GM Service Manual Online
For 1990-2009 cars only
1-2 Shift Error: Range -6.38 to +6.38 seconds. This parameter is the difference between the desired 1-2 shift time and the actual 1-2 shift time.

1-2 Shift Time: Range 0.00-6.38 seconds. This parameter is the actual time of the last 1-2 shift. The time is measured from the start of the change in the ratio until the end of the change in the ratio.

1-2 Sol.: Displays On/Off. This parameter indicates the status of the 1-2 Shift Solenoid Valve. When the automatic Transmission is in first or fourth gear, the scan tool should display On. When the transmission is in second or third gear, the scan tool should display Off.

2-3 Shift Error: Range -6.38 to +6.38 seconds. This parameter is the difference between the desired 2-3 shift time and the actual 2-3 shift time.

2-3 Shift Time: Range 0.00-6.38 seconds. This parameter is the actual time of the last 2-3 shift. The time is measured from the start of the change in the ratio until the end of the change in the ratio.

2-3 Sol.: Displays On/Off. This parameter indicates the status of the 2-3 Shift Solenoid Valve. When the automatic Transmission is in first or second gear, the scan tool should display Off. When the transmission is in third or fourth gear, the scan tool should display On.

3-4 Shift Error: Range -6.38 to +6.38 seconds. This parameter is the difference between the desired 3-4 shift time and the actual 3-4 shift time.

3-4 Shift Time: Range 0.00-6.38 seconds. This parameter is the actual time of the last 3-4 shift. The time is measured from the start of the change in the ratio until the end of the change in the ratio.

A/C Clutch: Displays On/Off. This parameter indicates the commanded state of the A/C control relay. The clutch should be engaged when On is displayed.

Active Malfs: Displays DTC numbers. This parameter is a list of all currently active DTC numbers.

Adaptable Shift: Displays Yes/No. Yes indicates that the proper operating conditions were all within the proper operating range during the last shift, and the Shift Time was accurate. This shift information is then used through the adaptive function in order to update the adapt cells. No indicates that not all of the operating conditions were met in order to enable this function, and the adapt cells were not updated. Proper operating conditions include the TP Sensor Delta, Engine Torque, Vehicle Speed Delta, Engine Vacuum, Shift Delay, and others.

BARO: Range 11-105 kPa, 0-5.0V. The Barometric Pressure (BARO) sensor measures the change in the intake manifold pressure which is the result of altitude changes. This value is updated at ignition On and also at Wide Open Throttle (WOT).

Brake Switch: Displays Open/Closed. This parameter indicates the state of the 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 released).

Cruise Enabled: Displays On/Off. This parameter indicates whether the PCM is allowing cruise operation. The PCM has the ability to disable cruise control under certain conditions.

Current Gear: Displays 1, 2, 3, 4. This parameter indicates the current command state of the shift solenoid valves.

Current TAP: Displays TP Cells 0-16. This parameter indicates the current throttle position cell which is being used for fluid line pressure adaptation.

Curr. TAP Memory: Range -16 to +16 psi. This parameter is the amount of Current Transmission Adaptive Pressure that is added to the base line pressure in order to adjust the holding effort of a clutch or a band, while not engine braking.

DS (Downshift) Desired: Displays Yes/No. This parameter indicates when the PCM desires a downshift. Yes indicates that a downshift is desired. No indicates that a downshift is not desired.

DS (Downshift) in Progress: Displays Yes/No. This parameter indicates whether the transmission is currently in a downshift. Yes indicates that a downshift is in progress. No indicates that a downshift is not in progress.

DS (Downshift) Requested: Displays Yes/No. This parameter indicates when the PCM requests a downshift. Yes indicates that a downshift is requested. No indicates that a downshift is not requested.

Engine Run Time: Range 0:00:00-18:12:15. This parameter is 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: Range 0.00-8192 RPM. The PCM computes the engine speed from the fuel control reference input. This speed should remain close to the desired idle under various engine loads with the engine idling.

ETC: Range -40°C to 151°C (-40°F to 304°F). This parameter is the input signal of the Engine Coolant Temperature (ETC) sensor. Engine coolant temperature is high at 151°C (304°F) when the signal voltage is low (0V). Engine coolant temperature is low at -40°C (-40°F) when the signal voltage is high (5V).

Gear Ratio: Range 1:0.00 to 1:3.98. This parameter is the actual transmission gear ratio. The ratio is calculated from the A/T ISS and the A/T OSS sensors.

History Malfs: Displays DTC numbers. This parameter is a list of all DTC malfunctions that are currently stored in PCM memory.

Hot Mode: Displays Yes/No. This parameter monitors the transmission temperature. No indicates that the transmission temperature has not exceeded 135°C (275°F). Yes indicates that the transmission temperature has exceeded 140°C (284°F).

Ignition Volts: Range 0.0-15.0V. This parameter represents the system voltage which is measured by the PCM at its ignition feed.

Kickdown Enabled: Displays No/Yes. This parameter indicates whether conditions exist which would enable an acceleration mode downshift. No indicates that enabling conditions do not exist for the downshift. Yes indicates that enabling conditions do exist for the downshift. Enabling conditions include throttle position, vehicle speed, and input speed.

Latest Shift: Range 0.00-6.38 seconds. This parameter is the actual shift time of the last upshift.

Latest Shift Err (Error): Range -6.38 to +6.38 seconds. This parameter is the difference between the desired shift time and the actual shift time for the most recent shift.

Long Shift Delay: Displays Yes/No. This parameter indicates whether a long shift delay occurred during the last shift. No indicates that a long shift delay did not occur. Yes indicates that a long shift delay did occur. A shift delay is determined by the time that the PCM commands the shift until the start of the ratio change.

Long Shift Time: Displays Yes/No. This parameter indicates whether a long shift time occurred during the last shift. No indicates that a long shift time did not occur. Yes indicates that a long shift time did occur. Shift time is calculated from the beginning of the ratio change to the end of the ratio change.

Loop Status: Displays Open/Closed. A reading of Closed indicates that the PCM is controlling fuel delivery according to voltage from the oxygen sensor. A reading of Open indicates that the PCM is ignoring the oxygen sensor, and the PCM bases fuel delivery on inputs from the TP sensor, the ECT sensor, and the MAP sensor.

MAP: Range 11-105 kPa, 0-5.0V. The Manifold Absolute Pressure (MAP) sensor measures the change in the intake manifold pressure which are the result of engine load and speed changes. As the intake manifold pressure increases, the air density in the intake also increases and additional fuel is required.

MPH/Km/h: Range 0.00-255 mph. This parameter is the input signal from the A/T OSS sensor.

PC Act. Current: Range 0.00-4.98 amps. This parameter is the actual current of the Pressure Control (PC) solenoid valve circuit at the PCM. A reading of 0.00 amps (no current is flowing) indicates an actual high line pressure. A reading of 1.18 amps (a high flow of current) indicates an actual low line pressure.

PC (Pressure Control) Duty Cycle: Range 0-100%. This parameter is the commanded state of the Pressure Control (PC) solenoid valve, which is expressed as a percent of it energized ON time. A reading of 0% indicates zero ON time (a non-energized commanded OFF state). A reading of 100% represents an energized commanded ON state.

PC (Pressure Control) Enable: Displays On/Off. This parameter indicates the commanded state of the Pressure Control (PC) solenoid valve

PC (Pressure Control) Pressure: Range 0-90 psi. This parameter is the desired torque signal pressure. The pressure is a calculated value based upon the current vehicle conditions.

PC Ref. Current: Range 0.00-4.98 amps. This parameter is the commanded (Reference) current of the Pressure Control (PC) solenoid valve circuit . A reading of 0.00 amps (no current is flowing) indicates a commanded high line pressure. A reading of 1.18 amps (a high flow of current) indicates a commanded low line pressure.

Power Enrichment: Displays Active/Inactive. The scan tool indicates when power enrichment mode is active. Power enrichment is defined as moderate to heavy acceleration.

Shift Delay: Range 0.00-6.38 seconds. This parameter is the time between the commanded change in the solenoid state until the start of the change in the ratio for the most recent shift.

Standard TAP: Displays Yes/No. The Standard Transmission Adaptive Pressure (TAP) is an amount of pressure that is added to the base line pressure. If the last shift was adaptable and was not a long or a delayed shift, then the scan tool will display Yes. If the shift requires more or less than the standard TAP in order to achieve the shift, then the scan tool will display No.

TCC Duty Cycle: Range 0-100%. This parameter is the commanded percentage of On time of the TCC solenoid valve. A reading of 100% represents an On (energized) commanded state. A reading of 0% represents a non-energized commanded Off state.

TCC Release Pres. (Pressure): Displays On/Off. This parameter monitors the normally closed TCC Release switch. When the TCC Release fluid pressure is present, the switch is On, indicating that the TCC is released. When the fluid pressure is not present, then the switch is Off, indicating that the TCC is applied.

TCC Release Sw.: Displays Open/Closed. This parameter monitors the normally closed TCC Release switch. When the TCC Release fluid pressure is present, then the switch is Open, indicating that the TCC is released. When the fluid pressure is not present, then the switch is Closed, indicating that the TCC is applied.

TCC Slip Speed: Range -4095 to +4095. This parameter displays the amount of slip in RPM between the engine and the transmission input shaft.

TFP Switch: Displays On/Off, On/Off, On/Off. These parameters are the three inputs from the Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) Off represents a B+ voltage signal and On represents a 0 voltage signal.

TFT: Range -40°C to 151°C (-40°F to 304°F). The PCM converts the resistance of the Transmission Fluid Temperature (TFT) sensor into degrees. Transmission temperature is used in order to determine Hot Mode TCC operation and to modify the commanded transmission pressure.

TP Angle: Range 0-100%. The PCM computes Throttle Position (TP) angle from the input of the TP sensor voltage. The TP angle is automatically set to 0% at idle (TP voltage is below 0.90 volt) and reads 100% at WOT.

TP Delta: Displays Normal/Exceeded. This parameter indicates when the TP is within a range that allows shift adapts. A TP Delta range is defined to be the amount of TP movement during the shift calculation. Normal indicates that the TP is within the range. Exceeded indicates that the TP is not within the range.

TP (Throttle Position) Range: Displays Normal/Exceeded. This parameter indicates when the throttle position is within a range that will enable the transmission to perform an adaptable shift. Normal indicates that the TP is within this range. Exceeded indicates that the TP is not within this range.

TP Sensor: Range 0-5.0V. The Throttle Position (TP) sensor is used by the PCM in order to determine the amount of throttle demanded by the operator of the vehicle. The TP sensor reads between 0.36-0.96 volt at idle to above 4 volts at WOT.

TR Switch: Displays Park/Reverse/Neutral/Overdrive/Drive 3/Drive 2/Low/Invalid. The scan tool displays the decoded position of the transmission range switch PRNDL inputs. This information is then sent by UART serial data to the Instrument Panel Cluster (IPC). This information is displayed to the operator on the IPC. If a valid combination of inputs is not seen by the PCM, Invalid will be displayed.

TR Switch: Displays High/Low. A Transmission Range (TR) switch is used as an input in order to let the PCM know the current position of the gear select lever. Scan tool status will switch from High to Low as different combinations are met. In Park, the PRNDL P and A will be Low. The PRNDL B and C will be High.

Trans. ISS: Range 0.00-8192 RPM. This parameter indicates the rotational speed of the Automatic Transmission Input(Shaft) Speed Sensor (Trans. ISS), which is expressed as revolutions per minute (RPM).

Trans. OSS: Range 0.00-8192 RPM. This parameter indicates the rotational speed of the Automatic Transmission Output(Shaft) Speed Sensor (Trans. OSS), which is expressed as revolutions per minute (RPM).

Upshift: Displays Yes/No. This parameter indicates whether the PCM considers that an upshift is in progress. Yes indicates that an upshift has been commanded. No indicates that an upshift has not been commanded.

Upshift Desired: Displays Yes/No. This parameter indicates when the PCM desires an upshift. Yes indicates that an upshift is desired. No indicates that an upshift is not desired.

Upshift Request: Displays Yes/No. This parameter indicates when the PCM requests an upshift. Yes indicates that an upshift is requested. No indicates that an upshift is not requested.

VSS Delta: Displays Normal/Exceeded. This parameter indicates when the VSS is within a range that enables shift adapts. Normal indicates that the VSS is within the range. Exceeded indicates that the VSS is not within the range.