For 1990-2009 cars

## Transmission Control Module Scan Tool Information 4T45

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 | 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.
1-2 Shift Time | Varies | Seconds | This parameter displays the actual time of the last adaptable 1-2 shift. The shift time is based on the gear ratio change after the commanded 1-2 shift.
1-2 Sol. | On | On/Off | 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 | OK | OK, Open/Short to GND, Short to Volts, 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 | Varies | kPa (psi) | 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 Time | Varies | Seconds | 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. | Off | On/Off |

#### 2nd Gear Default

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 OFF, current is not flowing trough the solenoid. When the transmission is in THIRD and FOURTH gear, the display should indicate ON, current is flowing through the solenoid.

#### 3rd Gear Default

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 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 | OK | OK, Open/Short to GND, Short to Volts, 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 | Varies | kPa (psi) | 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.
3-4 Shift Time | Varies | Seconds | 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 | Varies | kPa (psi) | 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 3-4 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.
Brake Switch | Released | Applied/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%, where 0% represents an idle or coast request and 100% represents a request for wide open throttle (WOT).
Commanded Gear | 1 | 1, 2, 3, 4 | 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 | Varies | 4-16 | 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.
Driver Shift Control | Inactive | Active/Inactive | This parameter displays Active or Inactive. The scan tool displays Active when the gear selector is in the manual (M) position which enables TAP Shift. The scan tool displays Inactive when the gear selector is not in the M position, TAP Shift disabled.
Driver Shift Request | None | Upshift, Downshift, None, Invalid | This parameter displays the current request from the TAP Shift System. This parameter will display up shift, downshift or invalid depending on the amount of voltage measured at the remote shift selector input and also will display none when there is no request.
ECT Sensor | 85-105°C (185-220°F) | °C (°F) | 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 Speed | Varies | RPM | This parameter displays the rotational speed of the engine expressed as revolutions per minute.
Engine Torque | Varies | N·m (lb ft) | 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 lb ft) of actual measured engine torque.
Gear Ratio | 3.98:1 | Ratio | This parameter displays the actual transmission gear ratio. The scan tool displays the gear ratio calculated from the automatic transmission input speed sensor (ISS) and the automatic transmission output speed sensor (OSS) inputs.
Ignition Voltage | 12.6-14.7 | Volts | This parameter displays the system voltage measured at the ignition feed.
Last Shift Time | Varies | Seconds | 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 | Varies | 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 | Varies | % | 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 | Varies | 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 | Varies | kPa (psi) | 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 | Varies | kPa (psi) | 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 | Varies | kPa (psi) | 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 | Varies | kPa (psi) | 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 | Varies | kPa (psi) | 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 | Varies | kPa (psi) | 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 | Varies | kPa (psi) | 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 | Varies | kPa (psi) | 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 of 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 | OK | OK, Open/Short to GND, Short to Volts, 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 | Yes/No | This parameter displays the status of the normally closed TCC release switch and displays YES or NO. When 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 | Varies | RPM | This parameter displays 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 applied.
TFP Sw. | Park/Neutral | Park/Neutral, Reverse, Drive, or invalid | 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. Sig. B/ Sig. C | HI/HI | HI/LOW | This parameter displays HI/LOW, HI/LOW. The displays are the two inputs from the automatic transmission fluid pressure manual valve position switch. HI represents an ignition voltage signal, switch open. LOW represents a low voltage signal, switch closed.
TR Sw. | Park | Park, Reverse, Neutral, Drive 4, Drive 3, Drive 2, Drive 1 or invalid | 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 | LOW/HI/HI/LOW | HI/LOW | 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.
Traction Control Signal | Inactive | Active/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. | 80-90°C (176-194°F) | °C (°F) | 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.
Transmission Hot Mode | Off | On/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 more that 5 seconds. Note: these numbers are approximate. They differ with transmissions.
Transmission 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).
Transmission OSS | 0 | RPM | 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 | 0 | km/h (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 automatic transmission output shaft speed sensor.

#### Scan Tool Output Controls

Output Control | Description
--- | ---
1-2 Solenoid |

• | The powertrain control module (PCM) or the transmission control module (TCM) 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 table.

• | 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/TCM.

• | 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/TCM.

2-3 Solenoid |

• | The PCM/TCM 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 table.

• | 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/TCM.

• | 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/TCM.

Reset Transmission Adapts |

• | The PCM/TCM clears, resets, the transmission adaptive pressures (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/TCM commands the amperage, current, to the pressure control solenoid 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/TCM. The PCM/TCM 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/TCM, 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/TCM 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 table.

• | 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 Commanded Gear selected.

• | When the engine is running, the following control limits apply:

- | The PCM/TCM 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/TCM 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/TCM 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/TCM 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/TCM 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/TCM commands the duty cycle of the TCC PWM solenoid. 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/TCM.

• | 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 control solenoid 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 control solenoid 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.