6R75 Automatic Transmission

Diagnostics

Special Tool(s):

Diagnosing an electronically controlled automatic transmission is simplified by using the following procedures. One of the most important things to remember is that there is a definite procedure to follow. Do not take shortcuts or assume that critical checks or adjustments have already been made. Follow the procedures as written to avoid missing critical components or steps. By following the diagnostic sequence, the technician will be able to diagnose and repair the concern the first time.

On-Board Diagnostics With Scan Tool

NOTE: For detailed instruction and other diagnostic methods using the scan tool, refer to the scan tool tester manual and Computers and Control Systems. These quick tests should be used to diagnose the powertrain control module (PCM) and should be carried out in order.

^ Quick Test 1.0 - Visual Inspection
^ Quick Test 2.0 - Set Up
^ Quick Test 3.0 - Key On, Engine Off (KOEO)
^ Quick Test 4.0 - Continuous Memory
^ Quick Test 5.0 - Key On, Engine Running (KOER)
^ Special Test Mode
- Wiggle Test
- Output Test Mode
^ PCM Reset Mode
^ Clearing DTCs
^ OBD II Drive Cycle

Other Scan Tool Features
For information on other diagnostic testing features using the scan tool, refer to Computers and Control Systems.

Output State Control (OSC) Mode

On-Board Diagnostics

Output State Control (OSC) Mode
Output state control (OSC) allows the technician to take control of certain parameters to function the transmission.

For example, OSC allows the technician to shift the transmission only when commanding a gear change. If the technician commands 1st gear in OSC, the transmission will remain in 1st gear until the technician commands the next gear.

Another example of the OSC features is that a technician can command the torque converter to turn ON or OFF to check operation.

This transmission OSC has one mode of operation; DRIVE. This mode has a unique set of operating requirements that the technician must meet before allowed to operate the torque converter or select gears.

NOTE: To operate OSC, the digital transmission range (TR) sensor and the output shaft speed (OSS) sensor must be operational. No diagnostic trouble codes (DTCs) related to the digital TR sensor or the OSS can be present.

^ The vehicle requirements MUST BE MET when SENDING the OSC value. Refer to the vehicle requirements for each test.
^ If the vehicle requirements are NOT MET when SENDING the OSC value, an ERROR MESSAGE will appear. OSC is aborted and must be restarted.
^ If, after the sent value is substituted, the vehicle requirements are no longer met, the powertrain control module (PCM) will cancel the OSC value and resume normal operations. No error message will be sent.
^ The OSC value XXX may be sent anytime to cancel OSC.

Output State Control (OSC) Procedures
^ Carry out a visual inspection and prepare the vehicle as necessary.
^ Select the "Vehicle and Engine Selection" menu.
^ Select the appropriate vehicle and engine.
^ Select "Diagnostic Data Link."
^ Select "Powertrain Control Module."
^ Select "Diagnostic Test Mode."
^ Select "KOEO On-Demand Self Test and KOER On-Demand Self Test."
^ Carry out the tests and record the DTCs.
^ Repair all non-transmission DTCs.
^ Repair all VSS and digital TR sensor DTCs.
^ Make sure that the OSS and digital TR sensors are functional.
^ Select "Active Command Mode."
^ Select "Output State Control."
^ Select "Trans-Drive Mode."

OSC - Transmission in Drive Mode
The OSC provides the following DRIVE Mode functions:
^ GEAR - Allows upshifts and downshifts.
^ TCC - Engages or disengages the torque converter clutch (TCC).

GEAR in Drive Mode
The DRIVE Mode allows the technician to choose the following options:
^ 1 - TCM selects 1st gear.
^ 2 - TCM selects 2nd gear.
^ 3 - TCM selects 3rd gear.
^ 4 - TCM selects 4th gear.
^ 5 - TCM selects 5th gear.
^ 6 - TCM selects 6th gear.

The DRIVE Mode for GEAR operates ONLY when:
^ The OSS and digital TR sensor are operational.
^ No OSS and digital TR sensor DTCs are set.
^ The Key is ON, engine running.
^ The transmission shifter is in the D position.
^ Vehicle speed is above 3 km/h (2 mph).

OSC Command Values:
^ 1 - TCM selects 1st gear.
^ 2 - TCM selects 2nd gear.
^ 3 - TCM selects 3rd gear.
^ 4 - TCM selects 4th gear.
^ 5 - TCM selects 5th gear.
^ 6 - TCM selects 6th gear.
^ XXX - Cancels a value sent to the TCM.
^ SEND - Sends a value to the TCM.

Drive Mode Procedure for GEAR
Follow operating instructions from scan tool menu screen.
^ Select "Output State Control."
^ Select "Trans - Drive Mode."
^ Select "PIDs" to be monitored.
^ Monitor all selected PIDs during tests.
^ Select "Parameters - GEAR."
^ Select value "1-6."
^ Press "SEND" to send the command.
^ Select "XXX" to cancel at any time.
^ Press "SEND."

TCC in Drive Mode
The DRIVE Mode allows the technician to choose the following options:
^ TCC - Activates TCC OFF and ON.
^ ON - Turns TCC solenoid ON.
^ OFF - Turns TCC solenoid OFF.

DRIVE Mode for "TCC OFF" operates only when:
^ The OSS and digital TR sensor are set.
^ NO OSS and digital TR sensor DTCs are set.
^ The key is ON, engine running.
^ The transmission shifter is in the D position.
^ Vehicle speed is above 16 km/h (10 mph).

DRIVE Mode for "TCC ON" operates only when:
^ The OSS and digital TR sensor are operational.
^ No OSS and digital TR sensor DTCs are set.
^ The key is ON, engine running.
^ The transmission shifter is in the D position.
^ Vehicle speed is above 16 km/h (10 mph).
^ TFT is above 38°C (100°F).
^ The brake is not applied below 32 km/h (20 mph).
^ Steady vehicle speed is maintained.

OSC Command Values:
^ OFF - Turns TCC OFF.
^ ON - Turns TCC ON.
^ XXX - Cancels OSC value sent to the TCM.
^ SEND - Sends the values to the TCM.

Drive Mode Procedures for TCC
Follow operating instructions from the scan tool menu screen.
^ Select "Output State Control."
^ Select "Trans - Drive Mode."
^ Select "PIDs" to be monitored.
^ Monitor all selected PIDs during tests.
^ Select "Parameters - TCC."
^ Select "ON" to turn the TCC solenoid ON.
^ Press "SEND" to send the ON command.
^ Select "OFF" to turn the TCC solenoid OFF.
^ Press "SEND" to send the OFF command.
^ Select "XXX" to cancel at any time.
^ Press "SEND."