Kick Down Switch Circuit Range/Performance
The P278B code indicates that the Powertrain Control Module (PCM) has detected an issue with the kick down switch circuit, which is used to signal a full throttle request for downshifting. The switch or its circuit is not performing within the expected range, often due to a faulty switch, wiring issues, or a misadjusted pedal position sensor.
1. Most Common Causes
- Faulty kick down switch
- Damaged or corroded wiring/connectors
- Misadjusted accelerator pedal position sensor
- PCM software or hardware failure
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Delayed or harsh downshifts when accelerating
- No kick down function at full throttle
- Reduced fuel economy
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and freeze frame data.
Step 2: Visually inspect the kick down switch and wiring for damage or corrosion.
Step 3: Test the switch continuity and resistance with a multimeter.
Step 4: Check accelerator pedal position sensor adjustment and signal.
Step 5: If all else fails, replace the kick down switch and clear codes.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally safe to drive short distances, but the vehicle may not downshift properly when passing or climbing hills, which could be dangerous. It's best to have it repaired soon.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on the vehicle and the specific cause.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.