Emission codes
P0135: oxygen sensor heater circuit (bank 1 sensor 1)
Oxygen sensors only read correctly once their tip is several hundred degrees hot, so each one has a small electric heater. P0135 means the computer has found that heater circuit open, shorted or drawing the wrong current.
P0135: can I drive, and what will the labor cost?
Estimated labor, replace upstream oxygen sensor (bank 1 sensor 1)
$33 to $110
| Labor time (estimate) | 0.3 to 1 h |
| Rate used | $110/h |
| Technician wage, United States (average) | $27.13/h |
| Low: fix when convenient Safe to drive; the engine runs a little richer after a cold start until the sensor warms up on exhaust heat alone. | |
Labor only: parts and the diagnostic fee are not included. Hours are our estimate for a typical car; book times vary by model. Wage: BLS, May 2025.
P0135 is the generic OBD-II code for "O2 sensor heater circuit, bank 1 sensor 1". A cold oxygen sensor gives no useful signal, so the sensor contains a heating element that brings it to working temperature within a minute or so of starting, long before the exhaust alone would. The engine computer powers that heater and watches its current; when it sees an open circuit, a short or a current outside the expected range, it sets P0135. The heater element is inside the sensor and cannot be repaired, so the usual fix is a new upstream sensor. A blown fuse that feeds several sensor heaters, wiring or a connector melted by the exhaust, and, rarely, a fault in the computer's heater driver account for the rest. It is safe to drive: the engine simply stays in open-loop fuel control a little longer after each cold start, running slightly rich. We rate it low: fix when convenient.
After the repair: when does the light go off?
Light off by itself after about
2 days
| Fault-free trips needed | 3 |
| Warm-up cycles before the code can be erased | 40 |
| Stored code gone after about | 40 days |
Federal rule for model years up to 2016 (40 CFR 86.1806-05); a misfire or fuel fault must also stay away under similar conditions. Clearing codes with a scanner also resets the readiness monitors an inspection checks.
Codes, rules and labor data checked by Radif Partners · Editorial policy · Method and sources
P0135 at a glance
| Code | P0135 |
| Standard description | O2 Sensor Heater Circuit (Bank 1 Sensor 1) |
| System | Oxygen sensors |
| Severity | Low: fix when convenient |
| Common symptoms | usually none, slightly lower mileage on short trips |
A five-minute check before buying a sensor
With the engine off, unplug the sensor and measure the resistance between the two heater wires on the sensor side; the wiring diagram for your car shows which ones, and a typical value is a few ohms. A reading of infinity confirms an open heater. Then check the fuse for the oxygen sensor heaters: if several heater codes appear at once, such as P0135 and P0141, a shared fuse or power feed is far more likely than two sensors failing on the same day.
Why heater failures are common
The element goes through a full heat cycle at every start and sits in a vibrating, hot exhaust pipe. Moisture in the exhaust on short winter trips adds thermal shock. Heater failure is one of the most frequent ways an oxygen sensor reaches the end of its life, often before the sensing part itself has worn out. If the sensor is also slow (P0133), one replacement addresses both.
After the repair
The heater monitor runs early in a drive, so the computer can confirm the fix quickly; the light then needs 3 fault-free trips to go off by itself. The counter on this page estimates the days for your driving pattern.
Likely causes of P0135, in order
| Cause | How often |
|---|---|
| Heater element open inside the sensor | most frequent |
| Blown fuse for the oxygen sensor heaters | frequent |
| Damaged wiring or melted connector near the exhaust | frequent |
| Engine computer heater driver fault | less frequent |
P0135 repairs and labor time
| Repair | Labor (estimate) | At $110/h |
|---|---|---|
| Replace upstream oxygen sensor (bank 1 sensor 1) | 0.3 to 1 h | $33 to $110 |
| Repair heater wiring or connector | 0.5 to 1.5 h | $55 to $165 |