Case IH 19432 – Engine Control Unit (ECU): Engine compression brake high side driver circuit short to battery failure

The Engine Control Unit (ECU) has detected that the high side of the electrical circuit controlling the engine compression brake actuator is receiving unintended battery voltage (a short to battery). This prevents the ECU from properly modulating the compression brake.

• Tier 4b
• Case IH 240 Series Axial-Flow Combines (7240, 8240, 9240)
• Case Construction STM N Series Loaders

1. 1

   Check for related codes, specifically DTC 77F3 (low side driver circuit short to ground) or DTC 41F3 (high side short to battery AND low side short to ground). Troubleshoot these first if present.

2. 2

   Visually inspect the engine wiring harness running from the ECU to the engine compression brake actuator for chafing, melted insulation, or pinched wires.

3. 3

   Disconnect the harness at the ECU and at the compression brake actuator, then test the high-side driver circuit pin for continuity to battery positive (B+).

4. 4

   Test the compression brake actuator itself for an internal short to its housing or power supply.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the negative battery cable to prevent electrical spikes during testing.

2. 2

   Isolate the Short

   Using the results from your multimeter test, determine if the short to battery is located in the main engine harness, the actuator pigtail, or internally within the actuator.

3. 3

   Repair the Wiring

   If the harness is chafed and shorting to a power wire, open the loom, repair the damaged wire using OEM-approved heat-shrink butt connectors, and re-loom the harness. Ensure it is routed away from high-heat or high-vibration areas.

4. 4

   Replace Component

   If the wiring tests perfectly but the short is internal to the compression brake actuator, replace the actuator. If the actuator and wiring are both good, the ECU's internal driver may be shorted, requiring ECU replacement.

5. 5

   Clear and Verify

   Reconnect the battery, turn the key to the ON position, and use a diagnostic tool (like the Case IH Electronic Service Tool) to clear the inactive code. Run the engine and command the compression brake to verify the fault does not return.