Rev 2 and 3
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WIRING DIAGRAM
COMPONENT LOCATION VIEW
COMPONENT ID
22A Main fuse board on short side of dashboard.
102 Fuel pump relay on main relay board in dashboard.
136 Preheated oxygen sensor, cylinder bank 2, on front section of exhaust pipe.
156 A/C compressor relay on main relay board in the engine bay.
157 Spark plugs
166 3-stage pressure switch for A/C on receiver between front grille and radiator.
171 Antifrost thermostat behind glove box on evaporator housing.
178 Knock sensor, cylinder bank 2, below the exhaust manifold for cylinder bank 2.
178A Knock sensor, cylinder bank 1, below the exhaust manifold for cylinder bank 1.
202 Coolant temperature sensor, engine management system, on coolant bridge between the cylinder heads.
203 Throttle position sensor on the throttle body.
205 Mass air flow sensor adjacent to the air cleaner.
206 Injectors at top of intake manifold.
229 Main relay, engine management system, on main relay board in dashboard.
271 Oxygen sensor preheater integrated with oxygen sensor.
272 [1][2]Idle air control valve on bottom of intake manifold.
321 EVAP canister purge valve in the engine bay on the right-hand side.
323 Fuel pump in the fuel tank.
342A Main fuse board in the engine bay.
345 Crankshaft position sensor below the oil filter.
407 Intake air temperature sensor on intake manifold.
445 16-pin data link connector under the dashboard adjacent to the
(H16-1) steering column.
500 Integrated Central Electronics (ICE) control module
LHD: above main relay board in dashboard
RHD: behind main relay board in dash- board
501 Main fuse board for maxi fuses behind the battery.
502 Transmission control module (TCM) in cabin on right-hand side of bulkhead partition.
507 TCS control module under the right-hand front seat.
510 Motronic 2.8.1 control module on right-hand side behind the side trim.
515 Preheated oxygen sensor, cylinder bank 1, on front section of exhaust pipe.
524 Relay, secondary air injection pump, on main relay board in engine bay.
540 Main instrument display panel on the dashboard.
547 ABS control module integrated with the brake unit behind the battery.
548 Secondary air injection pump between wing and wing liner in the left-hand front wheel housing section.
549 Secondary air injection control valve, on the hose between the secondary air injection pump and the non-return valve.
552 Ignition coil module above the engine flywheel.
555 Camshaft position sensor integrated with the distributor.
2-Pin Connector
H2-9 Under the rear seat adjacent to the fuel pump.
4-Pin Connector
H4-7 Under the rear seat adjacent to the fuel pump.
1O-Pin Connector
H10-2 On the bracket below the left-hand A pillar.
16-Pin Connector
H16-2 On the engine.
33-Pin Connectors
H33-1 Grey connector on the bracket below the left-hand A pillar.
H33-2 Black connector on bracket below the left-hand A pillar.
H33-4 On the bulkhead partition behind the glove box.
Grounding Points
G3 Battery ground, left-hand wheel housing.
G5 Grounding point, under left-hand part of rear seat.
G7L Grounding point, engine (oxygen sensor), on metal bracket at rear of engine.
G7P Grounding point, engine (Power), on metal bracket at rear of engine.
G7S Grounding point, engine (Signal), on metal bracket at rear of engine.
G30 Grounding point, left-hand structural member behind the battery.
DESCRIPTION OF OPERATION
The Motronic is an engine management system which controls both ignition timing and fuel injection from a single control module.
The Motronic 2.8.1 has sequential injection and individual control of ignition timing in connection with the occurrence of knocking in any of the cylinders. (This function is adaptive.)
Expressed in simplified terms, it could be said that the Motronic system is a combined electronic fuel injection system and electronic ignition system with knock sensor.
The fuel injection system has an advanced function in that injection is sequential. With regard to the ignition system, special mention may be made of the fact that the power stage is integrated with the control module.
M2.8.1 Control Module
Control module 510 monitors and controls a number of functions.
The Control Module Obtains Information From:
^ Front oxygen sensor 136
^ A/C via antifrost thermostat 171
^ Front knock sensor 178
^ Rear knock sensor 178A
^ Engine coolant temperature sensor 202
^ Throttle position sensor 203
^ Mass air flow sensor 205
^ Crankshaft position sensor 345
^ Intake air temperature sensor 407
^ Transmission control module (TCM) 502
^ Rear oxygen sensor 515
^ ABS control module 547
^ Camshaft position sensor 555
The Control Module Sends Information To:
^ Fuel pump relay 102
^ A/C compressor relay 156 (via pressure switch 166)
^ Throttle position sensor 203
^ Injectors 206
^ Main relay 229
^ Idle air control valve (IAC) 272
^ EVAP canister purge valve 321
^ Data link connector 445
^ Main instrument display panel 540B (CHECK ENGINE and rpm)
^ Secondary air injection pump
^ 548 Ignition coil unit 552
Power Supply
The system is supplied with positive voltage on relays 443 and 102 via fuse 17 when the ignition switch is in the Start or Drive position and with a constant power supply (+30 circuit) on relay 229 and the Motronic control module.
Grounding
The control module has a power ground (G7P), an oxygen sensor ground (G7L) and a signal ground (G7S).
The grounding points are located on a metal bracket at the rear of the engine.
Ignition System
The ignition system consists of an ignition coil unit and HT cables.
The Motronic control module adjusts ignition timing on the basis of the following conditions:
^ Engine speed
^ Engine load
^ Knock indication, if any
Data Link Connector 445
The data link connector for connecting an Intellegant Saab Tester (ISAT) Scan Tool is located under the dashboard adjacent to the steering column (16-pin connector).
Cars With Automatic Transmission
The Motronic.control module obtains information on the current gear selector position, R-1-2-3-D, from the transmission control module (TCM).
Idling compensation takes place in gear selector positions R-D-1-2-3. Compensation is carried out by the control module opening the IAC valve to increase the air flow.
The first time R or D is selected, the control module is programmed for automatic transmission.
Tachometer (rev counter) 110
Engine rpm signals are obtained from Motronic control module 510 so that engine rpm can be shown on the tachometer.
Oxygen Sensors 136 And 515
The oxygen sensors, one for the front cylinder bank and one for the rear cylinder bank, are mounted on the exhaust pipe. Their purpose is to provide the control module with information on the composition of the exhaust emissions (oxygen content).
Since the sensors continuously measure the oxygen content of the exhaust emissions, the control module can adjust the fuel-air mixture so that it is as close as possible to lambda = 1.
To work efficiently, the sensor must be hot. To attain operating temperature as quickly as possible, the sensors are fitted with a heating element known as a preheater.
Air Conditioning, A/C
The Motronic control module receives information from the A/C switch/climate control unit, the ICE control module, antifrost thermostat 171 and pressure switch 166 to the effect that the A/C system is engaged. The control module then grounds A/C relay 156.
When the A/C compressor is engaged, the control module increases engine idling speed to compensate for the increased load represented by the compressor.
Grounding of the A/C relay is interrupted at wide open throttle, which results in disconnection of the A/C compressor for a few seconds. This has been discontinued on M94 models.
Should the coolant temperature rise to 126 °C, the ICE control module will break the connection to the antifrost thermostat and the compressor will stop.
Coolant Temperature Sensor 202
The coolant temperature sensor is of NTC type and supplies the control module with information on the temperature of the coolant.
If an open circuit occurs, the control module will simulate a temperature of 80 °C (176 °F).
Throttle Position Sensor 203
The throttle position sensor provides the control module with information on the position (angle) of the throttle butterfly.
The sensor gives the angle continuously from idling speed to wide open throttle.
Malfunction Indicator (CHECK ENGINE) Lamp 47O
The malfunction (CHECK ENGINE) lamp in main instrument display panel 540 lights up when serious and emission-related faults occur in the engine management system.
[1][2]Idle Air Control Valve 272
The idle air control valve is regulated by the control module which adjusts the opening angle of the valve to maintain idling speed constant.
For instance, this means that the valve opens so that idling speed (which would otherwise drop) is adjusted to compensate for the increased load when the A/C is switched on or Drive is engaged.
If a fault occurs in the circuit, the valve is automatically adjusted down to a fixed idling speed of at least 1000 rpm.
EVAP Canister Purge Valve 321
The EVAP canister purge valve is located in the engine bay on the right-hand side. It is controlled by the control module on the basis of information on coolant temperature, engine speed and load.
The valve opens under specified conditions and allows the fuel vapors from the evaporative emission canister to pass into the intake manifold where they are burnt together with the regular fuel-air mixture.
Crankshaft Position Sensor 345
The control module obtains information on the position and speed of the crankshaft from the crankshaft position sensor.
The sensor consists of a slotted ring on the crankshaft at the flywheel end and an inductive sensor mounted on the engine block.
The inductive sensor works somewhat like a small alternator, the sinusoidal voltage of which increases with increasing speed.
The sinusoidal voltage alternates between positive and negative polarity, which is brought about through alternating holes and "ribs" on the slotted ring.
This alternation of polarity is used by the control module for the transmission of pulses.
The control module can in this way identify which cylinder pair's pistons are at, or on the way up to, TDC.
Should the sensor fail to work or in the event of a break in the circuit (no continuity), the engine will not start.
Camshaft Position Sensor 555
The camshaft position sensor is of Hall sensor type and, apart from the Hall sensor element, consists of a special "pimple" on the exhaust side camshaft in the front bank of cylinders.
When the camshaft is rotating and the "pimple" passes the Hall sensor, this indicates when cylinder 1 is ready for ignition.
Mass air flow-sensor 205
The mass air flow sensor measures the air mass consumed by the engine, which is proportional to the engine load.
If the sensor develops a fault, the control module obtains the necessary information from the throttle potentiometer.
Knock Sensors 178 And 178A
The knock sensors, one for the front bank of cylinders and one for the rear bank, sense the knocking tendencies in the engine and convert any knocking into a voltage which the control module processes to adjust the ignition timing so that optimum performance and emissions are obtained.
Intake Air Temperature Sensor 407
The intake air temperature sensor is located in the intake manifold. It is of NTC type and provides the control module with continuous information on the temperature of the intake air.
Low temperature = High voltage
High temperature = Low voltage
Secondary Air
To get the catalytic converter working as soon as possible after a cold start, ambient air is pumped into the exhaust manifold where the oxygen in the air starts a chemical combustion process.
Once the engine has started, the secondary air injection pump starts up and the secondary air injection control valve opens the connection to the exhaust manifold.
operation is dependent on temperature and time.
The secondary air injection control valve closes and the pump stops after a maximum period of 80 seconds or when engine temperature reaches 65°C.
Vehicle Speed Signal
Wheel speed information comes from the ABS control module. This information is used to adjust idling speed to 800 rpm when road speed is 0 km/h.
FAULT DIAGNOSIS HINTS
Use an Intellegant Saab Tester (ISAT) Scan Tool when carrying out fault diagnosis and obtaining readouts of diagnostic trouble codes.