What it means
Voltage on the pressure control solenoid F control line is below the expected window. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
How it works
The TCM controls pressure control solenoid F through a monitored circuit, and the solenoid regulates transmission pressure. P2738 sets when voltage on the solenoid F control line falls below the expected range, which can happen with a short to ground, an internally shorted coil, or a poor connection.
Common causes
Most likely first.
- Control wire shorted to ground
- Internal short in solenoid coil
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine or transmission warning light on
- Harsh or delayed shifts
- Slipping or reduced drive
- Transmission may enter limp mode
How to diagnose it
- Record freeze-frame data and use live data to confirm the low-voltage fault is associated with solenoid F and when it occurs.
- Check transmission fluid level and condition using the manufacturer's procedure, and note any pressure-related shift symptoms.
- Inspect solenoid F's connector and harness for chafing, water entry, corrosion, pushed-back pins, or a wire contacting ground.
- While monitoring the fault, gently move the accessible solenoid F harness to check whether the low reading changes with movement.
- Use the wiring diagram to test the control line for a short to ground and check solenoid F coil resistance against the manufacturer's specification.
- If the wiring and coil pass, check the TCM connector and output circuit for a low-voltage fault.
Common fixes
- Repair chafed solenoid F wiring that is shorted to ground.
- Clean or replace corroded or pushed-back connector terminals and restore the seal.
- Replace solenoid F if its coil is internally shorted.
- Repair the TCM output circuit if testing confirms the fault is at the module.
Can I keep driving?
Keep driving to a minimum if shifting is harsh, delayed, or slipping, and avoid towing or hard acceleration. Stop if the transmission loses drive or shifts unpredictably, as continued slipping can cause further damage.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.