What Does P2643 Mean?
The PCM has detected an abnormally low voltage signal from torque management feedback circuit B. This indicates the feedback signal is below the acceptable threshold, suggesting a circuit fault or sensor issue.
Common Causes
35%
Wiring harness short to ground or damaged insulation in torque feedback circuit B
25%
Failed torque converter clutch pressure switch or transmission pressure sensor
20%
Faulty transmission control module with internal circuit failure
15%
Open circuit or high resistance in sensor ground circuit
5%
Defective engine load sensor or throttle position sensor providing low voltage feedback
Diagnostic Steps
1
Step 1: Measure voltage on torque feedback signal B circuit at the PCM connector with key on; should read within specification (typically 0.5-4.5V)
2
Step 2: Check continuity and resistance of the signal circuit from sensor/TCM to PCM; verify no short to ground exists
3
Step 3: Inspect all ground connections for the transmission control module and related sensors; clean and tighten as needed
4
Step 4: Test transmission pressure sensors and switches with appropriate pressure gauge and multimeter while monitoring live data
5
Step 5: If all circuits test within specification, substitute known-good TCM or sensor to isolate the faulty component
Estimated Repair Cost
$150 - $1,400
Parts + labor, varies by vehicle and location
The PCM has detected an abnormally low voltage signal from torque management feedback circuit B. This indicates the feedback signal is below the acceptable threshold, suggesting a circuit fault or sensor issue.
The most common cause of P2643 (Torque Management Feedback Signal "B" Low) is: Wiring harness short to ground or damaged insulation in torque feedback circuit B
Typical repair costs for P2643 range from $150 to $1,400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
May result in transmission staying in limp mode, harsh shifts, or disabled torque converter lockup. Safe to drive short distances but repair soon to avoid transmission damage.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P2643 to identify the root cause.
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Quick Info
Category
Powertrain
System
Torque Management / Transmission Control
Difficulty
Type
Generic (SAE)
Recommended Tools
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