What Does P278B Mean?
The PCM has detected that the kickdown switch circuit voltage or resistance is outside the expected operating range during normal operation. This switch allows the driver to command a downshift for passing power in vehicles with automatic transmissions.
Common Causes
35%
Faulty kickdown switch assembly
30%
Damaged or corroded wiring harness or connectors in kickdown switch circuit
20%
Poor ground connection in kickdown switch circuit
10%
PCM internal fault or software issue
5%
Misadjusted kickdown switch or linkage
Diagnostic Steps
1
Step 1: Visually inspect kickdown switch and connector for damage, corrosion, or loose connections
2
Step 2: Test kickdown switch operation with multimeter - verify resistance values change when actuated per manufacturer specifications
3
Step 3: Check wiring harness continuity between switch and PCM; verify no shorts to ground or power
4
Step 4: Monitor switch circuit voltage with scan tool while actuating switch; verify signal transitions properly
5
Step 5: If all circuits test good, verify PCM ground circuits and consider PCM replacement or reprogramming
Estimated Repair Cost
$100 - $350
Parts + labor, varies by vehicle and location
The PCM has detected that the kickdown switch circuit voltage or resistance is outside the expected operating range during normal operation. This switch allows the driver to command a downshift for passing power in vehicles with automatic transmissions.
The most common cause of P278B (Kick Down Switch Circuit Range/Performance) is: Faulty kickdown switch assembly
Typical repair costs for P278B range from $100 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle remains safe to drive but may lack passing power when needed. Normal driving functions are not significantly impaired.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P278B to identify the root cause.
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Quick Info
Category
Powertrain
System
Transmission Control System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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