Heater element inside the oxygen sensor has failed or been damaged; OBD-Codes.com notes this often happens from age or impact. Open in the heater's ground (on some vehicles, the computer-controlled) circuit. Open or short in the heater's 12-volt battery feed, often with a blown fuse. Wiring damaged by contact with the exhaust. Engine computer (ECM/PCM) failure, listed by both sources but called less likely by OBD-Codes.com.

Replace the Bank 1 Sensor 1 oxygen sensor if its heater has failed (the heater can't be repaired separately). Repair open, shorted or exhaust-damaged wiring and connectors in the heater circuit. Replace a blown fuse, and find and fix the short that blew it. Diagnose or replace the engine computer only after the sensor and wiring have been proven good.

P0030🌫 Emissions / oxygen sensorsDrive with caution, fix soon

P0030: HO2S Heater Control Circuit (Bank 1, Sensor 1) (Meaning, Causes, Fixes)

Q: What does P0030 mean?

P0030 means the engine computer has found a fault in the heater control circuit of the front (upstream) oxygen sensor on Bank 1. A heater element that has failed inside the sensor is a common cause, but an open or short in the heater's power feed or ground wiring, a blown fuse, or (less likely) the engine computer can also set it. The heated oxygen sensor (HO2S) at Bank 1 Sensor 1 sits before the catalytic converter on the side of the engine with cylinder #1 (a 4-cylinder inline engine has only Bank 1). It only reads accurately once it is hot, so it contains an electric heater that warms it faster than the exhaust alone could, shortening the time before the engine enters closed-loop fuel control. OBD-Codes.com explains that on some vehicles the heater gets a fused 12-volt feed whenever the key is on and the computer switches its ground; on others the computer controls the 12-volt feed and the ground is constant. Either way, P0030 sets when the computer detects a fault in that heater circuit. RepairPal describes it more simply as the PCM detecting that the heater wire is not operating. P0030 focuses on the heater control circuit itself, while P0135 is the broader Bank 1 Sensor 1 heater performance code; the two often appear together. P0031 and P0032 are the circuit-low and circuit-high versions of the same circuit, and P0036 is the equivalent code for the downstream sensor (Bank 1 Sensor 2).

Q: Can I keep driving with P0030?

Drive with caution, fix soon. Usually drivable. RepairPal rates P0030 Moderate: not an immediate safety threat, but get it diagnosed within a reasonable time. Until the upstream sensor heats up, the engine takes longer to reach closed-loop fuel control, which can cost fuel economy, and a car with an active check engine light will likely fail an OBD2 emissions inspection.

Reviewed 2026-10-22 · Based on 2 cited source(s)

What P0030 means

The heated oxygen sensor (HO2S) at Bank 1 Sensor 1 sits before the catalytic converter on the side of the engine with cylinder #1 (a 4-cylinder inline engine has only Bank 1). It only reads accurately once it is hot, so it contains an electric heater that warms it faster than the exhaust alone could, shortening the time before the engine enters closed-loop fuel control. OBD-Codes.com explains that on some vehicles the heater gets a fused 12-volt feed whenever the key is on and the computer switches its ground; on others the computer controls the 12-volt feed and the ground is constant. Either way, P0030 sets when the computer detects a fault in that heater circuit. RepairPal describes it more simply as the PCM detecting that the heater wire is not operating. P0030 focuses on the heater control circuit itself, while P0135 is the broader Bank 1 Sensor 1 heater performance code; the two often appear together. P0031 and P0032 are the circuit-low and circuit-high versions of the same circuit, and P0036 is the equivalent code for the downstream sensor (Bank 1 Sensor 2).

Severity: can I keep driving?

Drive with caution, fix soon

Usually drivable. RepairPal rates P0030 Moderate: not an immediate safety threat, but get it diagnosed within a reasonable time. Until the upstream sensor heats up, the engine takes longer to reach closed-loop fuel control, which can cost fuel economy, and a car with an active check engine light will likely fail an OBD2 emissions inspection.

Common symptoms

Check engine light on (both sources)
Longer time before the engine reaches closed-loop fuel control (OBD-Codes.com)
Possibly worse fuel economy (OBD-Codes.com says depending on the fault; RepairPal lists increased fuel consumption)
Decreased engine performance (RepairPal)

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

Heater element inside the oxygen sensor has failed or been damaged; OBD-Codes.com notes this often happens from age or impact
Open in the heater's ground (on some vehicles, the computer-controlled) circuit
Open or short in the heater's 12-volt battery feed, often with a blown fuse
Wiring damaged by contact with the exhaust
Engine computer (ECM/PCM) failure, listed by both sources but called less likely by OBD-Codes.com

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

Read all stored codes. If P0030 appears with other heater codes (for example P0036, P0050 or P0135), suspect a shared fuse, relay or power feed before replacing sensors.
Visually inspect the Bank 1 Sensor 1 sensor (upstream, before the catalytic converter on the cylinder #1 side), its wiring and its connector. Repair any wiring melted or chafed by the exhaust.
If you have a scan tool that shows heater data, check the heater current. OBD-Codes.com says a reading of 0 amps points to an open in the circuit.
Check for blown fuses, then unplug the sensor and, with the key on and engine off, check for 12 volts on the heater feed at the harness. No voltage means an open or short in the feed circuit (replace any blown fuse after fixing the short).
If the feed is good, check the ground (control) circuit back to the computer for an open, using your vehicle's wiring diagram.
If the wiring checks out, measure the heater resistance across the sensor's heater terminals against your vehicle's specification; an open heater means the sensor needs replacing.

Typical fixes

Replace the Bank 1 Sensor 1 oxygen sensor if its heater has failed (the heater can't be repaired separately)
Repair open, shorted or exhaust-damaged wiring and connectors in the heater circuit
Replace a blown fuse, and find and fix the short that blew it
Diagnose or replace the engine computer only after the sensor and wiring have been proven good

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

The code stays after a new sensor is fitted (OBD-Codes.com forum threads show this happening, which points to wiring, power or the computer)
You need wiring diagrams to tell whether your vehicle switches the heater's ground or its 12-volt feed
The sensor is seized in the exhaust and won't come out without heat or special tools

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

What's the difference between P0030 and P0135?

Both involve the Bank 1 Sensor 1 oxygen sensor heater. P0030 is the heater control circuit code, while P0135 covers the heater circuit or its performance more broadly. They often show up together, and one OBD-Codes.com forum post describes P0135 clearing after a new sensor while P0030 stayed, which suggests checking the wiring and power feed too.

Can I keep driving with P0030?

Usually, yes, for a while. RepairPal rates it Moderate. Expect possibly worse fuel economy, and get it fixed before an emissions inspection.

Do the sources agree on the symptoms?

Mostly. OBD-Codes.com lists the check engine light, a longer warm-up to closed loop, and possibly worse fuel economy depending on the fault. RepairPal lists decreased engine performance and increased fuel consumption. Neither describes it as a safety problem.

Sources

Last reviewed 2026-10-22. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.