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Idle speed sensor on the VAZ-2109 (injector): where is it located, purpose, possible malfunctions and repairs
Idle speed sensor on the VAZ-2109 (injector): where is it located, purpose, possible malfunctions and repairs

In injection cars, a power system is used that is different from the carburetor with its channel for idling the engine. To support the operation of the engine in XX mode, an idle speed sensor, the VAZ-2109 injector, is used. Experts call it differently: XX sensor or XX regulator. This device practically does not cause problems for the car owner, but sometimes it still fails.


The sensor is needed to regulate the air flow that enters the motor when the throttle is closed. That is, the element automatically regulates the specified engine speed in idle mode. The regulator is also involved in warming up the power unit after a cold start.

vaz 2109 injector idle speed sensor


At the initial stage of development of injection engines as regulatorsidle, rotary and solenoid devices were used. They could have two working positions - here you can draw an analogy with a stop valve. The sensor was operated in a fully open or fully closed position. This did not effectively stabilize the idle speed.

Later, AvtoVAZ engineers created an idle speed sensor injector VAZ-2109 in the form of a step valve. It is distinguished by the presence of stepwise adjustment of the air supply through the bypass channel in the throttle valve.

The IAC is arranged as follows: it is based on a small stepper motor, and the device also has a rod, a spring and a needle.

vaz 2109 injector idle speed sensor malfunction

Operation principle

When the car is moving and the throttle is open, the IAC is not involved in the process, its valve is closed, and the stem is stationary. When the damper closes and the engine goes into idle mode, voltage is applied to the electric motor, and the stem moves in the direction of opening - the valve comes into operation. It opens a little, and air enters the engine bypassing through a special hole.

When the driver turns on the ignition, the IAC rod fully extends to its extreme position and closes the calibration hole in the throttle pipe. The sensor then counts the steps and the valve returns to its base position. As for this basic position, it may be different and depends on the firmware installed in the ECU. For firmware "January 5.1" the position is 120 steps, forfirmware "Bosch" - 50 steps.


Knowing the principle of operation of the idle speed sensor VAZ-2109 (injector), it is easy to guess the place of its installation. On this vehicle, it is located near the throttle and throttle position sensor. The device is fixed with screws on the damper body. In the event of a failure, the owner of the car can easily replace it himself.

replacement of the idle speed sensor vaz 2109 injector

DHX switching circuit

The idle speed controller is connected with a single four-wire cable. The idle speed sensor wire VAZ-2109 is connected to the computer. Such wiring creates certain problems when trying to diagnose the sensor with your own hands. It will not work just to take and apply voltage to the terminal for testing: the ECU supplies voltage to the windings of the stepper motor in a pulsed mode. Therefore, checking with a multimeter in case of a malfunction is not very effective.

idle speed sensor vaz 2109 check

Signs of malfunction

This element is responsible for the operation of the engine at idle, which means that any malfunction of it will affect the stability of the XX. Among the main symptoms of HPP failure are:

  • erratic idling;
  • drop in crankshaft speed when additional electrical consumers are turned on;
  • no increased warm-up speed during cold start of the power unit;
  • stop the internal combustion engine when turning off or shifting gears.

These symptoms will not always bebe the cause of a malfunction of the idle speed sensor VAZ-2109 (injector), since the same signs will be in case of failure of the TPS. But if there is a problem with the throttle position sensor, the check engine light will come on. Since the IAC, or idle speed sensor, does not have its own diagnostic system, the lamp will not light with the same symptoms.

Typical breakdowns

These symptoms usually occur if the bypass passage in the throttle valve is clogged with dust, dirt. The integrity of the electrical part may also be violated. The same symptoms can be obtained if the firmware in the car's ECU computer does not match the installed idle sensor.

How to diagnose IAC

In an ideal situation, the regulator should be checked on professional stands where you can reproduce the supply of pulses similar to the ECU. In practice, such stands are far from being available everywhere, and all diagnostics come down to simpler verification methods. This is a check of the sensor visually and manually, tests with a multimeter.

Simple diagnosis of DXH

The easiest way to check the idle speed sensor VAZ-2109 is the following method. You need the help of a friend. The sensor is disconnected from the connector, then the fastening screws are unscrewed and the device is dismantled. Next, the regulator will reconnect to the connector, but is held in the hands.

At this time, the assistant starts the power unit, and the IAC rod must at this moment retract completely and then extend a certain distance. If the device behavesso, it is operational - the stem is not bent, it does not jam inside the valve. But there is no guarantee that the device matches the ECU firmware. The stem extends, but the number of steps is unknown. There is a marking on the connector - it can be used to verify the compliance of the ECU sensor.

This is the initial stage of diagnosis. Next, they check the electrical part, the condition of the valve, the degree of wear of the needle.

How to check the sensor with a multimeter

Using a multimeter, you can diagnose the idle speed sensor VAZ-2109 (injector) in two ways: first, measure in ohmmeter mode, then in voltmeter mode.

If you close the contacts on the plug C-D and A-B, then the multimeter should show resistance in the range of 40-80 ohms. If you close contacts D-C and A-D with probes, then the multimeter on a working IAC will show infinity.

In the voltmeter mode, the voltage at the sensor with the ignition on should be 12-20 V.

replacing the idle speed sensor with a vaz 2109

Diagnostics on the stand

The simplest stands for checking IAC will cost an ordinary motorist 1500-2000 rubles. Replacing the idle speed sensor VAZ-2109 will cost 300 rubles. Therefore, buying a stand is not economically feasible. You can assemble a simple stand with your own hands. The circuit consists of a charger from any mobile equipment with a voltage of 6 V, a plug block and a control lamp. If during the test the lamp glows, then the IAC is faulty. If the lamp burns at half heat, then the device is working properly.

Cleaning the needle and valveDHH

Before changing the sensor, you can try to clean it - very often this solves the problem. The element is disconnected from its block, the contacts are cleaned with WD-40 or any other similar liquid. Then unscrew the screws and remove the regulator itself. It is not necessary to completely disassemble the device for cleaning - just spray the rod, needle, springs with cleaning liquid, and while the IAC dries, spray liquid into the idle channel in the throttle assembly.

How to replace the idle speed sensor

If the cleaning did not help, and the IAC does not work, then you need to replace the idle speed sensor VAZ-2109 (injector). This is done very simply.

The sensor is mounted on the throttle body. It is fastened with two screws, like the fuel pump. To remove, unscrew the mounting bolts and disconnect the plug from the device. Before installing a new DHX, it is recommended to clean the seat with emery.

The new IAC is installed in the same way, in reverse order. The element is put in place, fixed with bolts, wires are connected. But sometimes it happens that the replacement does not solve the problem, and the idle speed floats even with a new sensor. Here the reason is in the quality of spare parts in stores - before installing it is better to make sure that the new sensor is working.

idle speed sensor wire vaz 2109

Nuances of choice

The stores offer a huge number of different sensors from different manufacturers. The original part must be marked XX-XXXXXXX-XX. By the last two digits, you can figure out compatibility. So, numbers 01and 03 are interchangeable, you can also swap 02 and 04. Instead of 02, you cannot put 01 or 03. If the sensor is original and new, it is better to additionally lubricate the spring and stem with grease.

When buying a sensor, even in a trusted store, you should look at the following nuances:

  • there are no labels on the packaging that can distinguish the manufacturer;
  • sticker on the body of the device is yellow and has no frame;
  • needle has a dark tip;
  • O-ring thin and black;
  • rivet heads less than 3 mm in diameter;
  • white spring;
  • body length is less than the length of the standard AvtoVAZ sensor by 1 mm.
idle speed sensor vaz 2109 photo

All these nuances indicate that a counterfeit idle speed sensor VAZ-2109 is being offered. You can see photos of real and fake devices above.

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