P278B - Kick Down Switch Circuit Range/Performance
The P278B code indicates that the Powertrain Control Module (PCM) has detected a malfunction in the kick-down switch circuit, which is used to signal a full-throttle downshift request in automatic transmissions. The switch's signal is out of the expected range or performance parameters, often due to a faulty switch, wiring issues, or a misadjusted pedal linkage.
01. Most Common Causes
- Faulty kick-down switch
- Damaged or corroded wiring/connectors in the kick-down switch circuit
- Misadjusted accelerator pedal linkage or kick-down cable
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission fails to downshift when accelerator is fully depressed
- Reduced acceleration or sluggish performance
03. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for related codes.
Step 2: Visually inspect the kick-down switch and its wiring for damage, corrosion, or loose connections.
Step 3: Test the kick-down switch operation using a multimeter to verify continuity when the accelerator is fully pressed.
Step 4: Check and adjust the accelerator pedal linkage or kick-down cable per manufacturer specifications.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally safe for short trips, but the transmission may not downshift properly, leading to reduced performance and potential transmission wear. It is recommended to diagnose and repair promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150, including parts (switch) and labor. If wiring repairs are needed, costs may be higher.