22 2-4 Pressure Switch Circuit

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THEORY OF OPERATION:
The transmission system uses three pressure switches to monitor the fluid pressure in the L-R, 2-4, and OD elements. The pressure switches are continuously monitored for the correct states in each gear as shown below:





This code is set if the 2-4 pressure switch is open or closed at the wrong time in a given gear (see chart above)

LIMP-IN:
YES

WHEN MONITORED/SET CONDITIONS:
Whenever the engine is running.

TRANSMISSION EFFECTS:
- 89-95 model year + 96 model year V-1 calibration - relay open in limp-in mode
- 96 model year V-2 calibration (default desensitization) and 97 model year

If the 2-4 pressure switch is identified as being closed, in 1st or 3rd gear, and was not identified as being closed in P or N. then 2nd gear, or 4th gear, will be substituted for 1st or 3rd gear depending on throttle angle and vehicle speed. A short period of time after gear substitution, the transmission will return to normal operating mode. If the transmission is shifted back into 1st or 3rd gear through normal operation, and the 2-4 pressure switch remains closed, 2nd or 4th gear will be substituted briefly, and then resume normal operation. If four gear substitutions occur in a given key start, the transmission will go into limp-in mode by opening the relay contacts.

If the 2-4 pressure switch is open (indicating no 2-4 clutch pressure) in 2nd or 4th gear, the TCM sets code 22 and continues with normal operation. The transmission will only go into relay open limp-in mode if a code 28 is also present. If no 2-4 clutch pressure is present a speed ratio code 52 or 54 will be set and cause the limp-in condition.

POSSIBLE CAUSES:
- If code 35 is present, ignore code 22 and perform code 35 diagnostic procedures
- 2-4 pressure switch sense circuit open or shorted to ground between TCM and solenoid pack
- 2-4 pressure switch sense circuit shorted to battery
- Solenoid pack defective
- Transmission overheated - Excessive regulator valve leakage in valve body causing high line pressure which results in 2-4 solenoid blow-off into 1st or 3rd gear. This may require a new valve body if it happens only when hot
- Loose valve body bolts
- Plugged filter - internal transmission or torque converter failure
- Defective TCM