DDEC III/IV Single ECM Troubleshooting – Section 23.3 Troubleshooting Flash Code 23

Section 23.3
Troubleshooting Flash Code 23

The following procedure will troubleshoot Flash Code 23.‪

Section 23.3.1
Sensor Check

Perform the following steps to check the sensor:‪

1. Turn ignition OFF.
2. Disconnect the FTS connector.
3. Install a jumper wire between sockets A and B of the FTS harness connector. see Figure "Fuel Temperature Sensor" .
4. Turn ignition ON.
5. Read active codes.
   1. If code 174/4 and any other codes except code 174/3 are logged, refer to "23.3.2 Check for Short to +5 Volt Line" .
   2. If any code except 174/4 is logged, refer to "23.3.4 Open Line Check" .
   

   Figure 1. Fuel Temperature Sensor

Section 23.3.2
Check for Short to +5 Volt Line

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

1. Turn ignition OFF.
2. Remove jumper wire.
3. Disconnect the engine harness connector at the ECM.
4. Measure resistance between sockets R3 and W1 on the engine harness connector. See Figure "ECM Engine Harness Connector" .
   1. If the measured resistance is greater than 100 Ω or open, refer to "23.3.3 Check Fuel Temperature Sensor Connectors" .
   2. If the measured resistance is less than or equal to 100 Ω, the signal line #472 is shorted to the engine +5 volt line #416. Repair the short; refer to "23.3.6 Verify Repairs" .
   

   Figure 2. ECM Engine Harness Connector

Section 23.3.3
Check Fuel Temperature Sensor Connectors

Perform the following steps to check the FTS connectors:‪

1. Check terminals at the FTS harness connector (both sensor and harness side) for bent, corroded, and unseated pins or sockets. See Figure "Fuel Temperature Sensor" .
   1. If terminals and connectors are damaged, repair them. Refer to "23.3.6 Verify Repairs" .
   2. If terminals and connectors are not damaged, replace the FTS. Refer to "23.3.6 Verify Repairs" .
   

   Figure 3. Fuel Temperature Sensor

Section 23.3.4
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. The jumper wire is still in place at the FTS connector.
3. Measure resistance between sockets R3 and Y2 on the engine harness connector. See Figure "ECM Engine Harness Connector" .
   1. If the measured resistance is greater than 5 Ω or open, the signal line #472 or return line #452 is open. Repair the open; refer to "23.3.6 Verify Repairs" .
   2. If the measured resistance is less than or equal to 5 Ω, refer to "23.3.5 Check ECM Connectors" .
   

   Figure 4. ECM Engine Harness Connector

Section 23.3.5
Check ECM Connectors

Perform the following steps to check the ECM connectors:‪

1. Check terminals at the ECM harness connector (both ECM and harness side) for bent, corroded, and unseated pins or sockets. See Figure "ECM Engine Harness Connector" .
   1. If terminals and connectors are damaged, repair them. Refer to "23.3.6 Verify Repairs" .
   2. If terminals and connectors are not damaged, install a test ECM. Refer to "23.3.6 Verify Repairs" .
   

   Figure 5. ECM Engine Harness Connector

Section 23.3.6
Verify Repairs

Perform the following steps to verify repairs:‪

1. Turn ignition OFF.
2. Reconnect all connectors.
3. Turn ignition ON.
4. Clear codes with DDR.
5. Start and run the engine for eight minutes.
6. Stop engine.
7. Read codes.
   1. If no codes are logged, troubleshooting is complete.
   2. If code 174/3 and any other codes are logged, all system diagnostics are complete. Review this section from the first step to find the error. Refer to "23.3.1 Sensor Check" .
   3. If code 173/4 is not logged, but other codes are logged, refer to "9.1 First Step for Diagnosing a Fault Within the DDEC System" .