P278C: Kick Down Switch Circuit Low
The P278C code indicates that the powertrain control module (PCM) has detected a low voltage condition in the kick-down switch circuit. The kick-down switch is typically located under the accelerator pedal and signals the transmission to downshift when the pedal is fully depressed. A low circuit voltage suggests a short to ground, faulty switch, or wiring issue, which can prevent proper downshifting and affect vehicle performance.
1. Most Common Causes
- Faulty kick-down switch
- Short to ground in the kick-down switch circuit
- Damaged wiring or connector
- Corroded terminals
- PCM failure (rare)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission fails to downshift when accelerator is fully depressed
- Reduced acceleration or sluggish performance
- Transmission stuck in higher gears
3. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for other 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 with a multimeter for proper continuity and resistance.
Step 4: Check for voltage at the switch connector; compare with manufacturer specifications.
Step 5: If wiring and switch are okay, test the PCM for proper signal reception.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code as it can cause poor acceleration and transmission shifting issues, potentially leading to unsafe driving conditions.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150, depending on whether the switch or wiring needs replacement and labor rates.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.