Code
P0135
GWM
P — Powertrain
- Heated oxygen sensor circuit fault (bank 1, sensor 1)
Views:
UK: 3
EN: 6
RU: 19
AI status
Completed
Completed
100%
Causes
- Blown fuse or failed relay for O2 heater circuit
- Open or short in sensor heater wiring or harness (damage, chafing)
- Corroded or loose sensor connector or terminal
- Failed oxygen sensor (heater element open or shorted)
- Faulty ECM / driver circuit (rare)
- Aftermarket or incorrect sensor installed causing wrong resistance
Symptoms
- Check Engine Light / MIL illuminated (P0135 stored)
- Longer than normal time to reach closed‑loop after cold start
- Failed emissions test (high tailpipe HC/CO)
- Rough or unstable idle during cold start
- Reduced fuel economy
What to check
- Read and record freeze frame data and pending codes with a scan tool
- Visually inspect Bank 1 Sensor 1 connector and wiring for corrosion, heat damage, or open terminals
- Check related fuses and relays for continuity and correct operation
- Backprobe heater supply pin at sensor connector with key ON (engine OFF) — look for battery voltage on the power feed
- Measure resistance of the sensor heater element (disconnect sensor) with an ohmmeter
- Check ground continuity from sensor ground circuit to chassis/ECM ground
Signal parameters
- Typical heater resistance (narrowband) approximately 2–14 Ω (manufacturer specific) — compare to GWM spec
- Heater supply voltage: approximately battery voltage (11–14 V) on the fused/relay feed with key ON (engine OFF)
- ECM switches/pulses the heater ground; observed control may be a pulsed ground (duty cycle varies)
- Heater current draw typically in the amp range (depends on sensor); excessive or zero current indicates short or open
Diagnostic algorithm
- Use a scan tool: read freeze frame and freeze data, confirm P0135 and clear codes; see if it returns. 2) Visually inspect the Bank 1 Sensor 1 connector, wiring harness and nearby heat sources for damage or corrosion. 3) Check fuses and relays related to oxygen sensor heaters; replace if blown or faulty. 4) With connector disconnected, measure supply voltage at the heater power pin with key ON (should be near battery voltage). 5) Measure heater element resistance at the sensor (engine cold). Compare to spec; infinite/very high = open heater. 6) Check continuity and shorts: inspect for short to battery or ground in the heater wiring using an ohmmeter. 7) Reconnect sensor and backprobe the ground/control pin; with key ON (engine OFF) observe whether ECM is pulling the line to ground or pulsing it. 8) Wiggle wiring while monitoring voltage/continuity or scan tool data to detect intermittent faults. 9) If wiring, connectors, fuses and relay are good but heater open or out of spec, replace the Bank 1 Sensor 1 oxygen sensor. 10) After repair/parts replacement, clear codes and perform drive cycle to confirm code does not return. 11) If problem persists with correct wiring and new sensor, suspect ECM driver fault and proceed per manufacturer guidance.
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Likely causes
- Open heater element in the Bank 1 Sensor 1 oxygen sensor
- Corroded connector or poor ground at the sensor
- Blown fuse or failed heater relay supplying sensor power
- Short to ground or short to battery in heater wiring
- Wiring damage from heat/chafing near exhaust
Fault status
Status
Heated oxygen sensor (Bank 1 Sensor 1) heater circuit malfunction. ECM detected incorrect heater circuit behavior (open, short, or no heater current) preventing the sensor from reaching operating temperature.
Repair difficulty: Medium
Diagnostic time: 0.5-2 hours
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