O2 Sensor Heater Circuit (Bank 1 Sensor 2)
What it means
The engine computer has found a fault in the heater of the bank 1 downstream oxygen sensor, the one that monitors the catalytic converter. Without its heater the sensor does not reach working temperature quickly enough, so converter monitoring is delayed or stops, while the engine usually runs normally.
Related lights
Dashboard lights that may come on with this code.
Symptoms4
- Check engine light on, usually with no other symptoms.
- Catalytic converter self-test does not complete.
- A downstream no-activity code such as P0140 may appear with it.
- Failed emissions test.
Possible causes5
- Burned-out heater element inside the downstream sensor (most common).
- Wiring or connector under the car damaged by water, stones or heat.
- Blown fuse shared by the sensor heaters.
- Corroded connector terminals.
- Fault in the control circuit inside the engine computer (rare).
How to diagnose5
- Check the oxygen sensor heater fuse, and note any heater codes on other sensors that share it.
- Unplug the downstream sensor and measure heater resistance, comparing it with the manufacturer specification.
- Confirm supply voltage reaches the connector with the ignition on.
- Inspect the connector under the car for water or corrosion.
- Check the control wire between the connector and computer for an open.
How to fix4
- Clean the connector or repair damaged wiring.
- Replace a blown fuse after finding why it blew.
- Replace the downstream oxygen sensor if the heater is open or out of specification.
- Clear the codes, start from cold, and drive to confirm the code does not return.
Repair cost
In Saudi riyals; the highlighted part is the expected range for this fault.
In the Saudi market: SAR 100–900 (≈ USD 27–240)
Our prices come from the Saudi market, converted at a fixed rate (SAR 3.75 per USD). Prices in your country may differ a lot, so we show the cost level.
A wiring or fuse repair is cheap; a new downstream sensor raises the cost, and labor grows if the sensor is rusted in place.
Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026
Frequently asked questions
Is this code serious?
No. It rarely affects driving, but it stops the computer from monitoring the converter, and the car will fail an emissions test.
Why do downstream sensor heaters fail so often?
The sensor is exposed to water splash under the car, and sudden cooling of the hot element stresses the heater over time, on top of normal aging.
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