6–48 Copyright © 1998 General Motors Corp.
WTEC II ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL
6. If, after detecting leaking pressure and replacing solenoids, the problem persists, check for worn
clutch or piston seals. Remove the transmission and repair or replace as necessary (refer to the
proper transmission Service Manual).
7. This code requires accurate output and turbine speed readings. If there were no transmission
problems detected, use the diagnostic tool and watch the speed readings for noise (erratic signals)
from low speed to high speed in the range indicated by the code.
8. If a noisy sensor is found, check the sensor resistance (refer to the sensor resistance chart below)
and check its wiring for opens, shorts, and shorts-to-ground (see Code 22 XX). Also closely check
the terminals in the connectors for corrosion, contamination, or damage. Ensure the wiring to the
sensors is a properly twisted wire pair. Remove the sensor and check for damage at the tone wheel
end. Check for looseness of the tone wheel. Refer to the appropriate Service Manual if repair of a
loose tone wheel is necessary. Replace the sensor if it is damaged or if its resistance (refer to
Service Manual for proper procedure) is incorrect and isolate and repair any noted wiring
problems. (Use twisted-pair if new speed sensor circuit is needed in external harness. Service
Harness Twisted Shielded Pair P/N 29522703 is available for this procedure.)
9. If no apparent cause for the code can be located, replace the turbine and output speed sensors.
Refer to the appropriate transmission Service Manual for proper procedure.
10. 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.
Resistance Temp. °C Temp. °F
200
Ω
–40 –40
300
Ω
20 68
400
Ω
110 230
CODE 25 XX — OUTPUT SPEED SENSOR, DETECTED AT ZERO SPEED,
X RANGE
(Figures 6–13, 6–14)
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