Diagnostic Starting Point - Automatic Transmission
Begin the system diagnosis with Diagnostic System Check - Vehicle . The Diagnostic System Check provides the following information
- The identification of the control module or modules which commands the system
- The ability of the control module or modules to communicate through the serial data circuit
- The identification and status of stored DTCs
The use of the Diagnostic System Check - Vehicle identifies the correct procedure for diagnosing the system and the procedure location.
Symptoms
When it has been determined through Diagnostic System Check - Vehicle 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 table Symptoms - Automatic Transmission . The table Symptoms - Automatic Transmission provides common diagnostic categories which relate directly to diagnostic information or procedures.
Scan Tool Output Controls
| Scan Tool Output Control | Additional Menu Selections | Description |
|---|---|---|
| 1-2 Solenoid | 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 table Shift Solenoid Valve State and Gear Ratio . 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 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 TCM. | |
| 2-3 Solenoid | The 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 table Shift Solenoid Valve State and Gear Ratio . 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 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 TCM. | |
| 3-2 Downshift Solenoid | The TCM 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 TCM. 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 TCM. | |
| PC Solenoid | The 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 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 TCM commands upshifts and downshifts. The scan tool Commanded Gear parameter should correspond with the shift solenoid combination. Refer to table Shift Solenoid Valve State and Gear Ratio . 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 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 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 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 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 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 TCM commands the duty cycle of the torque converter clutch pulse width modulated (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 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. | |
| TCC Enable | The TCM 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 TCM. When the engine is running, the following control limits apply: If the transmission range is Park or Neutral, the TCC enable 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. If the transmission range is Park or Neutral and the TCC control solenoid duty cycle is less than maximum capacity, the TCC enable solenoid may not be commanded ON. If the solenoid is requested ON during these conditions, the message "TCC Control Solenoid is not set to maximum Pressure" appears on the scan tool display. If the TCC control solenoid duty cycle is less than maximum capacity, the TCC enable solenoid may not be commanded ON. If the solenoid is commanded ON during these conditions the message "TCC Control Solenoid is not set to maximum Pressure" appears on the scan tool display. If the transmission is in hot mode, the TCC enable 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. |
Scan Tool Output Controls
Scan Tool Data List (4.2L)
Use the scan tool data list under the following conditions
- The Diagnostic System Check - Vehicle 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. CKT Status | F2 | OK, Short to GND, Short to Volts, Indeterminate | OK |
| 1-2 TAP Cell 4-14 | 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. CKT Status | F3, F5 | OK, Short to GND, Short to Volts, Indeterminate | OK |
| 2-3 TAP Cell 4-14 | F7/F1 | KPa (psi) | Varies |
| 3-2 Downshift Sol. | F0, F5 | On/Off | On |
| 3-2 Sol. CKT Status | F5 | OK, Short to GND, Short to Volts, Indeterminate | OK |
| 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 | KPa (psi) | 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) |
| 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 CKT Status | F1 | OK, Short to GND, Short to Volts, Indeterminate | OK |
| TCC Enable Sol. | F0, F1 | Yes/No | No |
| TCC Enable CKT Status | F1 | OK, Short to GND, Short to Volts, Indeterminate | OK |
| 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 |
| Torque Converter Efficiency | F0, F1, F2, F3, F4 | Ratio | .00:1 |
| TP Indicated Angle | F0, F1, F2, F3, F4, F5, F6 | Percent | 0% |
| TR Sw. | F0 | Park/Neutral, Reverse, Drive4, Drive3, Drive2, Drive1 or Invalid | Park/Neutral |
| TR Sw. A/B/C/P | F0 | HI/LOW | LOW/HI/HI/LOW |
| 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 | 0.00:1 |
| 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
Scan Tool Data List (5.3L)
Use the scan tool data list under the following conditions
- The Diagnostic System Check - Vehicle 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. CKT Status | F2 | Indeterminate, OK, Open/Short to GND, Short to Volts | Indeterminate |
| 1-2 TAP Cell (4-14) | 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. CKT Status | F3 | Indeterminate, OK, Open/Short to GND, Short to Volts | Indeterminate |
| 2-3 TAP Cell (4-14) | F7/F1 | KPa (psi) | Varies |
| 3-2 Downshift Sol. | F0, F5 | On/Off | On |
| 3-2 Sol. CKT Status | F5 | Indeterminate, OK, Open/Short to GND, Short to Volts | Indeterminate |
| 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 |
| Calc. Throttle Position | F0, F1, F2, F3, F4, F5, F6 | Percent | Varies |
| Commanded Gear | F0, F1, F2, F3, F4, F5, F6 | 1, 2, 3, 4 | 1 |
| Current TAP Cell | F7/F0, F7/F1 | 4-16 | Varies |
| ECT | F0, F1 | °C (°F) | Varies |
| Engine Speed | F0, F1, F2, F3, F4, F5, F6 | RPM | Varies |
| Engine Torque | F0, F1 | N.m (lb ft) | Varies |
| Gear Ratio (5.3L) | F0, F1, F2, F3, F4, F5 | Ratio | 8.00:1 |
| Gear Ratio | F0, F1, F2, F3, F4, F5, F6 | 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 Solenoid Duty Cycle | F0, F6 | Percent | Varies |
| PC Sol. Ref. Current | F0, F6 | Amps | Varies (0.1-1.1 amps) |
| TCC Brake Switch | F0, F1 | Open/Closed | Closed |
| TCC Duty Cycle | F0, F1 | Percent | 0% |
| TCC Duty Cycle CKT Status | F1 | Indeterminate, OK, Open/Short to GND, Short to Volts | Indeterminate |
| TCC Enable Sol. | F0, F1 | On/Off | No |
| TCC Enable Sol. CKT Status | F1 | Indeterminate, OK, Open/Short to GND, Short to Volts | Indeterminate |
| 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 |
| TR Sw. | F0 | Park, Reverse, Neutral, Drive4, Drive3, Drive2, Drive1 or Invalid | Park |
| TR Sw. A/B/C/P | F0 | HI/LOW | LOW/HI/HI/LOW |
| 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 ISS (6.0L) | F0, F1, F2, F3, F4, F5 | RPM | Varies |
| Transmission OSS | F0, F1, F2, F3, F4, F5 | RPM | 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
Diagnostic Trouble Codes (DTCs) are grouped into several types. Each type has a unique set of characteristics for MIL operation, DTC storage, and DTC clearing. The following list contains a brief summary of the DTC types and the associated properties of each.
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 P0562 | C | C | C |
| DTC P0563 | C | C | C |
| DTC P0601 | C | C | C |
| DTC P0602 | A | A | C |
| DTC P0603 | A | A | C |
| DTC P0604 | A | A | C |
| DTC P062F | A | A | C |
| DTC P0705 | C | C | C |
| DTC P0711 | C | C | C |
| DTC P0712 | C | C | C |
| DTC P0713 | C | C | C |
| DTC P0716 | B | B | C |
| DTC P0717 | B | B | C |
| DTC P0719 | C | C | C |
| DTC P0722 | B | B | C |
| DTC P0723 | B | B | C |
| DTC P0724 | C | C | 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 P0756 | A | A | C |
| DTC P0757 | A | A | C |
| DTC P0787 | A | A | C |
| DTC P0788 | A | A | C |
| DTC P0851 | C | C | C |
| DTC P0852 | C | C | C |
| DTC P0894 | B | B | C |
| DTC P0961 | B | B | C |
| DTC P0973 | B | B | C |
| DTC P0974 | B | B | C |
| DTC P0976 | A | A | C |
| DTC P0977 | A | A | C |
| DTC P1621 | A | A | C |
| DTC P1810 | B | B | C |
| DTC P1815 | B | B | C |
| DTC P1816 | B | B | C |
| DTC P1818 | B | B | C |
| DTC P2534 | A | A | C |
| DTC P2763 | B | B | C |
| DTC P2764 | B | B | C |
| DTC P2769 | B | B | C |
| DTC P2770 | B | B | C |
| DTC U0073 | B | B | C |
| DTC U0100 | B | B | C |
| DTC U0121 | C | C | C |
| DTC U0140 | C | C | C |
| DTC U2104 | B | B | C |
| DTC U2105 | B | B | C |
| DTC U2107 | B | B | C |
Diagnostic Trouble Code (DTC) List/Type