GM Service Manual Online
For 1990-2009 cars only
1-2 Shift Error: This parameter is 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 is 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: 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 through 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: 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 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.

2-3 Shift Error: This parameter is 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 is the actual time of the last 2-3 shift. The shift time is based on the engine RPM drop after the commanded 2-3 shift. This value is only accurate if the shift was adaptable.

2-3 Sol: This parameter displays the commanded state of the 2-3 shift solenoid valve. When the transmission is in FIRST an SECOND gear the display should indicate ON, current is not flowing through 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: 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.

3-2 Downshift Sol.: This parameter displays if the 3-2 shift solenoid valve assembly is currently commanded ON or OFF. The solenoid commanded state is based on the transmission temperature. The solenoid will change states during a 3-2 downshift to regulate the appropriate pressure. The commanded state of the solenoid occurs at approximately 48 km/h (30 mph) with a throttle increase. The scan tool displays ON or OFF.

3-2 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.

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 3-4 shift. The shift time is based on the engine RPM drop after the commanded 3-4 shift. This value is only accurate if the shift was adaptable.

4WD: This parameter indicates whether the vehicle is currently in a four-wheel drive mode.

4WD Low: This parameter displays the signal state of the four-wheel drive low circuit. Enabled indicates a 0 voltage signal requesting 4WD low. Disabled indicates a B+ voltage signal which does not request 4WD low. Displays Enabled or Disabled.

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 PCM is allowing cruise control operation. When the display indicates DISABLED, the PCM has disabled cruise control operation. When the cruise control display is ENABLED, shift patterns will be altered for 2-3 and 3-4 up shifts or 4-3 and 3-2 downshifts.

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.

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

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.

Engine Speed: This parameter displays the rotational speed of the engine expressed as revolutions per minute.

Engine Torque: 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 15 ft/lb of actual measured engine torque.

Estimated Gear Ratio: This parameter displays the estimated turbine speed divided by the transmission output speed. Estimated turbine speed is calculated from engine speed and engine torque.

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

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 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.

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.

Speed Ratio: This parameter displays the calculated speed ratio of the transmission. The ratio is calculate 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 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. Zero percent represents an OFF, non-energized, commanded state.

TCC Duty Cycle 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.

TCC Enable Sol.: Displays Yes or No. This parameter is the commanded state of the TCC solenoid. Yes indicates a commanded energized state, current is flowing through the solenoid. No indicates a commanded non-energized state, current is not flowing through the solenoid. This commanded state occurs at various vehicle speeds between applications.

TCC Enable Sol. CKT Status: This parameter displays whether an open or short to ground or voltage exist in TCC solenoid valve feedback signal. If the TCC solenoid is commanded OFF the scan tool will display open or short to ground. If the TCC solenoid is commanded ON the scan tool will display short to voltage. If no circuit fault is present the scan tool will display OK.

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

TFP Sw.: This parameter displays Park/Neutral, Reverse, Drive4, Drive3, Drive2, Drive1 or invalid. This parameter is the decoded status of the three A/B/C inputs from the automatic transmission fluid pressure manual valve position switch. If a valid combination of inputs is not detected, invalid will be displayed.

TFP Sw. A/B/C: This parameter displays HI/LOW, HI/LOW, HI/LOW. This parameter indicates the status of the three inputs from the Automatic Transmission Fluid Pressure Manual Valve Position Switch Assembly. LOW represents a zero voltage signal. HI represents an ignition voltage signal.

Torque Converter Efficiency - Ratio: This parameter displays a ratio of .00:1 to 2:1. The ratio is calculated by multiplying the speed ratio by a value related to the "K factor" of the torque converter. The "K factor" is the looseness or tightness of the torque converter for a given torque. The nearer the torque converter is to full coupling, i.e. 1:1, the closer the torque converter efficiency number will be to 1.

TP Indicated Angle: This parameter displays the desired throttle angle for operating conditions present at the time.

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. If a valid combination of inputs is not detected, invalid will be displayed.

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

Transfer Case Ratio: This parameter displays the ratio of the transfer case calculated from engine speed divided by transmission output speed based on the commanded gear.

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. Slip Counter: This parameter is the number of times the P0894 Diagnostic test has identified a slipping condition. This diagnostic test is required to identify a slipping condition three times in a row in order to set the DTC P0894 Transmission Component Slipping Diagnostic code.

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 OSS: This parameter displays the rotational speed of the transmission output shaft expressed as revolutions per minute. On four-wheel drive applications, the transfer case output shaft speed is measured.

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.