Measure the voltage between ECM connector and chassis ground.
Connector & terminal
(B135) No. 3 (+) — Chassis ground (−):
(B135) No. 4 (+) — Chassis ground (−):
Is the voltage less than 1 V?
Repair the poor contact of ECM connector. Replace the ECM if defective.
Repair the following item.
• Further tighten the engine ground terminal.
• Poor contact in ECM connector
• Poor contact of coupling connector