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.

APP Angle: The engine control module (ECM) computes the accelerator pedal position (APP) sensor angle from the APP sensor voltage input. The ECM sends the APP angle information to the transmission control module (TCM) via the control area network (CAN) serial data link line. The scan tool displays the APP angle in percentage. The APP angle is automatically set to 0 percent at idle, when the APP voltage is below 0.90 volts, and reads 100 percent at wide open throttle (WOT) when APP voltage is 5 volts. The ECM sends the APP angle information to the transmission control module (TCM) via the high speed GMLAN serial data line.

Brake Switch: This parameter displays the state of the brake switch. The scan tool will display Applied when the brake pedal is depressed and Released when the brake pedal is released.

Desired Speed Ratio: This parameter displays the current speed ratio commanded by the transmission control module (TCM).

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, 0 V. When the engine coolant temperature is low at -40°C (-40°F), the signal voltage is high, 5 V. The ECM sends the ECT information to the transmission control module (TCM) via the high speed GMLAN serial data line.

Engine Run Time: This parameter displays a measure in Hr:Min:Sec of how long the engine has been operating. When the ignition is cycled to OFF, the value is reset to zero. The ECM sends the engine run time information to the transmission control module (TCM) via the high speed GMLAN serial data line.

Engine Speed: This parameter displays a measure in Hr:Min:Sec of how long the engine has been operating. When the ignition is cycled to OFF, the value is reset to zero. The ECM sends the engine run time 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.

Ignition Voltage: This parameter displays the system voltage, which is measured by the transmission control module (TCM) at the TCM ignition voltage input circuit. The scan tool displays the TCM input voltage in volts.

Line PC Sol. Actual Current: This parameter displays the actual current flow of the line pressure control (PC) solenoid valve circuit at the transmission control module (TCM). The scan tool displays current flow in amps. A reading of 0.00 amps, no current is flowing, indicates high line pressure. A reading of 1.10 amps, a high flow of current, indicates low pressure.

Line PC Sol. Duty Cycle: This parameter displays the commanded state of the line pressure control (PC) solenoid valve. The scan tool displays the percentage of the PC solenoid valve energized On time. A reading of 0 percent indicates zero On time, or a non-energized, commanded Off, state. A reading of 100 percent represents a fully energized, commanded On, state.

Line PC Sol. Ref. Current: This parameter displays the commanded reference current flow of the line pressure control (PC) solenoid valve circuit commanded by the transmission control module (TCM). The scan tool displays current flow in amps. A reading of 0.00 amps, no current is flowing, indicates high line pressure. A reading of 1.10 amps, a high flow of current, indicates low pressure.

Line Pressure Actual: This parameter displays the transmission fluid pressure (TFP) sensor signal to the transmission control module (TCM). The TFP sensor sends a signal proportional to the pressure in the tier 2 feed pressure circuit. When the pressure in this circuit is low a low signal voltage signal will be sent, and a high signal voltage is sent when the pressure in the circuit is high.

Line Pressure Commanded: This parameter displays the commanded main line pressure by the transmission control module (TCM).

Ratio Ctrl. Mtr. Actual: This parameter displays the commanded position of the ratio control motor position in counts. The higher the number of counts, the higher the speed ratio. The ratio control motor will compensate for varying driving conditions and driver input.

Ratio Ctrl. Mtr. CKT A1 Status: This parameter displays whether an open/short to ground, or short to voltage exists in the ratio control motor A1 control circuit. The scan tool displays OK, Open/Short to GND, Short to Volts.

Ratio Ctrl. Mtr. CKT A2 Status: This parameter displays whether an open/short to ground, or short to voltage exists in the ratio control motor A2 control circuit. The scan tool displays OK, Open/Short to GND, Short to Volts.

Ratio Ctrl. Mtr. CKT B1 Status: This parameter displays whether an open/short to ground, or short to voltage exists in the ratio control motor B1 control circuit. The scan tool displays OK, Open/Short to GND, Short to Volts.

Ratio Ctrl. Mtr. CKT B2 Status: This parameter displays whether an open/short to ground, or short to voltage exists in the ratio control motor A2 control circuit. The scan tool displays OK, Open/Short to GND, or Short to Volts.

Ratio Ctrl. Mtr. Commanded: This parameter displays the commanded position of the ratio control motor pintle in counts. During steady state operation, 40 counts would indicate the lowest speed ratios being commanded and approximately 2700 counts would correspond to the highest speed ratios being commanded.

Ratio Ctrl. Mtr. Dither: This parameter displays whether the ratio control motor is being commanded to vibrate rapidly. The scan tool displays Active, or Inactive.

Sheave Ratio: This parameter displays the calculated speed ratio of the transmission. The ratio is calculated by dividing the input speed sensor signal by the output speed sensor signal. This ratio is similar to gear ratio in a step-gear transmission.

Shifter Inhibit: This parameter displays whether the shifter is being locked in the Park position because of low transmission fluid temperature. Once the transmission fluid temperature is above a calibrated value the shifter will operate normally. The scan tool displays Normal or Low TFT.

Speed Ratio: This parameter displays the calculated speed ratio of the transmission. The ratio is calculated by dividing the output speed sensor signal by the input speed sensor signal. Gear ratio in a step-gear transmission is calculated in the opposite manner.

TCC Enable Solenoid: This parameter displays the commanded state of the torque converter clutch (TCC) enable solenoid. The scan tool displays Enabled or Disabled.

TCC PC Sol. Actual Current: This parameter displays the actual current flow of the torque converter clutch (TCC) pressure control (PC) solenoid valve circuit at the transmission control module (TCM). The scan tool displays current flow in amps. A reading of 0.00 amps, no current is flowing, indicates a low TCC apply pressure. A reading of 1.10 amps, a high flow of current, indicates a high apply TCC pressure.

TCC PC Sol. Duty Cycle: This parameter displays the commanded On time of the torque converter clutch (TCC) pressure control (PC) solenoid valve. The scan tool displays On time in a percentage. A reading of 100 percent represents a fully energized, commanded On, state.

TCC PC Sol. Ref. Current: This parameter displays the reference current flow of the torque converter clutch (TCC) pressure control (PC) solenoid valve circuit commanded by the transmission control module (TCM). The scan tool displays current flow in amps. A reading of 0.00 amps, no current is flowing, indicates a low TCC apply pressure. A reading of 1.10 amps, a high flow of current, indicates a high apply TCC pressure.

TCC Slip Speed: This parameter displays the amount of torque converter clutch (TCC) slip between the engine and the transmission input shaft. The scan tool displays the TCC slip speed in revolutions per minute (RPM).

TCC Tap Cell 1-5: This parameter displays the offset pressure values stored in the TCC transmission adaptive pressure (TAP) cells for TCC operation. Each TAP cell stores the commanded pressure offset needed for proper TCC system operation within a fixed engine torque range. A low cell number corresponds to a low torque range and each subsequent cell corresponds to the next engine torque range. A positive value within a given cell indicates that the TCC system applied slowly or softer than expected and a pressure increase was commanded. Conversely, a negative value indicates that the TCC system applied faster or harsher than expected and a pressure decrease was commanded.

TR Sw.: This parameter displays the decoded status of the four A/B/C/P inputs from the transmission range switch. The scan tool displays Park, Reverse, Neutral, Drive, Intermediate, Low, and Invalid. Invalid is displayed when the transmission control module (TCM) does not recognize a valid combination of inputs.

TR Sw. A/B/C/P: This parameter displays the status of the four inputs from the transmission range switch to the transmission control module (TCM). The scan tool displays Hi/Low. Hi indicates ignition voltage input to the TCM. Low indicates a zero voltage input to the TCM.

Trans. Fluid Temp.: This parameter displays the transmission fluid temperature (TFT) sensor input to the transmission control module (TCM). The scan tool displays the TCM converted TFT sensor resistance in degrees. Transmission fluid temperature is used in order to determine when to execute hot mode operation.

Trans. Component Slip: This parameter displays the amount of slip calculated in the components between the input shaft and the output shaft. The components that can be responsible for this slip may be the forward or reverse clutch, and the drive belt. The calculations are performed continuously, and during harsh transitions slip may report when all the drive components are performing well. However, when driving at a constant speed over a level surface, slip above 800 RPM may indicate a problem with the transmission components.

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

Transmission OSS: This parameter displays the rotational speed of the transmission output shaft. The scan tool displays output shaft speed in revolutions per minute (RPM).

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 transmission control module (TCM) calculates vehicle speed based on the input signal from the automatic output shaft speed sensor.