Page 41
H 78 LH fuel system 2.2: T16 Lambda, US, CA, JP, SE, EU, AU
LH fuel system 2.2: T16 Lambda, US, CA, JP,
SE, EU, AU
AUT 1 :
RD_16.0 '
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US,-CA, JP, AU 9
Saab 900
Page 42
ee
LH fuel system 2.2: T16 Lambda, US, CA, JP, SE, EU, AU 79
Operation
The Bosch LH Jetronic fuel injection system is used
for cars with the 16-valve engine. LH is an abbrevia-
tion of Luftmassenmesser Hitzdraht (Air mass meter
with hot filament). The fuel injection system is con-
trolled and supervised by control unit 200, which
includes a microprocessor.
The system receives a positive supply from fuse 22
when the ignition switch is in the start or drive posi-
tion, and a constant supply from +30 to relays 229
and 102.
On the basis of the data stored in the control unit and
the incoming information from various sensors, the
control unit calculates and controls the opening
times of the electrically operated fuel injection
valves (206). The control unit receives information on
the engine speed by sensing the ignition pulses from
ignition pulse amplifier 147 (1987 model) or ignition
system amplifier 146 (1988 model).
Throttle valve angle transmitter 203 provides infor-
mation \on the throttle angle, i.e. the engine load.
The transmitter has two contact positions, i.e. 0°
(idling speed) and 72° throttle angle.
Temperature transmitter 202 is of Negative Tempera-
ture Coefficient (NTC) type and provides continuous
information to the control unit on the engine tem-
perature. In the event of loss of this signal, the con-
trol unit will simulate, by default, an engine tempera-
ture of +20 °C.
Air mass meter 205 includes a platinum filament
known as the hot filament. Regardless of the compo-
sition of the air and the air flow, the temperature of
the filament is maintained constant at about 100 °C
above the temperature of the intake air.
The current necessary for maintaining the tempera-
ture of the filament constant is controlled by means
of a bridge circuit and a sensing resistor, the voltage
variation of which is directly proportional to the in-
take air mass flow.
Since the filament is located in the intake air, it will
gradually become fouled, which affects the mea-
surement results. To keep the filament clean, its
temperature is raised to about 1000 °C for one sec-
ond. This takes place four seconds after the engine
has been stopped, provided that the engine speed
has earlier been in excess of 2000 r/min. This pro-
cess is controlled by the control unit.
In the event of a loss of signal from the air mass
meter, e.g. if the filament should fail, an emergency
system known as the ”Limp-home” function in the
control unit will come into operation. The car can
then be driven, although its driveability will be limit-
ed. When the ”Limp-home” function is operative,
warning lamp 47P, CHECK ENGINE, will light up. It is
located in the combined instrument, and is supplied
from fuse 7. (The lamp can also be energised from
EZK-type ignition systems.)
The engine is supplied with fuel by electrically driven
fuel pump 103 and feed pump 101 drawing fuel from
the fuel tank and building up a pressure in the fuel
system. Boost pressure switch 144 is fitted on cars
equipped with a turbocharger and will trip the fuel
pumps if the boost pressure should exceed a prede-
termined value.
The idling speed is controlled by motor 272 for auto-
matic idle control (AIC). The AIC test connector is
used for the basic setting of the engine idling speed.
Test connector 204 has the following terminals:
1 Voltage to the test connector
2 "Limp-home” (CHECK ENGINE)
3 Timing ratio, Lambda
The control unit is connected to the air-conditioning
system via pin 16, "AC 156”. When the AC compres-
sor is running, the control unit will compensate for
the increased load applied by the compressor at
engine idling speed. A signal (earth) is applied from
pin 12 at full throttle.
Exhaust gas emission control, Lambda
Components for precision control of the fuel/air mix-
ture have been added to the fuel system. Lambda
sensor 136 continually measures the oxygen content
of the exhaust gases, thus enabling the control unit
to adjust the mixture to the most beneficial ratio. The
sensor is heated by preheater 271 (protected by fuse
285 in the wiring).
Automatic transmission
Cars with automatic transmission are also equipped
with switch 76 which will close when the selector
lever is set to "Drive”, and the control unit will then
compensate for the increased load applied by the
automatic transmission when the engine is running
at idling speed.
Saab 900
Page 43
80 _LH fuel system 2.2: T16 Lambda, US, CA, JP, SE, EU, AU
Fault-tracing hints
When fault-tracing in the wiring for the fuel system,
always observe the following:
1. Always disconnect the 25-pole connector on the
control unit and the connector on the air mass
meter. N.B. These two components can easily
be seriously damaged if measurements are car-
ried out on their terminal pins.
2. Always disconnect the connection to the sus-
pected component.
3. Use an ohmmeter — not a buzzer — for checking
the wiring.
Before checking the wiring, always start by checking
fuse 22 and checking that the supply to it is live. Also
check fuse 7 and the fuse in the wiring for the
Lambda sensor preheater.
For comprehensive fault-tracing instructions for the
system, see the Service Manual, Group 2:3, Fuel
system, fuel injection.
Earthing point 204 on the engine lifting lug is import-
ant for correct operation of the fuel system. If the
location of the earthing point is altered, such as
‘in when other work is being carried out on the engine,
the performance of the system may be disturbed.
_ a eC
Page 44
LH fuel system 2.2: T16 Lambda, US, CA, JP SE, EU, AU 84.
Locations of components
The locations of the components presented below
are the same for all variants of LH fuel system 2.2.
Ze
22A
31
47P
Biz,
59
60
67
(5
Battery
on the right-hand side of the engine com-
partment
Earthing point, radiator cross-member
Earthing point in the luggage compartment
Fuse holder
in the electrical distribution box, in the en-
gine compartment, on the left-hand wheel
housing
Reversing light switch
under the centre console, at the selector
lever
CHECK ENGINE warning lamp
in the combined instrument in the instru-
ment panel
3-pole connector (116, 116 Lambda)
in the engine compartment, on the right-
hand side, at the air intake
2-pole connector
two at the fuel pump, under the luggage
compartment floor
at the control unit, forward of the right-hand
front door, below the facia (under the trim)
one (for the Lambda sensor) in the engine
compartment, on the right-hand wheel
housing, next to the distribution block for
the positive supply from the battery
Single-pole connector
one (for the Lambda sensor) in the engine
compartment, on the right-hand wheel
housing, next to the distribution block for
the positive supply from the battery
one (AIC test connector) in the engine com-
partment, behind the right-hand wheel
housing
one, for connecting the main relay and the
fuel pump relay (116, 116 Lambda)
one in the electrical distribution box
two for boost pressure switch 144 (T16, T16
Lambda) and two for the automatic trans-
mission, at the control unit, forward of the
right-hand front door, below the facia (be-
hind the trim) :
one under the centre console, at the se-
lector lever (auto.)
6-pole connector
in the engine compartment, on the right-
hand side at the air intake
Distribution block
in the engine compartment, on the right-
hand side
Saab 900
Page 45
82 LH fuel system 2.2: T16 Lambda, US, CA, JP, SE, EU, AU
76 Switch for raising the idling speed, auto. 201 Engine earthing point
transm. at the engine lifting lug
Psi the centre console, at the selector 202 Engine temperature transmitter
on the intake manifold flange, between cyl-
95 Auxiliary air valve (116, T16) inders 2 and 3
at the extreme front of the engine intake 203 Throttle angle transmitter
manifold : :
on the engine throttle housing
101 Fuel feed pump (US, CA, JP, AU, ME, FE)
in the fuel tank, under the luggage compart- cs pA lies :
in the engine compartment, behind the
ment floor : :
right-hand wheel housing
102 Fuel pump relay :
at the control unit, forward of the right-hand =e ety ga ‘thesia
front door, below the facia (behind the trim) OF eS OS ee
103 Fuel pump 206 tte bee —
in the fuel tank, under the luggage compart- Se
ment floor 214 Earthing point on the gearbox
136 Lambda sensor (116, T16 Lambda) 229 Main relay for the fuel injection system
on the exhaust manifold, beside the tur- forward of the right-hand front door, below
bocharger the facia (behind the trim)
144 Boost pressure switch (T16, T16 Lambda) PEL Preheater (116 Lambda, T16 Lambda)
under the facia, to the left of the steering in the Lambda sensor, on the exhaust mani-
column (behind the knee shield) fold
146 Amplifier for the electronic ignition system 212 Idling speed adjustment motor (I16
(T16, T16 Lambda) Lambda, T16 Lambda)
in the engine compartment, forward of the at the extreme front, on the left-hand side of
left-hand wheel housing the cylinder head
147 Ignition pulse amplifier 285. ~~ Fuse for Lambda sensor (116 Lambda, T16
in the electrical distribution box in the en- Lambda)
gine compartment, on the left-hand wheel in the engine compartment, on the right-
housing hand side, at the air intake
152A 29-pole white connector
152B 29-pole red connector
152C 29-pole black connector
in the electrical distribution box in the en-
gine compartment, on the left-hand wheel
housing.
The connectors are accessible from the inte-
rior of the car
156 Relay for the AC compressor (116 Lambda,
T16 Lambda)
in the electrical distribution box in the en-
gine compartment, on the left-hand wheel
housing
159 Distribution terminal +15
in the electrical distribution box, in the en-
gine compartment, on the left-hand wheel
housing
176 Control unit for EZK ignition system (116, 116
Lambda)
in the engine compartment, forward of the
left-hand wheel housing
200 Control unit for the LH system
forward of the right-hand front door, below
the facia (behind the trim)
‘Saab 900
Page 46
en cyl-
id the
below
mani-
LH fuel system 2.2: T16 Lambda, US, CA, JP, SE, EU, AU
83
Components
146 (M1988)
22A,60 (M1988)
147 (M1987)
152A
152B
152C
156
159
Page 47
pon ' ’ .
84 LH fuel system 2.4: 116 Lambda, 1988, US, CA, JP, SE, EU, AU .
a a
j V j j
1
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qq 2
AUT |] 2
al @
+54 +54 +15
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| | 75
nc 11M 5598 123k
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J Ni
86 30
7 |22A | 22A nS 229 22A 22
fas faze Yor 60
560 BR/VT 0.5 S60A BR/VT 0.5 559C RD 1.0
86 30 2]
ee 102 =
q
as Jor fore z
z
— Fs
a
570 "
BL/RD 0.75 15—m159
+
561
CHECK JeL/n0 2.5
ENGINE St as
| 0 bY Fs 2 2 a
a & 3 a ol 3 a 2
c=)
g e 2 g| & 2 a & 5
8 i | 206 3 a5 & a 3
322 1 1 1 1
11272 1 ROA2 3 4
g 2 2
$ 3 3 3 a LAK 4136
% ql 5 4 pA d
w} ‘a Le a al & 4
o Rg 3
2 = 5] & 3 a a BY
8S bt et lad Id < rs) |
a <q 2 ir Fy : FE Fi 60
v4 a ai 4 ee) wo o w rs)
oO} ce) a) cc) <
5 3 3 a] 8 562 1.0
a) 3 3 alo oF
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é
30 21 33 | | 9 29 15 | | 18 20 24 | | 4
19.17 16 13 eT cL 27 115.252 3 11 135
4
o R tl eee 566A 532 565 bhai
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-|> @ o| S| ofS} S| 566 SV 0.75 J
al ai 8 a a] 52) 8) alo fi Le hipe a 2 di
+] - + oy ol ol st onl oo a ol = x
3] 8 8 3 of Leela] 3} og 201 i et | 203 |sesa a a - a
q z g| of & GN/RO 0.75] SF S <
7 3 5 % 1 3 S|
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2] ij ALS Slcls al as 9
| | +t] ©} 19) 2 3 o| +
o 5 5 3] 8] 3 ES 4
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n a ar) aI ia a
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5 5 3 a a3 a
20 324 20% 71 erat
| 176 | 156 s0f22A
17
I 152B és | A _ peat |
530 BL_0.75 204 GL/VT 0.5 pe 284C BL_O.5 284 BL 05 AC 261
| 1s er O GR/RO 2.5
25 152A
| VT_0.75, 261A GR 1.5
262A SV 1.5
US, CA, JP, AU
Saab 900
Page 48
LH fuel system 2.4: 116 Lambda, 1988, US, CA, JP, SE,EU,AU 85
Operation
Sixteen-valve engines with Lambda are equipped
with version 2.4 of the Bosch LH Jetronic fuel in-
jection system, which is an update of version 2.2. LH
is an abbreviation of Luftmassenmesser Hitzdraht
(Air mass meter with hot filament). The fuel injection
system is controlled and monitored by control unit
200, which includes a microprocessor.
Anumber of new features have been introduced, such
as:
e Adaptive Lambda control system
@ AIC (Automatic Idle Control) valve with built-in
"limp-home” function. When necessary, the valve
provides a high, fixed idling speed of 1200 r/min.
@ Adaptive idle control system. Normal changes are
compensated for automatically. The idling speed
is controlled by means of valve 272.
® Built-in deceleration function. During overrun
braking, it cuts off the fuel supply within certain
engine speed ranges.
e Anew, electrically-operated relief valve (321) for
the charcoal canister. Controlled by signals from
the control unit. The charcoal in the canister ab-
sorbs fuel fumes in the vent line from the tank.
@ Built-in fault diagnosis system. Gives fault codes
via the CHECK ENGINE lamp.
The system receives a positive supply from fuse 22
when the ignition switch is in the start or drive posi-
tion, and a constant supply from +30 to relays 229
and 102.
On the basis of the data stored in the control unit and
the incoming information from various sensors, the
control unit calculates and controls the opening
times of the electrically operated fuel injection
valves (206). Control unit 200 receives information
on the engine speed by sensing the pulses from the
ignition system.
Throttle valve angle transmitter 203 provides infor-
mation to the control unit on the throttle angle. The
transmitter has two contact positions, i.e. 0° (idling
speed) and 72° throttle angle.
Temperature transmitter 202 is of Negative Tempera-
ture Coefficient (NTC) type and provides continuous
information to the control unit on the engine tem-
perature. In the event of loss of this signal, the con-
trol unit will simulate, by default, an engine tempera-
ture of +45 °C.
Air mass meter 205 is built into a plastic housing. In
the event of a loss of signal from the air mass meter,
e.g. if the filament should fail, an emergency system
known as the "Limp-home” function in the control
unit will come into operation. The car can then be
driven, although its driveability will be limited. When
the "Limp-home’” function is operative, warning lamp
47P, CHECK ENGINE, will light up. It is located in the
combined instrument, and is supplied from fuse 7.
(The lamp can also be energised from EZK-type igni-
tion systems.)
The engine is supplied with fuel by electrically driven
fuel pump 103 and feed pump 101 drawing fuel from
the fuel tank and building up a pressure in the fuel
system.
The control unit is connected to the air-conditioning
system via pin 16, "AC 156”. When the AC compres-
sor is running, the control unit will compensate for
the increased load applied by the compressor at
engine idling speed. A signal (earth) is applied from
pin 3 at full throttle, which disconnects the AC com-
pressor.
Test connector 204 should be used for all fault trac-
ing. When pin 2 in the socket is earthed, flashing
codes will be obtained on the CHECK ENGINE lamp.
Exhaust gas emission control, Lambda
The car is equipped with an adaptive Lambda system,
which compensates for variations in the fuel/air mix-
ture caused by changes in the fuel system.
Lambda sensor 136 continually measures the oxy-
gen content of the exhaust gases, thus enabling the
control unit to adjust the mixture to as close to = 1
as possible. The sensor is heated by preheater 271
(protected by fuse 285 in the wiring).
Automatic transmission
Cars with automatic transmissian are also equipped
with switch 76 which will close when the selector
lever is set to "Drive”, and the control unit will then
compensate for the increased load applied by the
automatic transmission when the engine is running
at idling speed.
Saab 900
Page 49
86 __LH fuel system 2.4: 116 Lambda, 1988, US, CA, JP, SE, EU, AU
Fault-tracing hints
When fault-tracing in the wiring for the fuel system,
always observe the following:
1. Always disconnect the 35-pole connector on the
control unit and the connector on the air mass
meter. N.B. These two components can easily
be seriously damaged if measurements are car-
ried out on their terminal pins.
2. Always disconnect the connection to the sus-
pected component.
3. Use an ohmmeter — not a buzzer — for checking
the wiring.
Before checking the wiring, always start by checking
fuse 22 and checking that the supply to it is live. Also
check fuse 7 and the fuse in the wiring for the
Lambda sensor preheater.
For comprehensive fault-tracing instructions for the
system, see the Service Manual, Group 2:3, Fuel
system, fuel injection.
Earthing point 201 on the engine lifting lug is import-
ant for correct operation of the fuel system. If the
location of the earthing point is altered, such as
when other work is being carried out on the engine,
the performance of the system may be disturbed.
Saab 900
Page 50
LH fuel system 2.4: 116 Lambda, 1988, US, CA, JP, SE, EU, AU 87
Locations of components
1
22A
3t
47P
59
60
67
lO
76
101
102
Battery
on the right-hand side of the engine com-
partment
Earthing point, radiator cross-member
Earthing point in the luggage compartment
Fuse holder
in the electrical distribution box, in the en-
gine compartment, on the left-hand wheel
housing
Reversing light switch
under the centre console, at the selector
lever
CHECK ENGINE warning lamp
in the combined instrument in the instru-
ment panel
2-pole connector
two at the fuel pump, under the luggage
compartment floor
one at the control unit, forward of the
right-hand front door, below the facia (under
the trim)
one (for the Lambda sensor) in the engine
compartment, on the right-hand wheel
housing, next to the distribution block for
_the positive supply from the battery
Single-pole connector
one (for the Lambda sensor) in the engine
compartment, on the right-hand wheel
housing, next to the distribution block for
the positive supply from the battery
one, for connecting the main relay and the
fuel pump relay
and one for the automatic transmission, at
the control unit, forward of the right-hand
front door, below the facia (behind the trim)
one under the centre console, at the se-
lector lever (auto.)
one in the electrical distribution box
6-pole connector
two in the engine compartment, on the
right-hand side at the air intake
Distribution block
in the engine compartment, on the right-
hand side
Switch for raising the idling speed, auto.
transm.
under the centre console, at the selector
lever
Fuel feed pump
in the fuel tank, under the luggage compart-
ment floor
Fuel pump relay
at the control unit, forward of the right-hand
front door, below the facia (behind the trim)
Saab 900
saere