What it means
The control module monitors torque management feedback signal A and sets this code when the reported value falls below its expected level.
At a glance
- Usually lights the check-engine light
How it works
Torque management feedback signal A is a torque-related value sent over the vehicle network for engine or drivetrain coordination. P2639 sets when the receiving module sees that value fall below its expected level, including when the source module sends an invalid low value or the bus signal is stuck low.
Common causes
Most likely first.
- Source module sends invalid low value
- Signal stuck low on the bus
Symptoms
- Reduced engine power or torque
- Hesitation or sluggish acceleration
How to diagnose it
- Save freeze-frame data and check live data for torque feedback signal A to confirm it is low or remains fixed when operating conditions change.
- Scan all modules for communication faults and source-module codes that could explain an invalid low signal A report.
- Inspect the signal A source module's connectors and accessible network wiring for corrosion, damage, loose pins, or shorts affecting communication.
- Compare signal A with related torque request and feedback values, if available, to determine whether only signal A is implausibly low.
- Test network continuity and the source module's power and grounds according to the manufacturer's wiring and diagnostic information.
Common fixes
- Clean and secure a corroded or loose signal A network connector.
- Repair damaged wiring or a short affecting the network message.
- Resolve a confirmed fault in the module sending torque feedback signal A.
- Replace a faulty module only after its network circuit, power, and grounds pass checks.
Can I keep driving?
A low torque feedback value can cause reduced power or hesitation, so drive gently and avoid fast traffic, steep climbs, and towing. Stop if the vehicle cannot maintain a safe speed.
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.