WTEC II ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL
3–2 Copyright © 1998 General Motors Corp.
BASIC KNOWLEDGE
3–3. SYSTEM OVERVIEW
WT Series Electronic Control functions are controlled by the ECU. The ECU reads shift selector range selection,
output speed, and throttle position to determine when to command a shift. When a shift occurs, the ECU monitors
turbine speed, output speed, and throttle position to control the oncoming and off-going clutches during the shift.
When the ECU detects an electrical fault, it logs a diagnostic code indicating the faulty circuit and alters the
operation of the transmission to prevent or reduce damage.
When the ECU detects a non-electrical problem while trying to make a shift, the ECU may try that shift a second or
third time before setting a diagnostic code. Once that shift has been retried, and a fault is still detected, the ECU
sets a diagnostic code and holds the transmission in a fail-to-range mode of operation.
3–4. IMPORTANT INFORMATION IN THE TROUBLESHOOTING PROCESS
Before beginning the troubleshooting process, read and understand the following:
•
Shut off the engine and ignition before any harness connectors are disconnected or connected.
•
Remember to do the following when checking for shorts and opens:
— Minimize movement of wiring harnesses when looking for shorts. Shorts involve wire-to-wire or
wire-to-ground contacts and moving the harnesses may eliminate the problem.
— Wiggle connectors, harnesses, and splices when looking for opens. This simulates vehicle move-
ments which occur during actual operation.
•
When disconnecting a harness connector, be sure that pulling force is applied to the connector itself and
not the wires
extending from the connector.
•
When conducting circuit checks that include the external harness, add 1 Ohm to the values shown.
•
Inspect all connector terminals for damage. Terminals may have bent or lost the necessary tension to
maintain firm contact.
•
Clean dirty terminals or connectors with isopropyl alcohol and a cotton swab, or a good quality,
non-residue, non-lubricating, cleaning solvent such as LPS Electro Contact Cleaner
®
or LPS NoFlash
Electro Contact Cleaner
®
.
•
Diagnostic codes displayed after system power is turned on with a harness connector disconnected can
be ignored and cleared from memory. Refer to Section 6, Diagnostic Codes, for the code clearing
procedure.
CAUTION:
The cleaning solvent must not be chlorine based, contain petroleum distillates, or
conduct electricity. The cleaning solvent should evaporate quickly to prevent the
possibility of condensation within the connectors. Always blow or shake any excess
cleaner from the connector before assembling it to its mating connector or hardware.
Cleaner trapped in the connector can affect the connector seal. (Refer to SIL 17-TR-94
for detailed information on the recommended cleaners.)
CAUTION:
Care should be taken when welding on a vehicle equipped with electronic controls.
Refer to Appendix G, Paragraph 1–1.
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