Emissions

P1135 — Air/Fuel Sensor Heater Circuit, Bank 1 Sensor 1

Severity: medium Safe to drive

What P1135 means

P1135 is a manufacturer-specific code. On Toyota and Lexus it points to a fault in the heater circuit of the wide-range air/fuel ratio sensor upstream of the catalytic converter (bank 1, sensor 1). The heater brings the sensor to operating temperature quickly so the ECU can control the mixture accurately after startup. The ECU sets the code when heater current or resistance is outside the expected range. Other brands define this code differently.

Symptoms

  • Check Engine light on
  • Worse fuel economy
  • Rough running on a cold engine
  • Failed emissions test
  • Sensor slow to enter closed-loop control

Possible causes

  1. Failed heater element inside the air/fuel sensor
  2. Blown fuse for the sensor heater
  3. Damaged wiring or connector near the exhaust manifold
  4. Corroded terminals or poor ground
  5. Faulty relay or, rarely, the ECU
  6. Exhaust leak near the sensor that wears it out early

How to diagnose

  1. Read all codes and freeze frame data, clear the code and see whether it returns
  2. Check the heater circuit fuse and relay using your model's wiring diagram
  3. Inspect the harness and sensor connector for chafing, melting and corrosion
  4. Unplug the sensor and measure heater resistance, comparing it with the factory spec
  5. Check for power and the control signal at the harness connector with the ignition on
  6. Verify the ground and wire continuity back to the ECU
  7. Look for exhaust leaks at the manifold and joints
  8. If wiring is good and the heater is out of spec, replace the sensor

Common fixes

  • Replace the bank 1 sensor 1 air/fuel sensor
  • Replace the fuse after finding why it blew
  • Repair or replace damaged wiring and connectors
  • Fix the exhaust leak
  • Clean the terminals and restore the ground

P1135 on different brands

Chevrolet · manuals
HO2S Lean/Mean, bank 1 sensor 1: the code points to this oxygen sensor's circuit or function rather than one specific failure.
Dodge · manuals
Glow plug control module voltage supply concern (diesel applications).
Ford · manuals
Pedal position sensor 'A' circuit intermittent.
Hyundai · manuals
Injection timing servo malfunction.
Jaguar
Crankshaft position (CKP) sensor fault.
Mazda · manuals
HO2S 1, bank 1 heater control circuit low.
MINI
O2 sensor heater circuit low voltage, bank 1 sensor 1.
Subaru · manuals
Front left oxygen sensor circuit open.

Questions and answers

What does P1135 mean?

On Toyota and Lexus it means a fault in the heater circuit of the bank 1 air/fuel sensor ahead of the catalytic converter. Other brands use the code for different faults, so check your model's documentation.

Can I drive with P1135?

For a short time, yes, but fuel economy and emissions will get worse. Get it diagnosed soon to avoid straining the catalytic converter.

What most often causes P1135?

Most often the sensor's internal heater has failed. Still, check the fuse, wiring and connector before buying a new sensor.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.