Mass Air Flow (Maf) Sensor; Removing And Installing - BMW 5251 Service Manual

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Mass A i r Flow Sensor
1 "
Intake air temp. (NTC)
Sensor qround
Reference voltage
.
. .
-.,
f
fitr mass
signal I
Fuel Injection
I
Release fuel injector locking clips (arrow).
-
Remove fuel injector loom boxes and lay to one side.
-
Remove 4 fuel rail mounting fasteners.
4
Disconnect fuel line at quick-disconnect. To disconnect,
press in plastic collar (arrow) and separate fuel line.
WARNING
-
Fuel may be expelled underpressure. Do not srnol(e or work
near heaters or other fire hazards. Keep a fire extinguisher
handy. Before disconnecting fuel hoses, wrap a cloth around
fuel hose to absorb anv leakinq fuel. Plug all open fuel lines.
-
Lifl fuel rail and injectors straight up to remove.
-
lnstallation is reverse of removal. Use new injector seals and
clamps during installation.
Mass air flow
(MAF)
sensor,
removing and installing
4
The MAF sensor is provided with operating power from the
ECM relay. Based on intake air mass, the MAF sensor gen-
erates a varying voltage (approx. 0.5
-
4.5 vdc) as an input
signal back to the ECM. A separate intalte air temperature
sensor is not used.
-
Removing MAF sensor:
Remove upper air filter housing locking clips
Unscrew and remove sensor harness.
Disconnect air temperature sensor harness.
Loosen hose clamp.
Remove upper filter housing with sensor.
-
lnstallation is reverse of removal