Case IH 3498 – Vehicle Control Module (VCM) or Engine Control Unit (ECU/ECM): Signal level low error for vehicle speed signal over tachometer or hardware sensor

The control module is receiving a voltage or frequency signal from the vehicle speed sensor (VSS) or tachometer hardware sensor that falls below the normal operating range. This typically points to a failing sensor, an improper sensor gap, or a wiring issue such as a short to ground or an open circuit.

• Case N-Series Tractor Loader Backhoes (TLBs)
• Case IH Magnum
• Case IH Maxxum
• Case IH Farmall
• Case IH Puma
• Case IH Steiger
• Case IH MX series

1. 1

   Inspect the vehicle speed sensor / tachometer sensor and its connector for physical damage, moisture, or corrosion

2. 2

   Check the wiring harness between the sensor and the ECU/VCM for open circuits, chafing, or shorts to ground

3. 3

   Verify that the sensor is properly adjusted and gapped relative to the tone ring or gear it is reading

4. 4

   Verify the sensor's internal resistance using a multimeter to ensure it falls within OEM specifications

1. 1

   Verify fault code

   Turn the keyswitch to the ON position and connect the recommended CNH Electronic Service Tool (EST) or EASY diagnostic tool to verify that fault code 3498 is active.

2. 2

   Locate sensor

   Locate the vehicle speed sensor (VSS) or ground speed sensor (typically mounted on the transmission housing, gearbox, or wheel hub depending on the specific machine model).

3. 3

   Perform diagnostic checks

   Disconnect the sensor harness and perform the diagnostic continuity and resistance checks outlined above.

4. 4

   Remove faulty sensor

   If the wiring harness is intact but the sensor fails the resistance test or is physically damaged, remove the faulty sensor.

5. 5

   Install replacement sensor

   Install the replacement speed sensor. If the sensor is threaded, ensure it is installed to the correct depth/gap to properly read the rotational speed without striking the internal gear.

6. 6

   Reconnect harness

   Reconnect the wiring harness securely.

7. 7

   Clear fault code and test

   Use the diagnostic service tool to clear the fault code, then test drive or operate the machine to verify that the vehicle speed signal registers correctly and the code does not return.