Case IH 3344 – Engine Control Module (ECM): Power Stage Air Heater 2 Actuator - Signal Low

The control module has detected that the voltage signal on the circuit controlling the intake air heater (grid heater) stage 2 relay/actuator is lower than expected. This is typically caused by a short to ground in the wiring harness, a failed/shorted relay coil, or a disconnected ground/supply wire.

• Case IH Magnum 235 - 340 (Series 4)
• Case IH Puma Series
• Case IH Puma 185
• Case IH Puma 210
• Case IH Farmall Series

1. 1

   Inspect the wiring harness from the ECM to the intake air heater relay for chafed insulation, bare wires touching the chassis (short to ground), or pinched wires.

2. 2

   Test the relay coil by disconnecting the intake air heater relay and measuring resistance across the control coil pins; an extremely low reading indicates an internal short.

3. 3

   Verify the relay is receiving proper supply voltage from the battery/fuse panel and that the ground connection to the chassis or engine block is clean and tight.

4. 4

   Inspect the ECM connectors for water intrusion, bent pins, or corrosion that could pull the signal voltage low.

1. 1

   Disconnect Power

   Turn off the ignition and disconnect the negative battery cable to prevent accidental short circuits while working on the high-amperage grid heater system.

2. 2

   Locate the Relay

   Locate the intake air heater relay, typically mounted on a bracket near the engine block or directly adjacent to the intake manifold.

3. 3

   Disconnect Wiring

   Remove the control wiring harness connector from the relay. Unbolt the heavy-gauge cables connecting the relay to the battery and the intake grid heater.

4. 4

   Repair Wiring

   If the diagnostic checks revealed a short to ground in the harness, repair the damaged wire using heat-shrink connectors and protect it with corrugated wire loom.

5. 5

   Replace the Relay

   If the relay coil was found to be shorted, unbolt the old relay from its mounting bracket and install the new OEM relay.

6. 6

   Reassemble

   Reattach the heavy-gauge cables and plug in the control harness. Ensure all terminal nuts are torqued to spec so they do not vibrate loose.

7. 7

   Clear Codes

   Reconnect the battery, turn the key to the ON position, and use a diagnostic scan tool to clear the 3344 fault code.

8. 8

   Verify Operation

   Cycle the key in cold conditions to trigger the grid heater and verify that the code does not return.