Car owners who are faced with the first signs of unstable engine operation often hear from mechanics the mysterious acronym “MZ”. It's abbreviation of Mass Charge.This element of the engine control system is responsible for the precise dosing of fuel. If you notice that the car has become “sluggish” or fuel consumption has suddenly increased, the problem may lie in this node.
In fact, Mass Charge Sensor (often called DMRV) is an intelligent air meter that helps an electronic control unit (ECU) form the correct fuel-air mixture. Without the correct indications of this device, a modern injection engine will not be able to work economically and environmentally friendly. Understanding the principle of its work will help you avoid unnecessary costs on the service.
In this article, we will analyze the device of the sensor in detail, consider the typical symptoms of its failure and learn to conduct primary diagnosis with your own hands. You'll find out why. enrichment dangerous for the catalyst and how to distinguish the breakdown of the sensor from the air sucker.
Operating principle and sensor device
The main task of the MC element is to measure the volume of air entering the engine cylinders. Based on these data Electronic Control Unit Calculate the amount of fuel required for injection. Most modern sensors are based on thermoanemometric measurement method. Inside the case is a sensitive element – a thin platinum thread or film that is heated by electric current.
When the airflow passes through the sensor channel, it cools the heated element. Electronics instantly respond to a change in the resistance of the thread and adjust the current strength to return the temperature to a given value. The amount of energy expended is directly proportional to air-mass.
Structurally, the device is a plastic case with an inlet and outlet holes, inside which a measuring tube is fixed. It is important to note that to compensate for the temperature of the incoming air in the case is also installed additional thermistor. This allows the system to take into account the air density depending on weather conditions.
Why is the MH sensor called a “flowmeter”?
The term “flowmeter” is used because the device measures not just pressure, but mass air flow in kilograms per hour. The ECU uses this figure as the baseline for all fuel supply calculations.
Typical symptoms of DMRV malfunction
Determine that the sensor MOH failed, you can by a number of characteristic signs that are manifested in the behavior of the car. Most often, drivers notice a sharp increase in fuel-flow. The machine begins to “eat” 2-3 liters more than usual, since the ECU, receiving an understated reading from the sensor, pours more gasoline than necessary.
The second alarm bell becomes unstable operation of the engine at idling. The turns can float, the engine can stall when changing gears or after stopping. Also, there is often a loss of acceleration dynamics: when pressing the gas pedal, the car reacts with a delay, jerks or thrust failures occur.
- 🚗 Floating speeds idling, especially on a warmed-up engine.
- ⛽ Spending spikes fuel without changing driving style.
- 💨 Black smoke from the exhaust pipe, indicating the re-enrichment of the mixture.
- 📉 Loss of power and a sluggish response to the accelerator pedal.
In some cases, the indicator lights up on the dashboard. Check Engine. However, do not rely only on the light bulb: the sensor can give incorrect readings within the permissible range, and the error in the memory of the ECU will not be recorded, but the behavior of the machine will change.
Effect of a faulty sensor on engine operation
Ignoring the symptoms of a faulty MOH can lead to serious consequences for the entire power unit. If the sensor understates the air flow readings, the control unit forms too-mix. Excess fuel does not burn completely and burns out already in the exhaust manifold, which causes overheating of the exhaust system elements.
The catalytic converter is at the highest risk. The constant ingestion of unburned fuel heats the cells of the catalyst, leading to their melting and destruction. Replacing this unit costs significantly more than installing a new sensor. In addition, the rich mixture washes the oil film from the cylinder walls, increasing the wear of the piston group.
⚠️ Attention: Long driving with a faulty MOH sensor can lead to failure of spark plugs and oxygen sensors (lambda probes) due to the formation of soot.
On the other hand, if the sensor overstates the readings, the mixture becomes too poor. It leads to knock-off (fingers), engine overheating and valve or pistons burnout. Modern ECU tries to compensate for these errors with adjustments, but its possibilities are not unlimited.
Diagnostic methods and multimeter testing
The most reliable way to check the sensor MH is the use of a car scanner that reads the readings in real time. However, if only a multimeter is available, you can conduct a basic voltage check on the signal wire. To do this, you need to turn on the ignition, but do not start the engine.
Find the signal wire (usually yellow in the Bosch connector or green in some versions) and measure the voltage between it and the “minus” of the battery. A correct sensor at rest (idle) must give a voltage in the range of 0.996 B before 1.01 V. If the device shows the value above 1.05 VThe sensor life is coming to an end, and the values are higher. 1.07 V V They talk about the need for replacement.
You can also check the sensor response to changes in airflow. When the throttle is opened sharply, the voltage should instantly jump to 1.3–1.5 InAnd then slowly return to the original value. If there is no jump or it occurs with a delay, the sensitive element has degraded.
☑️ Diagnostics of DISW
Table: Voltage standards and error codes
For ease of diagnosis, the following table is given with indicative voltage values and corresponding error codes that may appear when the air measurement system malfunctions.
| Status of the sensor | Voltage (B) | Probable error code | Description of the error |
|---|---|---|---|
| New sensor | 0.996 – 1.01 | — | No mistakes. |
| Worker (wear and tear) | 1.01 – 1.04 | — | Within tolerance |
| Requires replacement. | 1.05 – 1.07 | P0171 / P0172 | Too poor/rich mix |
| Faulty. | > 1.07 | P0100 / P0102 | DISW circuit malfunction |
| Breakdown/KZ | 0.00 or 5.00 | P0103 | High signal strength |
It is important to note that error codes P0171 and P0172 They may indicate not only the sensor itself, but also air suction or fuel pressure problems. Therefore, a comprehensive approach to diagnosis is always required.
Voltage above 1.05 V at idling is a “gray zone” when the sensor is still working, but already lying. Replacing at this point will return the car to its previous dynamics and reduce consumption.
Recovery or Replacement: Which to Choose?
The question of whether the MH sensor can be restored remains open. Theoretically, if only platinum filament is contaminated, it can be gently washed with a special carburetor cleaner or alcohol. However, mechanical strictly prohibited: the thread is extremely fragile and easily breaks from touching with a cotton swab or brush.
Practice shows that washing gives only a temporary effect, since the geometry of the sensitive element is already disturbed by thermal aging. In addition, there may be microcracks inside the case, through which unaccounted air is sucked, which makes the readings incorrect even after cleaning.
⚠️ Caution: Using “folk” cleaning methods such as WD-40 or aggressive solvents can permanently destroy the sensor by dissolving the protective coating of the thread.
The most rational solution is to install a new certified analogue. The market offers many substitutes, but it is better to give preference to original catalog numbers or proven brands like Bosch, Pierburg or Siemens. Cheap Chinese copies often have measurement error out of the box.
When replacing, be sure to check the integrity of the air pipe between the sensor and the throttle. Any crack in the corrugated corrugation will cause the new sensor to also show incorrect data, so some of the air will go around it.
When installing a new sensor, lubricate the rubber sealing ring with a thin layer of silicone sealant. This will prevent the suction of unfiltered air in the future.
Frequently Asked Questions (FAQ)
Can I drive with the MZ sensor disabled?
Technically, the car will go, as the ECU will go into emergency mode, using averaged table values. However, fuel consumption will increase by 15-20%, dynamics will fall, and the engine may not work smoothly. Long-term operation in this mode is harmful to the catalyst.
How often should I change the MH sensor?
The sensor’s life is usually between 100 and 150 thousand kilometers, but it depends on the condition of the air filter. If you miss the timeline for replacing the filter, dust settles on the sensitive element and the sensor fails much earlier.
Will the Zero Resistance Filter be installed?
Zero resistance filters often pass more fine dust than standard paper filters. This can lead to faster contamination and failure of the MH sensor. In addition, they can create swirls of airflow, which knocks down the flowmeter readings.
Why did the sensor not drop after the replacement?
If replacing the sensor didn’t help, the problem could be in the air sucker after DMRV, malfunctioning of the lambda probe, low fuel pressure, or clogged injectors. The ECU may also have failed to reset old adaptations, which may require computer diagnostics.