P0030: HO2S Heater Control Circuit (Bank 1 Sensor 1)

P0030 means the engine computer has found a fault in the heater circuit of the upstream oxygen sensor on bank 1, the one before the catalytic converter. The heater brings the sensor up to working temperature quickly after a cold start; without it the engine waits for exhaust heat before it can fine-tune the fuel mixture. The usual causes are a burned-out heater inside the sensor, a blown fuse or a damaged connector. A new upstream sensor typically costs about 100 to 300 EUR fitted.

P0030 is a emissions-related diagnostic trouble code classified as low severity. When your vehicle's ECU detects this condition, it stores P0030 and illuminates the check engine light.

If your vehicle has triggered P0030, you may notice one or more of these symptoms:

• Check engine light on, often with no change in how the car drives
• Slightly higher fuel use on short trips and in cold weather
• Engine stays in open loop (fixed, richer mixture) longer after a cold start
• Oxygen sensor heater readiness monitor incomplete after the code is cleared
• Possible rejection at an emissions inspection while the warning light is on

Here are the most common causes of P0030:

Generally yes, for short-term driving. Safe to drive in the short term. The upstream sensor still works once hot exhaust has warmed it, so the engine runs normally when warm; the cost is a longer warm-up on a richer mixture, a little more fuel on short trips and higher cold-start emissions. Book the repair soon, because the lit warning light hides any new fault and can get the car rejected at an emissions inspection.

Follow these steps to pinpoint the root cause of P0030:

1. Read all stored codes and freeze frame. Several heater codes at once (for example P0030 with P0036 or P0141) point to a shared fuse, relay or supply wire, not to several failed sensors
2. Find the oxygen sensor heater fuse in the owner's manual or the fuse box lid and check it. If it is blown, replace it and watch whether it blows again, which would mean a short circuit
3. Unplug the Bank 1 Sensor 1 connector and measure the resistance across the two heater pins. Most heaters read roughly 2 to 15 ohms at room temperature (check your car's specification). An open circuit means the heater has burned out; close to 0 ohms means it is shorted
4. With the key on, check for battery voltage on the heater supply pin of the harness side of the connector. No voltage points to the fuse, relay or supply wire
5. Inspect the connector and wiring for green corrosion, pushed-back pins, melted insulation or chafing against the exhaust, and repair as needed
6. After the repair, clear the code and do a cold start and a normal drive. With a generic OBD2 reader, check that the fuel system reports closed loop within a few minutes of starting and that the oxygen sensor heater readiness monitor completes

Repair costs for P0030 vary depending on the root cause and your vehicle. Here are typical estimates:

P0030 behaves differently depending on your vehicle. Select your car below for model-specific causes and known issues:

These codes are often seen alongside P0030 or indicate related issues: