Section 29.2
SPN 110/FMI 3

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.‪

Section 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.
   1. If codes 110/3, 174/3, 175/3 and 3510/3 are active, go to step 3 .
   2. 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.
   1. 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 "24.2.3.1 Verify Repairs" .
   2. 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 "24.2.3.1 Verify Repairs" .
5. Disconnect the ECT Sensor.
6. Measure the resistance across pins 1 and 2 of the ECT Sensor. See Figure "Engine Coolant Temperature Sensor Wiring" .
   

   Figure 1. Engine Coolant Temperature Sensor Wiring

   1. If the resistance is greater than 4 kΩ, replace the sensor. Refer to "24.2.3.1 Verify Repairs" .
   2. 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.
   1. If the voltage is between 2.75 and 3.25 volts, refer to "24.2.3.1 Verify Repairs" .
   2. 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.
   1. 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 "MCM Connector" ). Refer to "24.2.3.1 Verify Repairs" .
   2. 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 "MCM Connector" ). Refer to "24.2.3.1 Verify Repairs" .
   

   Figure 2. MCM Connector

Section 29.2.1.1
Verify Repairs

Verify repairs as follows:‪

1. Turn ignition OFF.
2. Reconnect any electrical connections that were disconnected to perform the diagnosis.
3. Clear codes with DDDL 7.0 or latest version.
4. Start and bring engine up to operating temperature (over 140°F/60°C).
5. Verify operation is satisfactory and no warning lamps illuminate. If warning lamps illuminate, troubleshoot the codes. If assistance is required, call the Detroit Diesel Customer Support Center at 313–592–5800.