Code
P1150
SCION
P — Powertrain
Air-fuel ratio sensor circuit range / performance malfunction
Views:
UK: 2
EN: 4
RU: 1
AI status
Completed
Completed
100%
Causes
- Faulty air‑fuel ratio (wideband) sensor
- Damaged wiring or poor connector (open, short to ground/voltage, high resistance)
- Contaminated sensor (oil, coolant, silicone, silicone grease or carbon fouling)
- Heater circuit fault (open, short, poor ground or fused supply)
- Exhaust leak upstream of the sensor or manifold leak
- Vacuum or intake air leak affecting sensor readings
Symptoms
- Check Engine MIL/EFI light illuminated
- Poor fuel economy or drivability (hesitation, stumble, rough idle)
- Rich or lean running conditions, black smoke or strong fuel smell
- Failed emissions test or elevated tailpipe emissions
- Stored freeze‑frame data and live A/F sensor values out of expected range
What to check
- Read and record freeze frame and live data with a scan tool (A/F sensor voltage/current, heater status, short/long term fuel trim, fuel trims)
- Visual inspection of sensor, connector and wiring for damage, corrosion or disconnection
- Verify sensor warms up (heater ON) in live data or check heater supply and ground
- Backprobe sensor signal and heater circuit at connector to confirm proper voltages and continuity
- Check fuel pressure and inspect for vacuum/intake/exhaust leaks
- Confirm no recent silicone or oil contamination near intake/exhaust or sensor
Signal parameters
- Sensor output should change and oscillate around stoichiometric as engine runs in closed loop when warmed
- Heater circuit should show power supply and ground and sensor should reach operating temperature quickly (heater ON at key ON/start, then steady)
- Open circuit: no sensor signal or constant invalid voltage; short to voltage/ground: fixed high/low reading
- Approximate typical narrowband‑style behavior: rapidly varying voltage around a center point when warmed; wideband sensors may use a different voltage/current scale — compare to manufacturer specification
Diagnostic algorithm
- Retrieve codes and freeze frame; note engine temp, load, fuel trims and A/F sensor raw/filtered values.
- With a scan tool, observe live A/F sensor output and heater status during cold start and after warm‑up. Confirm whether response is sluggish, absent, or out of range.
- Perform visual inspection of sensor, threads and wiring harness. Repair any physical damage or corrosion.
- Check continuity and resistance of heater circuit and supply voltage at the sensor connector (key ON). Verify ground integrity.
- Backprobe the signal wire with the engine running (warmed up). Confirm signal varies as expected and compare to manufacturer specs. Wiggle the harness to check intermittent faults.
- Inspect for intake vacuum leaks and exhaust leaks upstream of the sensor; repair if found and retest.
- Check fuel pressure and injector operation to rule out fuel delivery problems that could cause abnormal sensor readings.
- If wiring and upstream systems are good but sensor output is incorrect or nonresponsive, replace the A/F sensor and clear codes.
- After replacement, perform relearn/initialization if required, then road test and recheck for codes and proper sensor behavior.
- If replaced sensor and wiring checks fail to correct the issue, consider ECU/PCM diagnosis or intermittent wiring harness faults; consult service information.
Likely causes
- Sensor failure (most common)
- Wiring or connector corrosion/damage at sensor or harness
- Heater power or ground fault preventing proper sensor temperature
- Contamination from oil or coolant leak
- Intake or vacuum leak causing abnormal readings
Fault status
Status
Air‑fuel ratio sensor circuit range/performance malfunction detected. Sensor output or heater performance outside expected range — may affect fuel control and emissions.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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