System Descriptions - Honda 2004 Odyssey Service Manual

Fuel and Emissions Systems

System Descriptions

Electronic Control System
The functions of the fuel and emission control systems are managed by the powertrain control module (PCM).
Fail-safe Function
When an abnormality occurs in the signal from a sensor, the PCM ignores that signal and assumes a pre-programmed
value for that sensor that allows the engine to continue to run.
Back-up Function
When an abnormality occurs in the PCM, the injectors are controlled by an independent back-up circuit to permit
minimal driving.
Self-diagnosis
When an abnormality occurs in the signal from a sensor, the PCM supplies ground for the malfunction indicator lamp
(MIL) and stores the diagnostic trouble code (DTC) in erasable memory. When the ignition is first turned on, the PCM
supplies ground to the MIL for 2 seconds ('99-01 models) or for 15 to 20 seconds ('02-04 models) to check the MIL bulb
condition.
Two Driving Cycle Detection Method
To prevent false indications, the ''two driving cycle detection method'' is used for some self-diagnostic functions.
When an abnormality occurs, the PCM stores it in its memory. When the same abnormality recurs after the ignition
switch is turned OFF and ON (II) again, the PCM turns on the MIL.
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