Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSSAAB19879000 L4-1985CC 2.0L DOHCREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSRELAYS AND MODULES - COMPUTERS AND CONTROL SYSTEMSENGINE CONTROL MODULEDESCRIPTION AND OPERATION
1987 Saab 9000 L4-1985cc 2.0L DOHC
Engine Control Module: Description and Operation
1987 Saab 9000 L4-1985cc 2.0L DOHCSECTION Description and Operation
Control Module
Description, LH 2.2
The LH control module is located in the engine bay on the left-hand side at the bulkhead partition.
The control module contains a microprocessor with a memory holding all the comparative data needed by the processor, such as for engine speed limitation, full-load enrichment, filament burn-off, etc.
The control module processes the signals from the mass air flow sensor and various other sensors, as well as from the memory, and calculates (controls) injector opening duration.
Also incorporated in the control module are help functions in the form of permanently stored signals which are activated in the event of a break in the signals from the mass air flow sensor or temperature sensor:
- Mass air flow sensor: "Limp Home" function
- Temperature sensor: Simulated signal, +45°C (+20°C for LH 2.2) engine temperature
The "CHECK ENGINE" warning lamp (MIL) lights up in the event of these two faults occurring.
Power supply
When the ignition switch is in the ON position, a +15 current is supplied to pin 18 via fuse 13. Voltage 10 and from the main relay is supplied via pins 21 and 9.
The control module is connected to ground via pins 5,6, 11,15 and 25.
Description, LH 2.2
The LH control module is located in the engine bay on the left-hand side at the bulkhead partition.
The control module contains a microprocessor with a memory holding all the comparative data needed by the processor, such as for engine speed limitation, full-load enrichment, filament burn-off, etc.
The control module processes the signals from the mass air flow sensor and various other sensors, as well as from the memory, and calculates (controls) injector opening duration.
Also incorporated in the control module are help functions in the form of permanently stored signals which are activated in the event of a break in the signals from the mass air flow sensor or temperature sensor:
- Mass air flow sensor: "Limp Home" function
- Temperature sensor: Simulated signal, +45°C (+20°C for LH 2.2) engine temperature
The "CHECK ENGINE" warning lamp (MIL) lights up in the event of these two faults occurring.
Power supply
When the ignition switch is in the ON position, a +15 current is supplied to pin 18 via fuse 13. Voltage 10 and from the main relay is supplied via pins 21 and 9.
The control module is connected to ground via pins 5,6, 11,15 and 25.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.