2001 BMW 525i Air sensor

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130-1 0
Fuel Injection
Remove MAF sensor:
Release clips from air filter housing
(A).
Disconnect harness connector (B).
Loosen intake boot clamp (C) and remove MAF sensor.
Note large sealing O-rings.
Installation is reverse of removal.
No adjustment to MAF sensor is possible.
Check intake hoses for cracks and vacuum leaks.
Engine coolant temperature (ECT) sensor,
testing and replacing
R
1 -4 The ECT sensor is located below cylinder 1 intake port
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 for the engine by monitoring an applied volt-
age
(5 vdc) to the sensor. The voltage drop across the sensor
varies as the coolant temperature (sensor resistance) chang-
es.
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
OED II fault criteria are exceeded. The ECM
assumes asubstitute value
(80°C1 176°F) to maintainengine
operation. The ignition timing is set to a
conse~ativelsafe ba-
sic setting.
- Check ECT sensor resistance using a multimeter at sensor
terminals.
-
WARNING -
Due to risk of personal injury, be sure the engine is cold be-
fore disconnecting or reconnecting ECT sensor.
ECT sensor resistance @ 20" C (68°F) 2.2 - 2.7
Temperature gauge sensor resistance @ 20°C (~B"F)( 6.7 k

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Fuel Injection
CAUTION-
Be sure ignition is OFF before disconnecting or reconnecting
DME system components.
Remove engine coolant temperature sensor:
Unclip crankcase vent hose
(C) from cylinder head cover.
Remove plastic cover
(6) from atop intake manifold run-
ners.
Working under front of intake manifold, disconnect ECT
harness.
Unscrew ECT sensor
(C) from cylinder head.
Installation is reverse of removal:
Use new copper sealing washers when installing sensor.
Replace any engine coolant lost.
Tightening torque
Temperature sensor to cylinder head
13 Nm (10 it-lb)
Intake air temperature ([AT) sensor,
testing and replacing
4 The intake air temperature (IAT) sensor (arrow) signal is
used by the ECM to monitor intake air temperature for fuel
and
igntion adaptation. The sensor is .ocared in rne 'ntane
man:lold behind the throttle housng.
The ECM monitors an applied voltage (5 vdc) to the sensor
The voltage drop across the sensor varies as the intake air
temperature (sensor resistance) changes.
NOJE-
The IATsensor is an NTC (negative temperature coefficient)
type sensor. In other words, as the temperature rises, resis-
tance through the sensor decreases.
If the IAT sensor input is implausible, a
fault code is set.The
MIL is illuminated when OED II fault criteria are exceeded.
The ECM then operates the engine using only the engine
coolant temperature (ECT) sensor input.
The intake air temperature sensor can be tested using a
mul-
timeter across its terminals:
/ IAT sensor resistance @ 20" C (68°F) / 2.2 - 2.7 lkCk
~ -- ~~ -
CAUTION--
Be sure ignition is
OFFbefore disconnecting or reconnecting
DME system components.

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130-1 2
Fuel Injection
- Disconnect intake air boot from throttle housing. Unbolt throt-
tle housing and lay aside. It is not necessary to disconnect
throttle cable or electrical harness connectors from throttle housing.
- Remove electrical harness connector from IAT sensor.
- Unclip temperature sensor and remove from intake manifold.
- Installation is reverse of removal. Use a new gasket at throttle
housing.
Throttle position sensor (TPS),
testing and replacing
4 The throttle position sensor (arrow) is located on top of the
throttle valve housing and provides the ECM with a voltage
value that represents throttle position (angle) and rate of
movement.
TheTPS is non-adjustable. If the throttle position sensor is re-
placed, the previous 'learned' TPS settings must be cleared
from the ECM using a BMW-compatible scan tool.
If the throttle position sensor signal is defective, afault code is
stored and the
MILis illuminated when OBD II fault criteria are
exceeded. The ECM still operates the engine using the mass
air flow
(MAF) sensor and engine rpm inputs.
- Check throttle position sensor function by disconnecting har-
ness connector and checking continuity across terminals. If
test results are incorrect,
replace throttle position sensor. The
sensor is non-adjustable.
Throttle
~osition sensor testina values -
Terminals Test
values
1 and ground in harness 5 vdc (approx.)
connector, ltey on
1 and 3 at sensor 4.0 itR(appr0x.)
1 and 2 at sensor Throttle
plate rotated from idle to
lull throttle, continuously variable
from 1.0
- 4.0 1tR
CAUTION-
Be sure ignition is OFF before disconnecting or reconnecting
DME svstem components. r

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130-1 3
Fuel Injection I
< Unplug harness connector (arrow) from sensor.
CAUTION-
Be sure ignition is OFF before disconnecting or reconnecting
DME system components.
NOTE-
Do not confuse the throttle position sensor on the main Nirot-
tle body with the throttle position switch on the secondary
throttle body, where applicable.
- Remove two mounting screws holding sensor to throttle
housing.
- Installation is reverse of removal. Clear adaptation settings
from ECM using BMW-compatible scan tool.
NOTE-
Poor idle quality may be noticeable for a period if the adapta-
tion settings are not cleared after installing new TPS.
ldle speed control valve,
checking and replacing
The idle speed control valve regulates idle speed by redirect-
inq airaround the throttlevalve.The idlespeed control valve is
mounted on the underside of the intake manifold adjacent to
the dipstick tube bracket. Accessing the valve is best accom-
plished by first removing the air filter housing and the throttle
body assembly.
The valve issupplied with
batteryvoltagefrom the ECM relay.
The idle speed control valve incorporates a two-coil rotary ac-
tuator. The ground sides of each coil are pulsed
sirnulta-
neously by the ECM. The duty cycle of each circuit is varied to
achieve the required idle speed.
Afaulty ldle speed control valve sets afault code and the MIL
is illuminated when
OED II fault criteria are exceeded.
Before checking the idle speed control valve, confirm that the
throttle position sensor is working correctly.
- With engine running, check that idle speed control valve is
buzzing.
- Turn on AIC system or shift transmission into drive. ldle
should remain steady or increase slightly.

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I Fuel Injection
Release injector locking clips at each injector and pry injector
wiring duct up off injectors.
Clamp off fuel supply line and fuel return line at end of fuel
rail. Disconnect fuel supply fuel return lines from fuel rail.
WARNING -
Clamp off the fuel lines and then wrap a clean shop towel
around the lines before removing them. Residual
fuelpres-
sure is present in the lines.
Fuel is discharged. Do not disconnect any wires that
could cause electrical
sparks. Do not smoke or work
near heaters or other fire hazards. Keep an approved
I fire extinguisher handy. I
- Remove fuel rail mounting fasteners
- Pull up on fuel rail and remove individual injectors by remov-
ing injector retaining clip and pulling injector from rail.
- Installation is reverse of removal. Fit new O-rings when in-
stalling injectors. For ease of installation, lightly lubricate in-
jector O-ring with
SAE9O gear lube.
Tightening torque Fuel rail to
intake manifold 10 Nm (89 in-lb)
Evaporative emissions, overview
On E39 MS 41 .I cars, the evaporative emissions system is
combined with the tank ventilation system. The evaporative
system is monitored by the ECM for correct purge operation
and leak detection.
The carbon (purge) canister is purged using engine vacuum
via the
purgevalve.The purgevalve (located nextto the mass
airflow sensor) is ECM controlled and regulates the purge
flow into the intake manifold. The valve is powered open and
closed by an internal spring.
If the evaporative emission valve circuit is faulty, a fault code
is set and the MIL is illuminated when OBD
II fault criteria are
exceeded. If the valve is mechanically faulty, poor driveability
may result and a mixture adaptation fault is stored in the
ECM.
The leak diagnosis pump (LDP) is activated by the ECM and
pressurizes the fuel tank and evaporative system as apart of
theOED I1 leakdetection monitor. If the LDP orthe LDP circuit
is defective, afault code is set and the MIL is illuminated when
OBD
I1 fault criteria are exceeded. The LDP is mounted the
left rear wheel well behind the fender liner.

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Fuel Injection 1
NOTE-
The 1998 5281' with MS 41.1 requires a barometric pressure
sensor input signal for activation of the
LDP check. This sen-
sor is located on the passenger side strut tower
fo~lard of
ABS/ASC hydraulic unit.
Evaporative emissions
1. ECM
2. Purge valve
3. Leak detection pump (LDP) (in
lefl rear wheel housing)
4. Filter
5. Liquid vapor separator
6. Purge canister
7. Fuel tank
Secondary air injection, overview
The secondary air system pumps ambient air into the exhaust
stream afler a cold engine start to reduce the warm up time of
the catalytic converters and to reduces HC and CO emis-
sions. The ECM controls and monitors the secondary air in-
jection system. The secondary air pump operates at a start
temperature of between 10°C (50°F) and 40°C (104°F) and
continues to operate for a maximum of
2 minutes at idle
speed.
The electric air pump draws in ambient air and supplies it to
the divertervalve. The vacuum ventvalve (solenoid) switches
vacuum to open the divertervalve when activated by the
ECM. Once opened, the diverter valve allows air to be
pumped into the exhaust stream.

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130-1 8
1 Fuel injection Secondary air injection
1. Secondary air pump (in right
front wheel housing)
2. Secondary air vacuum vent
valve solenoid (on intake mani-
fold)
3. Secondary air check valve
4. Intake manifold
5. Exhaust manifolds
6. Diverter valve (at exhaust mani-
fold)
Engine control module (ECM),
removing and installing
The ECM uses stored functions and processing programs to
process the input signals from the sensors. These input sig-
nals are used to calculate the control (output) signals to the
actuators
(e.g., ignition coils, injectors).
NOTE-
Consult an authorized BMW dealer before replacing the
ECM.
- Disconnect negative (-) battery cable. Wait approximately
one minute.
Prior to disconnecting the
battely, read the battery discon-
nection cautions in
001 General Warnings and Cautions.
Access engine control module (ECM):
Release interior ventilation filter cover latch
(A) and re-
move cover.
Release plastic locking tab
(B).
Rotate air duct inward (arrow) to unloclc from bulk head
and remove duct.
Release spring lock
(C) to remove lower filter housing.
Slide filter housing away from inner fender to remove.
- Remove electrical box (E-box) cover fasteners and remove
cover.
- If testing ECM or connected components, use breakout box
to allow tests to be made with connector attached to the
ECM. This prevents damage to small terminals in connector.

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I Fuel Injection
Table b. Siemens MS 41.1 ECM pin assignments (continued)
Pin
l~iqnal I Componentlfunction 1 Notes I - I I
5 loutput I Fuel injector control, cyl. 2 I Pulsed ground (pulse width in ms), cyl. 2 I I I
6 loutput /Fuel injector control, cyi. 1 I Pulsed ground (pulse width in ms), cyl. 1
I I I
14 linput I Intake air temp. sensor (IAT) I Intake air temperature signal
- 7
8
9
10
11
12
13
ground
input
output
input
input
15
16
17 18
19
20
21
22
I - I I
35 loutput /Secondary air injection ISecondary air inj. pump relay control
25
26
27
28
29
30
31
32
33
36
/output I Engine speed output IEngine speed signal
Mass air flow sensor
Mass air flow sensor
instrument cluster
Engine coolant
temp.
(ECT) sensor
Not used
Throttle position sensor (TPS)
Not used
input
input
input
input
output
output
out~ut
37 1 - /Not used I
Mass air flow sensor signal
Mass air flow sensor signal
Fuel consumption signal
ECT signal
Throttle position signal
ground
input
output
ground
output
output
output
ground
output
Traction control (rear engine speed signal) Automatic climate control
Not used Electronic immobilizer control (EWS)
Auto. climate control
(AIC on input)
instrument
cluster
Camshaft actuator control (VANOS)
Fuel iniector control, cvl.
3
AES/ASC module
Automatic climate control instrument cluster (CARE signal)
Camshaft actuator (VANOS), switched ground
Pulsed ground (pulse width in
ms), cyl. 3
Oxygen sensor heater (no. 1 in front of catalytic
converter)
Power supply (terminal
30)
Idle speed control valve
Ground
Ignition coil control, cyl.
1
Ignition coil control, cyl. 3
Ignition coil control, cyl. 5
Ground Fuel injector control, cyl.
5
Oxygen sensor heater ground
Battery voltage
(E+) at all times
Pulsed ground-open signal (See pin
53)
Ground
Primary signal, ignition coil
1
Primary signal, ignition coil 3
Primary signal, ignition coil 5
Ground
Pulsed ground (pulse width in ms), cyl
5