1.8T Runs Only Without MAF Sensor

Hello,


It's not a diesel engine, but maybe one of the other professionals has encountered this issue before.

A Seat Ibiza 1.8 Turbo, engine code: AQX.
Control unit part number: 6K0 906 032.
Component and/or version: 1.8L R4/20VT SEA

The engine only runs when the mass airflow sensor is disconnected.
If it's stuck in that position, it won't draw in any fuel, it won't idle, and the vehicle won't be drivable.
The error memory is clear, except for the disconnected mass airflow sensor.

My suspicion is that the problem lies with the engine control unit (ECU). The engine is running well with the mass airflow sensor (MAF) disconnected because it's in a limp-home mode.

Does anyone have more experience? Or any additional data for measurements on the engine control unit?

Thank you.

Mati.

Oh, the mass airflow sensor (MAF) has already been replaced.

Greetings.

Mati.

Hi Mati,

It is not an emergency if the LMM is disconnected!
Without an LMM, a replacement value is set.
You can distinguish a diesel engine from a gasoline engine by the fact that, in limp mode, the glow plugs will flash, whereas they will not flash if the mass airflow sensor (MAF sensor) has been disconnected (or replaced with a faulty one).

I suspect that the mass airflow sensor (MAF) is providing extremely low, barely acceptable values. This prevents the engine control unit (ECU) from recognizing it as defective, and it continues to be influenced by its readings. Another possibility is a loose connection or a problem within the MAF sensor itself.
I once had a similar issue on an Ibiza TDI ASV. Whenever I accelerated hard, a cable to the mass airflow sensor (MAF) would bend, causing a short circuit that reported 0 mg/h of air mass. As a result, the TDI would abruptly cut off the fuel injection. This would eliminate the short circuit, and the engine would then return to full power. It was quite a wild ride. We detected it through a log recorded during acceleration.

Do you have the values that the LMM (Laminar Mass Flow Meter) outputs? Are they fluctuating? Are they plausible? Is it running with a diode instead of the LMM?

m;

Hello Dieselmartin,

First of all, thank you for your detailed explanation.
Subject:
It's impossible to drive the car with the mass airflow sensor plugged in.
But with the diagnostic tool connected, shouldn't the MSG display the replacement value? It's showing zero, and the diagnostic light is on. I can try the diode again, but I've already tried two new mass airflow sensors.
I think the problem might not be with the LMM itself, but perhaps with the cables, as you suggested.
All other values appear to be reasonable.
I will definitely try a cave riding log sometime.

Do you happen to have any additional data regarding the wiring, pinout, or circuit diagram of the mass airflow sensor (MAF) that I could use for troubleshooting?
I have a lot of data here, but unfortunately, I don't have .

Thank you very much.

Mati.