Critical Safety risk Powertrain-code

P0030

P0030 HO2S Heater Control Circuit B1S1

Detailed information on troubleshooting and repairing a P0030 DTC code which refers to a problem in the HO2S heater control circuit. Also includes links to relevant forum topics on the code.

Pull over safely and book service immediately

This code is flagged as a safety risk and rated Critical. Avoid driving until a technician has inspected the vehicle.

Symptoms

Lengthened time needed to achieve closed loop
MIL (Malfunction indicator lamp) illumination
Possibly decreased fuel mileage depending on fault

Likely causes

Failed or damaged heater circuit element inside the HO2S
Open on the O2 sensor heater's ground circuit
Open or short on O2 sensor heater's B+ battery feed (on some vehicles this may be the control circuit)
Possible ECM failure (less likely)

Labor estimate

2h typical

Range: 1h – 4h

Parts cost

$0 – $500

Range varies by year/make/model

Information shown is reference-grade and may vary by vehicle. Always have a qualified technician confirm the cause before any repair.