Table 1: | Scan Tool Data Parameters |
Table 2: | Scan Tool Output Controls |
The Transmission Control Module Scan Tool Information 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.
Parameter | Expected Value | Description |
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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 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 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 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 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 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 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 | RPM, 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 | Volts, 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. HI 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 | Amps, 0.95-1.05 | 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 | Amps, 0.95-1.05 | 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. Zero 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 powertrain control module (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 | RPM, 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 | RPM, 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 | km/h (mph), 0 km/h | 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. |
Output Control | Description | ||||||||||||||||||
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1-2 Solenoid |
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2-3 Solenoid |
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Reset Transmission Adapts |
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PC Solenoid |
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Shift Transmission |
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TCC Control Solenoid |
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