John Deere 3353.31 – Engine Control Unit (ECU): Alternator Fault / Alternator without function / No Alternator Condition Exists / Alternator Excitation Condition Exists

The Engine Control Unit (ECU) has detected that the alternator is not providing the necessary electrical power to run the machine and charge the battery. This occurs when the alternator's output is not detected or falls outside of its expected range, which can lead to a depleted battery and unexpected machine shutdown.

• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 5E Series
• 5M Series
• 5065M
• 5075M
• 5085E
• 5085M
• 5090E
• 5100E
• 5115ML
• 8R/RW Series
• 8235R
• 8400R
• 700K
• 750K
• 850K
• 950K
• 1050K
• 670G
• 770G
• 772G
• 870G
• 250D
• 300D
• 310SK
• 410K
• 7400A TerrainCut
• 7760 Cotton Picker

1. 1

   Check if the DTC periodically goes away, which indicates an intermittent wiring connection rather than a failed alternator.

2. 2

   Inspect the engine for a broken, loose, or slipping alternator drive belt.

3. 3

   Inspect the wiring harness and connections at the alternator smart regulator and the ECU for an open circuit, short circuit, or bad connection.

4. 4

   Verify the actual voltage output at the vehicle controller or battery using a multimeter while the engine is running to confirm the low voltage condition.

1. 1

   Safety First

   Turn off the engine, remove the key, and disconnect the negative battery cable before servicing the electrical system.

2. 2

   Belt Replacement/Tensioning

   If the diagnostic check revealed a broken or loose serpentine/drive belt, replace the belt or adjust the tensioner.

3. 3

   Harness Repair

   If wiring damage or a loose connector was found during the visual inspection, clean the contacts, repair the broken wire, or replace the pigtail connector.

4. 4

   Alternator Replacement

   If the belt and wiring are intact but the alternator fails to output proper voltage (or fails bench testing), remove the drive belt, disconnect the B+ and regulator electrical connections, remove the mounting bolts, and extract the faulty alternator. Install the new alternator, torque mounting bolts to spec, and reattach the wiring.

5. 5

   Reassembly and Clearing Codes

   Reinstall the drive belt, reconnect the battery, start the engine, and verify that the charging system is operating at the correct voltage (typically ~14V for 12V systems or ~28V for 24V systems). Clear the 003353.31 fault code via the monitor or diagnostic tool.