Lambda sensor error codes are often misleading

In an earlier article, we pointed out how difficult it can be to find the root cause of a lambda sensor error message. That article mainly addressed the broadband type. However, troubleshooting for the causes of error codes for conventional lambda sensors can be a long process as well - and often the problem is not the lambda sensor.

Although the lambda sensor is a wear part - and the mileage determines its lifespan, one should be able to expect it to last at least the warranty period (three years in Triscan’s case). However, the Lambda sensor is part of a complex system whose functionality is affected by many factors that can lead to errors.

Noteworthy in this context, are the very popular universal lambda sensors, in which the original plug is reused. Here, the cable must be soldered, insulated and finally encapsulated, so that the entire compound can withstand heat, cold, moisture, salt and dirt. This method is slow, carries a high risk of connecting the sensor incorrectly and is very vulnerable at the soldered connection. For this reason, Triscan’s program includes only "plug & play" lambda sensors, which exclude this source of error and ensures trouble-free and long-lasting repairs. Unsurprisingly, the fist suspicion for the cause of a lambda sensor error code is a defective lambda sensor. 

  

Experience shows, however, that the error is very often found elsewhere. Below, we offer advice and guidance on how to effectively troubleshoot the problem.  

During the production of Triscan lambda sensors, each sensor is subjected to a 100%  functionality test 

If the replacement of the lambda sensor does not eliminate the problem
If installing a new sensor does not solve the problem immediately - and the error codes are still logged - you should firstly ensure that the correct lambda sensor has been installed. It is not uncommon to have to choose between several variants for a particular car model. Despite having the same connector, thread, and cable length, they are often different.  

Since Triscan lambda sensors are 100% functionality-tested during production, given you have selected the correct lambda sensor, you can assume the sensor is not the problem. Instead, troubleshooting should focus on:  

• Sooty spark plugs. Note: Sooted/damaged spark plugs can damage the ignition coil

• Blown fuse of lambda sensor heating element (relevant only for broadband-types)

• Fuel trim that has not been reset after replacing the sensor (for relevant vehicles)

• Pollution by oil, silicone, leaded fuel, additives, etc. can damage the new sensor (the photos in the next section point out what to look for)

• Leaks in general. For example, in the following parts: intake manifold, vacuum hose, turbo hose, EGR valve and so on

• The injection system - including pump, fuel filter, pressure regulator or injectors. Check the fuel pressure, the fuel filter, the pressure regulator for leaks and injectors for contamination

• Other defective sensors - as a trigger of the error codes. For example, air flow meter, cooling water temperature sensor, EGR valve, crankshaft or camshaft position sensors

 

In older Lambda sensors the cause can also be found here:
Before replacing an older lambda sensor, it is advisable to take a closer look at the sensor, to find any signs of error causes other than normal wear and tear. If this is the case, there are usually clear indications to be found on the lambda sensor itself, the wire or the connector. 

 

		POLLUTION FROM OIL Oil that finds its way through the wiring harness (capillary effect) and damages the lambda sensor. Note the pins of the connector. Even the slightest trace of oil, is a sign of pollution.
		POLLUTION FROM SILICONE Silicone from penetrating silicone-containing engine oil, grease that is applied to the thread of the lambda sensor during assembly or the use of silicone-containing sealants can damage the lambda sensor. (NOTE: Triscan lambda sensors are pre-lubricated and therefore do not require extra grease!)
		POLLUTION FROM COOLANT Coolant that enters the combustion chamber due to a leaking cylinder head gasket or cracks in the cylinder head
		CRACKED LAMBDA ELEMENT (protective cap removed for examination) Water in the exhaust system causes a thermal shock that breaks the lambda element. The water may come from condensation - or water from the cooling system, which eventually enters the exhaust system due to a leaking cylinder head gasket
		POLLUTION FROM A RICH FUEL MIXTURE POLLUTION FROM ENGINE OIL (results from excessive oil usage) Soot formation due to incomplete combustion or penetration of engine oil destroys the lambda sensor. For example, due to incorrectly adjusted fuel trim, defective spark plugs, defective injectors, leaking valve guides/valves, worn piston rings or cylinders
		THE RESULT OF A STONE CHIP Damage to the outside of the lambda sensor that causes damage to the internal ceramic elements, causing the chip to be damaged (e.g. by stone chips - replace the lambda sensor)
		THE RESULT OF HEAT INFLUENCE  The strain relief/protective boot of the cable is damaged (e.g. by heat - in these cases the lambda sensor must be replaced)
		THE RESULT OF A CABLE BREAK/THE RESULT OF TWISTING THE CABLE  Cable break - caused by pulling or twisting the cable. Do not connect the Lambda sensor until it is mounted, do not pull on the cable during installation, and do not fasten the cable too tightly
		POLLUTION FROM FUEL ADDITIVE
		POLLUTION FROM LEAD Usage of leaded fuel
		USE OF THE WRONG LAMBDA SENSOR Be sure to use the right one if there are more than one option

 

A simple error message with a variety of possible error sources
As this article illustrates, discussing the actual error source for a lambda sensors error message can be quite difficult and time consuming. Without the necessary insight, test equipment and patience, the first impulse - replacing the lambda sensor - does not necessarily solve the problem. We hope this article will help mechanics in these situations - and contribute to greater customer satisfaction.

WHAT IS THE PURPOSE OF THE LAMBDA SENSOR? The lambda sensor measures the amount of O2 (oxygen) in the exhaust system. The measurement is used by the ECU engine control unit to control the air-fuel ratio. For the first vehicles with lambda sensors, O2 measurement / control was based solely on measurements from a single lambda sensor located in front of the exhaust system catalytic converter. In newer car models, another lambda sensor is installed after the catalytic converter, whose task is to check if the O2 regulation is performed correctly.