Series 60 DDEC V Troubleshooting – Section 32.2 Troubleshooting Flash Code 27, PID 172/FMI 3

Section 32.2
Troubleshooting Flash Code 27, PID 172/FMI 3

This diagnostic condition is typically open sensor signal or return circuit.‪

Note: This code will only be logged during warm engine operation.

The following procedure will troubleshoot Flash Code 27.‪

Section 32.2.1
Sensor Check

Perform the following steps to check the sensor.‪

1. Turn vehicle ignition OFF.
2. Disconnect ATS/IAT Sensor connector.
3. Install a jumper wire between sockets 1 and 2 of the ATS/IAT Sensor harness connector. See Figure "Intake Air Temperature Sensor" .
   

   Figure 1. Intake Air Temperature Sensor

4. Turn ignition ON.
5. Start and run engine for one minute; (ensure oil temp is greater than 140°F).
6. Read active codes.
   1. If code p 172/4 or any other codes except p 172/3 are logged, refer to "32.2.2 Check for Short to +5 Volt Line" .
   2. If any codes except code p 172/4 are logged, refer to "32.2.3 Open Line Check" .

Section 32.2.2
Check for Short to +5 Volt Line

Perform the following steps to check for a short to the +5 volt line.‪

1. Turn ignition/engine OFF.
2. Remove jumper wire.
3. Disconnect the engine harness connector at the ECM/ECU.
4. Measure resistance between sockets E-2 and E-14 on the engine harness connector. See Figure "ECM/ECU Engine Harness Connector" .
   1. If the resistance measurement is less than or equal to 10 Ω, the signal line E-2 is shorted to the engine +5 volt line (E-14). Repair the short and refer to "32.2.4.1 Verify Repairs" .
   2. If the resistance measurement between sockets E-2 and E-14 is greater than 10 Ω or open, go to step 5 .
   

   Figure 2. ECM/ECU Engine Harness Connector

5. Check terminals at the ATS/IAT Sensor connector (both sensor and harness side) for damage; bent, corroded and unseated pins or sockets. See Figure "Intake Air Temperature Sensor" .
   

   Figure 3. Intake Air Temperature Sensor

   1. If terminals or connectors are damaged, repair them. Refer to "32.2.4.1 Verify Repairs" .
   2. If terminals and connectors are not damaged, replace the ATS/IAT Sensor. Refer to "32.2.4.1 Verify Repairs" .

Section 32.2.3
Open Line Check

Perform the following steps to check for an open line.‪

1. Turn ignition OFF.
2. Disconnect the engine harness connector at the ECM/ECU. (Jumper still in place.)
3. Measure resistance between sockets E-2 and E-14 on the engine harness connector. See Figure "ECM/ECU Engine Harness Connector" .
   1. If the resistance measurement is less than or equal to 5 Ω, .
   2. If the resistance measurement between sockets E-2 and E-14 is greater than 5 Ω or open, the signal line E-2 or return line E-14 is open. Repair the open. Refer to "32.2.4.1 Verify Repairs" .
   

   Figure 4. ECM/ECU Engine Harness Connector

4. Check terminals at the ECM/ECU engine harness connector (both ECM/ECU and harness side) for damage: bent, corroded and unseated pins or sockets. See Figure "ECM/ECU Engine Harness Connector" .
   1. If terminals or connectors are damaged, repair them. Refer to "32.2.4.1 Verify Repairs" .
   2. If terminals and connectors are not damaged, contact Detroit Diesel Customer Support Center (313–592–5800). Refer to "32.2.4.1 Verify Repairs" .

Section 32.2.4
Check ECM/ECU Connectors

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Section 32.2.4.1
Verify Repairs

Perform the following steps to verify repairs.‪

1. Turn vehicle ignition OFF and reconnect all connectors.
2. Turn vehicle ignition ON and clear codes. Start and run the engine for eight minutes.
3. Stop the engine and check the diagnostic tool for codes.
   1. If no codes are logged, troubleshooting is complete.
   2. If code p 172/3 and any other codes are logged, all system diagnostics are complete. Review this section to find the error. Refer to "32.2.1 Sensor Check" .
   3. If any codes except code p 172/3 are logged, refer to "18.3 First Step for Diagnosing a Fault Within the DDEC System" .