DDEC III/IV Single ECM Troubleshooting – Section 41.3 Troubleshooting Flash Code 41

Section 41.3
Troubleshooting Flash Code 41

The following procedure will troubleshoot Flash Code 41.‪

Section 41.3.1
Check for Signal Open

Perform the following steps to check for signal open.‪

1. Turn ignition OFF.
2. Disconnect engine harness connector at the ECM. See Figure "Engine Harness Connector" .
   

   Figure 1. Engine Harness Connector

3. Read resistance between sockets T1 and T2 on the engine harness connector.
   1. If the resistance reading is less than or equal to 200 Ω, refer to "41.3.2 Check for Short" .
   2. If the resistance reading is greater than 200 Ω or open, refer to "41.3.3 Open Timing Reference Sensor Line Check" .

Section 41.3.2
Check for Short

Perform the following steps to check for a short.‪

1. Disconnect the TRS connector.
2. Measure resistance between sockets T1 and T2 on the engine harness connector. See Figure "Engine Harness Connector to Timing Reference Sensor" .
   

   Figure 2. Engine Harness Connector to Timing Reference Sensor

3. Measure resistance between socket T1 and ground and between socket T2 and ground.
   1. If the resistance measurement is greater than 10,000 Ω or open, refer to "41.3.4 Check Timing Reference Sensor Resistance" .
   2. If the resistance measurement is less than or equal to 10,000 Ω, a short exists between #110 and #109 or where resistance reads less than 10,000 Ω. Repair the short. Refer to "41.3.15 Verify Repairs" .

Section 41.3.3
Open Timing Reference Sensor Line Check

Perform the following steps to check the open TRS line.‪

1. Disconnect the TRS connector.
2. Install a jumper wire between sockets A and B of the TRS harness connector.
3. Measure resistance between sockets T1 and T2 on the engine harness connector.
   1. If the resistance measurement is less than or equal to 5 Ω, refer to "41.3.4 Check Timing Reference Sensor Resistance" .
   2. If the resistance measurement is greater than 5 Ω or open, the signal line #110 or return line #109 is open. Repair the break. Refer to "41.3.15 Verify Repairs" .

Section 41.3.4
Check Timing Reference Sensor Resistance

Perform the following steps to check TRS resistance.‪

1. Measure resistance of TRS across sensor connector pins A and B. See Figure "Engine Harness Connector to Timing Reference Sensor" .
   

   Figure 3. Engine Harness Connector to Timing Reference Sensor

   1. If the resistance measurement is greater than 200 Ω, refer to "41.3.12 Check Timing Reference Sensor Connectors" .
   2. If the resistance measurement is less than 100 Ω, refer to "41.3.12 Check Timing Reference Sensor Connectors" .
   3. If the resistance measurement is between 100 and 200 Ω, refer to "41.3.5 Check Timing Reference Sensor Gap" .

Section 41.3.5
Check Timing Reference Sensor Gap

Perform the following steps to check the TRS gap.‪

1. Bar the engine until the TRS is over a TRS tooth of the pulse wheel.
2. Check the gap between TRS and the tooth of the pulse wheel (0.020 to 0.040 in.). A depth micrometer can be used.
   1. If the gap setting is correct, refer to "41.3.6 Synchronous Reference Sensor Code Check" .
   2. If the gap setting is not correct, adjust the TRS until the gap setting is correct. If the problem returns, the pulse wheel may be loose, bad, or damaged. Refer to "41.3.15 Verify Repairs" .

Section 41.3.6
Synchronous Reference Sensor Code Check

Perform the following steps to check for SRS code.‪

1. Check for SRS code.
   1. If code 21/1 is not logged, refer to "41.3.7 Check ECM Connectors" .
   2. If code 21/1 is logged, refer to "41.3.8 Synchronous Reference Sensor Resistance Check" .

Section 41.3.7
Check ECM Connectors

Perform the following steps to check the ECM connectors.‪

1. Check terminals at the ECM engine harness connectors (both the ECM and harness side) for damage: bent, corroded, and unseated pins or sockets.
   1. If terminals and connectors are damaged, repair them. Refer to "41.3.15 Verify Repairs" .
   2. If terminals and connectors are not damaged, install a test ECM. Refer to "41.3.15 Verify Repairs" .

Section 41.3.8
Synchronous Reference Sensor Resistance Check

Perform the following steps to check SRS resistance.‪

1. Measure resistance between sockets S1 and S2 on the engine harness connector. See Figure "Engine Harness Connector to Synchronous Reference Sensor" .
   

   Figure 4. Engine Harness Connector to Synchronous Reference Sensor

   1. If measured resistance is greater than 200 Ω or open, refer to "41.3.10 Open Synchronous Reference Sensor Line Check" .
   2. If measured resistance is less than 200 Ω , or open, refer to "41.3.9 Check for Short" .

Section 41.3.9
Check for Short

Perform the following steps to check for a short.‪

1. Disconnect the SRS connector.
2. Measure resistance between sockets S1 and S2 on the engine harness connector.
   1. If measured resistance is greater than 10,000 Ω or open, refer to "41.3.11 Synchronous Reference Sensor Test" .
   2. If measured resistance is less than or equal to 10,000 Ω, the signal line #111 is shorted to the return line #112. Repair the short. Refer to "41.3.15 Verify Repairs" .

Section 41.3.10
Open Synchronous Reference Sensor Line Check

Perform the following steps to check for an open SRS line.‪

1. Disconnect the SRS connector.
2. Install a jumper wire between sockets A and B of the SRS harness connectors.
3. Measure resistance between sockets S1 and S2 on the engine harness connector.
   1. If measured resistance is less than or equal to 5 Ω, refer to "41.3.11 Synchronous Reference Sensor Test" .
   2. If measured resistance is greater than 5 Ω or open, the signal line #111 or return line #112 is open. Repair the break and refer to "41.3.15 Verify Repairs" .

Section 41.3.11
Synchronous Reference Sensor Test

Perform the following steps to test the SRS.‪

1. Measure resistance of SRS across the sensor connector pins A and B.
   1. If measured resistance is less than or equal to 100 Ω, refer to "41.3.13 Check Synchronous Reference Sensor Connectors" .
   2. If measured resistance is greater than 200 Ω, refer to "41.3.13 Check Synchronous Reference Sensor Connectors" .
   3. If measured resistance is between 100 and 200 Ω, refer to "41.3.7 Check ECM Connectors" .

Section 41.3.12
Check Timing Reference Sensor Connectors

Perform the following steps to check TRS connectors.‪

1. Check terminals at the TRS (both the TRS and harness side) for damage: bent, corroded, and unseated pins or sockets. See Figure "Engine Harness Connector to Timing Reference Sensor" .
   

   Figure 5. Engine Harness Connector to Timing Reference Sensor

   1. If terminals and connectors are damaged, repair them. Refer to "41.3.15 Verify Repairs" .
   2. If terminals and connectors are not damaged, replace the TRS. Refer to "41.3.14 Verify Synchronous Reference Sensor / Timing Reference Sensor" .

Section 41.3.13
Check Synchronous Reference Sensor Connectors

Perform the following steps to check the SRS connectors.‪

1. Check terminals at the SRS (both the SRS and harness side) for damage: bent, corroded, and unseated pins or sockets, or bad contacts.
   1. If terminals and connectors are damaged, repair them. Refer to "41.3.15 Verify Repairs" .
   2. If terminals and connectors are not damaged, replace the SRS. Refer to "41.3.14 Verify Synchronous Reference Sensor / Timing Reference Sensor" .

Section 41.3.14
Verify Synchronous Reference Sensor / Timing Reference Sensor

Perform the following steps to verify operation of the SRS/TRS.‪

1. Reconnect all connectors.
2. Turn vehicle ignition ON.
3. Clear codes.
4. Start and run the engine for one minute.
5. Stop engine.
6. Check DDR for codes.
   1. If no codes are logged, troubleshooting is complete.
   2. If code 21/0 and any other codes are logged and the SRS was not replaced, refer to "41.3.6 Synchronous Reference Sensor Code Check" .
   3. If any codes except code 21/0 are logged, refer to "9.1 First Step for Diagnosing a Fault Within the DDEC System" .

Section 41.3.15
Verify Repairs

Perform the following steps to verify repairs.‪

1. Turn vehicle ignition OFF.
2. Reconnect all connectors.
3. Turn vehicle ignition ON.
4. Clear codes.
5. Start and run the engine for one minute.
6. Stop engine.
7. Check DDR for codes.
   1. If no codes are logged, troubleshooting is complete.
   2. If code 21/0 and any other codes are logged, all system diagnostics are complete. Review this section to find the error. Refer to "41.3.1 Check for Signal Open" or contact Detroit Diesel Technical Service.
   3. If any codes except code 21/0 are logged, refer to "9.1 First Step for Diagnosing a Fault Within the DDEC System" .