For 1986 and earlier models only, the logic module uses this solenoid to shut the EGR valve and prevent exhaust gasses from entering the engine when the temperature is below 70^F, at idle, and at WOT. This allows for proper warm-up, smooth idle, and maximum power, respectively. For some 1987 and all 1988 and later models, the EGR valve was installed mostly on California models only and is operated by the purge canister solenoid. When the engine temperature is below 80^F, is above 80^F for less than 7 seconds, at idle, or during boost, the solenoid is activated. This closes the EGR valve and stops gases from being drawn from the purge canister.
When the logic module is turning on or off the solenoid, it momentarily checks the output of the solenoid driver to see if it is responding the way it should. If it does not see about 0V when on (open circuit) or 12V when off (short circuit), a fault code 34 is stored.
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Copyright © 1996-2003 Russ W. Knize.