W T E C I I I E L E C T R O N I C C O N T R O L S T R O U B L E S H O O T I N G M A N U A L
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 tools CLUTCH TEST MODE.
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 (see Appendix B; pressure in 3C
would be the same as in 2C). 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. Disassemble, clean, and inspect the control module for
stuck or sticky valves (particularly the C solenoid second stage valve and C-1 latch valve). If no
obvious problems are found, replace the C solenoid and reassemble (see Figure 51 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 pressure switch wires in the transmission harness for opens, shorts, or
shorts-to-ground (see code 32þXX). If found, isolate and repair the C3 pressure switch circuit.
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 transmission harness, drain the fluid and remove the control module.
Check the feedthrough harness assembly for opens. If wiring problems are found, repair as
necessary. If no wiring problems are found, replace the C3 pressure switch (see Figure 51 for the
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)