Operation CHARM: Car repair manuals for everyone.
Home >> Saab >> 1987 >> 900 L4-1985cc 2.0L DOHC >> Repair and Diagnosis >> Powertrain Management >> Computers and Control Systems >> Relays and Modules - Computers and Control Systems >> Main Relay (Computer/Fuel System) >> Description and Operation
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

(Some people have issue connecting. LEMON is investigating. For now, use Firefox or change your DNS server)

Or, hide this message: temporarily or permanently

Main Relay (Computer/Fuel System): Description and Operation



PURPOSE
The main relay provides current to the fuel pump relay, idle air valve, fuel injectors, mass air flow sensor, oxygen sensor pre-heating resistor and to other ECU controlled functions or components.

LOCATION
Forward of the right A-pillar, below fascia.

OPERATION
The fuel injection ECU controls the relay ground connection. When ground is supplied, the system relay is activated and currant can flow to all the related components. If the ground connection is interrupted, no current can reach the components.
pro multis · About Operation CHARM