Case IH 3390 – Universal Control Module (UCM), Instrument Cluster (IC), and Engine Control Unit (ECU): Air Filter Restriction Switch Short To Ground

The ECM has detected the circuit for the air filter restriction switch is grounded (shorted to ground) for at least 1 second, pulling the circuit voltage below normal. This disables the monitoring of the air filter restriction while the engine is running.

• skid steer
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)
• SR130
• SR150
• SR175
• SV185
• SR200
• SR220
• SR250
• SV250
• SV300
• TR270
• TR320
• TV380
• tractors
• wheel loaders

1. 1

   Inspect the wiring harness from the air filter restriction switch back to the ECM for chafed insulation, pinched wires, or bare wires rubbing against the chassis.

2. 2

   Disconnect the electrical connector at the switch to test it. If the code changes to 'Open Circuit', the switch has failed internally. If it remains 'Short to Ground', the short is in the wiring harness.

3. 3

   Inspect the female terminals on the connector for moisture, dirt, or corrosion that could bridge the contacts to ground.

1. 1

   Locate the Switch

   Open the engine compartment and locate the main air cleaner assembly. The air filter restriction switch is threaded directly into or located just below the air filter housing.

2. 2

   Disconnect Wiring

   Carefully unplug the electrical connector from the switch.

3. 3

   Remove the Switch

   Unscrew the air filter restriction switch by hand from the air cleaner assembly.

4. 4

   Install the New Switch

   Thread the new air filter restriction switch into the air cleaner assembly by hand until snug.

5. 5

   Reconnect

   Plug the electrical connector back into the new switch.

6. 6

   Verify

   Turn the ignition on and verify that fault code 3390 has moved from 'Active' to 'Inactive/Stored', then clear the codes.