Case IH 56072 – Transmission Controller (TRANS / TCU): No Voltage detected on output of Transmission Neutral Latch Relay when it is ON

There is no voltage reaching the lockup valve group (which includes 1F, 1M, 1R, 2F, 2R, 5F, 5R, lube, and system pressure) when voltage is expected by the system. The transmission controller monitors the status of this relay using the switch common (lockup common, C027 cavity 10) output.

• STX Steiger
• Case IH Puma
• Case IH Steiger
• Case IH Magnum

1. 1

   Check for preceding codes TRANS 56088 or TRANS 560909 and correct them first before troubleshooting this code

2. 2

   Monitor relay function via display: Turn key ON, enter TRANS VIEW on instrumentation controller, navigate to SW #2. With lever in PARK, display should read 1 0 0 (1) 0 1 0 0. Monitor lockup common status (digit in parentheses)

3. 3

   Clean and check all ground wires and cables, as poor grounds or weak cab solenoids can throw random transmission codes

4. 4

   Unplug the transmission neutral latch relay (Relay #17) and measure resistance between pin 1 and pin 2 to check for internal coil failure

1. 1

   Replace the Relay

   Replace the transmission neutral latch relay (Relay #17) with a new relay.

2. 2

   Test the Tractor

   Start the tractor and run it for several minutes. Shut down the tractor and check the fault codes again.

3. 3

   Inspect Wiring

   If the fault code returns, the issue is not the relay itself. Trace the wiring harness between the neutral latch relay, the neutral relay, and the transmission controller.

4. 4

   Repair Harness

   Locate and repair any open circuits or shorts to ground/power in the wiring harness supplying the lockup valve group.