1997 BMW 528i Temperature

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( Mass Air 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

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130-75
Fuel Injection
Secondary air injection, overview
The secondary air system pumps ambient air into the exhaust
stream afteracoid engine start to reduce the warm-up time of
the catalytic converters and to reduces HC and CO emis-
sions. The ME
7.2 ECM controls and monitors the secondary
air injection system. The secondary air pump operates at a
starttemperature 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
checlc valve. The vacuum vent valve (solenoid) switches
vacuum to open the
checlc valve when activated by the ECM.
Once opened, the checlc
valve allows air to be pumped into
the exhaust stream.
4 The secondary air injection system consists of the following
components:
1. Secondary air pump relay
2. Oxygen sensors
3. Catalytic converters
4. Electric air pump
5. Non-return valve
6. Vacuum vent valve

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Fuel Injection I
Connector X60004 (continued)
8 10
11
12
13
14
15
16
9
Output 0
Input
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
39
llnput lsignal l~oolant outlet temperature sensor
Output
Output
Ground
Input
Output
I I - I
40 /output Istart signal Istarter relay
Pedal position sensor (PWG), signal
Output Input
Output
input
Input
Input
Input
Input
Input
input
Input
Output
Input/-output
Input/-output
37
Connector X60003
Pedal position sensor
Fuel pump relay, activation
Oil pressure indicator Pedal position sensor (PWG), ground
Pedal position sensor (PWG), signal
Pedal position sensor (PWG), power supply
Not used
Not used Fuel
pump relay
Instrument cluster
Pedal position sensor
Pedal position sensor
Pedal position sensor
Engine speed signal output (TD)
Not used
Signal
back-up light
DM-TL (diagnostic module,
tank leakage)
Signal oil level sensor
Right rear wheel speed, signal
Clutch pedal position switch, signal
Brake light switch, signal
Not used
Voltage supply, terminal
15
Data link, MFL (multi-function steering wheel)
Brake light test signal
AJC compressor signal
DM-TL (diagnostic module, tank
leakage)
Not used
Diagnosis signal
TxD
Communication link (EWS)
Not used
Not used
CAN-BUS hiqh
38 1 Ground l~round I Coolant outlet temperature sensor
OED II plug
Integrated instrument cluster control module (IKE)
Light module
ABSIDSC control module
Clutch pedal position switch
Brake light switch
Fuse
F14
Airbag contact coil spring
Brake light switch
Heating and
A/C control module
OBD
II plug
Electronic immobilizer (EWS)
CAN-Bus link
CAN-Bus link
Input/-output CAN-Bus low

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Fuel Tank and Fuel Pump
Evaporative system troubleshooting
- Start by accessing diagnostic trouble codes (DTCs) using a
BMW or BMW compatible aftermarket scan tool.
For purposes of OBD
II emissions compliance, the DME
system sets a diagnostic trouble code (DTC) when it de-
tects a leak that is equal or larger than minimum
lealc
sensed by system.
Malfunction Indicator Light (MIL) is illuminated upon sec-
ond recurrence of fault. See OBD On-Board Diagnostics.
- When leak testing, observe following conditions to obtain
plausible results:
Fuel tank
'1, to 'I., full.
0 Vehicle parked for at least 2 hours to allow fuel to reach
room temperature.
Ideal fuel temperature is 10"- 20°C
(50"
- 68" F).
Do not refuel immediately before
lealc test.
- If a leak is detected, check the following areas:
* Fuel filter cap (leaking or off).
Fuel tank ventilation lines leaking at fuel
tank or activated
carbon canister.
i
Tank ventilation valve leaking (in engine compartment).
Fuel level
sensorlfuel pump cap leaking.
Evaporative system component replacement is covered later
in
th~s group in Fuel Tank and Fuel Lines.

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Fuel Tank and Fuel Pump 1
Activated carbon canister I fuel tank leak
detection unit
(LDP or DMTL), removing . . -
and installing
- Raise rear end of car and support safely.
CAUTION-
Make sure the car is stable and well supported at all times.
Use a professional automotive lift
orjack stands designed for
the purpose.
A floor jack is not adequate support.
- Remove left rear wheel and inner fender panel
Remove carbon canisterlfuel tank leak detection unit
(V-8 model shown):
Disconnect electrical harness connector
(A) from fuel tank
leak detection unit.
Pinch and remove quick-disconnect fittings at intake line to
air filter housing
(5) and hose to expansion tank (C).
* Remove mounting clamp and lower canister with fuel tank
leak detection unit.
Installation is reverse of removal.
Tightening
torques
Hose clamp 8 - 13 mm dia. 2 Nrn (18 in-lb)
Hose clamp
13 - 16 rnm dia 3 Nm (27 in-lb)
Running losses (312-way) valve,
removing and installing
The running losses (312-way) valve is located under the car
beneath the driver's seat, just ahead of the fuel filter. A protec-
tive covershieldsfuel system components from road hazards
and dirt.
The engine control module
(ECM) controls the operation of
the 312-way valve (pulse-width modulated). On engine start
up, the valve solenoid is energized for 20 seconds in order to
supply full fuel volume to the fuel rail.
After20 seconds, the
solenoid is deactivated and sprung closed (the bypass is
opened). This reduces the amount of fuel circulating through
the fuel rail and diverts the excess to return to the fuel tank
through the fuel pressure regulator.
The fuel injectors are supplied with pressurized fuel, but ex-
cess fuel is diverted to the fuel tank without first passing
through the fuel rail. This prevents the excess fuel from ab-
sorbing heat in the engine compartment, thus lowering the
temperature and amount of vaporization in the fuel tank.

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-
I Radiator and Cooling System
Mechanical thermostat
(M52 engine)
4 The mechanical thermostat relies on coolant temperature to
operate. While coolant is cold, it remains closed, and circu-
lating coolant bypasses the radiator for rapid engine warm
up. At higher coolant temperature, the thermostat progres-
sively opens to allow coolant flow through the radiator, thus
controlling engine temperature. Port
A restricts coolant flow
from radiator, and port
B restricts coolant flow to radiator.
Electrically heated thermostat
4 The electrically heated thermostat is DME map-controlled.
The engine control module (ECM) activates the thermostat to
maintain engine coolant temperature within a narrow range.
In case of failure of the electronics, the mechanical function of
the thermostat acts as a fail-safe.
Radiator and expansion tank
The radiator is a crossflow design. An expansion tank pro-
vides for coolant expansion at higher temperatures and easy
monitoring of the coolant level.
On cars with automatic transmission, ATF is circulated
through an additional heat exchanger (ATF cooler).
Mechanical cooling fan with viscous clutch
The mechanical cooling fan is belt-driven via a viscous fluid
coupling (clutch) attached to the front of the coolant pump.
The fan clutch controls the speed of the fan based on the tem-
perature of the air flowing through the radiator core.
Electric (auxiliary) cooling fan
The electric cooling fan is mounted on the bumper side of the
radiator.
In models manufactured up to
911 998 (M52 or 1997 M62 en-
gine), the electric cooling fan is controlled by a dual tempera-
ture fan switch mounted in the side of the radiator.

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170-5
Radiator and Cooling System
Fan switch calibration (M52, M62 engine)
coniprairoi OUt rlgnal
Auto. ciimilte ~ontioi inpuls via CAN bus
Electric fan activation:
Low speed
91°C (196°F)
High speed 104' C (21 9' F)
< In models manufactured after 911998 (M52 TU engine, M54
engine.
M62 TU engine), the electric cooling fan is controlled
by the engine control module (ECM) via the output final
stage.
The output final stage is mounted on the fan housing, next to
the fan motor. The fan is operated using a pulse width modu-
lated signal. Fan circuit wiring is protected by a 50-amp fuse.
Electric fan activation is based on the following inputs to the
ECM:
Radiator outlet temperature
Calculated catalytic converter temperature
Vehicle speed
* Battery voltage
Calculated
A/C pressure
When the vehicle is first started, the ECM activates the elec-
tric fan briefly at 20% of its maximum speed, then switches
off. This is for diagnostic monitoring. The voltage generated
by the fan when it slows down (acting as a generator) must
match the stored rpm values in the fan output stage toconfirm
that the fan is operating correctly.
NOTE-
If the ECM fault memory indicates a cooling fan fault, check
that the fan is not seized and that it spins freely.
When
A/C is switched ON, the electric fan is not immedi-
ately turned on.
After the engine is switched
OFF the fan may continue to
run at varying speeds for up to 10 minutes, based on cal-
culated catalyst temperature.
Transmission fluid heat exchanger
Automatic transmission fluid lines circulate transmission fluid
(ATF) to and from a heat exchanger at the radiator.
All 6-cylinder
models andV-8 models produced to 911998 are
equipped with a transmission cooler located in a cooling cas-
sette in front of the radiator.

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.. - -
I Radiator and Cooling System
I I 4 The cooling cassette incorporates cooling coils for various
vehicle systems:
1. Steering fluid cooler
2. Transmission oil
coolel
3. AIC condenser
4 In V-8 cars produced after 911998 (M62 TU engine), the en-
gine radiator is divided into an upper chamber (about 80%)
and a lower chamber (about 20%). The ATF heat exchanger
is coupled to the lower chamber.
On cold engine start-up, the engine coolant is heated more
quicltly than the transmission fluid. Heat from engine coolant
is used to warm up the ATF faster, reducing drag in the trans-
mission and improving fuel mileage.
Once the ATF has reached normal operating temperature,
the ATF heat exchanger acts as cooling device. The lower
20% of the radiator
stays cooler than the upper chamber, so
the ATF is cooled more effectively.
4 M62 TU cooling system ducting at radiator:
1. Coolant distribution housing connection
2. Thermostat connection
3. Water cooled alternator connections
4. Transmission fluid heat exchanger connections