What Does P2784 Mean?
The Transmission Control Module (TCM) has detected a mismatch between input speed sensor A and B readings. These sensors monitor turbine speed and their signals should correlate closely during operation.
Common Causes
35%
Faulty input/turbine speed sensor (A or B)
30%
Wiring harness damage, corrosion, or loose connections to speed sensors
20%
Internal transmission mechanical fault causing actual speed differential
10%
Transmission Control Module (TCM) software issue or failure
5%
Low transmission fluid level or contaminated fluid affecting sensor operation
Diagnostic Steps
1
Step 1: Monitor live data for both input speed sensors during driving to identify which sensor signal is erratic or incorrect
2
Step 2: Inspect sensor wiring harness and connectors for damage, corrosion, chafing, or loose connections
3
Step 3: Check transmission fluid level and condition; top off or replace if needed
4
Step 4: Test resistance and voltage output of both speed sensors according to manufacturer specifications
5
Step 5: If sensors and wiring test normal, perform internal transmission inspection for mechanical faults
Estimated Repair Cost
$150 - $1,200
Parts + labor, varies by vehicle and location
The Transmission Control Module (TCM) has detected a mismatch between input speed sensor A and B readings. These sensors monitor turbine speed and their signals should correlate closely during operation.
The most common cause of P2784 (Input/Turbine Speed Sensor "A"/"B" Correlation) is: Faulty input/turbine speed sensor (A or B)
Typical repair costs for P2784 range from $150 to $1,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
May cause harsh shifting, unexpected gear changes, or transmission entering limp mode. Continue driving with caution and avoid aggressive acceleration.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P2784 to identify the root cause.
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Quick Info
Category
Powertrain
System
Transmission Control System
Difficulty
Type
Generic (SAE)
Recommended Tools
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