Check and Replace ECU

First check the ECU ground circuit. If it is faulty, repair it. If it is normal, the ECU could be faulty, so replace the ECU with a known good one and check if the symptoms appear.

1. Measure the resistance between the ECU ground terminal and the body body ground.
   Resistance: 1 Ω or less
2. Disconnect the ECU connector, check the ground terminals on the ECU side and wire harness side for bend and check the contact pressure.