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For 1990-2009 cars only
Makes 🢒 Buick 🢒 2008 🢒 LaCrosse 🢒 Transmission/Transaxle 🢒 Automatic Transaxle - 4T65-E 🢒 Transmission Control Module Scan Tool Information
Table 1: Scan Tool Data Parameters
Table 2: Scan Tool Output Controls

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.

Important: 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 parts.

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

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.

1-2 Shift Error

Seconds, Varies

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

Seconds, Varies

This parameter displays the actual time of the last 1-2 shift. The shift time is based on the engine RPM drop after the commanded 1-2 shift. This value is only accurate if the shift was adaptable.

1-2 Sol.

On

This parameter displays the commanded state of the 1-2 shift solenoid valve. When the transmission is in FIRST and FOURTH gear, the display should indicate ON, current is flowing trough the solenoid. When the transmission is in SECOND and THIRD gear, the display should indicate OFF, current is not flowing through the solenoid.

1-2 Sol. CKT Status

Indeterminate

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)

kPa/psi, Varies

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

Seconds, Varies

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

Seconds, Varies

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.

On

This parameter displays the commanded state of the 2-3 shift solenoid valve. When the transmission is in FIRST and SECOND gear, the display should indicate ON, current is not flowing trough the solenoid. When the transmission is in THIRD and FOURTH gear, the display should indicate OFF, current is flowing through the solenoid.

2-3 Sol. CKT Status

Indeterminate

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)

kPa/psi, Varies

This parameter displays the amount of 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 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.

3-4 Shift Error

Seconds, Varies

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

Seconds, Varies

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)

kPa/psi, Varies

This parameter displays the amount of 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 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.

Brake Switch

Released

This parameter displays the status of the brake switch circuit input. Applied indicates a zero voltage input, brake pedal applied. Released indicates a voltage input, brake pedal released. The scan tool displays Applied or Released.

Calc. Throttle Position

%, 0

This parameter displays a calculated value, which is determined by the accelerator pedal position and the actual throttle position, used to optimize transmission controls. It represents the driver’s intended request for torque or acceleration. The range is 0-100 percent, where 0 percent represents an idle or coast request and 100 percent represents a request for wide open throttle (WOT).

Commanded Gear

1

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

Current TAP Cell

4-16, Varies

This parameter displays the current 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 upshift occurs.

ECT

°C (°F), Varies

This parameter displays the input signal from the engine coolant temperature (ECT) sensor. ECT is high at 151°C (304°F) when the signal voltage is low, 0 volt. ECT is low at -40°C (-40°F) when the signal voltage is high, 5 volt.

Engine Speed

600-850 RPM

This parameter displays the rotational speed of the engine expressed as revolutions per minute (RPM).

Engine Torque

N·m (lb ft), Varies

This parameter displays a calculated value based on engine load, throttle position, mass air flow, and other engine inputs. This parameter is accurate to within 20 N·m (15 ft lb) of actual measured engine torque.

Gear Ratio

Ratio, 3.98

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

12.5-14.5 Volts

This parameter displays the system voltage measured at the ignition feed.

IMS

PARK

This parameter displays PARK, PARK/REVERSE, REVERSE, REVERSE/NEUTRAL, NEUTRAL, NEUTRAL/DRIVE 4, DRIVE 4, DRIVE 4/DRIVE 3, DRIVE 3, DRIVE 3/DRIVE 2, DRIVE 2, DRIVE 2/DRIVE 1, DRIVE 1 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 which position the manual valve is in at any time.

IMS A/B/C/P

LOW/HI/HI/LOW

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. LOW indicates a 0 voltage signal. The scan tool will display HI/LOW, HI/LOW, HI/LOW, HI/LOW.

Last Shift Time

Seconds, Varies

This parameter displays the actual time of the last upshift. This value is only accurate if the shift was adaptable.

PC Sol. Actual Current

0.95-1.05 Amps

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. Duty Cycle

45-55%

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.

PC Sol. Ref. Current

0.95-1.05 Amps

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.

Steady State TAP 1GR

kPa/psi, Varies

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 2GR

kPa/psi, Varies

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 2GR/TCC

kPa/psi, Varies

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 3GR

kPa/psi, Varies

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 3GR/TCC

kPa/psi, Varies

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 4GR

kPa/psi, Varies

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 4GR/TCC

kPa/psi, Varies

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 Reverse

kPa/psi, Varies

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 Duty Cycle

0%

This parameter displays the commanded percentage of ON time for 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

Indeterminate

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 Release Pressure

Yes

This parameter displays the status of the normally closed TCC release switch and displays YES or NO. When TCC release fluid pressure is present, the switch is open, indicating that the TCC is released. When the fluid pressure is not present, the switch is closed, indicating that the TCC is applied.

TCC Slip Speed

RPM, Varies

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

Traction Control

Inactive

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.

°C (°F), Varies

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 volt. Transmission fluid temperature is low, -40°C (-40°F), when signal voltage is high, 5 volt.

Transmission Hot Mode

Off

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 greater that 5 seconds. These numbers are approximate and differ with transmissions.

Transmission ISS

650-800 RPM

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

Transmission OSS

0 RPM

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

Vehicle Speed

0 km/h (0 MPH)

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 vehicle speed sensor.

Scan Tool Output Controls

Output Control

Description

1-2 Solenoid
    • The powertrain control module (PCM) commands the 1-2 shift solenoid valve ON and OFF. The scan tool 1-2 Sol. parameter should match the commanded state. The scan tool Commanded Gear parameter should correspond with the shift solenoid combination. Refer to Shift Solenoid Valve State and Gear Ratio .
    • 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 PCM.
    • When the engine is running, the following control limits apply:
       - Only sequential gear changes are allowed. For example, 1st to 3rd is not allowed. If a non-sequential gear change is attempted, the message "Non-sequential gear changes not allowed. Gear changes must be in order" appears on the scan tool display.
       - The vehicle speed must be below a calibrated value. If the vehicle speed is too high, the message "Vehicle speed too high" appears on the scan tool display.
       - The gear requested may not be greater than the current selected transmission range (PRNDL). For example, 3rd gear is not allowed if the transmission range is D2. If the gear requested is greater than the current selected transmission range, the message "Eng. running and gear request is greater than the current TR" appears on the scan tool display.
       - The solenoid remains ON until commanded OFF, and vice versa. When the output control is exited, the solenoid state is determined by the PCM.

2-3 Solenoid
    • The PCM commands the 2-3 shift solenoid valve ON and OFF. The scan tool 2-3 Sol. parameter should match the commanded state. The scan tool Commanded Gear parameter should correspond with the shift solenoid combination. Refer to Shift Solenoid Valve State and Gear Ratio .
    • When the ignition is ON, and the engine is OFF, there are no limits to this control. The solenoid will remain ON until commanded OFF, and vice versa. When the output control is exited, the solenoid state is determined by the PCM.
    • When the engine is running, the following control limits apply:
       - Only sequential gear changes are allowed. For example, 1st to 3rd is not allowed. If a non-sequential gear change is attempted, the message "Non-sequential gear changes not allowed. Gear changes must be in order" appears on the scan tool display.
       - The vehicle speed must be below a calibrated value. If the vehicle speed is too high, the message "Vehicle speed too high" appears on the scan tool display.
       - The engine speed must be below a calibrated value. If the engine speed is too high, the message "Engine speed too high" appears on the scan tool display.
       - Downshifts are allowed only when the vehicle speed is below a calibrated value. If the vehicle speed is too high, the message "Eng. is on and veh. speed too hi for 3-2 or 2-1 downshift" appears on the scan tool display.
       - The gear requested may not be greater than the current selected transmission range (PRNDL). For example, 3rd gear is not allowed if the transmission range is D2. If the gear requested is greater than the current selected transmission range, the message "Eng. running and gear request is greater than the current TR" appears on the scan tool display.
       - The solenoid remains ON until commanded OFF, and vice versa. When the output control is exited, the solenoid state is determined by the PCM.

Reset Transmission Adapts
    • The PCM clears, or resets, the TAP cells to the original base value.
    • There are no limits to using this output control. It may be performed with the engine running or when the ignition is ON, and the engine is OFF.

PC Solenoid
    • The PCM commands the amperage, current, to the pressure control solenoid valve in order to control transmission line pressure. As the amperage increases, the line pressure decreases. As the amperage decreases, the line pressure increases. The amperage range is 0.00-1.10 and may be commanded in one-tenth amp increments.
    • When the ignition is ON, and the engine is OFF, the reference, commanded, amperage may be controlled within calibrated limits. The scan tool parameter "PC Sol. Ref. Current" changes, but the parameter "PC Sol. Actual Current" does not change. The reference current remains until commanded otherwise.
    • When the engine is running, the following control limits apply:
       - When the transmission range is PARK or NEUTRAL, the reference, commanded, amperage may be controlled within calibrated limits. The engine speed must be less than 1,500 RPM. If the engine speed is greater than 1,500 RPM, the message "TR in park/neutral and engine speed over 1,500 RPM" appears on the scan tool display. Both the scan tool parameters "PC Sol. Ref. Current" and "PC Sol. Actual Current" change. Both current readings remain until commanded otherwise.
       - When the transmission range is not in PARK or NEUTRAL, the reference amperage can only be controlled less than the current determined by the PCM. The PCM does not allow a value to be selected that may cause damage to the transmission. If the requested amperage is more than allowed by the PCM, the message "Requested current for the PC Solenoid is too high" appears on the scan tool display.
       - Transmission range DTCs must not be active. If a transmission range DTC is active, the message "Engine running with transmission DTC present" appears on the scan tool display.

Shift Transmission
    • The PCM commands upshifts and downshifts. The scan tool Commanded Gear parameter should correspond with the shift solenoid combination. Refer to Shift Solenoid Valve State and Gear Ratio .
    • When the ignition is ON, and the engine is OFF, there are no limits to this control. The scan tool shift solenoid states change to match the Current Gear selected.
    • When the engine is running, the following control limits apply:
       - The PCM does not allow a shift if it causes the engine RPM to exceed a calibrated limit. If a gear is requested and the engine speed is too high, the message "Engine speed too high" appears on the scan tool display.
       - The PCM does not allow a 3-2 or 2-1 downshift if the vehicle speed exceeds a calibrated limit. If either downshift is requested and the vehicle speed is too high, the message "Eng. is on and veh. speed too hi for 3-2 or 2-1 downshift" appears on the scan tool display.
       - The PCM does not allow a 4-3 downshift if the vehicle speed exceeds a calibrated limit. If a 4-3 downshift is requested and the vehicle speed is too high, the message "Vehicle speed too high" appears on the scan tool display.
       - The PCM does not allow an upshift if the vehicle speed exceeds a calibrated limit. If an upshift is requested and the vehicle speed is too high, the message "Vehicle speed too high" appears on the scan tool display.
       - The PCM does not allow an upshift that is greater than the current selected transmission range (PRNDL). For example, 3rd gear is not allowed if the transmission range is D2. If an upshift is requested that is greater than the current selected transmission range, the message "Eng. running and gear request is greater than the current TR" appears on the scan tool display.

TCC Control Solenoid
    • The PCM commands the duty cycle of the TCC PWM solenoid valve. The duty cycle is represented by a percentage of ON energized time. Approximately 90-100 percent duty cycle represents an ON energized commanded state. Zero percent represents an OFF non-energized commanded state. The scan tool TCC Duty Cycle parameter should match the commanded state.
    • When the ignition is ON, and the engine is OFF, there are no limits to this control. The solenoid remains ON, 90-100 percent duty cycle until commanded OFF, zero percent duty cycle, and vice versa. When the output control is exited, the solenoid duty cycle is determined by the PCM.
    • When the engine is running, the following control limits apply:
       - If the transmission range is PARK, and the transmission is in hot mode, the TCC PWM solenoid valve may not be commanded OFF. If the solenoid is requested OFF, the message "TCC OFF command disabled in Hot Mode" appears on the scan tool display.
       - The TCC PWM solenoid valve may not be commanded OFF for more than a calibrated amount of time. If the solenoid is commanded OFF, for a certain amount of time, the message "TCC OFF time has been exceeded" appears on the scan tool display.