Diagnostic Starting Point - Automatic Transmission
Begin the system diagnosis with Diagnostic System Check - Engine Controls in Engine Controls - 4.3 L or Diagnostic System Check - Engine Controls in Engine Controls - 4.8 L, 5.3 L and 6.0 L. The Diagnostic System Check provides the following information
- The identification of the control module(s) which commands the system.
- The ability of the control module(s) to communicate through the serial data circuit.
- The identification and status of stored diagnostic trouble codes (DTCs).
The use of the Diagnostic System Check - Engine Controls in Engine Controls - 4.3 L or Diagnostic System Check - Engine Controls in Engine Controls - 4.8 L, 5.3 L and 6.0 L identifies the correct procedure for diagnosing the system and the procedure location.
Symptoms
When it has been determined through Diagnostic System Check - Engine Controls in Engine Controls - 4.3 L or Diagnostic System Check - Engine Controls in Engine Controls - 4.8 L, 5.3 L and 6.0 L that no DTCs are present, begin symptom diagnosis by reviewing the Transmission Component and System Description .
Reviewing the Transmission Component and System Description information enables you to understand the operation of the system. This helps you determine if the condition described by the customer is normal or if a malfunction exists. If it is determined that a malfunction exists, identify the concern by referring to the Symptoms - Automatic Transmission table. The Symptoms - Automatic Transmission table provides common diagnostic categories which relate directly to diagnostic information or procedures.
Circuit Description
The Automatic Transmission Diagnostic System Check is an organized approach to identify a problem created by an automatic transmission. The Diagnostic System Check is the diagnostic starting point for an automatic transmission complaint. The Diagnostic System Check directs you to the next logical step for diagnosing a transmission concern. Perform this check only if there is a driveability complaint or if you have been directed here from another service information section.
Follow the table to help reduce diagnostic time and help prevent unnecessary replacement of good parts.
Diagnostic Aids
| IMPORTANT | Do not clear the DTC unless directed by a diagnostic procedure. Clearing the DTCs will erase all Freeze Frame and Failure Records stored in PCM memory. Poor engine performance can sometimes be diagnosed as a transmission driveability condition. In order to avoid mis-diagnosis of the automatic transmission, always perform the Diagnostic System Check - Engine Controls in Engine Controls - 4.3L or in Diagnostic System Check - Engine Controls Engine Controls - 4.8L, 5.3L and 6.0L. |
- Use a scan tool that is known to function correctly. If necessary, test the scan tool on another vehicle.
- Ensure the scan tool contains the most current file available.
- The scan tool will display a loss of communication error message under the following conditions: PCM power is interrupted. The ignition switch is turned OFF. The battery voltage level is very low. A poor connection at the data link connector (DLC).
Test Description
The numbers below refer to the step numbers on the diagnostic table.
- 1: This step determines if the scan tool is receiving power through the DLC connector.
- 2: The MIL should illuminate whenever the ignition is ON and the engine is not running.
- 3: This step determines if the PCM is transmitting class 2 serial data to the DLC and that the class 2 data circuit is not open or shorted.
- 4: This step determines if a DTC is current or stored in history.
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| 1 | Install a scan tool. IMPORTANT: Check for applicable service bulletins before proceeding with this test. Perform this test only if there is a driveability complaint or if you have been directed to this table from another section in the service information. IMPORTANT: Do not turn the ignition OFF when performing this diagnostic procedure. Do not clear the DTCs unless instructed by this diagnostic procedure. Turn ON the ignition, with the engine OFF. Does the scan tool turn ON? | Go to Step 2 | Go to Diagnostic Starting Point - Data Link Communications in Data Link Communications | |
| 2 | Is the MIL ON? | Go to Step 3 | Go to Malfunction Indicator Lamp (MIL) Inoperative in Engine Controls - 4.3L or Malfunction Indicator Lamp (MIL) Inoperative in Engine Controls - 4.8L, 5.3L and 6.0L | |
| 3 | Attempt to establish communication with the PCM. Does the scan tool communicate with the PCM? | Go to Step 4 | Go to Diagnostic Starting Point - Data Link Communications in Data Link Communications | |
| 4 | IMPORTANT: Diagnostic trouble codes (DTCs), engine performance, and transmission default actions can greatly affect the transmission performance. Ensure that these items are not the cause of a transmission concern. Use the scan tool Capture Info function in order to save or capture (Store Info) any DTC Information.Are there any DTCs present? | Go to Diagnostic Trouble Code (DTC) List/Type | Go to Symptoms - Automatic Transmission |
| IMPORTANT |
|---|
| Check for applicable service bulletins before proceeding with this test. Perform this test only if there is a driveability complaint or if you have been directed to this table from another section in the service information. |
| IMPORTANT |
|---|
| Do not turn the ignition OFF when performing this diagnostic procedure. Do not clear the DTCs unless instructed by this diagnostic procedure. |
| IMPORTANT |
|---|
| Diagnostic trouble codes (DTCs), engine performance, and transmission default actions can greatly affect the transmission performance. Ensure that these items are not the cause of a transmission concern. |
Diagnostic System Check - Automatic Transmission
Scan Tool Output Controls
| Scan Tool Output Control | Additional Menu Selections | Description |
|---|---|---|
| 1-2 Solenoid | The PCM 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. 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. | |
| 2-3 Solenoid | The PCM 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. 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. | |
| 3-2 Downshift Solenoid | The PCM commands the 3-2 shift solenoid valve ON and OFF. The scan tool 3-2 Downshift Sol. 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 until commanded OFF, and vice versa. When the output control is exited, the solenoid state is determined by the PCM. When the engine is running, the following control limits apply: The transmission range (PRNDL) must be in Park or Neutral. If the transmission range is not in Park or Neutral, the message "Engine running and transmission range is not Park/Neutral" 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. | |
| Clear TAP (Transmission Adaptive Pressures) | The PCM clears, or resets, the 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 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. The PCM 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, 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 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 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 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 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 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 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 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. | |
| TCC Enable | The PCM commands the TCC enable solenoid valve ON and OFF. The scan tool TCC Enable 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 until commanded OFF, and vice versa. When the output control is exited, the solenoid state is determined by the PCM. |
Scan Tool Output Controls
Scan Tool Data List
Use the scan tool data list under the following conditions
- The Diagnostic System Check - Automatic Transmission is complete.
- The on-board diagnostics are functioning properly.
- No DTCs are present.
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 in this manual for diagnosing. If a scan tool displays other parameters, the values are not recommended by General Motors for use in diagnosis.
Scan tool values below were recorded under the following conditions
- Engine at idle
- Upper radiator hose hot
- Closed throttle
- Transmission in PARK
- Closed Loop operation
- Accessories OFF
- Brake pedal not applied
| Scan Tool Parameter | Data List* | Units Displayed | Typical Data Value |
|---|---|---|---|
| 1-2 Shift Error | F2, F7/F0 | Seconds | Varies |
| 1-2 Shift Time | F0, F2, F7/F0 | Seconds | Varies |
| 1-2 Sol. | F0, F2, F3, F4 | On/Off | On |
| 1-2 Sol. Open/Short to GND | F2 | Yes/No | No |
| 1-2 Sol. Short to Volts | F2 | Yes/No | No |
| 1-2 TAP Cell (4-16) | F7/F0 | KPa/Psi | Varies |
| 2-3 Shift Error | F3, F7/F1 | Seconds | Varies |
| 2-3 Shift Time | F0, F3, F7/F1 | Seconds | Varies |
| 2-3 Sol. | F0, F2, F3, F4 | On/Off | On |
| 2-3 Sol. Open/Short to GND | F3 | Yes/No | No |
| 2-3 Sol. Short to Volts | F3 | Yes/No | No |
| 2-3 TAP Cell (4-16) | F7/F1 | KPa/Psi | Varies |
| 3-2 Downshift Sol. | F0, F5 | On/Off | On |
| 3-2 Sol. Open/Short to GND | F5 | Yes/No | No |
| 3-2 Sol. Short to Volts | F5 | Yes/No | No |
| 3-4 Shift Error | F4 | Seconds | Varies |
| 3-4 Shift Time | F0, F4 | Seconds | Varies |
| 4WD | F0 | Enabled/Disabled | Disabled |
| 4WD Low | F0 | Enabled/Disabled | Disabled |
| A/C Clutch | F0 | On/Off | Off |
| Commanded Gear | F0, F1, F2, F3, F4, F5, F6 | 1, 2, 3, 4 | 1 |
| Cruise | F0 | Enabled/Disabled | Disabled |
| Current TAP Cell | F7/F0, F7/F1 | 4-16 | Varies |
| ECT | F0, F1 | ° C (° F) | Varies |
| Engine Run Time | F0 | Hr/Min/Sec | Varies |
| Engine Speed | F0, F1, F2, F3, F4, F5, F6 | RPM | Varies |
| Engine Torque | F0, F1 | N.m (lb ft) | Varies |
| Estimated Gear Ratio | F0, F1, F2, F3, F4 | Ratio | 8.00:1 |
| Ignition Voltage | F0 | Volts | 12-14 Volts |
| Last Shift Time | F0 | Seconds | Varies |
| PC Sol. Actual Current | F0, F6 | Amps | Varies (0.1-1.1 amps) |
| PC Sol. Duty Cycle | F0, F6 | Percent | Varies |
| PC Sol. Ref. Current | F0, F6 | Amps | Varies (0.1-1.1 amps) |
| Power Take Off | F0 | On/Off | On |
| Speed Ratio | F0, F1, F2, F3, F4, F5 | Ratio | 8.00:1 |
| TCC Brake Switch | F0, F1 | Open/Closed | Closed |
| TCC Duty Cycle | F0, F1 | Percent | 0% |
| TCC Duty Cycle Open/Short to GND | F1 | Yes/No | No |
| TCC Duty Cycle Short to Volts | F1 | Yes/No | No |
| TCC Enable | F0, F1 | Yes/No | No |
| TCC Enable Open/Short to GND | F1 | Yes/No | No |
| TCC Enable Short to Volts | F1 | Yes/No | No |
| TCC Slip Speed | F0, F1 | RPM | +/-50 RPM from Engine Speed |
| TFP Sw. | F0 | Park/Neutral, Reverse, Drive4, Drive3, Drive2, Drive1 or Invalid | Park/Neutral |
| TFP Sw. A/B/C | F0 | HI/LOW | HI/LOW/HI |
| TFT Sensor | F0, F1, F6 | Volts | Varies |
| Torque Converter Efficiency | F0, F1, F2, F3, F4 | Ratio | .00:1 |
| Tow/Haul Mode | F0 | Active/Inactive | Inactive |
| TP Angle (Vehicles w/o Traction Control) | F0, F1, F2, F3, F4, F5, F6 | Percent | 0% |
| TP Indicated Angle (Vehicles with Traction Control) | F0, F1, F2, F3, F4, F5, F6 | Percent | 0-10% |
| TP Sensor (Vehicles w/o Traction Control) | F0, F1, F2, F3, F4, F5 | Volts | 0.3-0.9 V |
| TR Sw. | F0 | Park, Neutral, Reverse, Drive4, Drive3, Drive2, Drive1 or Invalid | Park |
| TR Sw. A/B/C/P | F0 | HI/LOW | LOW/HI/HI/LOW |
| Traction Control | F0 | Active/Inactive | Inactive |
| Trans. Fluid Temp. | F0, F1, F5, F6 | ° C (° F) | Varies |
| Trans. Slip Counter | F0, F1 | 0, 1, 2 | 0 |
| Transfer Case Ratio | F0, F2, F3, F4 | Ratio | 2.61:1 |
| Transmission Hot Mode | F0, F1 | On/Off | Off |
| Transmission OSS | F0, F1, F2, F3, F4, F5 | RPM | 0 |
| Vehicle Speed | F0, F1, F2, F3, F4, F5 | Km/h (mph) | 0 |
| *Data List Legend F0: Transmission Data F1: TCC Data F2: 1-2 Shift Data F3: 2-3 Shift Data F4: 3-4 Shift Data F5: 3-2 Down Shift Data F6: PC Solenoid Data F7: Transmission Adapts F7/F0: 1-2 Adapt. Data F7/F1: 2-3 Adapt. Data | |||
Transmission Scan Tool Data List
Diagnostic Trouble Code (DTC) Type Definitions
The DTC Type Definitions contain the characteristics for all types of DTCs. Each DTC type may or may not be found in this section. The DTC type is based on the action that the PCM takes when storing DTC information and whether or not the PCM illuminates a service lamp or displays a message on a driver information center (DIC). The DTC descriptions in the Diagnostic Trouble Code List/Type are listed in numeric order and indicate the DTC types for domestic and export vehicle applications. Each DTC is categorized into one of the following types
Type A
This DTC is emissions related. The PCM stores the DTC in History, Freeze Frame and Failure Records during the first trip in which the conditions for setting the DTC are met. The PCM also illuminates the malfunction indicator lamp (MIL) during the first trip in which the conditions for setting the DTC are met.
Type B
This DTC is emissions related. The PCM stores the DTC in Failure Records during the first trip in which the conditions for setting the DTC are met. The PCM stores the DTC in History and Freeze Frame during the second consecutive trip in which the conditions for setting the DTC are met. The PCM also illuminates the MIL during the second consecutive trip in which the conditions for setting the DTC are met.
Type C
This DTC is non-emissions related. The PCM stores the DTC in History and Failure Records during the first trip in which the conditions for setting the DTC are met. The PCM does not store the DTC in Freeze Frame and does not illuminate the MIL. For some type C DTCs, a message may be displayed on a DIC, if equipped. For other type C DTCs, a separate service lamp, other than the MIL, may be illuminated. Type C DTCs that do not display a message on the DIC or illuminate a separate service lamp were formerly referred to as type D.
Type X
This DTC is available in the PCM software, but has been disabled, or turned off. In this case, the diagnostic does not run, DTCs are not stored, and the MIL does not illuminate. Type X DTCs are used primarily for export vehicles that do not require MIL illumination or DTC storing.
The service information contained in this manual refers to the domestic, federal, calibration package. Domestic calibrations apply to vehicles sold in the United States, Canada and Japan. Export calibrations exist for both leaded and unleaded vehicles. DTC types may change for some export vehicles, and some DTCs may be turned off for leaded export vehicles. Differences between domestic and export calibrations are not reflected on DTC support information pages. DTC types for export calibrations are referenced only in the Diagnostic Trouble Code List/Type.
Diagnostic Trouble Code (DTC) List/Type
| DTC | Domestic | Unleaded Export | Leaded Export |
|---|---|---|---|
| DTC P0218 | C | C | C |
| DTC P0502 | B | B | C |
| DTC P0503 | B | B | C |
| DTC P0706 | C | C | C |
| DTC P0711 | C | C | C |
| DTC P0712 | C | C | C |
| DTC P0713 | C | C | C |
| DTC P0719 | C | C | C |
| DTC P0724 | C | C | C |
| DTC P0740 | B | B | C |
| DTC P0741 | B | B | C |
| DTC P0742 | B | B | C |
| DTC P0748 | C | C | C |
| DTC P0751 | B | B | C |
| DTC P0752 | B | B | C |
| DTC P0753 | B | B | C |
| DTC P0756 | A | A | C |
| DTC P0757 | A | A | C |
| DTC P0758 | A | A | C |
| DTC P0785 | B | B | C |
| DTC P0894 | B | B | C |
| DTC P1810 | B | B | C |
| DTC P2761 | B | B | C |
DTC List
See also:
• Diagnostic System Check - Engine Controls
• Diagnostic System Check - Engine Controls
• Transmission Component and System Description
• Symptoms - Automatic Transmission
• Diagnostic Starting Point - Data Link Communications
• Malfunction Indicator Lamp (MIL) Inoperative
• Malfunction Indicator Lamp (MIL) Inoperative
• Shift Solenoid Valve State and Gear Ratio
• DTC P0218
• Diagnostic Trouble Code (DTC) List/Type