GM Service Manual Online
For 1990-2009 cars only
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 high speed GMLAN serial data line. The scan tool displays the APP angle in percentage. The APP angle is automatically set to 0 percent at idle, when APP voltage is below 0.90 volts, and reads 100 percent at wide-open throttle (WOT) when APP voltage is 5 volts.

Brake Switch: This parameter displays the state of the brake switch circuit input, based on a signal from the engine control module (ECM). The scan tool will display Applied when the brake pedal is depressed and Released when the brake pedal is released. The ECM sends the brake switch information to the transmission control module (TCM) via the high speed GMLAN serial data line.

Commanded Gear: This parameter displays the current gear commanded by the transmission control module (TCM). 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 displays Enabled/Disabled. The ECM sends the cruise control information to the transmission control module (TCM) via the high speed GMLAN serial data line.

ECT: This parameter displays the input signal from the Engine Coolant Temperature (ECT) sensor. The scan tool displays -40C (-40F) to 151C (304F). When the engine coolant temperature is high at 151C (304F) the signal voltage is low, 0V. When the engine coolant temperature is low at -40C (-40F) 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 Run Time: This parameter displays a measure in Hr:Min:Sec or 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 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.

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

Last 1-2 Shift Status: This parameter displays the shift quality of the last 1-2 gearshift. The scan tool displays Good, Long, Short, Tie-Up, Flare, or Inconclusive. Inconclusive is displayed if the conditions for determining the last shift status were not met.

Last 2-1 Shift Status: This parmaeter displays the shift quality of the last 2-1 gearshift. The scan tool displays Good, Long, Short, Tie-Up, Flare, or Inconclusive. Inconclusive is displayed if the conditions for determining the last shift status were not met.

Last 2-3 Shift Status: This parameter displays the shift quality of the last 2-3 gearshift. The scan tool displays Good, Long, Short, Tie-Up, Flare, or Inconclusive. Inconclusive is displayed if the conditions for determining the last shift status were not met.

Last 2-4 Shift Status: This parameter displays the shift quality of the last 2-4 gearshift. The scan tool displays Good, Long, Short, Tie-Up, Flare, or Inconclusive. Inconclusive is displayed if the conditions for determining the last shift status were not met.

Last 3-2 Shift Status: This parameter displays the shift quality of the last 3-2 gearshift. The scan tool displays Good, Long, Short, Tie-Up, Flare, or Inconclusive. Inconclusive is displayed if the conditions for determining the last shift status were not met.

Last 3-4 Shift Status: This parameter displays the shift quality of the last 3-4 gearshift. The scan tool displays Good, Long, Short, Tie-Up, Flare, or Inconclusive. Inconclusive is displayed if the conditions for determining the last shift status were not met.

Last 4-2 Shift Status: This parameter displays the shift quality of the last 4-2 gearshift. The scan tool displays Good, Long, Short, Tie-Up, Flare, or Inconclusive. Inconclusive is displayed if the conditions for determining the last shift status were not met.

Last 4-3 Shift Status: This parameter displays the shift quality of the last 4-3 gearshift. The scan tool displays Good, Long, Short, Tie-Up, Flare, or Inconclusive. Inconclusive is displayed if the conditions for determining the last shift status were not met.

Last 4-5 Shift Status: This parameter displays the shift quality of the last 4-5 gearshift. The scan tool displays Good, Long, Short, Tie-Up, Flare, or Inconclusive. Inconclusive is displayed if the conditions for determining the last shift status were not met.

Last 5-4 Shift Status: This parameter displays the shift quality of the last 5-4 gearshift. The scan tool displays Good, Long, Short, Tie-Up, Flare, or Inconclusive. Inconclusive is displayed if the conditions for determining the last shift status were not met.

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, indicated high line pressure. A reading of 1.10 amps, a high flow of current, indicates low line pressure.

Line PC Sol. CKT Status: This parameter displays whether an open, short to voltage or ground exists in the line pressure control (PC) solenoid valve feedback signal circuit to the transmission control module (TCM). The scan tool displays OK, Open/Short to Volts, Short to GND.

Line PC Solenoid 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 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 line pressure.

Shift PC Sol. Actual Current: This parameter displays the actual current flow of the shift 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 an actual high shift pressure. A reading of 1.10 amps, a high flow of current, indicates low shift pressure.

Shift PC Sol. CKT Status: This parameter displays whether an open, short to voltage or ground exists in the shift pressure control (PC) solenoid valve feedback signal circuit to the transmission control module (TCM). The scan tool displays OK, Open/Short to Volts, Short to GND.

Shift PC Sol. Duty Cycle: This parameter displays the commanded state of the shift pressure control (PC) solenoid valve. The scan tool displays the percentage of the shift PC solenoid valve energized ON time. A reading of 0 percent indicates zero ON time, a non-energized commanded OFF state. A reading of 100 percent represents an energized commanded ON state.

Shift PC Sol. Ref. Current: This parameter displays the commanded reference current flow of the shift 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 an actual high shift pressure. A reading of 1.10 amps, a high flow of current, indicates low shift pressure.

Shift Solenoid 1: This parameter displays the commanded state of the reverse, 1st shift solenoid valve (S1). The scan tool displays On/Off.

Shift Solenoid 1 CKT Status: This parameter displays whether an open, short to voltage or ground exists in the shift solenoid valve 1 feedback signal circuit to the transmission control module (TCM). The scan tool displays OK, Open/Short to Volts, Short to GND.

Shift Solenoid 2: This parameter displays the commanded state of the 2-3, 3-4 shift solenoid valve (S2). The scan tool displays On/Off.

Shift Solenoid 2 CKT Status: This parameter displays whether an open or short to voltage or ground exists in the 2-3, 3-4 shift solenoid valve (S2) feedback signal circuit to the transmission control module (TCM). The scan tool displays OK, Open/Short to Volts, or Short to GND.

Shift Solenoid 3: This parameter displays the commanded state of the 1-2, 2-3 reverse shift solenoid valve (S3). The scan tool displays On/Off.

Shift Solenoid 3 CKT Status: This parameter displays whether an open or short to voltage or ground exists in the 1-2, 2-3 reverse shift solenoid valve (S3) feedback signal to the transmission control module (TCM). The scan tool displays OK, Open/Short to Volts, or Short to GND.

Shift Solenoid 4: This parameter displays the commanded state of the 3-4, 4-5 shift solenoid valve (S4). The scan tool displays On/Off.

Shift Solenoid 4 CKT Status: This parameter displays whether an open or short to voltage or ground exists in the 3-4, 4-5 shift solenoid valve (S4) feedback signal to the transmission control module (TCM). The scan tool displays OK, Open/Short to Volts, or Short to GND.

Shift Solenoid 5: This parameter displays the commanded state of the reverse shift solenoid valve (S5). The scan tool displays On/Off.

Shift Solenoid 5 CKT Status: This parameter displays whether an open or short to voltage or ground exists in the reverse shift solenoid valve (S5) feedback signal circuit to the transmission control module (TCM).The scan tool displays OK, Open/Short to Volts, or Short to GND.

TCC PC Sol. Actual Current: This parameter displays the actual current of the torque converter clutch (TCC) lock up 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 flowing, indicates a low TCC apply pressure. A reading of 1.10 amps, a high flow of current, indicates a high TCC apply pressure.

TCC PC Sol. CKT Status: This parameter displays whether an open or short to voltage or ground exists in the torque converter clutch (TCC) pressure control (PC) solenoid valve feedback signal to the transmission control module (TCM). The scan tool displays OK, Open/Short to Volts, Short to GND.

TCC PC Sol. Duty Cycle: This parameter displays the commanded ON time of the torque converter clutch (TCC) solenoid valve. A scan tool displays On time in percentage. A reading of 100 percent represents an ON, energized, commanded state. A reading of 0 percent represents a non-energized commanded OFF state.

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

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, or 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 an 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. Oil Life: This parameter displays the transmission oil life remaining. The scan tool displays remaining oil life in percentage. The transmission control module (TCM) determines transmission oil life by calculating transmission fluid temperature and engine run time.

Trans. Protection Mode: This parameter displays if the transmission control module (TCM) is in transmission protection mode. The scan tool displays Yes/No. Yes indicates that a fault has occurred, and that the transmission protection mode is active and has inhibited certain gears as well as taken other actions to prevent damage.

Transmission Hot Mode: This parameter monitors the transmission temperature. The scan tool displays On/Off. Off indicates that the transmission temperature has not exceeded 135C (275F). On Indicates that the transmission temperature has exceeded 140C (284F).

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

Transmission OSS: This parmaeter displays the rotational speed of the automatic transmission output shaft. The scan tool displays output shaft speed as 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 transmission output shaft speed sensor.