When the alternator does not generate electricity, current flows from the IG2 relay to power heater resistors No. 1 and No. 2. Then the current flows to the diode (for power heater), terminal E82-4 (L) of the alternator, and then to ground. As a result, the power heater ECU will not activate.

Inspect the intake air duct.

Inspect the intake air duct.

Lexus IS250 IS220d GSE20 ALE20 HEATER

Inspect the intake air duct.

Disconnect the connector from the combustion heater assembly.

Check for engine coolant leaks .

Check for engine coolant leaks .

Lexus IS250 IS220d GSE20 ALE20 HEATER

Remove the PWR HTR fuse from the engine room R/B and J/B No. 1.