DD15 Troubleshooting – Section 34.2 SPN 174/FMI 3

Section 34.2
SPN 174/FMI 3

SPN 174/FMI 3 indicates a indicates a Supply Fuel Temperature Sensor (SFT Sensor) open circuit.‪

Check as follows:‪

1. Check for multiple codes.
   1. If faults 174/3, 175/3, and 4076/3 are active at the same time, repair the open circuit between pin 55 of the MCM 120-pin connector and pin 1 of the Supply Fuel Temperature Sensor, (or) pin 1 of the Engine Oil Temperature Sensor, (or) pin1 of the Engine Coolant Inlet Temperature Sensor, (or) pin 1 of the Engine Coolant Outlet Temperature Sensor. Refer to "34.2.1 Verify Repairs" .
   2. If only fault 174/3 is active, go to the next step.
2. Disconnect the Supply Fuel Temperature Sensor.
3. Measure the resistance across pins 1 and 2 of the SFT Sensor.
   1. If the resistance is greater than 2.2k Ω, replace SFT Sensor.
   2. If the resistance is less than 2.2k Ω, go to the next step.
4. Turn the ignition ON (key ON, engine OFF).
5. Measure the voltage between pins 1 and 2 of the SFT Sensor harness connector.
   1. If the voltage is between 2.75 and 3.25 volts, go to step 7 .
   2. If the voltage is less than 2.75 volts, go to the next step.
6. Measure the voltage between pin 2 of the SFT 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 SFT Sensor harness connector and pin 55 of the MCM 120-pin connector. Refer to "34.2.1 Verify Repairs" .
   2. If the voltage is less than 2.75 volts, repair the open circuit between pin 2 of the SFT Sensor harness connector and pin 77 of the 120-pin MCM connector. Refer to "34.2.1 Verify Repairs" .
7. Disconnect the 120-pin MCM connector and measure the resistance between pins 1 and 2 of the SFT Sensor harness connector.
   1. If the resistance is less than 5 Ω, repair the short between pins 55 and 77 of the MCM 120-pin connector. Refer to "34.2.1 Verify Repairs" .
   2. If the resistance is greater than 5 Ω, replace the sensor. Refer to "34.2.1 Verify Repairs" .

Section 34.2.1
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.

   ENGINE EXHAUST ‪
   To avoid injury from inhaling engine exhaust, always operate the engine in a well-ventilated area. Engine exhaust is toxic.‪

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.