Copyright © 1998 General Motors Corp. 6–97
WTEC II ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL
3. If fluid level and main pressure are adequate, connect a pressure gauge to the C3 pressure tap on
the transmission and make the shift indicated by operating the vehicle using the Pro-Link
®
diagnostic tool’s CLUTCH TEST MODE.
NOTE: When using the CLUTCH TEST MODE on the Pro-Link
®
, be sure to use the correct pressure
specification. If testing is done with the vehicle stopped, the lockup clutch is not applied, so
use the clutch pressure specification for converter operation. If testing is done with the vehicle
moving, the lockup clutch may be applied depending upon the vehicle speed and throttle
position. Be sure to use the clutch pressure specification for lockup operation (see
Appendix B).
4. If, when making the shift and producing the code, the C3 clutch does not show any pressure, drain
the fluid and remove the control module (refer to the transmission Service Manual). Disassemble,
clean, and inspect the control module for stuck or sticky valves (particularly the solenoid C second
stage valve and C-1 latch valve). If no obvious problems are found, replace the C solenoid and
reassemble (see Figure 6–1 for location of the C solenoid).
5. If the gauge shows inadequate pressure being sent to the clutch, the clutch is probably worn, has
leaking piston or face seals, or the control module gaskets are damaged. See Appendix B for clutch
pressure specification. Drain the fluid, remove the control module and inspect the face seals and
valve body gaskets. If the face seals or control module gaskets are not damaged, remove and repair
the transmission (refer to the transmission Service Manual for repair procedure).
6. If the gauge shows adequate clutch apply pressure, the problem is with the C3 pressure switch or
its wires. Check the C3 switch wires in the chassis harness for opens, shorts, or shorts-to-ground
(see Code 32 XX). If found, isolate and repair the C3 circuit. See Appendix E for connector
service information.
NOTE: A leakage problem may be temperature related. Be sure to check pressures at the sump temperature
where the problem occurred.
7. If the problem is not in the chassis harness, drain the fluid and remove the control module. Check
the internal harness and feedthrough connector for opens. If wiring problems are found, repair as
necessary (refer to Appendix E). If no wiring problems are found, replace the C3 pressure switch
(see Figure 6–1 for the location). Refer to the transmission Service Manual for proper procedure.
8. If the condition persists, replace the ECU. If replacing the ECU corrects the problem, reinstall the
original (bad) ECU to confirm that the problem is in the ECU. If the original ECU now works,
inspect the ECU connectors for any corrosion or damage which may cause an intermittent
condition. If the original problem recurs, reinstall the replacement ECU.
CODE 55 XX — ONCOMING C3 PRESSURE SWITCH (AFTER SHIFT)
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