What it means
The shift-by-wire gear shift control module A reports a supply voltage below the operating range.
At a glance
- Usually lights the check-engine light
How it works
Shift control module A manages electronic gear selection in a shift-by-wire system and relies on its supply voltage to operate. P273C sets when the module reports voltage below its operating range, which can occur if the battery voltage sags or the charging system output is low.
Common causes
Most likely first.
- Weak battery sags voltage under load
- Alternator output below regulation point
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
How to diagnose it
- Record freeze-frame data and scan for other low-voltage or communication codes to see whether module A's supply drop affected other systems.
- Check battery terminals and the module A power and ground connections for looseness, corrosion, or damaged wiring.
- Have the battery tested under load and compare its condition with the manufacturer's specification.
- Check charging system operation and alternator output against the manufacturer's specification, including under electrical load.
- Inspect the shift control module A supply and ground circuits for excessive voltage drop using the wiring diagram.
- If battery, charging, and wiring checks pass, check module A's reported supply and its power connection for an internal fault.
Common fixes
- Clean and tighten the battery terminals and module A power or ground connections.
- Replace a weak battery that fails the manufacturer's load test.
- Repair damaged or high-resistance supply and ground wiring to shift control module A.
- Repair or replace the alternator if charging output is outside the manufacturer's specification.
- Replace shift control module A only if its supply remains low with verified power and ground circuits.
Can I keep driving?
If gear selection or shifting is unpredictable, avoid driving and arrange a safe way to move the vehicle; low module voltage can lead to lost gear control. If it shifts normally, limit driving and address the battery or charging fault promptly.
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.