Case IH 19205 – Engine Control Module (ECM): External actuator relay 1 low side power stage - Over temperature

The control module has detected an over-temperature condition on the internal low-side driver (power stage) that grounds and controls 'External Actuator Relay 1'. This means the circuit inside the module is getting too hot, which is typically caused by an excessive electrical load, a partial short circuit, high system/battery voltage, or excessive ambient heat soaking into the control unit itself.

• Tier 4b
• Case IH Puma Series: 150, 165, 185, 200, 220, 240 (Tier 4B / Final)
• Case IH Magnum Series: 180, 200, 220, 240 (Tier 4B)

1. 1

   Test the tractor's battery and alternator charging voltage to rule out an overcharging alternator causing the ECM's internal power stages to overheat.

2. 2

   Consult the specific tractor's electrical schematic to identify what 'External Actuator Relay 1' is controlling (e.g., cold-start grid heater relay, fuel heater, or emissions reverting valve).

3. 3

   Unplug the relay/actuator and measure the resistance of the coil to check for a shorted or degraded coil pulling too much amperage.

4. 4

   Inspect the wiring harness between the ECM and the relay for chafing, melting, or pinched wires causing a partial short to ground or battery.

5. 5

   Verify that the ECM is not covered in heavy debris or mud that is preventing it from dissipating heat normally.

1. 1

   Disconnect Power

   Turn off the battery disconnect switch to prevent accidental shorts during testing.

2. 2

   Isolate the Circuit

   Disconnect the wiring harness at the ECM and at External Actuator Relay 1.

3. 3

   Test the Harness

   Using a digital multimeter, check for continuity to ground and continuity to power on the relay control wire. If a short is found, repair the chafed wire or replace that section of the engine harness.

4. 4

   Replace the Relay/Actuator

   If the wiring tests good but the relay coil resistance is out of spec (or if it smells burnt), replace the relay.

5. 5

   Test the ECM

   Reconnect the new relay and the harness. Power the tractor on and use the CNH Electronic Service Tool (EST) to clear the fault code. Run an active test on the actuator.

6. 6

   ECM Replacement (Worst Case)

   If the code immediately returns and the wiring/relay are verified good, the low-side driver inside the ECM has been permanently damaged by the heat/overload. The ECM must be replaced and flashed with the correct software for the tractor's PIN using the CNH EST.