SPN 110/FMI 3 indicates that the Engine Coolant Temperature Sensor (ECT Sensor) input to
the MCM has exceeded 95% of the sensor supply voltage. The diagnostic condition is typically
engine coolant temperature open circuit or short to power.
29.2.1
Open Circuit/Short to Power Check
Check as follows:
1. Turn the ignition ON (key ON, engine OFF).
2. Check for multiple codes.
[a] If codes 110/3, 174/3, 175/3 and 3510/3 are active, go to step 3.
[b] If only fault 110/3 is active, go to step 6.
3. Disconnect the Supply Fuel Temperature Sensor.
4. Measure the voltage between pin 1 of the SFT Sensor and ground.
[a] If the voltage is greater than 2.75 volts, repair the short to power between pin 55 of
the MCM 120–pin connector and the Engine Coolant Temperature Sensor, the Engine Oil Temperature Sensor and the Supply Fuel Temperature Sensor. Refer to section 29.2.1.1.
[b] If no voltage is present on pin 1 of the SFT Sensor, repair the open between pin 55 of the MCM 120–pin connector and the Engine Coolant Temperature Sensor, the Engine Oil Temperature Sensor and the Supply Fuel Temperature Sensor. Refer to section 29.2.1.1.
5. Disconnect the ECT Sensor.
6. Measure the resistance across pins 1 and 2 of the ECT Sensor. See Figure 29-1.
[a] If the resistance is greater than 4 kΩ, replace the sensor. Refer to section 29.2.1.1.
[b] If the resistance is less than 4 kΩ, go to step 7.
7. Turn the ignition ON (key On, engine OFF).
8. Measure the voltage between pins 1 and 2 of the ECT Sensor harness connector.
[a] If the voltage is between 2.75 and 3.25 volts, refer to section 29.2.1.1.
[b] If the voltage is less than 2.75 volts, go to step 9.
9. Measure the voltage between pin 2 of the ECT Sensor harness connector and ground.
[a] If the voltage is between 2.75 and 3.25 volts, repair the open circuit between pin 1
of the ECT Sensor harness connector and pin 55 of the 120–pin MCM connector (see Figure 29-2). Refer to section 29.2.1.1.
[b] If the voltage is less than 2.75 volts, repair the open circuit between pin 2 of the ECT
Sensor harness connector and pin 110 of the 120–pin MCM connector (see Figure 29-2). Refer to section 29.2.1.1.
