BMW 1989-1995 525i Service Manual page 175

FUEL INJECTION-DME
130-7
Engine coolant temperature (ECT) sensor location
• M20. M30 engine .. . . front of engine. in coolant outlet
(blue plug)
• M50 engine in cylinder head. left side
of engine (front position)
• M60 engine . . . . . rear of engine. in coolant crosspipe
(white plug)
2. Turn the ignition on and check for 5 volts (VDC) be-
tween the supply voltage wire in the connector and
ground. If voltage is not present. test the ECM in-
puts/outputs as described later.
ECT sensor supply voltage check
• M20. M30.
M50 engines. . . . . . . . . . . brown/red wire and ground
• M60 engines yellow /green wire and ground
3. With the harness connector disconnected. check the
resistance across the sensor terminals . See Fig. 6. Ta-
ble c lists sensor resistances. If any faults are found.
the sensor should be replaced.
Fig. 6. ECT sensor (arrow, resistance being checked on M20 engine.
Table c. Engine Coolant Temperature Sensor or
Intake Air Temperature Sensor Test Values
Intake air temperature sensor, testing
(M50 and M60 engines)
On M50 and M60 engines (with mass air flow sensor). a
separate intake air temperature sensor is mounted in the in·
take manifold. This signal is used as a correction factor for fuel
injection and ignition timing. See Fig. 7.
Fig. 7. Intake a" temperature sensor ioca ion on M50 engine (arrow).
NOTE -
On M20 and M30 engines without traction control. the
intake air temperature (tAT) sensor
IS
integrated into
the volume air /low sensor. On M30 engines with trac-
tion control.
a
separate intake air temperature sensor
is
used by the electronic throttfe control system and can
be tested as described below.
1. Disconnect the harness connector from the intake air
temperature sensor.
Intake air temperature (IAT) sensor location
• Intake air temperature (IAT) sensor
M50 engine in intake manifold.
near throttle housing
M60 engine in intake manifold.
front of engine. right side
Test temperature
14 1 2 ' F (- 10 ± 1° C )
68 ± 2 F (20 ± 1 C)
176
±
2°F (80
±
1
Q
C)
Resistance (k Ohms)
7- 11.6
2.1 -2.9
0.27-0.40
2. Turn the ignition on and check for 5 volts (VDC) be-
tween the supply voltage wire in the connector and
ground. If voltage is not present. test the ECM in-
putsloutputs as described later.
NOTE -
The test vatues listed represent only three test points
tram
a
continuous resistance
Nrc
senso r. For
a
more
accura te test. the sensor can be removed and tested in
a
oath 01 hot water usmg
a
thermometer.
IAT sensor supply voltage check
• M50 engines grey wire and ground
• M60 engines yellowlred wire and ground
ELECTRICAL CHECKS AND COMPONEN T TESTING