Checking air flow meter Bosch. How to Check the Mass Air Flow Sensor?

Subject: How to check the electrics

Greetings all! I will actually start without preludes. I can not find (even the BZ is silent on the subject) the method of testing the flowmeter. Not how to remove the logs, but exactly check the electrics. If there is a problem with electrics, you may as well burn a new engine with a new FMR. I remember in the old version of the forum, someone shared info and posted a pdf, which describes with respect to what on which leg of the flowmeter what voltage should be and in what engine mode (like not starting and ignition on). Therefore I ask those who have valuable information to share. Really Needed Information. Thanks in advance. I promise to try to make this information to the BZ.

No job is impossible for a man who does not have to do it himself. VW Passat B5 Variant 2002 AZM 2.0

To All Peppers. Pepper Club! Register 01.02.2006 Address Veliky Novgorod Age 59 Messages 8,000 Diary entries 3

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Possible problems with FMRV: signs and causes

How to clean and what to flush the mass airflow sensor? We will talk about this below, but first let’s break down the signs and causes of malfunction of the device. The parameters conveyed by the flow meter greatly affect the formation of the combustible mixture, which is very important for any modern engine. If the device fails, it can also provoke an inability to start the engine.

What are the symptoms to understand that the regulator needs to be replaced or cleaned:

  • The appearance of the Check Engine indicator on the control panel;
  • The fuel consumption of the car has increased;
  • the power of the vehicle has significantly decreased, the car now needs more time to gain speed;
  • decreased dynamics, in particular, when speeding up;
  • the engine does not start, it is possible to start the power unit with great difficulty;
  • if the car is idling or standing at a traffic light, the crankshaft RPM may be floating.
checking, flow, meter, bosch

As for the causes of malfunction, there are several:

  • The flow meter is clogged, it is quite normal, in this case you can perform its flushing.
  • The device is out of order, only replacement will help to solve the problem.
  • Impaired contact of the expansion valve with the onboard network, it may be caused by damaged wiring.

Naturally, such symptoms of failure can also indicate a malfunction of other systems and devices, which is why every car owner should be able to diagnose problems.

How to check the DMRV for serviceability

There are several basic techniques for checking the mass air flow sensor to see if it is malfunctioning.

Checking the expansion valve in motion

The easiest way to diagnose the flow meter is to analyze the engine operation by forcing the sensor off. Check as follows:

It is highly discouraged to operate the vehicle for a long time with the DMRV disconnected.

Checking the FMRV with a multimeter

You can diagnose a problem with the sensor using a multimeter. To do this, you must first understand the construction of the device and its pinout, that is the pinout of wires on the board. There are four wires coming out of the mass airflow sensor. Depending on the DMRV model and manufacturer, their colors may vary, but in most cases they are as follows:

  • Pink (or pink-black): wire to the main relay;
  • Green: wire to ground;
  • Gray: wire to power;
  • Yellow: signal input.
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To check the mass airflow sensor, set the multimeter to the constant voltage measurement mode and set the limit to 2 volts. Then turn on ignition, but do not start the engine. When that is done, connect the red multimeter probe to the sensor signal input (yellow wire) and the black probe to ground (green wire). You can do it without “uncovering” the wires, sticking the probe of the diagnostic device through the rubber seal of the connector.

You can draw conclusions about the sensor condition according to the measurement results:

    Fully serviceable device (new): 0.996. 1.01 volts;

  • The sensor is in good condition, but it has already worked: 1.01 to 1.02 volts;
  • The sensor has been running for a long time, but is still serviceable: 1.02 to 1.03 volts;
  • DMRV will need to be replaced soon: 1-03 to 1.04 volts;
  • The flow meter is close to failing, but continues to do the job: 1.04 to 1.05 volts;
  • The sensor must be changed: 1.05 Volt and above.

Some modern on-board computers allow you to watch the voltage on the mass airflow sensor. You can do without a multimeter in these situations.

Visual inspection of the air mass flow sensor

Experienced motorists can determine the malfunction of the mass air flow sensor by its appearance. The first thing to do is to remove the DMRV, and then carefully inspect it. Signs of malfunction are leakage of liquid into the air pipe and sensor of SMDR (or presence of mechanical damages).

Most often, the fluid can get in the sensor for the following reasons:

  • Elevated oil level in the crankcase. In such a situation, oil gets into the sensor;
  • Clogged crankcase ventilation system oil eliminator;
  • untimely replacement of the air filter, because of which the dirt gets on the thermo-anemometer of the air pressure monitor.

The easiest and most reliable way to diagnose problems with the mass air flow sensor is to replace it with a working device. For example, it is possible to remove a suitable working sensor from another car, install it and make sure that the engine operation is stabilized. In such a situation, you can go straight out and buy a new sensor without diagnosing it with a multimeter or other methods.

Where is the installation of the air temperature sensor?

The sensor is located between the air filter and the air inlet hose (picture 3).

DMRV catalog numbers on LADA cars:

  • LADA Priora, Kalina and Niva 4×4. 21083-1130010-20.
  • LADA Granta and Kalina 2. 11180-1130010-00.
  • LADA Vesta, Largus and XRAY. no LMRV. On modern VAZ engines (21127, 21129, 21179) and Renault engines (K7M and K4M) there is no air sensor, instead of it there is an absolute pressure sensor (DAP) and air temperature sensor (ATS).

Air sensor inspection

There are several basic techniques for checking the mass airflow sensor, which allow you to verify its malfunction.

Checking the DMRV in motion

The easiest way to diagnose the flow meter is to analyze the operation of the engine by forcibly disconnecting the sensor. To check it you should do the following:

    It is necessary to open the hood and disconnect the connector from the mass air flow sensor. After that, close the hood;

It is highly discouraged to run the vehicle for a long time with the sensor disconnected.

Checking the FMRV with a multimeter

You can diagnose a problem with the sensor by using a multimeter. To do this, you must first understand the construction of the device and its “pinout”, that is, the pinout of the wires on the board. There are 4 wires coming out of the mass air flow sensor. Depending on the DMRV model and manufacturer, their colors may vary, but in most cases they are as follows:

  • Pink (or pink-black): wire to the main relay;
  • Green: Ground wire;
  • Gray: wire to the power supply;
  • Yellow: Signal input.
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To check the sensor of the mass air flow, the multimeter should be set to a constant voltage measurement mode and set the limit to 2 volts. Next is to turn the ignition on, but do not start the vehicle. When this is done, connect the red multimeter probe to the sensor signal input (yellow wire) and the black probe to ground (green wire). You can do this without “exposing” the wires, by slipping the probes of the diagnostic device through the rubber seal of the connector.

According to the measurement results you can draw conclusions about the state of the sensor:

Fully serviceable device (new): 0.996. 1.01 volts;

Some modern onboard computers allow you to watch the voltage on the mass airflow sensor. In these situations, you can do without a multimeter.

Visual inspection of the DMRV

Experienced motorists can tell if a mass airflow sensor is defective by its appearance. First of all you need to remove the expansion valve and then carefully examine it. Signs of malfunction are liquid ingress in the air pipe and the sensor of SMART (or presence of mechanical damages).

Most often, the fluid can be in the sensor for the following reasons:

  • High oil level in the crankcase. In such a situation, oil gets into the sensor;
  • Clogged crankcase ventilation system oil eliminator;
  • untimely replacement of the air filter, because of what the dirt gets on the thermo-anemometer of the air pump.

The easiest and most reliable way to diagnose problems with the mass air flow sensor is to replace it with a working device. For example, you can remove a suitable working sensor from another car, install it and make sure that the engine stabilized. In such a situation, you can immediately go buy a new sensor without diagnosing it with a multimeter or other methods.

Signs of DMRV malfunction:

  • Bad engine starting;
  • Unstable floating revolutions;
  • CHECK ENGINE” appears on the dashboard;
  • Too high or low “idle speed”;
  • Deterioration of dynamic characteristics (sluggish acceleration, no traction);
  • Increased fuel consumption.

However, you should understand that all of the above symptoms may also indicate other malfunctions. For example, if your engine starts eating too much fuel. it doesn’t mean that your dimmer is faulty, it could be something else entirely.

checking, flow, meter, bosch

Checking the Bosch air flow meter

HFM5 mass airflow sensor (Mass Airflow Meter)

Diagnose on a vehicle with KTS 5xx/6xx.Extended diagnostics of a car implies comparison of normative and actual values of air mass. In this diagnostic section, the HFM5 is diagnosed directly on the vehicle. If the actual values are out of tolerance, the expansion valve must be replaced. detailed information for the vehicle to be diagnosed can be taken from the ESI[tronic] software.

Performing extended testing of HFM5 already removed from the vehicle with a multimeter.

Necessary instruments:. battery or power supply (12V / 3A). digital multimeter. test cable (with chip voltage stabilizer)- microscope with tenfold magnification (like MBS-10)- screwdriver “star” type

Using a test cable with integrated voltage regulator chip, 5V voltage is created on pin 4 of the plug of the expansion chamber temperature sensor.

The test cable with an integrated stabilizer chip can be made in-house or purchased from a commercial network (international index 7805, the domestic equivalent is KREN5).

pin assignment of the HFM5:1. Temperature sensor for incoming air2. Power supply voltage 12V (red wire)3. Mass (black wire)4. Reference voltage 5V (yellow wire)5. Measuring signal (blue wire)

Test 1. Static Connect the test cable 0 986 610 129 to HFM5 connector, observing the polarity as follows:Red wire to power supply black wire to power supply (-)blue wire to multimeter black wire to multimeter (-)

To eliminate air movement in the sensor measuring channel close the inlet and outlet sections of the FMRV housing with plastic covers (included).Apply voltage (12V) to HFM5 using a power supply. A reference voltage (5V) is created via a voltage regulator chip in the test cable and fed to pin 4.

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Standard voltage value 0.98. 1.02VIf the actual measured voltage is outside the tolerance range there is a high probability that the pressure expansion valve is contaminated. Contamination leads to a malfunction of the HFM5 and consequently to its failure.This means: The expansion valve is defective.Further information can be found in the damaged parts catalog.

If the air flow changes, the measured voltage must increase as the air flows in and out The cable connection is the same. Create an air flow and direct it to HFM5 according to the direction indicated on the housing of the expansion valve. When the air flow rate changes, the measured voltage must increase. If the voltage does not change, the sensor diaphragm is defective.This means: HFM5 is defective.And vice versa, the DMV is considered to be faulty if the voltage changes.Max. value can be up to 4.5V (depending on sensor diameter and air weight).

Check the input air temperature sensor (if present)Connect the blue banana plug of the 0 986 610 129 test cable to pin 1 of the HFM5 plug. Use this plug to measure the resistance of the air temperature sensor between pin 1 and pin 3 (ground).At the end of the cable list HFM5 with air temperature sensors.

The actual value measured must be within the range of the given standards.Note: with this test HFM5 without air temperature sensor the result is an infinitely (∞) high resistance value.

Visual check. Using the catalog of defective products.In addition to the above described diagnostics, a visual check can also be carried out. The following pictures show typical cases of contaminated SMART or sensors that have been tampered with.

The HFM5 sensor is not considered for warranty claims if it is heavily contaminated. In some cases the air filter, filter housing and the pipe between the filter and the air regulator should be checked for contamination.

Note: Before installing a new expansion valve it is obligatory to remove dust and dirt from the air filter box, install a new air filter and clean the pipe between the filter and the sensor. Pressurised air blowing out of the filter and spigot is not permitted and must be done with a soft dry cloth.

External interference. Ч

The sensor is not secured or has been replaced: Special “star” screws loose Screws other than the original screws have been screwed in.

Attempting to remove screws. Screw splines are loose.

The mass flow sensor is a device that is indispensable for proper engine operation.

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checking, flow, meter, bosch

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