P0135
Low SeverityO2 Sensor Heater Circuit (Bank 1, Sensor 1)
Emissions System
P0135 — Instant Answer
O2 Sensor Heater Circuit (Bank 1, Sensor 1)
Severity: LOW SEVERITY
Meaning: The heater in the upstream O2 sensor on bank 1 is not working properly. The heater brings the sensor to operating temperature quickly.
Safe to drive? Usually yes with caution, but confirm root cause before long trips.
Estimated repair cost: $30 - $100
Most common causes:
- 1. Failed O2 sensor heater (35-45% of cases)
- 2. Blown O2 heater fuse (10-25% of cases)
- 3. Wiring issue (10-25% of cases)
- 4. Corroded connector (10-25% of cases)
Symptoms
- ⚠️Check engine light
- ⚠️Slow warm-up fuel trim
- ⚠️Slightly increased emissions
- ⚠️Failed emissions test
Related Symptoms
Common Causes
How to Diagnose P0135
- 1Check O2 heater fuse
- 2Measure heater resistance (2-30 ohms normal)
- 3Check power and ground at sensor
- 4Replace sensor if heater open
OEM Procedures for P0135
O2 Sensor Heater Circuit (Bank 1 Sensor 1) Found 58 OEM service manual procedures.
11 51 000 Removing and installing/replacing the coolant pump (X5 M) - Replacement: Prepare the coolant pump
11 51 000 Removing and installing/replacing the coolant pump (X5 M) - Replacement: Prepare the coolant pump
11 51 000 Removing and installing/replacing the coolant pump (X5 M) - Replacement: Prepare the coolant pump
11 51 000 Removing and installing/replacing the coolant pump (X5 M) - Replacement: Prepare the coolant pump
11 51 000 Removing and installing/replacing the coolant pump (X5 M) - Replacement: Prepare the coolant pump
11 51 000 Removing and installing/replacing the coolant pump (X5 M) - Replacement: Prepare the coolant pump
11 51 000 Removing and installing/replacing the coolant pump (X5 M) - Replacement: Prepare the coolant pump
11 51 000 Removing and installing/replacing the coolant pump (X5 M) - Replacement: Prepare the coolant pump
Showing 8 of 58 procedures
OEM Diagnostic Flowchart
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Parts & Tools for This Job
Common parts shoppers buy for P0135 O2 Sensor Heater Circuit (Bank 1, Sensor 1).
Oxygen Sensor
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Catalytic Converter
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EVAP Purge Valve
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Gas Cap
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OBD2 scanner
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Check SpecificationsBattery tester
Check cranking and charging health before replacing expensive parts.
A weak battery can mimic alternator or starter problems.
Check SpecificationsMultimeter kit
Confirm voltage, continuity, and sensor power with one simple kit.
A meter is the cheapest way to rule out a bad circuit fast.
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Related Resources
Repair guides, symptom pages, and wiring diagrams related to P0135.
OEM Manual Evidence
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Related Symptoms
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Related Codes
The oxygen sensor heater circuit on the upstream (pre-cat) sensor of bank 1 has a fault. The heater gets the O2 sensor to operating temperature quickly for proper fuel trim.
The heater in the downstream O2 sensor on bank 1 has failed.
Heater failure in the upstream O2 sensor on bank 2.
Frequently Asked Questions
- Can a heater fault affect the O2 sensor reading?
- Not directly, but the sensor will take longer to warm up. In cold weather, fuel economy suffers during warm-up.
- Do all O2 sensors have heaters?
- All modern vehicles (1996+) have heated O2 sensors. The heater ensures accurate readings from cold start.
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Author & Review
Published by AllOEMManuals, founded by Lyndon Bedford, an automotive technician with 20 years of experience. He owned and operated a mechanic shop in Hurst, Texas from 2014 to 2022 and continues hands-on repair work.
Content may combine manual references, general repair templates, and AI-assisted drafting. Confirm the source, vehicle configuration, and applicability before working. Report corrections through our contact page.
Last updated: 2026-10-28