P1135

Air/Fuel Sensor Heater Circuit (Bank 1 Sensor 1)

Car Fault Codes Lexus 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 100 to 900

What it means

This is a code specific to Lexus (and the Toyota group); the same number may mean something else on other makes. The engine computer detected that the heater in the Bank 1 upstream air/fuel (A/F) sensor is not working properly because of an open or short in its circuit. On V6 engines such as those in the ES300 and RX300, Bank 1 is one specific side of the engine, and identifying the right side prevents replacing the wrong sensor.

Models covered: Lexus models with A/F sensors, mainly around 1998–2004 (e.g. ES300, RX300).

Symptoms4

Check engine light on.
Slightly higher fuel use on short city trips.
Driving performance usually feels normal.
The car may fail an emissions inspection because of the code.

Possible causes5

Heater element inside the sensor burnt out with age.
Blown fuse feeding the heater, or a failed relay where fitted.
Wiring damaged by exhaust manifold heat.
Water or corrosion in the sensor connector.
Control circuit fault inside the engine computer (rare).

How to diagnose4

Identify the Bank 1 side of the engine (the side with cylinder 1) before removing any sensor.
Check the heater fuse; if P1155 is also stored, start with the shared power feed.
Measure the sensor heater resistance and compare with the factory specification.
Confirm voltage at the connector with the ignition on, and inspect the wiring route.

How to fix4

Repair wiring or the connector, or replace the fuse after removing the cause of the short.
Replace the Bank 1 A/F sensor if its heater is open, using a part that matches the vehicle.
Apply suitable anti-seize to the new sensor threads if it is not pre-coated.
Clear the codes and confirm they do not return after a cold start.

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.

A fuse or wire is at the low end and a genuine sensor at the high end; labor can rise a little depending on where the sensor sits on the engine.

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

How do I know which sensor is Bank 1 on a V6 Lexus?

Bank 1 is the side of the engine that holds cylinder 1. The side depends on how the engine is mounted, so check the service manual or ask the technician before buying a sensor.

Should I replace both upstream sensors together?

It is not required. If only P1135 is stored, replace just the Bank 1 sensor once its heater is confirmed faulty. Replacing both is a preventive choice, not a must.

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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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