6–96 Copyright © 1998 General Motors Corp.
WTEC II ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL
Main code 55 indicates the C3 clutch is the oncoming clutch in a shift and the C3 pressure switch did not close at
the end of the shift. When this code is set, the DO NOT SHIFT response and Neutral with No Clutches is
commanded. On the N1 to R shift the transmission is commanded to the previous range. Additional codes could be
logged for other shifts where “X” indicates the range from and “Y” indicates the range to. Main code 55 can also
be caused by the EEPROM being calibrated for a close ratio transmission and installed in a wide ratio
transmission, or vice versa.
NOTE: When sump temperature is below 10˚C (50˚F), and transmission fluid is C4 (not DEXRON), follow
this procedure when making directional change shifts:
• To shift from forward to reverse; select N (Neutral) and then R (Reverse).
• Failure to follow this procedure may cause illumination of the CHECK TRANS light and then
transmission operation will be restricted to N (Neutral).
Active Indicator Clearing Procedure:
• Power down
• Manual — subcode 87 only
NOTE: Intermittent connections or lack of battery-direct power and ground connections may cause this and
other codes.
NOTE: Check battery and ECU input voltages before troubleshooting.
NOTE: Energizing the solenoids and listening for ball/plunger movement is sometimes useful in
troubleshooting.
Troubleshooting:
NOTE: Do not bring the transmission to operating temperature if the problem occurs at sump temperatures
below that level. Do troubleshooting at the temperature level where the problem occurs.
1. After the transmission is at operating temperature, allow vehicle engine to idle on level ground for
3–4 minutes. Check transmission fluid level. If improper fluid level is found, correct as necessary.
Improper fluid level could be the cause of the code (not enough or too much fluid may produce
inadequate clutch pressure).
2. Connect a pressure gauge and check main pressure. If pressure is not adequate, the pump is
possibly worn. See Appendix B for main pressure specifications.
Main
Code
Subcode Meaning
55 07 Oncoming C3PS (after shift), L–R shift
55 17 Oncoming C3PS (after shift), 1–R shift
55 27 Oncoming C3PS (after shift), 2–R shift
55 87 Oncoming C3PS (after shift), N1–R shift
55 97 Oncoming C3PS (after shift), N1–L to R shift
55 XY Oncoming C3PS (after shift), X to Y shift
CODE 55 XX — ONCOMING C3 PRESSURE SWITCH (AFTER SHIFT)
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