P0036
PowertrainTurbocharger/Supercharger Bypass Valve Control Circuit Range/Performance
The heater control circuit on the bank 1 sensor 2 oxygen sensor (the rear one, after the cat) has a fault. The rear sensor monitors cat efficiency and like the front sensor needs its heater to function quickly after a cold start.
ⓘ Information only. This page provides general educational information about fault code P0036. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does P0036 mean?
P0036 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Turbocharger/Supercharger Bypass Valve Control Circuit Range/Performance.
This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms commonly associated with this code
Symptoms that drivers often report alongside this code. Not all may apply to every case:
- • Engine warning light, often within a minute of starting cold
- • Sometimes very mild emissions increase during warm-up
- • Drivability typically unaffected
- • Slight increase in cold-start fuel use on some cars
Possible causes
Causes commonly associated with P0036, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Sensor heater element failed (most common, sensors are wear items)
- 2. Blown fuse for the heater circuit
- 3. Wiring damaged from heat exposure, the rear sensor's loom often runs close to the exhaust
- 4. Connector contaminated with road grime, water, or salt
- 5. Ground connection corroded
- 6. ECU output fault (rare)
How mechanics typically diagnose
A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.
- 1. Check the heater circuit fuse first
- 2. Resistance-test the heater (typical 5-15 ohms; infinite means open)
- 3. Verify 12V supply with ignition on
- 4. Check ground continuity back to the ECU
- 5. Inspect the connector physically, water ingress is more common at the rear sensor than the front because of road spray
Common questions about P0036
Front sensor versus rear sensor, what's the difference? +
Front sensor (bank 1 sensor 1) sits before the catalytic converter and is what the ECU uses to control fuel mixture in real time, the live data from this one is constantly cycling. Rear sensor (bank 1 sensor 2) sits after the cat and is mainly used to monitor cat efficiency by comparing against the front sensor. The rear one is much less critical to drivability but still throws codes when its heater fails.
Will P0036 affect my fuel economy? +
Only marginally, because the rear sensor's primary job is monitoring rather than fuelling control. The front sensor is what matters for fuel mixture, and as long as that's working the engine runs in proper closed-loop mode. P0036 might add 1-2% fuel use during warm-up but it's not a significant economy hit.
Do oxygen sensors actually wear out, or is this a manufacturing fault? +
They genuinely wear out. The sensing element relies on a thin platinum/zirconia structure that gradually degrades from heat cycling. The heater is a separate element that also fatigues over thousands of heat cycles. UK oxygen sensors typically last 80,000-120,000 miles; some go further, some fail earlier. After 80k they're considered consumables.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →