Volvo Workshop Manuals
XC90 AWD L6-2.9L Turbo VIN 91 B6294T (2004)
Relays and Modules > Relays and Modules - Powertrain Management > Relays and Modules - Computers and Control Systems > Engine Control Module > Component Information > Description and Operation > System Overview > Page 934
Engine Control Module: Description and Operation
The engine control module (ECM) checks itself and all input and output signals.
Four different conditions for diagnostics
When all diagnostic functions have been gone through.
Begins 15 seconds after the engine starts and finishes when the engine is switched off.
Begins when the engine starts and engine coolant temperature (ECT) is below 40°C (104°F) and finishes when the engine temperature is above 84°C
Some diagnostics are carried out a set amount of time after a particular occurrence (for example when vehicle speed is above 23 km/h (14.3 mph)).
Emissions related diagnostic functions
The engine control module (ECM) checks that the emissions related functions are working. These systems are checked by an ongoing diagnostic
Diagnostic trouble code (DTC) memory
When the engine control module (ECM) detects a fault, the diagnostic trouble code (DTC) is stored with the qualifier and status in the unit DTC
Malfunction indicator lamp (MIL) activation
Emissions related diagnostic trouble codes (DTC) are stored even when it is lit. A counter counts down to determine when the malfunction indicator
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