P0133

O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)

Car Fault Codes Emissions & exhaust

Can you still drive? Yes, normally

Who can fix it? DIY with some experience

Typical repair time 30 minutes – 1.5 hours

Typical cost SAR 150 to 900

What it means

The engine computer measures how quickly the upstream oxygen sensor signal switches between rich and lean. When the response is slower than allowed, this code is set; the usual cause is an aged or contaminated sensor, which makes fuel control less precise.

Symptoms4

Check engine light on, often with no other clear symptoms.
Gradual increase in fuel consumption.
Occasionally a slightly less smooth idle.
Failed emissions test.

Possible causes6

Aged upstream oxygen sensor after high mileage.
Sensor contaminated by engine oil, coolant or silicone.
Exhaust leak ahead of the sensor.
Weak sensor heater slowing warm-up.
Extra resistance in the wiring or connector from corrosion.
Mixture disturbance from a vacuum leak or the MAF sensor.

How to diagnose5

Watch the sensor signal on a scan tool at a steady, fairly high engine speed and compare its switching speed with the manufacturer data.
Remove the sensor and inspect its tip; white or shiny black deposits point to coolant or oil contamination.
Check the exhaust for leaks ahead of the sensor.
Make sure there are no heater or mixture codes that explain the slow response.
Inspect the connector and wiring for corrosion or looseness.

How to fix5

Repair any exhaust leak.
Clean the connector or repair corroded wiring.
Fix any mixture problem found.
Replace the upstream oxygen sensor, the most common fix for this code.
If the sensor is fouled by oil or coolant, fix the source first, then clear the codes and confirm the self-test completes.

Repair cost

0–500

500–2,000

2,000–5,000

5,000+

In Saudi riyals; the highlighted part is the expected range for this fault.

The job usually ends with a new sensor; the price depends on its type (conventional or wide-range) and on genuine versus aftermarket, and rises if an exhaust leak also needs repair.

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

Can I clean the sensor instead of replacing it?

It is not recommended. The contamination is inside the sensing element, cleaning rarely restores the response, and replacement is the accepted fix.

Why did my new sensor fail quickly?

Usually because of oil burning, coolant entering the exhaust or an unsuitable silicone sealant, which must be fixed before fitting another sensor.

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This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.

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