How to check the lambda probe?

Anna Tkach

AutoPortal editorial team

716 views 3 min read

Lambda probe is an important sensor of the engine management system, responsible for measuring the oxygen level in exhaust gases. A faulty sensor leads to increased fuel consumption, reduced power, and unstable engine operation. In this article, we will tell you how to check a lambda probe with a tester with 4 wires, with 5 wires, and also how to do it without a tester - using improvised methods.

The lambda probe is an important sensor in the engine management system, responsible for measuring the oxygen level in exhaust gases. A faulty sensor leads to increased fuel consumption, reduced power, and unstable engine operation. In this article, we will tell you how to check a lambda probe with a tester with 4 wires, with 5 wires, and also how to do it without a tester - using improvised methods.

Signs of a faulty lambda probe

Before you start checking, it is important to understand whether the hub is humming, whether the probe itself is at fault, or another system. The main signs of a faulty sensor are:

Increased fuel consumption;
Unstable idle;
Smell of gasoline from the exhaust pipe;
Error on the dashboard (Check Engine).

If you observe one or more symptoms, you can proceed to the check.

How to check a lambda probe with a multimeter

Checking with a multimeter is the most accessible diagnostic method. It is suitable for both 4-pin and 5-pin sensors.

Preparation:

Multimeter (tester);
Access to the sensor connector (sometimes you need to remove the engine protection);
Knowledge of the wire pinout (usually 2 wires for heating, 1 - signal, 1 - ground).

How to check a lambda probe with a tester with 4 wires:

Check the heater:
- Switch the multimeter to resistance mode (Ohms).
- Measure the resistance between two wires of the same color (usually this is the heater).
- The norm is from 5 to 14 Ohms.
Check the signal wire:
- Switch the multimeter to direct voltage (DCV).
- Start the engine, let it run for 2-3 minutes.
- Connect one probe to the signal wire, the second to ground.
- The voltage should fluctuate from 0.1 to 0.9 V. If the voltage does not change, the probe is faulty.

How to check a lambda probe with a tester with 5 wires:

The principle is the same, but taking into account the additional control signal. One of the wires may go to the ECU. It is important to use the pinout of your specific car. An erroneous check can lead to a short circuit!

How to check a lambda probe without a tester

If you do not have a tester, you can use indirect methods:

By the color of the ceramic on the old probe - white deposit indicates normal operation, black - a rich mixture, shiny - excessive enrichment.
By fuel consumption and idle - if after warming up the engine runs unstable, there is a high probability of a faulty probe.
Disconnect the probe and check the engine operation. If the behavior has not changed, the sensor may have been non-working for a long time.

Tips and recommendations

For an accurate check, use a multimeter or an OBD2 scanner.
After replacing the probe, it is necessary to reset the error in the ECU.
Do not check the sensor "hot" with your hands - possible burns.

Now you know how to check a lambda probe with a multimeter, with 4 or 5 contacts, and also how to determine its condition without a tester. Proper diagnostics will help avoid unnecessary costs and extend the engine's service life. Do not postpone the check at the first signs of a malfunction!