IN–35 INTRODUCTION – HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS Check and Replace ECU First check the ECU ground circuit. If it is faulty, repair it. If it is nor- mal, the ECU could be faulty, so replace the ECU with a known good one and check if the symptoms appear. Example Ground IN0383 (1) Measure the resistance between the ECU ground terminal and the body body ground. Resistance: 1 Ω or less ECU Side Ground W/H Side Ground Ground IN0384 (2) Disconnect the ECU connector, check the ground terminals on the ECU side and wire harness side for bend and check the contact pressure.