P0030: OBD-II code P0030 flags a fault in the upstream O2 sensor heater circuit on bank 1 — the sensor can't reach operating temperature fast enough for closed-loop control.

Symptoms

• Check engine light is on; the engine may run rich longer than usual after a cold start.
• Poor fuel economy at start-up as the PCM stays in open-loop enrichment waiting for a valid O2 signal.
• The vehicle will fail an OBD-II emissions test until the O2 heater monitor completes and reports ready.

Common causes

• A failed O2 sensor heater element (open circuit inside the sensor housing) — the most common cause.
• A blown fuse feeding the O2 sensor heater circuit, or a corroded ground.
• Damaged wiring or a corroded connector on the sensor heater side of the harness.

What to do?

Measure the heater resistance across the two heater pins with a DMM — most read 8-15 Ω cold. An infinite reading means open heater — replace the sensor. Check the fuse and verify battery voltage at the heater feed pin with ignition on. Replace the sensor if the heater is open, or repair wiring as needed.