A P0738 code in your 2022 Cadillac XT5 indicates high voltage in the transmission control module enable circuit. This circuit provides power or enable signals to the TCM, allowing it to operate. High voltage suggests an open circuit or other issue preventing proper current flow, leaving the TCM unable to function correctly.
Understanding the TCM Enable Circuit
The TCM requires proper power supply and enable signals to operate. The enable circuit may control when the TCM is active or provide reference signals for internal operation. High voltage in this circuit typically indicates an open condition where current cannot flow, causing the voltage to remain at supply level.
Common Causes
An open circuit in the enable wiring prevents current flow. Disconnected or corroded connectors at the TCM create open conditions. The TCM's internal enable circuit may have failed. Related fuses or relays that power the TCM may be faulty. Wiring damage from rodents, heat, or mechanical stress can create opens.
Symptoms in Your XT5
The transmission may enter failsafe or limp mode. Shift quality may be affected or shifts may not occur properly. Multiple transmission-related warning lights may illuminate. In severe cases, the transmission may not function at all if the TCM is disabled.
Diagnostic Steps
Using GM GDS2, verify TCM communication and power status. Check fuses and relays related to TCM power supply. Measure voltage at the TCM connector with key on—compare to specifications. Check for continuity in the enable circuit. Inspect TCM connector for damage, corrosion, or loose pins.