DEFINITION: Harsh forced downshifts

Customer Driving Habits

Road test the vehicle in an attempt to duplicate the concern. If unable to duplicate the concern, scan the system to verify that there is no other concern present, perform a bulletin search, and verify the calibration level.

Fluid level low and/or contaminated, or unit filled with the wrong type of automatic transmission fluid (ATF)

Inspect the ATF level and color. Perform Transmission Fluid Check and make sure that the fluid does not smell burnt, and shows no sign of coolant cross-contamination. If unable to determine if the transmission has the correct type of fluid, drain the unit and refill with the correct ATF and retest.

Calibration

Using a scan tool, verify that the current calibration level downloaded into the transmission control module (TCM) is correct for this platform, including that the correct TCM is being used for the platform. Refer to the appropriate service information to verify that both engine and transmission calibrations are the most current up-to-date level.

Automatic Transmission Input Speed Sensor Assembly (73)

Inspect the automatic transmission input speed sensor assembly (73) for loose electrical connection and/or signs of physical damage that could cause erratic output. The magnetic end of the sensor should be free of any metal shavings/particles, including heavy friction material build-up. If metal or heavy friction material is found, diagnose the cause and repair as necessary.

Automatic Transmission Fluid Temperature Sensor (36) - part of the Automatic Transmission Wiring Harness Assembly (33)

Using a scan tool, verify that the transmission fluid temperature is correct. If the transmission fluid temperature is NOT correct, diagnose and correct as necessary.

External Automatic Transmission Control Valve Body Assembly (39)

Verify that all solenoids respond electrically. If there is no response, perform an electrical diagnosis. If there are no electrical concerns, remove the solenoid valve assemblies as needed, and inspect the solenoid O-ring seals, and the solenoid bores for signs of damage and/or missing seals. If the solenoid valves responded electrically and there are no bore or seal concerns, replace the solenoid valve assemblies as necessary due to possible internal mechanical concerns and retest. If a condition is still present after replacing the solenoid valve assembly, replace the complete automatic transmission control valve body assembly (39).

Internal Automatic Transmission Control Valve Body Assembly (39)

Remove the automatic transmission control valve body assembly (39) and inspect the items listed. Inspect the internal bores and the valves for signs of wear and/or damage, including internal contamination. If unable to verify any repairable concerns, replace the complete automatic transmission control valve body assembly (39).