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Replace a Spare part Lambda sensor – a defective one or if the limit of use has been already reached. Find out useful information about Lambda sensor
Faults of lambda probe
mechanical breakdowns;
thermal overload due to misfires;
separation of connection circuits;
closure;
clogging with fuel combustion products.
Symptoms of lambda probe failure
increase in exhaust emissions;
increase in fuel consumption;
unstable idling;
reduction in vehicle dynamics;
breakdown of the catalyst;
car jerks even if the engine is warmed up.
Causes of lambda probe faults
brake fluid and antifreeze getting to the part;
poor state of oil rings;
сleaning lambda probe housing with chemically active substances;
exposure to the concentrated air-fuel mixture;
increased concentration of lead compounds in fuel;
clogging of the fuel filter;
leakage of the lambda probe housing;
ingress of air or the exhaust gases;
improper or interrupted power supply, which leads to the main control unit;
oxygen sensor elements overheating due to poor quality of the fuel mixture;
worn-out state of the part.
Diagnostics
In order to diagnose the lambda probe state, start the engine and warm it. The level of residual oxygen in the exhaust gas is displayed correctly at 300-400 °C. Use the oscilloscope to assess the frequency and waveform. The next step is to identify indicators of the part heater resistance at room temperature (the norm is from 2 to 14 ohms). Now check the voltage of the heater with the ignition on (the required indicator is 10.5). We remind you that lambda probe inspection is necessary every 30 thousand kilometers.
Repair and replacement of lambda probe
The only kind of repair work that is relevant to this item, is cleaning the sensor from contamination with fuel combustion products. To remove the oxygen sensor, heat it to 50 ° C. For cleaning experts recommend the use of phosphoric acid. Soak the item for 15-20 minutes in acid, then rinse it with clean water. Dry the item, check the thread, then be sure to use mounting paste. At the same time, make sure that the paste does not touch the part’s protection tube. The connector, through which the oxygen is supplied should not be processed. If the cleaning process has not given the expected results, there is only replacement option. You can replace the defective part by yourself or refer to specialists.
Helpful tips on operation, causes of faults, troubleshooting, and service intervals
The mounting location of car lambda sensors depends on the type and capacity of the engine and the exhaust system design. Usually, there are two sensors in vehicles with the engine displacement of up to 2 litres: an upstream and a downstream one. The former is mounted before the catalytic converter and the latter after it.
As a rule, vehicles with engines of more than 2 litres are equipped with 4 oxygen sensors: 2 upstream and 2 downstream ones. Their exact location can be found in the vehicle’s service manual.
What are the signs of oxygen sensor failure?
Possible failure is indicated by:
increased fuel consumption;
rough engine idling;
engine power loss;
jerky acceleration;
regular engine overheating;
poor throttle response;
thick black smoke from the exhaust pipe.
These abnormalities may also indicate problems with other parts. Professional auto mechanics can diagnose lambda sensor failure more accurately.
How can I check the oxygen sensor myself?
As for the downstream lambda sensor, which is difficult to access, it’s better to have it checked by mechanics at a garage. The upstream sensor can be tested with the help of a multimeter. Before getting down to work, read your vehicle repair manual and watch tutorial videos from experienced professionals. You might have to follow these steps:
Warm up the engine to its operating temperature and then turn it off.
Open the bonnet and find the terminals of the lambda sensor heater.
Connect the probes of the multimeter to them and measure the input voltage. The multimeter should give a reading of 12 V.
Disconnect the sensor connector and check the heater resistance. It should be within 2–10 ohms; precise values are specified by the car manufacturer.
Turn on the ignition and measure the reference voltage. Connect the multimeter to the two signal wires. The negative lead of the multimeter should be connected to the car chassis. The voltage should be around 0.45–0.5 V. Deviation of more than 0.5 V indicates a fault in the signal circuit or poor ground contact.
Connect the multimeter probes to the sensor connector. Turn on the engine and increase its RPM to 2,500. A properly functioning sensor will have a voltage of 0.2–0.9 V. If the voltage amplitude is too low or even absent, the part must be replaced.
