New Holland IC 3390 – Engine Control Unit (ECU): Air Filter Restriction Switch Short To Ground

The system has detected a signal to ground on the restriction switch circuit. This condition occurs when the engine air filter is severely clogged (causing intake vacuum to physically trip/close the switch) or if there is an electrical short to ground in the sensor's signal wire.

• L218
• L220
• L223
• C232
• C234
• C238
• C245
• C332
• T4.75
• T4.85
• T4.105
• T4.120
• T5 Series
• Farmall series
• Workmaster series
• T8/T9 series
• W270C
• E215B
• E385B

1. 1

   Inspect the primary and secondary engine air filter elements for severe dirt accumulation, debris, or blockages (clogged filter cause).

2. 2

   Inspect the wiring harness from the air filter restriction switch to the instrument cluster/ECU for chafed wires causing a short to ground (wiring short cause).

3. 3

   Disconnect the air filter restriction switch to test if the fault code status changes or clears, indicating an internally shorted switch (faulty switch cause).

1. 1

   Prepare machine

   Park the machine on a level surface, lower any attachments, turn off the engine, and remove the key.

2. 2

   Locate air cleaner

   Open the engine hood and locate the engine air cleaner assembly.

3. 3

   Remove filters

   Unlatch the air filter housing cover and remove the primary air filter (and secondary safety filter, if equipped).

4. 4

   Replace filters

   If the filters are dirty or clogged, replace them with new elements. Do not attempt to blow them out with compressed air if they are heavily restricted.

5. 5

   Locate switch

   If the filters are clean, locate the air filter restriction switch, which is threaded into the air intake piping or the side of the air cleaner housing.

6. 6

   Test and repair wiring

   Disconnect the electrical connector from the switch. Use a multimeter to verify the wiring harness does not have continuity to ground on the signal wire. Repair the harness if a short is found.

7. 7

   Remove faulty switch

   If the wiring is intact, the switch is faulty. Unscrew the old air filter restriction switch from the intake housing.

8. 8

   Install new switch

   Thread the new OEM restriction switch into the housing and tighten it securely.

9. 9

   Reconnect switch

   Reconnect the electrical connector to the switch.

10. 10

    Clear fault codes

    Turn the ignition on and use an Electronic Service Tool (EST) to clear the fault codes, or allow the system to run a self-check to verify the amber warning light turns off.