Oxygen Sensor Failures
New oxygen sensors have an average service life. We suggest testing the sensor every 20,000 km. If it fails prematurely, the underlying vehicle problem should be eliminated before replacement.
| Failure | Causes | Effects |
|---|---|---|
| Coolant antifreeze contamination | Worn or damaged engine gaskets allow coolant into the exhaust. | Slower or missing signal; grey scaling. |
| Silicone contamination | Silicone particulates enter through fuel or the air/fuel mixture. | Slower or missing signal; whitened head. |
| Lead contamination | Poor-quality fuel may still contain lead. | Red-brown sensor head and missing output. |
| Hydrocarbon deposits | A rich mixture contaminates the sensor. | Black deposits and incorrect output. |
| Oil fumes | Worn rings or seals allow oil into the exhaust. | Greasy deposits and slow output. |
| Bad electrical connection | Moisture, dirt, corrosion or incorrect wiring alters the circuit. | Shifted signal levels or no output. |
| Overheating | Incorrect ignition timing raises exhaust temperature. | Permanent sensor damage. |
| Ceramic substrate fracture | Cold water rapidly cools a hot sensor. | Broken ceramic and no output. |
| External damage | Road debris or mechanical shock damages the case or cable. | Short circuit or interrupted wiring. |