Allison B 300, Руководство по устранению неисправностей

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Copyright © 1998 General Motors Corp. 6–99
W T E C I I E L E C T RO N I C C O N T RO L S T RO U B L E S H O OT I N G M A N UA L
4. If a clutch is leaking pressure, drain the fluid, remove the control module and check for damaged
control module gaskets and stuck or sticking valves (see the transmission Service Manual). Also
look for damaged or missing face seals. If no problems are found, replace the solenoids for the
clutches used in the range indicated by the code.
5. If replacing solenoids does not correct the pressure problem, a worn clutch or worn piston seals are
probably the source of the pressure leak. Remove the transmission and repair or replace as
necessary (refer to the transmission Service Manual).
6. This code requires accurate output and turbine speed readings. If there were no transmission
problems detected, use the diagnostic tool and check the speed sensor signals for noise (erratic
signals) from low speed to high speed in the range indicated by the code.
7. If a noisy sensor is found, check the resistance of the sensor (300 ± 30 Ohms, refer to the Code 22
XX temperature variation chart) and its wiring for opens, shorts, and shorts-to-ground (refer to
Code 22 XX). Carefully check the terminals in the connectors for corrosion, contamination, or
damage. Ensure the wiring to the sensors is a properly twisted wire pair. Replace a speed sensor if
its resistance is incorrect. Isolate and repair any wiring problems. (Use a twisted-pair if a new
speed sensor circuit is needed — Service Harness Twisted Shielded Pair P/N 29522703 is available
for this purpose.)
8. If no apparent cause for the code can be found, replace the turbine and output speed sensors (refer
to the transmission Service Manual for proper procedure).
9. 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 56 XX — RANGE VERIFICATION RATIO TEST (BETWEEN SHIFTS)