Hello, I had the same error 1728, 401, 402, 405, check engine and power limitation. I fought EGR, even bought a second one. I also bought a second Bluetooth module with a program that connects to the PC. Thanks to this program, I noticed that there are 2 MAF airflow parameters, the first calculated by the engine at idle speed was supposed to have a value of 250, the second indicating the actual flow showed 0. I checked that the car works the same whether there is a flow meter or not and I decided to buy a new one (used original). Before it came, I took apart the one I had and it turned out that a hair-diameter leg in one element was broken. I soldered, but you know, the thickness of the tin changed the values measured by the element. I put everything back together, deleted the errors and, surprisingly, the error 1728 disappeared, the check engine went out, the engine regained the speed above 3000. Only error 401 remained - too low exhaust gas flow. After checking the flowmeter parameters, it turned out that instead of the calculated 250, it has twice as much, and on the turned off engine it shows the flow of 0.50g / s. So I had to wait for a new (used) one. After changing the flowmeter, the flow values were finally correct and the last error 401 disappeared, besides, the fuel consumption value during standstill decreased from 0.5l / h to 0.2l / h. The exhaust pipe from the EGR back to the engine has become hot (previously it was lukewarm). Summing up, error 1728 does not indicate a specific failure, but tells us that when collecting information from sensors, the computer calculates the speed incorrectly. It can be a rotation sensor, a flow meter (like mine), a rail pressure sensor, etc. Only after checking all parameters can we find the real fault.
