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 the actual shift time was longer than the desired shift time.

1-2 Shift Time: This parameter is the actual time of the last 1-2 shift. The shift time is based on the gear ratio change after the commanded 1-2 shift. This value is only accurate if the adaptable shift parameter indicates Yes.

1-2 Solenoid: Displays ON or OFF. These parameters are the commanded status of the 1-2 shift solenoid valve. ON represents a commanded energized state. Current is flowing through the solenoid. OFF represents a non-commanded state. Current is not flowing through the solenoid.

1-2 Solenoid Open/Short to Ground: Displays Yes or No. This parameter indicates if an open or a short to ground exists in the feedback signal from the 1-2 shift solenoid valve to the PCM.

1-2 Solenoid Short to Volts: Displays Yes or No. This parameter indicates if a short to B+ exists in the feedback signal from the 1-2 shift solenoid valve to the PCM.

1-2 TAP Cell (4-16): Displays kPa or psi. This parameter displays the amount of pressure varied from a calibrated base line pressure for shifts. Each TAP cell is based on a calibrated shift torque value. Each TAP cell value is calculated from the last shift time. This cell pressure is used in addition to the calibrated base line pressure to adjust the apply of a clutch or band during the next shift.

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 the actual shift time was longer than the desired shift time.

2-3 Shift Time: This parameter is the actual time of the last 2-3 shift. The shift time is based on the gear ratio change after the commanded 2-3 shift. This value is only accurate if the adaptable shift parameter indicates Yes.

2-3 Solenoid: Displays ON or OFF. These parameters are the commanded status of the 2-3 shift solenoid valve. ON represents a commanded energized state. Current is flowing through the solenoid. OFF represents a non-commanded state. Current is not flowing through the solenoid.

2-3 Solenoid Open/Short to Ground: Displays Yes or No. This parameter indicates if an open or a short to ground exists in the feedback signal from the 2-3 shift solenoid valve to the PCM.

2-3 Solenoid Short to Volts: Displays Yes or No. This parameter indicates if a short to B+ exists in the feedback signal from the 2-3 shift solenoid valve to the PCM.

2-3 TAP Cell (4-16): Displays kPa or psi. This parameter displays the amount of pressure varied from a calibrated base line pressure for shifts. Each TAP cell is based on a calibrated shift torque value. Each TAP cell value is calculated from the last shift time. This cell pressure is used in addition to the calibrated base line pressure to adjust the apply of a clutch or band during the next shift.

3-4 Shift Error: This parameter is the difference between the desired 3-4 shift time and the actual 3-4 shift time. A positive number indicates the actual shift time was longer than the desired shift time.

3-4 Shift Time: This parameter is the actual time of the last 3-4 shift. The shift time is based on the gear ratio change after the commanded 3-4 shift.

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

4WD Low: Displays Enabled or Disabled. This parameter is 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.

A/C Clutch: Displays ON or OFF. This represents the commanded state of the A/C clutch control relay. The clutch should be engaged whenever ON is displayed. The PCM compensates for the additional engine load that is accompanied with the A/C clutch engaged.

Commanded Gear: Displays 1, 2, 3, or 4. This parameter indicates the current commanded state of the shift solenoids.

Cruise: Displays ENABLED or DISABLED. This parameter indicates whether the PCM is allowing cruise operation. The PCM has the ability to disable cruise control under certain conditions.

Current TAP (Transmission Adaptive Pressure) Cell: Displays cells 4-16. This parameter indicates the current TAP cell in use for transmission line pressure adaptation. The cells are based on 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 (Engine Coolant Temperature):  This parameter is the input signal of the engine coolant temperature sensor. Engine coolant temperature is high when the signal voltage is low, 0 volts, and engine coolant temperature is low when the signal voltage is high, 5 volts.

Engine Run Time: This parameter measures how long the engine has been operating. When you turn the ignition switch OFF, the value resets to zero.

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

Engine Torque: This parameter is 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.

Gear Ratio: This parameter is the actual gear ratio of the current commanded gear. In the commanded gear of R, D3, D2, and D1, it is calculated by dividing the input speed by the output speed. In the current gear of D4 with TCC lock up, the gear ratio is calculated by dividing the turbine speed by the output speed.

Ignition Voltage: This parameter represents the system voltage measured by the PCM at the ignition feed.

Last Shift Time: This parameter is the actual shift time of the last upshift.

PC (Pressure Control) Solenoid Act. (Actual) Current:  This parameter is the actual current of the pressure control solenoid circuit at the control module. Zero amp (no current flow) indicates an actual higher line pressure. A reading of 1.1 amp, high current flow, indicates an actual lower line pressure.

PC (Pressure Control) Solenoid Duty Cycle: This parameter is the commanded state of the pressure control solenoid expressed as a percentage of energized ON time. A reading of 0 percent indicates zero ON time, non energized, or no current flow. Approximately 60 percent at idle indicates maximum ON time, energized, or high current flow.

PC (Pressure Control) Solenoid Ref. (Reference) Current: This parameter is the commanded current of the pressure control solenoid circuit at the control module. Zero amp, no current flow, indicates a commanded higher line pressure. A reading of 1.1 amp, high current flow, indicates a commanded lower line pressure.

Power Take-Off: Displays ON or OFF. This parameter indicates when the Power Take Off (PTO) is engaged. PTO mode disables all transmission diagnostics.

Speed Ratio: This parameter indicates engine speed divided by transmission output speed.

TCC Brake Switch (Gas Application): Displays Open or Closed. This parameter indicates the state of the TCC brake switch circuit input. Open indicates a zero voltage input. The brake switch is open and the brake pedal is applied. Closed indicates a B+ voltage input. The brake switch is closed and the brake pedal is not applied.

TCC Duty Cycle: This parameter is the commanded percentage of ON time of the TCC PWM solenoid. 90 percent represents an ON, energized, commanded state. 0 percent represents an OFF, non-energized, commanded state.

TCC Duty Cycle Open/Short to Ground: Displays Yes or No. This parameter indicates if an open or a short to ground exists in the feedback signal from the TCC PWM solenoid valve to the PCM.

TCC Duty Short to Volts: Displays Yes or No. This parameter indicates if a short to B+ exists in the feedback signal from the TCC PWM solenoid valve to the PCM.

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

TFP Sw.: 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. Invalid is displayed when the PCM does not recognize a valid combination of inputs.

TFP Switch A/B/C: Displays HI/LOW, HI/LOW, HI/LOW. These parameters are the three inputs from the automatic transmission fluid pressure manual valve position switch Assembly. HI represents a 0 voltage signal. LOW represents a B+ voltage signal.

TFT (Transmission Fluid Temperature) Sensor: When the transmission fluid is cold, the sensor resistance is high and the PCM senses a high signal voltage. As the transmission fluid temperature warms to normal operating temperature, the sensor resistance becomes less and the voltage decreases to about 1.5-2.0 volts.

TP (Throttle Position) Angle: The TP angle is computed by the PCM from TP voltage. The TP angle should display 0 percent at idle and 100 percent at wide open throttle (WOT).

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

TP (Throttle Position) Sensor: The PCM uses the TP sensor in order to determine the amount of throttle demanded by the driver. Voltage is below 1 volt at idle. Voltage is above 4 volts at wide open throttle (WOT).

Tow/Haul Mode: Displays Yes or No. This parameter indicates when the transmission is operating in a Tow/Haul mode. In Tow/Haul mode, the PCM commands a different shift pattern that increases performance when towing and hauling. Shift quality and TCC scheduling are also affected during Tow/Haul mode operation.

Traction Control: Displays Active or Inactive. When the PCM receives a request for torque reduction from the electronic brake control module Active is displayed.

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

Trans. Fluid Temp. (TFT): This parameter is the input signal of the transmission fluid temperature sensor. Transmission fluid temperature is high when the signal voltage is low, 0 volts, and transmission fluid temperature is low when the signal voltage is high, 5 volts.

Trans. Slip Counter: Displays 0, 1 or 2. 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: Displays ON or OFF. This parameter monitors the transmission fluid temperature. YES indicates that the transmission fluid temperature has exceeded 135°C (275°F).

Transmission ISS (Input Shaft Speed): This parameter measures the rotational speed of the input shaft expressed as revolutions per minute.

Transmission OSS (Output Shaft Speed): This parameter indicates 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.

TR Sw. A/B/C/P: Displays HI/LOW, HI/LOW, HI/LOW, HI/LOW. This parameter indicates the status of the four inputs from the transmission range switch to the PCM. HI indicates an ignition voltage input to the PCM. LOW indicates a zero voltage input to the PCM.

TR Sw.: Displays Park/Neutral, Reverse, Drive4, Drive3, Drive2, Drive1, or invalid. This parameter is the decoded status of the four A/B/C/P inputs from the transmission range switch. Invalid is displayed when the PCM does not recognize a valid combination of inputs.

Turbine Speed: This parameter indicates the rotational speed of the torque converter turbine shaft expressed as revolutions per minute. In commanded gears 1, 2, and 3, the turbine speed equals the input speed. In commanded gear 4, the turbine speed equals 3/4 of the input speed.

Vehicle Speed: This parameter is the input signal from the OSS sensor.