Page 81
240-42 Fuel injection system
Time relay P11
Time function of 3s
For a period of three seconds after starting, ter-
minal 11 of the Lambda ECU is earthed, and a
fixed pulse ratio of 92% is selected (fuel boost
on starting).
Time function of 140 + 20s
1 For a period of 140 seconds after starting,
the fuel-shut off function during decelera-
tion is disabled (no earthing via terminal X2
in the relay). This applies to non-turbo man-
ual cars only.
2 Cold engine (temperature below 45°C/
113 °F)
Fuel boosting during acceleration is availa-
ble when the fuel-booster pressure switch
(79) has been operated via the cold-start
valve (94), which is earthed via thermostatic
switch (97) and thermostatic time switch
(92). An earthing signal is also available to
terminal TKK in the relay.
3
Engine hot (at or above 45°C/113 °F)
Fuel boosting during acceleration is availa-
ble for 140 seconds if the fuel-booster pres-
sure switch (79) has operated. There will be
no earthing signal to terminal TKK via ther-
mostatic switch (97) and thermostatic time
switch (92).
Terminal TIP is energized, providing an ear-
thing signal to terminal 11 of the Lambda
ECU, resulting in a pulse ratio of 92% being
selected.
Deceleration relay Time relay P11 Speed relay, 4600 rpm
(N/A turbo) (Turbo only)
11 TKK 31
bi E le |, le [Xh , x1
ae * 4 af ae TD/31b BK
7 8 9 ioe el 12 4
30
hs 30. lis he TEX lis l; wlSe I,
14 17 8
a AT Papoy
Relay P11 terminal pins Pin 50 +12V supply when starter motor
Pin 87 +12V supply when fuel pump relay
102 operating.
Pin TIP +12V supply via terminal +54
when vacuum switch operating.
Pin TKK Earthing via cold-start valve 94,
thermostatic switch 97 and ther-
mostatic time switch 92.
running.
Pin 31 Earth
Pin 11 Earthed when above functions
operating (period limited to 140s).
Pin X2 Same as pin 11 (not connected)
Pin TRK Earthed via throttle-position sensor
(not connected).
Saab 900
Page 82
Fuel injection system 240-43
Deceleration relay, normally aspirated
engines
The deceleration function shuts off the supply of
fuel when the accelerator is released at engine
speeds above 1575 rpm and at engine tempera-
tures above 45°C (113°F) or, alternatively, dur-
ing a 140-second period after starting.
When the accelerator is released, earthing is
made via terminal 1 (idling position) in the throt-
tle-position sensor to terminal 30 in the deceler-
ation relay (105), thereby providing a signal from
terminal 87 to the fuel shut-off valve {260).
There is also a signal from terminal X1 to termi-
nal 12 in the Lambda ECU, anda pulse ratio of
60% is therefore selected (to compensate for
the weaker mixture sensed by the oxygen sen-
sor).
Terminal pins
Pin 15 +12V supply when fuel pump relay
102 operating.
Pin TD Ignition pulses from terminal TD-O in
ignition pulse amplifier 147.
Pin 30 Earthing via terminals X2 and 31 in
time relay 106.
Pin 31 Earth.
Pin X1 Earths terminal 12 in Lambda ECU
subject to above functions operat-
ing, throttle-position sensor 203
making contact between terminals 1
and 2 and engine speed having been
higher than 1575 rpm. The function
ceases to operate once the engine
speed has fallen below 1375 rpm.
Pin 87 Earthing of fuel shut-off valve 260
via terminal X1.
Pin X2 Earthing via time relay terminals X2
and 11.
Hi
x2 |, 2
51a TD/31b
BORG es
l7 BUS ib. Bry
8
XL b
si
6
la
Deceleration relay (normally aspirated engine)
Saab 900
Page 83
240-44 Fuel injection system
Speed relay (speed-governed fuel boost-
ing, Turbo only)
Speed-governed fuel boosting takes place at en-
gine speeds above 3800rpm (M88 onwards:
4600 rpm). Pulse ratio 85% or 92%.
At engine speeds above 3800rpm (M88 on-
wards: 4600rpm) and before the throttle but-
terfly has passed the 72° position, there is a sig-
nal from terminal 1 in the throttle-position sen-
sor to terminal 31A in the speed relay (138).
Thus, terminal 7 in the Lambda ECU is earthed
via terminal 87 in the relay, and terminal 31 in
the speed relay is earthed via terminal 31 in time
relay (106), resulting in a pulse ratio of 85%
being selected.
If the throttle butterfly passes the 72° position,
the circuit to terminal 314A in the speed relay is
broken, terminal 11 in the Lambda ECU is
earthed via terminal 3 in the throttle-position
sensor (203), terminal TK in the AC relay (156)
and terminal 11 in the time relay (106), and a
pulse ratio of 92% is selected.
Turbo cars, M88 onwards
Pressure-governed fuel boosting complements
the speed-governed fuel boosting and the boost-
ing governed by the position of the throttle but-
terfly (throttle-position sensor).
A pressure switch connected in parallel with the
speed relay senses the pressure in the inlet man-
ifold. When the pressure is between 0.25 and
0.30 bar (3.6 and 4.4 psi), the pressure switch
closes, earthing ECU pin 7 and providing fuel
boosting (fixed pulse ratio of 85%).
Speed relay (138) terminal pins (Turbo
only)
Ignition pulses from terminal TD-O in
Pin TD
ignition pulse amplifier 147.
Pin 15 +12V supply via terminal +54.
Pin 31A Earthed via throttle-position sensor
203.
Pin 87 Earth for terminal 7 of Lambda ECU
via terminal 31 in time relay 106.
x2 |, i x1 f
p18 TD/31b i
6
3014 5
l; “i l,
Speed relay 3800 rpm (M88 onwards: 4600
rpm), Turbo only.
Saab 900
Page 84
bo
din
ior
Fuel injection system 240-45
Electrical system - principle of
operation
Cl system
When the ignition key is turned to the starting
position, current (+50) flows to the starter motor
(4) and thermostatic time switch (92),
If the engine is cold (i.e. coolant temperature
below 45°C/113°F), thermostatic time switch
(92) makes the circuit. The cold-start valve (94),
which receives current from terminal 16 on the
starter motor, is then earthed. The valve is thus
open and the engine receives a boosted supply
of fuel while the starter motor is running (up to a
maximum of 9 seconds}.
When the ignition key is in the starting/drive pos-
ition, current (+15) flows to fuel pump relay
(102) via fuse 22. Relay (102) operates and the
fuel pump (103), which receives current via fuse
30, starts to run. Current also flows through the
heating coils in the auxiliary air valve (95) and
the warm-up regulator (96).
Ignition pulses are sent from the ignition pulse
amplifier (147) to the fuel pump relay and the
Lambda system. If the engine stops the pulses
cease, the relay is de-energized and the power
supply to the fuel system is cut off.
Oxygen-sensor regulated system (Lambda)
The Lambda system itself incorporates an oxy-
gen sensor (136), which provides continuous
data to the ECU (135) on the amount of oxygen in
the exhaust gases. On the basis of this and the
data the ECU receives from the other sensors and
relays, modulating valve (139) regulates the
amount of fuel injected. (The modulating valve is
operated by earthing of terminal 15.)
ECU (135) and relays (105) and (106) receive
power from terminal 87 in relay (102).
During the starting phase, relay (106), which re-
ceives control voltage (+50) when the ignition
switch (20) is in the start position, boosts the
supply of fuel via the ECU and modulating valve
(139).
Thermostatic switch (97) senses the engine
temperature and opens when the temperature is
higher than 25°C (77°F), breaking the circuit to
valve (94).
Fuel-booster switch (79) is used to control fuel
boosting during acceleration. When the engine
is cold, the switch opens the cold-start valve
(94). When the engine is hot, a signal is sent in-
stead to time relay (106), which boosts the sup-
ply of fuel via the ECU (the relay operates for a
maximum of 140 + 20s after starting).
Saab 900
ik
fi
Page 85
|
240-46 Fuel injection system
Speed relay (105), together with the solenoid
valve (260) and throttle-position sensor (203), is
used for fuel shut-off during engine overrun.
When the accelerator pedal is released, the
throttle-position sensor earths relay (105). This
function is also operative if the engine speed ex-
ceeds approx. 1375rpm. Note that this relay is
fitted to manual cars only.
Thermostatic switch (99) breaks at 45°C (113 °F)
and makes at 38°C (100°F). The switch helps to
improve the fuel-boosting function.
Socket (120) is provided for the connection of
special measuring instruments and is used when
the pulse ratio is being set. The socket receives
power when the ignition switch is in the drive
position.
Saab 900
Page 86
Fuel injection system 240-47
Component locations
The component locations are the same for 8-
valve engines with Cl injection and Lambda sys-
tem (EU), other injection engines and turbo en-
gines.
4 Starter motor
On LH (induction) side of engine
7 Earthing point on radiator member
9 Earthing point in luggage compartment
20 Ignition switch
On centre console between front seats
22A Fuse holder
On power distribution panel on top of LH
wing inside engine compartment
59 Two-pin connector
One on power distribution panel on LH
wing in engine compartment
One in luggage compartment adjacent to
fuel pumps
One socket (120) on LH wing in engine
compartment
60 Single-pin connector
One on power distribution panel on LH
wing in engine compartment
One on RH wing inside engine compart-
ment
Cr Starter-interlock switch (automatics
only)
Underneath centre console, adjacent to
selector lever
79 Fuel-booster pressure switch
On inside of LH tie-plate adjacent to fuel
filter in engine compartment
92 Thermostatic time switch
On coolant thermostat
94 Cold-start valve
On throttle housing
95 Auxiliary air valve
Adjacent to thermostat at front of engine
96 Warm-up regulator
Adjacent to thermostat at front of engine
97 Thermostatic switch, 45°C (Lambda)
On inlet manifold
99 Thermostatic switch, 25°C (Lambda)
On thermostat housing
100 Diode (Lambda)
Adjacent to deceleration relay (105) and
time relay (106)
102 Fuel pump relay
On power distribution panel on LH wing in
engine compartment
103 Fuel pump
Inside fuel tank under luggage compart-
ment floor
105 Deceleration relay (900i only)
Behind trim forward of RH front door
For further details of component locations, see
section 3:2 of the Manual.
106 Timerelay
Behind trim forward of RH front door
135 ECU (Lambda)
On RH side underneath rear seat
136 Oxygen sensor
On exhaust manifold
138 Speed relay (manual turbos only)
Behind trim forward of RH front door
139 Modulating valve (Lambda)
On inside of LH tie-plate in engine com-
partment
144 Pressure switch
Behind lower dash panel to the left of the
steering wheel (behind flasher unit)
147 Ignition pulse amplifier
On power distribution panel on LH wing in
engine compartment
152A 29-pin connector (white)
152C 29-pin connector (black)
On power distribution panel in engine
compartment
156 AC compressor relay
On power distribution panel on LH wing in
engine compartment
158 Distribution terminal block, negative (-)
159 Distribution terminal block, positive (+ .
15)
On power distribution panel on LH wing in
engine compartment
201 Engine earthing point
203 =‘ Throttle-position sensor
On throttle housing
260 Fuel shut-off solenoid valve (Lambda)
On rubber socket connector on top of air
cleaner
Saab 900
Page 87
emma ln
240-48 Fuel injection system
Checking
General
1 Connectipulse meter 83 93 597.
2 Turn the ignition key to the drive position.
The reading on the pulse meter should be
100%. The modulating valve and fuel pump
should start and run for a short time.
3 Start the engine.
a) Cold engine (< 19 °C/66 °F):
The needle on the pulse meter should
first indicate 0%, move to 90% and then,
after about three seconds, indicate a
steady pulse ratio of 60%.
b) Hot engine:
The needle on the pulse meter should
first indicate 0%, move to 90% and then,
after about three seconds, indicate a
fluctuating pulse ratio of approx. 50%.
4 Checking the fuel boosting at full load:
(Turbo cars):
a) Rev the engine up to a speed exceeding
3850 rpm and check that the reading on
the pulse meter is 85%,
b) Actuate the throttle-position sensor
(move butterfly). The pulse meter should
now indicate 92%.
Checking the Lambda system
1 Connect pulse meter 83 93 597.
2 Let the engine idle.
3 Unplug the oxygen-sensor loom from the
main wiring loom (on RH wing in engine com-
partment).
4 Earth the signal lead to the ECU. The pulse
meter should now indicate 92%.
5 Hold the signal lead in your left hand and
grip the positive (+) terminal pole on the
battery with the other. The reading on the
meter should now fall to 0%.
Checking the signal level from the oxygen sensor
Connect a multimeter between the signal lead
| from the oxygen sensor and earth. If the sensor is
sound, the reading on the meter should be be-
tween 0.1 and 1.0 V, depending on the tempera-
ture and oxygen content in the exhaust.
Saab 900
Page 88
240-60 Fuel injection system
Fault diagnosis using the LH-
system tester
Make absolutely certain that you refer to the ap-
propriate wiring diagram for the variant con-
cerned, i.e. (900/9000, model year and LH-sys-
tem generation (2.2/2.4).
The tester uses the following error codes
for the LH 2.2 (25-pin connector)
Error Pin Action -
Code No. Malfunctionindicated see page
E001 1 ignition pulse at pin 1 absent 28
E10t 2 Starter motor revs too low 28
ECO2 2 Temperature sensor signal absent 28
E102 2 Temperature sensor circuit shorting out 28
£003 3 idling contacts constantly open 29
F103 3 Idling contacts constantly closed 29
E005 5 ECU pin 5 not earthing 29
E006 6 Airmass meter notearthing 30
E007 7 Airmass meter signal absent 30
E107 7 Airmass meter signal too high 30
F207 7 Airmass meter signal too low 30
E008 8 Airmass meter burn-off function absent 31
E108 8 Airmass meter burn-off function constantly energized 31
FOOS 9g System relay 12 V supply absent 31
E109 9 System relay 12 V supply too tow 31
F010 10 Signal from AIC valve pin 10 absent 32
FOi1 14 ECUpiniinotearthing 32
F012 12 Full-throttle contactsconstantly open 32
£112 12 Full-throttle contacts constantly closed 33
F013 13 Injection pulses absent 33
£113 13 Injection pulses erratic 33
F014 14. Airmassmeter: break inCO-adjusting circuit 34
F017. 17 Pumprelaycontrol circuit faulty 34
£018 18 15Vsupplyabsent 34
£020 20 Oxygen (Lambda) sensor signal absent 35
£120 20 Oxygen (Lambda) sensor signal too low 35
E220 20 Oxygen (Lambda) sensor signa! too high 36
FO21 21 Systemrelaycontrol circuit faulty 36
£023 23. Signal fromAlCvalve pin 23 absent 37
AIcO 23 AlCvalve pulse ratio faulty 37
F024 24 Loadsignalabsent 37
F025 25 ECUpin25notearthing 37
The following codes may also appear on the display:
GLOU (Glow) Airmass meter filament burn-off function operating
C1 Turbo
C2 Turbo with AIC
C3 Turbo with AIC and catalytic converter
c4 Turbo with AIC and Saab DI
C5 Non-turbo with AIC
FPU Fuel pump relay and system relay operating
FUEL Fuel mode
OFF Starting point for injection valve test
Fin Injection valves open
MON Monitor mode
Saab 900
Page 89
Fuel injection system 240-61
Fault diagnosis
Prior to starting work
Many so-called fuel injection faults can be
traced to other unrelated engine or electrical
faults. Before Starting fault diagnosis work on
the LH system, check the following first:
* Battery condition
* Charging system
* Ignition system (timing, plugs, HT leads, dis-
tributor cap and rotor, etc.)
Battery connections and earthing points
Engine condition (compression, inlet man-
ifold vacuum, etc.)
* Airleaks inthe turbo/induction system
ltis often advisable to perform a quick check on
the system and Pump relays as follows:
1 Unplug the connectors from the LH-system
ECU and the air mass meter.
2 Remove the cover from the connector on the
loom to the LH ECU,
3 Connect pins 17 and 21 to earth via pin 25.
4 Checkthat voltage is reaching the following:
Pins 9 and 13 (loom connector for LH ECU)
Pin 2er5 (loom Connector for air mass meter
- 9000] M88)
Fuse 14 (fuel pump relay)
General procedure for fault-diagnosis
work
The words "Check the wiring between xx and yy"
are used frequently in the fault-diagnosis charts.
Sometimes the wiring may run through different
types of connector and, by implication, these
must also be checked for circuit continu ity’short
circuiting.
Be alert to the Possibility of interference from
components connected to the wiring concerned
and check that the wiring is in good condition
and not causing defective earthing.
Make absolutel y certain that you refer to the ap-
Propriate wiring diagram for the variant con-
cemed, i.e. 900/9000, model year and LH-sys-
tem generation (2.2/2.4),
Error codes given in brackets on the fault-diag-
nosis charts denote that the faults concerned
are attributable to the primary fault.
Saab 900
Page 90
240-62 Fuel injection system
Fault-diagnosis chart: LH 2.2
Error
Code
Malfunction
indicated
Action
=r
——
———
—————————
EOO1
(E010)
(E017)
E104
E002
E102
ignition pulse
absent
Starter motor
revs too low
N.8. engine temp
> 10°C
Temperature
sensor (NTC)
signal absent
Temperature
sensor (NTC)
circuit
shorting out
Check ignition system,
Check the wiring between ECU pin 1 and:
M85 onwards: pin 1 of ignition coil (5)
M&6 onwards (Turbo): pin TD-O on
ignition pulse amplifier (147)
M88 onwards, 9000i/9000S: pin 17 of ECU
for EZK (176)
M88 (Turbo): pin 7 of amplifier (147)
Fita new ECU forthe LH system
Check the battery voltage and capacity
Check the lead between the positive (+)
pole of the battery and terminal 30 on
the starter motor, and between the
negative (-) pole of the battery and
earthing point 7 and the earthing point
onthe engine
Check the starter motor
Checkthe wiring between pin 2 of the
ECU (200) and pin 1 of the temperature
sensor (202), and between pin 2 of the
temperature sensor (202) and earthing
point (201)
Check for good earth connection at
earthing point 201
Check the temperature sensor (202)
Fitanew LH ECU
See E002
Seab 900