The P0737 code in your 2019 Buick Enclave indicates that the transmission control module has detected a stuck-in-neutral condition. The transmission isn't engaging any gear despite being commanded to do so. This is a serious condition that typically prevents vehicle movement.
What Stuck in Neutral Means
When the TCM commands a gear but the output shaft doesn't turn relative to engine speed (or turns with the wrong ratio for all gears), it recognizes a neutral condition. This could mean no clutches are applying, or mechanical issues prevent power transmission. Your Enclave's 9-speed transmission requires multiple systems working properly to engage gears.
Common Causes
Severe low transmission fluid level preventing hydraulic operation. Failed transmission pump not generating pressure. Multiple solenoid failures preventing any gear engagement. Valve body stuck in neutral routing. Severe internal mechanical failure preventing gear selection. Electrical issues preventing TCM from commanding any gear.
Symptoms You'll Experience
The vehicle won't move in Drive or Reverse despite engine revving. The transmission feels like it's in neutral regardless of shifter position. No engagement felt when shifting between gears. Warning lights illuminate for multiple systems. The engine runs normally but the vehicle is immobile.
Diagnostic Approach
Using GM GDS2, verify TCM is commanding gears and check for response. Check transmission fluid level and condition immediately—this is often the cause. Test transmission line pressure. Check for multiple solenoid codes. Verify electrical connections and power supply to transmission. If pressure is zero, suspect pump failure.