.

8. 8

   Reconnect electrical connector

   Reconnect the 2-pin electrical connector.

9. 9

   Verify repair

   Reconnect the battery, start the engine, and use diagnostic software (such as Wintest or EDT) to clear the fault codes and verify the engine speed signal is registering correctly.