Symptom:
*TRANSMISSION SHIFTS EARLY WITH NO DTC’S
POSSIBLE CAUSES
VEHICLE BUS PROBLEMS
CHECK FOR INTERMITTENT WIRING & CONNECTORS
COLD TRANSMISSION
TEST ACTION APPLICABILITY
1 Using the DRBIIIt, check all other Modules for signs of a PCI bus problem such as
bus related DTC’s and/or communication problems.
Check and diagnose all 1 trip failures as a hard code.
Although it takes two occurences of a missed TRD link message to set the DTC
P1793, one missed message will cause the transmission to short shift until the next
start up. Ifthe vehicle has any indications of a bus problem, the bus must be repaired
first
Do any of the other modules show signs of a bus problem?
All
Yes → Refer to the Communication category and perform the appropri-
ate diagnostics.
No → Go To 2
2 The conditions necessary to set the DTC are not present at this time. Using the
schematics as a guide, inspect the wiring and connectors specific to this circuit.
Wiggle the wires while checking for shorts and open circuits.
Although it takes two occurences of a missed TRD link message to set the DTC
P1793, one missed message will cause the transmission to short shift until the next
start up. Ifthe vehicle has any indications of a bus problem, the bus must be repaired
first
Were there any problems found?
All
Yes → Repair as necessary.
No → Go To 3
3 If the transmission shifts too early when the transmission is cold, this is a normal
condition. The software is designed to protect the transmission from high torque
and/or high RPM shifts during cold operation.
Did the problem occur when the transmission temperature was cold?
All
Yes → This is a normal condition. The software is designed to protect the
transmission from high torque and/or high RPM shifts during
cold operation.
No → Test Complete.
177
TRANSMISSION - NGC
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