Emission Control Parameters

NOTE: These parameters indicate the input and output signals between the logic module and various sensors and actuators for the following emission control devices:

- Exhaust gas recirculation (EGR).

- Charcoal canister purge (CCP) operation.

- Air injection.

AIR SWITCHING SOLENOID
AIR SWITCH SOL - XXXX RANGE: OPEN - CLAST

This discrete parameter on 1989 and later fuel-injected truck engines, indicates that the logic module has energized the air switching solenoid to allow air injection to the manifold during engine warm-up. AIR SWITCH SOL should be ON during warm-up; OFF when the engine is at operating temperature. This parameter indicates that the logic module command has been given. It is not a feedback signal to indicate that the solenoid is operating.


EXHAUST GAS RECIRCULATION VALVE SOLENOID
EGR SOLENOID - XXX RANGE: ON - OFF

This discrete parameter on some 1989 and later cars and trucks, displays the logic module command to the solenoid that controls vacuum to the EGR valve. (It is not a feedback signal from the solenoid.) When EGR SOLENOID reads ON, the solenoid should be energized to block vacuum and turn off EGR. When EGR SOLENOID reads OFF, the solenoid should be de-energized to open the vacuum line and allow the EGR valve to operate.



EVAPORATIVE PURGE SOLENOID
PURGE SOL - XXXX RANGE: OPEN - CLAST

On 1989 and later vehicles, the logic module sends output commands to the fuel vapor solenoid to control vapor canister purging. When the PURGE SOL reading is OPEN, the solenoid should be deenergized to allow vapor purging. When the PURGE SOL reading is CLAST, the solenoid should be energized to block the canister vacuum line and not allow purging.