DIAGNOSING LAMBDA SENSOR ISSUES
ANTIFREEZE CONTAMINATION
Visual Signs
Sensor nose will be contaminated with a grainy white or light grey coating.
The Cause
Coolant with anti-freeze may have found it’s way into the combustion process and reached the Lambda Sensor.
The Solution
Always address the root cause of the failure before replacing the Lambda Sensor. In this case check the head gasket for leaks and repair if required.
ENGINE ADDITIVE CONTAMINATION
Visual Signs
Similar to anti-freeze, the sensor nose will be contaminated with white or red deposits.
The Cause
Excessive use of any engine or fuel additive can contaminate or block the lambda sensor.
The Solution
Again, address the root cause of the failure before replacing the Lambda Sensor. In this case cleaning the fuel system prior to replacement is required.
OIL CONTAMINATION
Visual Signs
Look for oily black deposits left on the sensor nose.
The Cause
The vehicle may be burning excessive oil which can contaminate and/or block the sensor.
The Solution
Thoroughly check the engine for leaks including all the usual seals that are prone to failure. Once repaired replace the sensor.
FUEL CONTAMINATION
Visual Signs
If fuel is burning too rich, a black soot may be seen on the sensor nose.
The Cause
A damaged lambda sensor or fault in the fuel system can result in a high air to fuel ratio producing black soot which damages the lambda sensor.
The Solution
Measure exhaust gases to ensure the fuel system is functioning correctly. Check the lambda sensor heater control and sensor heater. Rectify any faults before replacing the sensor.
LEAD CONTAMINATION
Visual Signs
The sensor nose may be contaminated with shiny grey deposits.
The Cause
Not as common now as this type of contamination is usually caused by leaded fuel attacking platinum parts or the sensor.
The Solution
Replace any leaded fuel in the system with unleaded before replacing the sensor.