DTC 13: Main Relay System (Inside of ECU): Diagnosis

Replace the transfer-ECU. 

Q: Is the malfunction eliminated? 

1. YES :  The procedure is complete. (If no malfunction is not found an intermittent malfunction is suspected). Refer to HOW TO USE TROUBLESHOOTING/INSPECTION SERVICE POINTS - How to Cope with Intermittent Malfunction.
2. NO :  Replace the PCM.