Engine Coolant Temperature (Ect) Sensor; Testing And Replacing - BMW 5251 Service Manual

Fuel Injection
Engine coolant temperature (ECT) sensor,
testing and replacing
4
The ECT sensor is located below cylinder 6 intake port at the
rear of the engine (1).
The ECT sensor is a dual temperature sensor. One circuit
provides coolant temperature information to the ECM while
the other circuit provides coolant temperature information to
the instrument cluster.
The ECM determines the correct ignition timing and airlfuel
mixture required forthe engine temperature by monitoring an
appliedvoltage (5vdc) to the sensor.Thevoltage drop across
the sensor varies as the coolant temperature (sensor resis-
tance) changes.
NOTE-
The ECT sensor is an NTC (negative temperature coeffi-
cient) type sensor. In other words, as the temperature rises,
resistance through the sensor decreases.
If the ETC sensor input is faulty or non-plausible, the MIL is il-
luminated when the MIL is illuminated when OED II fault crite-
ria are exceeded. The ECM assumes a substitute value
(80" C 11 76'F) to maintain engine operation. The ignition tim-
ing is set to a conservativelsafe basic setting.
-
Remove intake manifold to access ECT sensor on the
M52
TU and the M54 engines. See 113 Cylinder Head Removal
and Installation.
-
Check ECT sensor resistance using a multimeter at sensor
terminals.
WARNING
-
Due to rislc of personal injury, be sure the engine is cold be-
fore removing ECT sensor connector.
ECT
sensor resistance
@ 20°C
(68°F)
CAUTIOI\C
Be sure ignition is OFFbefore disconnecting or reconnecting
DME svstem components.
2.2
-
2.7 k
4
Disconnect ECT sensor harness connector (arrow). Un-
screw ECT sensor from cylinder head.