Case IH 19890 – VCM (Vehicle Control Module) or Engine ECU: Maximum threshold error for vehicle speed

Triggered when the control module receives a vehicle speed signal over the CAN bus that exceeds the maximum plausible limit or programmed threshold.

• Tier 4b
• Tier 4B models
• Case IH Puma
• Case IH Magnum
• Case Construction N-Series Loader Backhoes

1. 1

   Use the CNH Electronic Service Tool (EST) to check for other active CAN communication codes or speed sensor codes (e.g., 19887, 19888, 19891, 19892)

2. 2

   Verify that the physical tire size matches the parameters set in the display/controller (incorrect tire size calibration is a common cause)

3. 3

   Inspect the transmission output speed sensor or wheel speed sensor for physical damage, heavy debris buildup on the magnetic tip, or a loose mounting bracket

4. 4

   Inspect the wiring harness between the speed sensor, the Transmission Control Unit (TCU), and the VCM for chafing, corrosion, or loose pins

1. 1

   Connect Diagnostic Tool

   Connect the CNH EST laptop to the machine's diagnostic port.

2. 2

   Monitor Live Data

   Navigate to the VCM/Transmission live data parameters. Drive the machine at a slow, steady pace and monitor the 'Vehicle Speed' PID.

3. 3

   Identify Signal Spikes

   If the speed reading erratically spikes to impossible values (e.g., jumping from 5 mph to 50 mph), the issue is likely a failing speed sensor or a short in the sensor wiring.

4. 4

   Test the Wiring

   Disconnect the speed sensor and measure the resistance of the sensor circuit back to the controller. If resistance is out of spec or shorted to ground, repair the wiring harness.

5. 5

   Replace the Sensor

   If the wiring is intact but the signal is erratic, replace the transmission/vehicle speed sensor.

6. 6

   Recalibrate and Clear

   After replacing the sensor or repairing the wire, verify the correct tire size in the VCM settings. Clear the fault codes and test drive the machine to ensure code 19890 does not return.