Copyright © 1998 General Motors Corp. 6–101
WTEC II ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL
Main code 57 indicates failure of the range verification C3 pressure switch test. This test determines if the C3
pressure switch is closed when it should be open. The test occurs when a range is commanded that does not use the
C3 clutch (neutral, 1, 2, 4, and 6). The code is set if the C3 pressure switch is closed when it should be open. If C3
clutch comes on when not needed, three clutches are applied and a transmission tie-up occurs. The ECU will
command a range which does not use the C3 clutch and activate the DO NOT SHIFT response.
Active Indicator Clearing Procedure:
• Power down
• Manual
NOTE: Before troubleshooting, read Pages 6–17 and 6–18 of Section 6–5. Also, check battery and ECU input
voltages.
NOTE: Intermittent connections or lack of battery-direct power and ground connections may cause this and
other codes.
NOTE: Energizing the solenoids and listening for ball/plunger movement is sometimes useful in
troubleshooting.
Troubleshooting:
1. Disconnect the external harness from the transmission. Check the C3 pressure switch circuit at the
transmission for continuity (refer to Code 32 XX).
2. Continuity at the transmission indicates the C3 pressure switch is closed or the C3 circuit is shorted
together. Drain the fluid, remove the control module (refer to the transmission Service Manual), and isolate
the short. The fault is either a shorted internal harness or stuck C3 pressure switch. Repair or replace as
necessary.
3. If there is no continuity at the transmission, disconnect the harness connectors from the ECU and
check the C3 pressure switch wires in the external harness for shorts. Use the system wiring diagram
to identify wires which are connected. If a shorted C3 pressure switch circuit in the external harness is
found, isolate and repair.
4. If the C3 pressure switch or circuit is not shorted either in the transmission or the external harness, connect
a pressure gauge in the C3 pressure tap (refer to Appendix B for pressure tap location). Drive the vehicle in
the range indicated by the code or use the diagnostic tool’s clutch test mode to attain that range.
5. If the gauge shows C3 pressure is present in the range indicated by the code, drain the fluid and
remove the control module (refer to the transmission Service Manual). Check for damaged valve
body gaskets or stuck or sticking valves. Repair or replace as necessary. If no obvious defects are
found, replace the listed solenoid.
6. If the gauge shows C3 pressure is not present in the range indicated by the code, drain the fluid and remove
the control module (refer to the transmission Service Manual). Replace the C3 pressure switch.
7. 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 reoccurs, reinstall the replacement ECU.
Main
Code
Subcode Meaning
Replace
Solenoid
57 11 Range verification C3 pressure switch while in 1st B
57 22 Range verification C3 pressure switch while in 2nd C
57 44 Range verification C3 pressure switch while in 4th C
57 66 Range verification C3 pressure switch while in 6th A
57 88 Range verification C3 pressure switch while in N1 C
57 99 Range verification C3 pressure switch while in N2/N4 C
CODE 57 XX — RANGE VERIFICATION C3 PRESSURE TEST
(BETWEEN SHIFTS)
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