Case IH 3273 – Engine ECU: Fuel Low Pressure Sensor - Signal Below Range Min.

This code indicates that the signal voltage returning from the low-pressure fuel sensor has dropped below the minimum acceptable threshold programmed into the ECU. While it can occasionally be triggered by a severe mechanical vacuum/restriction in the fuel supply, a "Signal Below Range Min" error almost always points to an electrical fault—specifically an open circuit, a short to ground in the sensor wiring, or an internally failed sensor.

• Case IH Magnum 235 - 340 (Series 4)
• Case IH Steiger series
• Case IH Puma series
• Case IH Maxxum series

1. 1

   Inspect the wiring harness and the connector at the low fuel pressure sensor for chafed wires, corrosion, or backed-out pins (short to ground or open loop is the most common cause).

2. 2

   Disconnect the sensor and turn the key to the ON position to verify the sensor is receiving the correct reference voltage (typically 5V) and has a solid ground.

3. 3

   Check the signal wire for continuity back to the Engine ECU.

4. 4

   Install a mechanical compound pressure gauge (e.g., CNH test gauge 380100056) at the inlet of the low-pressure pump to rule out a severe mechanical restriction (operating pressure should be around 5 bar/72 psi minimum).

5. 5

   Check the fuel pre-filter and main fuel filter for severe clogs, gelling, or water contamination, which can cause extreme pressure drops.

1. 1

   Power Down

   Turn off the engine and remove the key. Disconnect the battery ground cable to protect the ECU during electrical work.

2. 2

   Locate the Sensor

   Locate the low fuel pressure sensor, which is typically mounted on the fuel filter housing or along the low-pressure fuel supply line leading to the high-pressure injection pump.

3. 3

   Harness Repair

   If your diagnostic checks revealed a short to ground or broken wire, repair the wiring harness using OEM-approved waterproof splices and heat shrink.

4. 4

   Sensor Replacement

   If the wiring is intact and the ECU is sending the correct 5V reference, the sensor has failed internally. Disconnect the electrical harness, unscrew the faulty sensor, and install the replacement. Torque the new sensor to the manufacturer's specifications.

5. 5

   System Priming

   If any fuel lines were opened or filters were changed during the diagnostic process, prime the fuel system to purge any air.

6. 6

   Clear Codes

   Reconnect the battery. Turn the key to the ON position and use the tractor's dashboard interface or a CNH EST diagnostic tool to clear fault code 3273.

7. 7

   Test Run

   Start the engine and check for leaks. Run the machine under load to ensure the code does not return and that the engine does not derate.