What Does P278C Mean?
The PCM has detected that the kickdown switch circuit voltage is below the expected threshold. This indicates a short to ground or internal switch failure preventing proper signal transmission.
Common Causes
35%
Kickdown switch shorted internally
30%
Wiring harness shorted to ground
20%
Corroded or damaged connector causing short
10%
Chafed wire creating intermittent ground
5%
PCM internal circuit fault
Diagnostic Steps
1
Step 1: Disconnect kickdown switch connector and measure circuit voltage at PCM side - should read reference voltage (typically 5V or 12V)
2
Step 2: Check for continuity between signal wire and ground with switch disconnected - should be open circuit
3
Step 3: Inspect wiring harness routing for areas of chafing, pinching, or contact with hot components
4
Step 4: Test kickdown switch resistance with ohmmeter; compare to specifications
5
Step 5: If wiring and switch test good, suspect PCM internal fault
Estimated Repair Cost
$80 - $400
Parts + labor, varies by vehicle and location
The PCM has detected that the kickdown switch circuit voltage is below the expected threshold. This indicates a short to ground or internal switch failure preventing proper signal transmission.
The most common cause of P278C (Kick Down Switch Circuit Low) is: Kickdown switch shorted internally
Typical repair costs for P278C range from $80 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive with no kickdown function available. Vehicle will shift normally but may lack forced downshift capability.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P278C 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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