Toyota P1135: A/F Sensor Heater (B1S1) — Fix
On Toyota vehicles, P1135 means a fault in the air/fuel-ratio (A/F) sensor heater circuit for bank 1, sensor 1 — the wideband sensor Toyota uses upstream.
- Applies to
- Toyota vehicles
- Est. repair cost
- $40 – $400
- Time to fix
- 30 minutes – 2 hours
What it means
Causes include a failed A/F sensor heater, a blown EFI/heater fuse, or wiring/connector faults. P1xxx codes are manufacturer-specific — P1135 is defined by Toyota (not part of the generic SAE J2012 set), so this definition applies to Toyota vehicles. Model years can vary, so confirm against the Toyota service manual. Fix the fault, then clear the code with a scan tool.
Symptoms
- Check engine light on
- Slower closed-loop when cold
- Worse cold-start economy
How to fix it
- 1
Check the heater fuse and wiring
1. Confirm the A/F heater fuse. 2. Inspect the sensor connector and wiring.
- 2
Replace the A/F sensor
1. Test the heater resistance. 2. Replace the A/F sensor if the heater is open, then clear the code.
Frequently asked questions
Is the A/F sensor the same as an O2 sensor?
It's a more precise wideband version Toyota uses upstream. P1135 is a fault in its heater circuit; the sensor usually needs replacing.
Last updated July 19, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.