This list explains each data message displayed on the scan tool. This information will assist you in tracking down emissions or driveability DTCs, because you can view the displays while you are driving the vehicle. Refer to Diagnostic System Check - Automatic Transmission for additional information.

1-2 Shift Error: This parameter displays the difference between the desired 1-2 shift time and the actual 1-2 shift time. A positive number indicates a firm or fast shift, the actual shift time was shorter than the desired shift time. A negative number indicates a soft or slow shift, the actual shift time was longer than the desired shift time. This value is only accurate if the shift was adaptable.

1-2 Shift Time: This parameter displays the actual time of the last adaptable 1-2 shift. The shift time is based on the gear ratio change after the commanded 1-2 shift.

1-2 Sol.:  This parameter displays the current commanded state of the shift solenoids. All three of the 5L50-E shift solenoids are normally-closed, which means that no fluid passes through when the solenoid is commanded OFF. When commanded ON, the solenoid opens and allows fluid to flow through. Refer to Shift Solenoid Valve State and Gear Ratio .

1-2 Sol. CKT Status: This parameter displays the solenoid valve feedback voltage signal circuit status on the scan tool. If the voltage is low when the solenoid is commanded OFF, the scan tool will display Open/Short to GND. If the voltage is high when the solenoid is commanded ON, the scan tool will display Short to Volts. If no circuit fault is present the scan tool will display OK.

1-2 TAP Cell (4-16): This parameter displays the amount of transmission adaptive pressure (TAP), based on 17 N·m (12.5 lb ft) of engine torque increment per cell, added to or subtracted from shift pressure during a 1-2 upshift. A positive number indicates that long shifts have been detected and PC solenoid pressure has been added in order to decrease shift time. A negative number indicates that short shifts have been detected and PC solenoid pressure has been subtracted in order to increase shift time.

2-3 Shift Error: This parameter displays the difference between the desired 2-3 shift time and the actual 2-3 shift time. A positive number indicates a firm or fast shift, the actual shift time was shorter than the desired shift time. A negative number indicates a soft or slow shift, the actual shift time was longer than the desired shift time. This value is only accurate if the shift was adaptable.

2-3 Shift Time: This parameter displays the actual time of the last adaptable 2-3 shift. The shift time is based on the gear ratio change after the commanded 2-3 shift.

2-3 Sol.: This parameter displays the current commanded state of the shift solenoids. All three of the 5L50-E shift solenoids are normally-closed, which means that no fluid passes through when the solenoid is commanded OFF. When commanded ON, the solenoid opens and allows fluid to flow through. Refer to Shift Solenoid Valve State and Gear Ratio .

2-3 Sol. CKT Status: This parameter displays the solenoid valve feedback voltage signal circuit status on the scan tool. If the voltage is low when the solenoid is commanded OFF, the scan tool will display Open/Short to GND. If the voltage is high when the solenoid is commanded ON, the scan tool will display Short to Volts. If no circuit fault is present the scan tool will display OK.

2-3 TAP Cell (4-16): This parameter displays the amount of transmission adaptive pressure (TAP), based on 17 N·m (12.5 lb ft) of engine torque increment per cell, added to or subtracted from shift pressure during a 2-3 up shift. A positive number indicates that long shifts have been detected and PC solenoid pressure has been added in order to decrease shift time. A negative number indicates that short shifts have been detected and PC solenoid pressure has been subtracted in order to increase shift time.

3-4 Shift Error: This parameter displays the difference between the desired 3-4 shift time and the actual 3-4 shift time. A positive number indicates a firm or fast shift, the actual shift time was shorter than the desired shift time. A negative number indicates a soft or slow shift, the actual shift time was longer than the desired shift time. This value is only accurate if the shift was adaptable.

3-4 Shift Time: This parameter displays the actual time of the last adaptable 3-4 shift. The shift time is based on the gear ratio change after the commanded 3-4 shift.

3-4 TAP Cell (4-16): This parameter displays the amount of transmission adaptive pressure (TAP), based on 17 N·m (12.5 lb ft) of engine torque increment per cell, added to or subtracted from shift pressure during a 3-4 up shift. A positive number indicates that long shifts have been detected and PC solenoid pressure has been added in order to decrease shift time. A negative number indicates that short shifts have been detected and PC solenoid pressure has been subtracted in order to increase shift time.

4-5 Shift Error: This parameter displays the difference between the desired 4-5 shift time and the actual 4-5 shift time. A positive number indicates a firm or fast shift, the actual shift time was shorter than the desired shift time. A negative number indicates a soft or slow shift, the actual shift time was longer than the desired shift time. This value is only accurate if the shift was adaptable.

4-5 Shift Time: This parameter displays the actual time of the last shift. The actual shift time is obtained by measuring the time required for the input shaft to decelerate from the previous ratio to the current ratio.

4-5 Sol.: This parameter displays the current commanded state of the shift solenoids. All three of the 5L50-E shift solenoids are normally-closed, which means that no fluid passes through when the solenoid is commanded OFF. When commanded ON, the solenoid opens and allows fluid to flow through. Refer to Shift Solenoid Valve State and Gear Ratio .

4-5 Sol. CKT Status: This parameter displays the solenoid driver feedback voltage signal and displays the circuit status on the scan tool. If the voltage is low when the solenoid is commanded OFF, the scan tool will display Open/Short to GND. If the voltage is high when the solenoid is commanded ON, the scan tool will display Short to Volts.

4-5 TAP Cell (4-16): This parameter displays the amount of transmission adaptive pressure (TAP), based on 17 N·m (12.5 lb ft) of engine torque increment per cell, added to or subtracted from shift pressure during a 4-5 up shift. A positive number indicates that long shifts have been detected and PC solenoid pressure has been added in order to decrease shift time. A negative number indicates that short shifts have been detected and PC solenoid pressure has been subtracted in order to increase shift time.

A/C Clutch: This parameter displays the commanded state of the air conditioning (A/C) compressor clutch relay driver circuit and displays On or Off. The A/C compressor clutch should be engaged when On displays. When the display indicates On, the line pressure and the shift times will be adjusted for the additional engine load.

Commanded Gear: This parameter displays the current commanded state of the shift solenoid valves. The scan tool displays 1, 2, 3, 4 or 5.

Cruise: This parameter displays the commanded state of the cruise control system. The scan tool display ENABLED or DISABLED. When the display indicates ENABLED, the ECM is allowing cruise control operation. When the display indicates DISABLED, the ECM has disabled cruise control operation. The TCM modifies up shift and downshift patterns when cruise control is enabled.

Current TAP Cell : This parameter displays the current transmission adaptive pressure (TAP) cell in use for transmission line pressure adaptation. The cells are based on 17 N·m (12.5 lb ft) of engine torque. The higher the engine torque, the higher the current TAP cell. The last cell used will remain displayed until the next adaptable up shift occurs.

Driver Shift Control: This parameter displays Active or Inactive. The scan tool displays Active when the gear selector is in the manual (M) position which enables TAP Shift. The scan tool displays Inactive when the gear selector is not in the (M) position, TAP Shift disabled.

Driver Shift Request: This parameter displays the current request from the TAP Shift System. This parameter will display up shift, downshift or invalid depending on the amount of voltage measured at the remote shift selector input and also will display none when there is no request.

ECT: This parameter displays the input signal from the Engine Coolant Temperature (ECT) sensor. The scan tool displays -40°C (-40°F) to 151°C (304°F). When the engine coolant temperature is high at 151°C (304°F), the signal voltage is low, 0V. When the engine coolant temperature is low at -40°C (-40°F), the signal voltage is high, 5V. The ECM sends the ECT information to the transmission control module (TCM) via the high speed GMLAN serial data line.

Engine Speed: This parameter displays the engine speed, based on a signal from the Engine Control Module (ECM). The scan tool displays engine speed in revolutions per minute (RPM). The ECM sends the RPM information to the transmission control module (TCM) via the high speed GMLAN serial data line.

Engine Torque: This parameter displays the estimated amount of torque that is delivered from the engine. The scan tool displays engine torque in N·m (lb ft). The ECM sends the engine torque information to the transmission control module (TCM) via the high speed GMLAN serial data line.

Gear Ratio: This parameter displays the actual transmission gear ratio. The scan tool displays the gear ratio calculated from the automatic transmission input shaft speed sensor (AT ISS) and the automatic transmission output shaft speed sensor (AT OSS) inputs.

High Side Driver 1 : This parameter displays the High Side Driver 1 status on the scan tool. When the High Side Driver 1 is commanded OFF this displays Disabled, when the High Side Driver 1 is commanded ON this displays Enabled.

High Side Driver 1 CKT Status: This parameter displays the High Side Driver 1 circuit status on the scan tool. If the voltage is low when the solenoid is commanded OFF, the scan tool will display Open/Short to GND. If the voltage is high when the solenoid is commanded ON, the scan tool will display Short to Volts. If no circuit fault is present the scan tool will display OK.

High Side Driver 2: This parameter displays the High Side Driver 2 status on the scan tool. When the High Side Driver 2 is commanded OFF this displays Disabled, when the High Side Driver 2 is commanded ON this displays Enabled.

High Side Driver 2 CKT Status: This parameter displays the High Side Driver 2 circuit status on the scan tool. If the voltage is low when the solenoid is commanded OFF, the scan tool will display Open/Short to GND. If the voltage is high when the solenoid is commanded ON, the scan tool will display Short to Volts. If no circuit fault is present the scan tool will display OK.

Ignition Voltage: This parameter displays the system voltage measured at the ignition feed.

IMS: This parameter displays PARK, PARK/REVERSE, REVERSE, REVERSE/NEUTRAL, NEUTRAL, NEUTRAL/DRIVE 5, DRIVE 5, DRIVE 5/DRIVE 4, DRIVE 4, DRIVE 4/DRIVE 3, DRIVE 3, DRIVE 3/DRIVE 2, DRIVE 2, or INVALID. The IMS Range display represents a decoded status of the four inputs from the IMS. The combination of IMS inputs are used to determine what position the manual valve is in at any time.

IMS A/B/C/P: This parameter displays the status of the four A/B/C/P inputs from the automatic transmission internal mode switch. I indicates an ignition voltage signal and LOW indicates a 0 voltage signal. The scan tool will display HI/LOW,HI/LOW,HI/LOW,HI/LOW.

Last Shift Time: This parameter displays the actual time of the last up shift. This value is only accurate if the shift was adaptable.

PC Sol. Actual Current: This parameter displays the actual current flow through the pressure control solenoid circuit which is measured by the control module. High current flow results in low line pressure. Low current flow results in high line pressure.

PC Sol. Ref. Current: This parameter displays the commanded current of the pressure control solenoid circuit. High current results in low line pressure. Low current results in high line pressure.

PC Solenoid Duty Cycle: This parameter displays the commanded state of the pressure control solenoid expressed as a percentage of energized ON time. A reading of low percent indicates zero ON time, non energized, or no current flow. A high percent at idle indicates maximum ON time, energized, or high current flow.

Steady State TAP 1 GR: This parameter displays a pressure modification which is added to the line pressure in 1st gear. The larger the value, the greater the increase to line pressure.

Steady State TAP 1 GR/TCC: This parameter displays a pressure modification which is added to the line pressure in 1st gear with TCC applied. The larger the value, the greater the increase to line pressure.

Steady State TAP 2 GR: This parameter displays a pressure modification which is added to the line pressure in 2nd gear. The larger the value, the greater the increase to line pressure.

Steady State TAP 2 GR/TCC: This parameter displays a pressure modification which is added to the line pressure in 2nd gear with TCC applied. The larger the value, the greater the increase to line pressure.

Steady State TAP 3 GR: This parameter displays a pressure modification which is added to the line pressure in 3rd gear. The larger the value, the greater the increase to line pressure.

Steady State TAP 3 GR/TCC: This parameter displays a pressure modification which is added to the line pressure in 3rd gear with TCC applied. The larger the value, the greater the increase to line pressure.

Steady State TAP 4 GR: This parameter displays a pressure modification which is added to the line pressure in 4th gear. The larger the value, the greater the increase to line pressure.

Steady State TAP 4 GR/TCC: This parameter displays a pressure modification which is added to the line pressure in 4th gear with TCC applied. The larger the value, the greater the increase to line pressure.

Steady State TAP 5 GR: This parameter displays a pressure modification which is added to the line pressure in 5th gear. The larger the value, the greater the increase to line pressure.

Steady State TAP 5 GR/TCC: This parameter displays a pressure modification which is added to the line pressure in 5th gear with TCC applied. The larger the value, the greater the increase to line pressure.

Steady State TAP Reverse: This parameter displays a pressure modification which is added to the line pressure in Reverse gear. The larger the value, the greater the increase to line pressure.

TCC Brake Switch: This parameter displays the status of the TCC brake switch circuit input. OPEN indicates a zero voltage input, brake pedal applied. CLOSED indicates a voltage input, brake pedal released. The scan tool display OPEN or CLOSED.

TCC Duty Cycle: This parameter displays the commanded percentage of ON time of the TCC PWM solenoid. A high percentage represents an ON, energized, commanded state. 0 percent represents an OFF, non-energized, commanded state.

TCC Duty Cycle CKT Status: This parameter displays the solenoid driver feedback voltage signal and displays the circuit status on the scan tool. If the voltage is low when the solenoid is commanded OFF, the scan tool will display Open/Short to GND. If the voltage is high when the solenoid is commanded ON, the scan tool will display Short to Volts. If no circuit fault is present the scan tool will display OK.

TCC Slip Speed: This parameter displays the difference between transmission input speed and engine speed. A negative value indicates that the engine speed is less than the input speed, deceleration. A positive value indicates that the engine speed is greater than the input speed, acceleration. A value of zero indicates that the engine speed is equal to the input speed, TCC applied.

TP Angle: This parameter displays the throttle position (TP) sensor angle based on the TP sensor voltage input. The ECM sends the TP angle information to the transmission control module (TCM) via the high speed GMLAN serial data line. The scan tool displays the TP angle in percentage. The TP angle is automatically set to 0 percent at idle, when TP voltage is below 0.90 volt, and reads 100 percent at wide-open throttle (WOT) when TP voltage is 5 volts.

Traction Control: This parameter displays Active or Inactive. When the PCM receives a request for torque reduction from the electronic brake traction control module (EBTCM), Active is displayed.

Trans. Fluid. Temp.: This parameter displays the input signal of the transmission fluid temperature sensor. Transmission fluid temperature is high 151°C (304°F) when signal voltage is low, 0 V, and transmission fluid temperature is low -40°C (-40°F ) when signal voltage is high, 5 V.

Trans. Oil Life: This parameter displays the transmission oil life remaining. The scan tool displays remaining oil life in percentage. The transmission oil life is calculations is based on transmission fluid temperature and engine run time.

Transmission Hot Mode: This parameter displays the automatic transmission fluid temperature (TFT) and displays On or Off. Off indicates that the TFT has not exceeded 130°C (266°F). On indicates that the TFT has exceeded 130°C (266°F) and has not cooled to 120°C (248°F) for more that 5 seconds. Note: these numbers are approximate. They differ with transmissions.

Transmission ISS: This parameter displays the rotational speed of the transmission input shaft. The scan tool displays input shaft speed is revolutions per minute (RPM).

Transmission OSS: This parameter displays the rotational speed of the transmission output shaft expressed as revolutions per minute.

Vehicle Speed: This parameter displays the speed at which the vehicle is traveling. The scan tool displays vehicle speed as kilometers per hour (km/h), (miles per hour (MPH)). The vehicle speed is calculated based on the input signal from the automatic transmission output shaft speed sensor.