Case IH 2000 – DCU (Dosing Control Unit), Engine ECU, TCU (Transmission Control Unit), EPC (Electronic PowrQuad Controller), or APC: Group error path NOx exceeded – NOx Trap Efficiency Below Threshold

Case IH Code 2000 (P2000) indicates the emissions system has detected that the Nitrogen Oxide (NOx) levels in the exhaust are too high, usually pointing to an issue with the SCR system or DEF delivery. The description 'Transmission enable relay driver is open circuit or shorted to ground' is a mismatch and belongs to Yale/Hyster forklift fault code (2000-31) or John Deere tractor codes.

• Steiger T4B
• Magnum 235-340 (Series 4)
• Steiger series
• Yale forklifts
• Hyster forklifts

1. 1

   If diagnosing Case IH Code 2000 (NOx Threshold): Check the DEF/Urea tank level and fluid quality.

2. 2

   If diagnosing Case IH Code 2000 (NOx Threshold): Inspect the NOx sensors and their wiring harnesses for damage.

3. 3

   If diagnosing the Transmission Enable Relay circuit: Verify fuses in the fuse panel (e.g., F5 location on Deere systems) to ensure a fuse hasn't blown or hasn't been incorrectly installed in a blank slot.

4. 4

   If diagnosing the Transmission Enable Relay circuit: Inspect the Transmission Enable Relay (often designated as K17 or K09/5). Swap it with a known good relay of the same amperage to see if the fault clears.

5. 5

   If diagnosing the Transmission Enable Relay circuit: Inspect the ground circuit associated with the transmission enable relay for damage, corrosion, or disconnections.

6. 6

   If diagnosing the Transmission Enable Relay circuit: Use a multimeter to check the control lead circuit from the TCU to the relay block for continuity (to rule out an open circuit) and test for continuity to ground (to rule out a short).

1. 1

   Disconnect Power

   Turn off the machine and disconnect the battery ground strap before servicing electrical components.

2. 2

   Access the Relay Panel

   Remove the trim panel behind the operator's seat or in the right console footwell to access the Load Center Secondary (LCS) or main relay box.

3. 3

   Replace the Relay

   If the relay failed the diagnostic swap test, remove the defective Transmission Enable Relay and install a new OEM relay.

4. 4

   Repair Wiring

   If the multimeter test showed a short to ground, trace the wiring harness from the relay block to the transmission controller. Locate the chafed wire, cut out the damaged section, splice in a new wire using weather-sealed heat-shrink connectors, and re-loom the harness.

5. 5

   Clear Codes

   Reconnect the battery, turn the key to the ON position, and use the diagnostic display or a service tool to clear the stored fault codes. Test drive to ensure the transmission engages properly.