GM Service Manual Online
For 1990-2009 cars only

Scan Tool Output Control

Additional Menu Selection(s)

Description

EGR Solenoid

Engine Output Controls

Activates the EGR solenoids that control EGR valve position. The normal commanded state is NONE. The system will INCREASE or DECREASE the amount of EGR valve opening by 5 percent increments, within a range of 0 to 100 percent. The PCM allows EGR solenoid control when the following conditions are met:

    • No diagnostic trouble codes (DTC) are set
    • The engine operating temperature is at least 80°C (176°F)
    • No vehicle speed is detected

If the engine is running, too much EGR will result in a rough idle or engine stalling. The system remains in the commanded state until cancelled by the scan tool or until vehicle speed is detected.

EVAP Purge Solenoid

Engine Output Controls / EVAP System

Activates the EVAP canister purge valve. The normal commanded state is NONE. The EVAP purge solenoid is pulse width modulated (PWM). When commanded ON, the purge solenoid operates by 10 percent increments, within a range of 0 to 100 percent. The PCM allows EVAP purge solenoid control when the following conditions are met:

    • No diagnostic trouble codes (DTC) are set
    • The engine is NOT RUNNING

The solenoid remains in the commanded state until cancelled by the scan tool or until engine speed is detected.

EVAP Vent Solenoid

Engine Output Controls / EVAP System

Activates the EVAP vent solenoid only when the engine is NOT RUNNING. The normal commanded state is NONE. When commanded ON, the vent solenoid valve switches to non-venting. The PCM allows EVAP vent solenoid control when the following conditions are met:

    • No diagnostic trouble codes (DTC) are set
    • The engine is NOT RUNNING

The solenoid remains in the commanded state until cancelled by the scan tool or until engine speed is detected.

Fixed Spark

Engine Output Controls

Controls the ignition timing advance. When entering the output control, the default commanded state is NONE or NORMAL. When commanded ON the ignition timing advance is fixed at 5 degrees. The PCM allows ignition timing control when the following conditions are met:

    • No diagnostic trouble codes (DTC) are set
    • The engine operating temperature is at least 80°C (176°F)
    • The engine is idling at less than 1,000 RPM

The ignition timing remains fixed until cancelled by the scan tool or until an increase in engine speed is detected.

Fuel Trim Reset

Fuel System

Activates the reset of fuel trim data in all of the fuel trim cells. The PCM can be commanded to reset all fuel trim values to zero when the following conditions are met:

    • No diagnostic trouble codes (DTC) are set
    • No engine speed is detected -- the engine is NOT RUNNING

Select data list on the scan tool and observe the Long Term FT parameters. Start the engine and notice that the fuel trim is zero.

Fuel Pump

Engine Output Controls

Controls the fuel pump relay. The normal commanded state is NONE. When commanded ON, the PCM turns the fuel pump relay ON.

The PCM allows the commanded state when the following conditions are met:

    • No diagnostic trouble codes (DTC) are set
    • No engine speed is detected -- the engine is NOT RUNNING

The relay remains in the commanded state until cancelled by the scan tool or until engine speed is detected.

Loop Status

Engine Output Controls

Activates Open or Closed loop fuel control. The normal commanded state is NONE or unchanged from the current state. When activated the fuel control status will match the commanded state.

The PCM allows the commanded state when the following conditions are met:

    • No diagnostic trouble codes (DTC) are set
    • The engine operating temperature is warm enough to allow closed loop fuel control
    • The HO2S is active enough to allow closed loop fuel control
    • No vehicle speed is detected

The system remains in the commanded loop status until cancelled by the scan tool or until vehicle speed is detected.

Malfunction Indicator Lamp

Engine Output Controls

Controls the illumination of the malfunction indicator lamp (MIL). The commanded states include NONE, ON, and OFF. When commanded ON or OFF, the system remains in the commanded state until cancelled by the scan tool.

Radiator Fan

Engine Output Controls

Controls the operation of the A/C condenser fan relay. The normal commanded state is NONE. When commanded ON, the scan tool data list indicates Fan Request YES.

The PCM allows the commanded state when the following conditions are met:

    • No diagnostic trouble codes (DTC) are set
    • The ignition is ON or the engine is running at idle.
    • No vehicle speed is detected
    • Throttle position (TP) sensor input is steady.

The system remains in the commanded state until cancelled by the scan tool, or when vehicle speed or TP sensor input is detected.

RPM Control

IAC System

Activates the Idle Air Control (IAC) valve in order to change engine RPM. The normal commanded state is 1,000 RPM, with a duty cycle of 18-24 percent. IAC valve operation can be monitored on the scan tool data parameter IAC Motor Command. In order to enable RPM control, the vehicle must be in Park or Neutral, and all instructions on the scan tool must be completed. The system will INCREASE or DECREASE the engine speed by 25 RPM increments, within a range of 600 to 1,800 RPM. The IAC Motor Command will increase or decrease accordingly from 15 to 35 percent, at an engine temperature of approximately 80° (176°F).

The PCM allows the commanded state when the following conditions are met:

    • No diagnostic trouble codes (DTC) are set
    • No vehicle speed is detected
    • Throttle position (TP) sensor input remains steady

The system remains in the commanded state until cancelled by the scan tool, or when vehicle speed or TP sensor input is detected.