52 Gear Ratio Error In 2ND

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Part 2 Of 2:

THEORY OF OPERATION:
The transmission system uses two speed sensors, one to measure input RPM and one to measure output RPM. These inputs are essential for proper transmission operation. Therefore, the integrity of his data is verified through the following checks:
1. When in gear, if the gear/speed ratio does not compare to a known gear ratio, the corresponding in-gear trouble code is set (codes 50 through 54).
2. An excessive change in input or output speeds indicating signal intermittence will result in codes 56 and/or 57 being set.
3. After a TCM reset in neutral, observing erratic output and input speed sensor signals indicates a loss of the common speed sensors ground. This sets a code 58.

LIMP-IN:
YES

WHEN MONITORED/SET CONDITIONS:
The transmission gear/speed ratio is monitored continuously while the transmission is in gear. This code is set if the gear/speed ratio is not correct for a period of time. A hard code sets within 3 seconds, an intermittent code sets within.15 seconds.
- Codes 50 through 54 set if the ratio of the input RPM (Nt) to the output RPM (No) does not match the given gear ratio.

TRANSMISSION EFFECTS:
93-95 MY + 96 MY V-1 calibration - At speeds below 45 MPH, the transmission goes into relay open limp-in mode. At speeds above 45 MPH, EMCC is aborted and the current gear is maintained until vehicle drops below 45 MPH, at which time the transmission goes into relay open limp-in mode.

96 MY V-2 calibration (default desensitization) and later - The transmission will not go into relay open limp-in mode until three gear/speed ratio error events occur in a given key start. This allows for intermittent problems to correct themselves without opening the relay. However, if a gear/speed ratio error develops, a code is always set, but if the condition corrects itself the transmission will continue without requiring the ignition key to be cycled on and off. Many different events could occur given the range of failures possible for codes 50 through 58. The following are a few examples:

Codes 51, 52, 53, 54, 56, and 57 (at speeds above 45 MPH) - If one of these codes is set above 45 mph, converter clutch operation is aborted and current gear is maintained. If the vehicle is still travailing over 45 mph and the gear ratio becomes valid, normal operation will resume. If the gear ratio becomes invalid three times in a given key start, converter clutch operation is aborted and current gear is maintained until the vehicle speed drops below 45 mph. Below 45 mph, current gear will be maintained until vehicle speed drops to 22 mph or until throttle is applied, at which time the transmission system will go into limp-in mode.

Codes 51, 52, 53, 53, 54, 56, and 57 (at speeds between 22 and 45 MPH) - If one of these codes is set between 22 and 45 MPH, current gear will be maintained unless throttle is applied, at which time the transmission will shift to second gear. If the gear ratio becomes valid, normal operation will resume. If the gear ratio becomes invalid three times in a given key start, the current gear will be frozen until vehicle speed drops to 22 mph or until throttle is applied, at which time the transmission system will go into limp-in mode.

Codes 51, 52, 53, 54, 56, and 57 (at speeds below 22 MPH) -If one of these codes is set below 22 mph, the transmission will shift to second gear. If the gear ratio becomes valid, normal operation will resume. If the gear ratio becomes invalid three times in a given key start, the transmission system will go into limp-in mode.

POSSIBLE CAUSES:
Excludes gear-train failures which should be obvious upon disassembly.

If code 35 is also set, follow diagnostic procedure for code 35 first
- Plastic accumulator - change to aluminum per TSB 21-15-95 (check for later TSB)
- 2-4 seal leakage (intermittent)
- Sticky accumulator seals (intermittent)

Failed or intermittent slipping UD clutch - may also set code 51 and/or 53
- UD seal leakage (intermittent)
- Worn input clutch hub bushing (hard code at heavy throttle)
- Sticky UD accumulator seals (intermittent)
- Worn reaction shaft support seal rings (hard code at heavy throttle)
- Defective solenoid pack (UD pressure in 4th gear)