GM Service Manual Online
For 1990-2009 cars only

Scan Tool Output Control

Additional Menu Selection(s)

Description

A/C Relay

Engine Output Controls

Activates the A/C compressor relay. The normal commanded state of the A/C relay is NONE. The relay status can also be monitored on the scan tool data parameter A/C Relay Command. The powertrain control module (PCM) will inhibit the operation of the A/C relay when the ambient air temperature is low enough to cause icing of the evaporator core.

EGR Solenoid

Engine Output Controls

Activates the EGR valve. The normal commanded state is NONE. When commanded ON, the EGR valve position is commanded in 10 percent duty cycle increments.

    • The transmission must be in Park or Neutral.
    • The engine coolant temperature is 85°C (185°F) or more.
    • No vehicle speed is detected

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

Engine Speed Control

Throttle Control System

Activates the throttle actuator control (TAC) motor in order to change engine speed. The normal commanded state is a 9-14 percent throttle plate opening. The PCM allows engine speed control when the following conditions are met:

    • The transmission must be in Park or Neutral.
    • The throttle position (TP) sensor is indicating the throttle is at idle.
    • The engine coolant temperature is 85°C (185°F) or more.
    • No vehicle speed is detected

The system will INCREASE or DECREASE the engine speed from 500-2,000 RPM. The system remains in the commanded state until cancelled by the scan tool or when 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 solenoid is commanded ON in 10 percent increments, with a maximum scan tool command of 20 percent duty cycle. The solenoid remains in the commanded state until cancelled by the scan tool or until vehicle speed is detected.

EVAP Vent Solenoid

Engine Output Controls / EVAP System

Activates the EVAP vent solenoid. The normal commanded state is NONE. When commanded ON, the vent valve switches to non-venting. The solenoid remains in the commanded state until cancelled by the tool or until vehicle speed is detected.

EVAP Purge/Seal

Engine Output Controls / EVAP System

Activates the EVAP purge and vent solenoids. The normal commanded state is NONE. When INCREASE is selected the following commands are executed:

    • The purge solenoid is commanded ON, open, at 10 or 20 percent duty cycle.
    • The vent solenoid is commanded ON, closed.

The purge solenoid will remain ON until cancelled or the FTP sensor detects a negative pressure greater than -23.45 mm Hg (-12.50 in H2O).

When SEAL is selected the following commands are executed:

    • The purge solenoid is commanded OFF, closed.
    • The vent solenoid is commanded ON, closed.

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

Fan Relay 1

Engine Output Controls / Fan Relays

Operates both engine cooling fans at low speed by enabling fan relay 1. The normal commanded state of the relay is NONE. The PCM allows relay control when the following conditions are met:

    • The ignition is ON, with the engine OFF.
    • The transmission must be in Park or Neutral.
    • The A/C request is OFF.
    • The engine coolant temperature is less than 100°C (212°F).

Fan Relay 2

Engine Output Controls / Fan Relays

This function operates both engine cooling fans at high speed by enabling all three cooling fan relays. The normal commanded state of the relay is NONE. The PCM allows relay control when the following conditions are met:

    • The ignition is ON, with the engine OFF.
    • The transmission must be in Park or Neutral.
    • The A/C request is OFF.
    • The engine coolant temperature is less than 100°C (212°F).

Fuel Injector Flow Test

Fuel System

This function activates the selected fuel injector in order to verify the correct fuel injector flow. The ECM commands the fuel pump ON when the test is initiated and pulses the selected fuel injector on the second prompt. The normal commanded state is None. The scan tool initiates the test when the following conditions are met:

    • The ignition is ON, with the engine OFF.
    • The vehicle speed is 0 km/h (0 mph).

If any fuel injector needs to be tested again, the engine must be started and idled for 30 seconds.

Fuel Pump

Fuel System

This function controls the fuel pump relay. The normal commanded state is NONE.

    • Condition 1--Engine is running
        When the engine is running the fuel pump relay can be commanded OFF if engine speed is less than 1,200 RPM and TP is at idle. The relay remains in the commanded state for 5 minutes or until cancelled by the scan tool.
    • Condition 2--Engine is not running
        When the engine is not running the fuel pump relay can be commanded ON. The relay remains in the commanded state until cancelled by the scan tool or until engine speed is detected.

HO2S Bank 1 Sensor 1 Heater

Engine Output Controls / HO2S Heater Controls

This function controls the selected HO2S heater control circuit. The normal commanded state is NONE. The system will command ON the heater for 1 second. In order to repeat the test, the ignition switch must be cycled On to Off, wait 5 seconds, then back to On. The PCM allows heater control when the following conditions are met:

    • The transmission must be in Park or Neutral.
    • The engine is not running.
    • The engine coolant temperature is less than 100°C (212°F).
    • No vehicle speed is detected

HO2S Bank 1 Sensor 2 Heater

Engine Output Controls / HO2S Heater Controls

This function controls the selected HO2S heater control circuit. The normal commanded state is NONE. The system will command ON the heater for 1 second. In order to repeat the test, the ignition switch must be cycled On to Off, wait 5 seconds, then back to On. The PCM allows heater control when the following conditions are met:

    • The transmission must be in Park or Neutral.
    • The engine is not running.
    • The engine coolant temperature is less than 100°C (212°F).
    • No vehicle speed is detected

HO2S Bank 2 Sensor 1 Heater

Engine Output Controls / HO2S Heater Controls

This function controls the selected HO2S heater control circuit. The normal commanded state is NONE. The system will command ON the heater for 1 second. In order to repeat the test, the ignition switch must be cycled On to Off, wait 5 seconds, then back to On. The PCM allows heater control when the following conditions are met:

    • The transmission must be in Park or Neutral.
    • The engine is not running.
    • The engine coolant temperature is less than 100°C (212°F).
    • No vehicle speed is detected

HO2S Bank 2 Sensor 2 Heater

Engine Output Controls / HO2S Heater Controls

This function controls the selected HO2S heater control circuit. The normal commanded state is NONE. The system will command ON the heater for 1 second. In order to repeat the test, the ignition switch must be cycled On to Off, wait 5 seconds, then back to On. The PCM allows heater control when the following conditions are met:

    • The transmission must be in Park or Neutral.
    • The engine is not running.
    • The engine coolant temperature is less than 100°C (212°F).
    • No vehicle speed is detected

Intake Rocker Arm Actuator Solenoid

Engine Output Controls

Activates the rocker arm oil control solenoid valve. The normal commanded state of the rocker arm oil control solenoid is NONE. When commanded ON, the rocker arm oil control solenoid opens the oil passage to the rocker arm assemblies. The PCM allows solenoid control when the following conditions are met:

    • DTC P2646, P2647, P2648, or P2649 are not set.
    • The engine is running and engine speed is more than 2,500 RPM.
    • The engine coolant temperature is 85°C (185°F) or more.
    • No vehicle speed is detected

The solenoid remains in the commanded state until any of the following conditions occur:

    • Cancelled by the scan tool
    • Engine speed drops below 2,500 RPM
    • Vehicle speed is detected

Reset TPS Learn Value

Throttle Control System

This function commands the PCM to set the TPS Learned Value in the control module to zero percent. The PCM accepts a TPS learned value reset command when the following conditions are met:

    • The engine is not running.
    • The APP sensors indicate there is no driver input.

Throttle Actuator Control

Throttle Control System

This function controls the throttle plate position in 1 percent increments. The PCM allows TAC motor control when the following conditions are met:

    • There are no TAC system or accelerator position (APP) system DTCs set.
    • The transmission must be in Park or Neutral.
    • The engine coolant temperature is 85°C (185°F) or more.
    • No vehicle speed is detected

TAC Module Power Inhibit

Throttle Control System

This function commands the throttle plate to the power inhibit position for approximately 2 seconds. The PCM sets the TAC motor to the power inhibit position when the following conditions are met:

    • There are no TAC system or accelerator position (APP) system DTCs set.
    • The engine is not running.