P0133

Code

GWM P — Powertrain

- The oxygen sensor responds late (bank 1, sensor 1)

Brand: GWM

Type: P — Powertrain

Views: UK: 16 EN: 28 RU: 28

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Page language: EN

Causes

Aging or failed upstream oxygen (O2) sensor (Bank 1, Sensor 1)
Contaminated sensor (oil, coolant, silicone, sulfur, fuel additives)
Damaged or corroded wiring or poor connector contact in sensor signal or heater circuits
Open or high resistance heater circuit (sensor does not reach operating temperature)
Exhaust leak upstream of the sensor
Intake vacuum leak or fuel delivery issue causing abnormal mixture

Symptoms

Check Engine Light (MIL) illuminated
Poor fuel economy
Rough idle or hesitation during acceleration
Increased tailpipe emissions (failed emissions test possible)
Longer closed‑loop entry or hunting fuel trims

What to check

Retrieve freeze frame and live data (O2 voltage, heater status, short‑/long‑term fuel trim) with a scan tool
Confirm engine is at normal operating temperature (sensor must be hot to operate)
Visually inspect sensor wiring, connector, and harness for damage, corrosion, or disconnection
Check for exhaust leaks upstream of the sensor
Verify fuel pressure and check for vacuum leaks
Measure sensor heater resistance and supply voltage

Signal parameters

Voltage range (narrowband zirconia): ~0.1 V (lean) to ~0.9 V (rich)
Switching behavior: upstream sensor should toggle frequently (several times/sec) when in closed‑loop at idle/steady throttle
Typical response time: healthy sensor switches within ~100–300 ms (manufacturer specific)
Heater circuit: resistance typically low (varies by sensor model — often ~2–20 ohms); heater supply should be near battery voltage when activated
When cold or heater faulty: sensor voltage remains low and response is sluggish

Diagnostic algorithm

Connect a professional scan tool and record freeze frame and live data for Bank 1 Sensor 1, short/long term fuel trims, and commanded closed‑loop status.
Warm the engine to normal operating temperature and observe the upstream O2 voltage. A healthy sensor should switch frequently between low and high voltages during closed‑loop.
If switching is slow, backprobe the sensor signal and capture waveform with an oscilloscope or high‑speed data logging to confirm slow transition times.
Inspect harness and connector for damage, corrosion, pin push‑out, water intrusion, or contact resistance. Wiggle wiring while watching live data to detect intermittent faults.
Verify heater circuit: with connector disconnected measure heater resistance against manufacturer spec and check for 12 V supply and proper switching from PCM when engine cold. Repair wiring or fuse if supply absent.
Check for exhaust leaks between cylinder head and sensor — fix any leaks and retest, as leaks can introduce air and slow sensor response.
Check for contamination sources (oil burning, coolant leak, silicone sprays, leaded gasoline) and address root cause before sensor replacement.
Inspect fuel system (fuel pressure, injectors) and intake (vacuum leaks, PCV) for conditions that could produce unstable mixtures that mask sensor behavior.
If wiring and heater are good and contamination/engine issues corrected, replace the upstream O2 sensor with OEM or equivalent. Clear codes and verify proper switching and fuel trims during a drive cycle.
If issue persists after sensor replacement, consider PCM diagnosis or further exhaust/catalyst inspection.

Likely causes

Normal sensor aging/slow response (most common)
Wiring harness damage or poor connector connection at the sensor
Heater circuit fault preventing proper sensor warm‑up
Sensor contaminated by oil or coolant
Exhaust leak between engine and sensor
Fuel trim or injector issues causing unstable mixture

Fault status

⚠️ Status

P0133 indicates the engine control module has detected the Bank 1, Sensor 1 oxygen sensor is responding slower than expected to changes in air/fuel mixture. This can be caused by a slow or failing sensor, heater circuit problems, wiring faults, contamination, or upstream exhaust/intake issues.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours

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P0133 — - The oxygen sensor responds late (bank 1, sensor 1)