Case IH 263 – Engine Control Module (ECM): Fuel Temperature Sensor voltage is too high

The control module monitors the signal voltage from the fuel temperature sensor to adjust engine protection systems and emissions. If the voltage exceeds 4.95 volts DC, the system logs Fault Code 263. This condition typically points to an open circuit or a short to a high-voltage source in the sensor wiring, or a completely failed sensor. When active, the engine defaults to a predetermined, fixed fuel temperature value, resulting in reduced engine power.

• MX Magnum
• STX Steiger
• MX180
• MX240
• MX255
• MX270
• MX285
• STX275
• STX325
• STX440
• 2388

1. 1

   Inspect the fuel temperature sensor, the electrical connector, and the wiring harness for physical damage, corrosion, or pushed-back pins

2. 2

   With the key ON and engine OFF, check the sensor supply voltage from the ECM (should typically read a 5V reference signal)

3. 3

   Test the signal wire between the sensor and the ECM for an open circuit or a short to a high-voltage source (like battery voltage)

4. 4

   Disconnect the sensor and measure its internal resistance. If it reads as an open circuit (infinite resistance), the sensor has failed internally

1. 1

   Turn off the engine and disconnect electrical power from the ECM (disconnect the battery).

2. 2

   Locate the fuel temperature sensor on the engine (typically mounted near the fuel injection pump, fuel rail, or fuel filter housing).

3. 3

   Disconnect the electrical harness connector from the sensor.

4. 4

   If the diagnostic checks revealed a wiring issue, repair the damaged section of the harness.

   Note: If updating an older CAPS system, you may need to splice in a new electrical repair connector, Cummins p/n 3164187.

5. 5

   If the sensor itself is faulty, use a wrench to unscrew the old fuel temperature sensor from its port.

6. 6

   Clean the threads on the mounting port to ensure a good seal and prevent contamination.

7. 7

   Install the new fuel temperature sensor and tighten it to the manufacturer's specified torque.

8. 8

   Reconnect the electrical harness securely until it clicks.

9. 9

   Reconnect the battery, turn the ignition ON, and use a diagnostic scan tool to clear Fault Code 263.

10. 10

    Start the engine and verify that the code does not return and that the engine operates with full power.