P0135 code meaning
O2 Sensor Heater Circuit Bank 1 Sensor 1
Powertrain system Generic code P01xx codes Check engine light
What P0135 means
The upstream oxygen sensor on bank 1 (sensor 1) has an electric heater so that it reaches its working temperature of about 300 °C soon after a cold start. The control module switches the heater on the ground side and checks driver voltage and heater current: GM fails it outside 0.3–2.5 A (or 3.1 A) and calls it 'heater performance', Ford outside roughly 0.22–0.465 A minimum to 3 A, Saab Trionic outside 0.5–2.3 A for 5 s. Manufacturers split heater faults differently between P0030–P0032, P0053 and P0135. With the heater dead, closed-loop control starts late after a cold start. If P0135 and P0141 appear together, check the shared fuse.
P0135 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.2 to 1.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P0135
- Check engine light on
- Longer cold-start phase without mixture control, more fuel and emissions
- Follow-up codes P0133/P0134 possible (cold sensor)
Common causes of P0135
- Most likelyHeater element of the sensor burnt out (sensor must be replaced)
- PossibleFuse or relay of the heater supply faulty
- PossibleHeater wiring or connector open, corroded or shorted
- Less likelyUnsuitable replacement sensor (different heater resistance)
- Less likelyHeater driver in the control module faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Oxygen sensor heater bank1 sensor1Oxygen sensor heater circuitFuses
What each part of P0135 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 1 | Area: fuel and air metering. |
| 35 | The exact fault in that area. |
What to do next
- Note P0135 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0135
What does P0135 mean?
P0135 means "O2 Sensor Heater Circuit Bank 1 Sensor 1". The upstream oxygen sensor on bank 1 (sensor 1) has an electric heater so that it reaches its working temperature of about 300 °C soon after a cold start. It is a generic code, so it means the same on every make.
Is it safe to drive with P0135?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0135 fail an emissions test?
Yes, it can. P0135 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0135 to fix?
Difficulty: easy. A typical repair takes 0.2 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0135 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.