Transmission Control Module Scan Tool Information

The Transmission Control Module Scan Tool Data List contains all transmission related parameters that are available on the scan tool. The list is arranged in alphabetical order. A given parameter may appear in any one of the data lists, and in some cases may appear more than once, or in more than one data list in order to group certain related parameters together.

The values below represent a typical display recorded from a properly functioning system.

NOTE:

Do not use a scan tool that displays faulty data. Report the condition to the scan tool manufacturer. The use of a faulty scan tool can result in misdiagnosis and the unnecessary replacement of components.

Only the parameters listed below are used/referenced in this manual for diagnosis. If a scan tool displays other parameters, those values are not recommended by General Motors for use in diagnosis.

If all values are within the expected range described below, refer to Symptoms - Automatic Transmission for diagnosis.

The scan tool values from a properly functioning transmission may be used for comparison with the transmission you are diagnosing. The values below represent a typical display recorded from a properly functioning system.

Scan Tool Data Parameters

Parameter	System State	Expected Value	Description
Operating Conditions: Engine at idle, upper radiator hose hot, closed throttle, transmission in Park, closed loop operation, accessories OFF, brake pedal not applied.
A/T ISS	Varies	RPM	This parameter displays the rotational speed of the transmission input shaft. The scan tool displays input shaft speed is revolutions per minute (RPM).
A/T OSS	Varies	RPM	This parameter displays the rotational speed of the transmission output shaft expressed as revolutions per minute.
Current Gear	P	P/N, 1st/2nd/3rd/4th/R gear	This parameter displays the current gear state.
Emergency Mode	Inactive	Active/Inactive	This parameter displays the status of the emergency mode. The scan tool displays Active/Inactive. Active indicates that a fault has occurred, and that the emergency mode is active and has inhibited certain gears, as well as taken other actions to prevent damage.
Engine Speed	Varies	RPM	This parameter displays the rotational speed of the engine expressed as revolutions per minute.
PC Sol. Duty Cycle	Varies	%	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.
PRND Position	P	P/N, 1, 2, D, R, Fault	This parameter displays the current commanded gear lever position state.
TCC PC Sol. Duty Cycle	Varies	%	This parameter displays the commanded On time of the torque converter clutch (TCC) solenoid valve. The scan tool displays On time in percentage. A reading of 100 percent represents an energized, commanded On state. A reading of 0 percent represents a non-energized commanded OFF state.
TCC Slip Speed	Varies	RPM	This parameter displays the difference between transmission input speed and engine speed. A negative value indicates the engine speed is less than the input speed, deceleration. A positive value indicates the engine speed is greater than the input speed acceleration. A value of zero indicates the engine speed is equal to the input speed, TCC applied.
Torque Reduction	Varies	%	This parameter displays the percentage for current torque made by the engine.
TP Angle	Varies	%	This parameter displays a percentage that is calculated based on TP sensor voltage. The TP angle should display 0 percent at idle and 100 percent at wide open throttle (WOT).
Transmission Fluid Temperature	Varies	°C	This parameter displays the input signal of the transmission fluid temperature sensor.
Vehicle Speed	Varies	km/h	This parameter displays the speed at which the vehicle is traveling. The scan tool displays vehicle speed as kilometers per hour (km/h). The vehicle speed is calculated based on the input signal from the automatic transmission output speed sensor.

Scan Tool Output Controls

Output Control	Description
Shift Solenoid: Shift Solenoid 1 Shift Solenoid 2	The TCM commands Shift Solenoid 1 and Shift Solenoid 2 ON and OFF. When the ignition is ON, and the engine is OFF, there are no limits to this control. The solenoid remains ON until commanded OFF, and vice versa. When the output control is exited, the solenoid state is determined by the TCM.
Lock-Up Duty Solenoid	The transmission control module (TCM) commands the torque converter clutch pressure control (TCC PC) solenoid pressure in order to apply and release the TCC. When the ignition is ON, and the engine is OFF, there are no limits to this control. The solenoid remains ON until commanded OFF and vice versa. This control is used to control the duty cycle for Lock Up Solenoid.
Line PC Solenoid	It regulates pilot pressure applied to pressure modifier valve. There are no limits to the output control when the engine is OFF.