E7B Checking the Hot Wire (Filament) Burn-Off Function
E7B Checking the hot wire (filament) burn-off function1 Detach the mass air flow sensor from the air cleaner and check whether the hot wire (filament) is OK.
2 Start the engine and warm it up to a temperature of at least 65°C (149°F) and then let it idle. Rev the engine up to 2500 rpm, release the accelerator and let it return to idling speed again.
3 Switch off the ignition. The hot wire (filament) should glow brightly about tour seconds afterwards for about a second. If nothing happens, check the wiring (see section E7A).
4 Start the engine and rev it up to 2500 rpm. Connect the test prods to pins 1 and 4 of the mass air flow sensor connector. Switch off the engine. Four seconds later the voltage should rise to 4 V for about one second.
5 If nothing happens, check the red/white (RD/VT) lead between pin 1 of the mass air flow sensor connector and pin 8 of the control module connector, and the black (SV) lead between pin 4 of the mass air flow sensor connector and one of the engine grounding points.
If the wiring is OK, test the system using a different control module.
6 Start the engine and repeat the above test procedure. If the correct voltage is now obtained but the burn-oft function does not come into operation, fit a new mass air flow sensor.
Note: The Limp-Home function takes over automatically if the hot wire (filament) breaks.