P278D: Kick Down Switch Circuit High
The P278D code indicates that the powertrain control module (PCM) has detected a high voltage signal from the kick down switch circuit. This switch is typically located at the accelerator pedal and signals the transmission to downshift for maximum acceleration. A high voltage reading suggests a short to power, a faulty switch, or a wiring issue. This can cause erratic transmission behavior, such as unexpected downshifts or failure to downshift when needed.
01. Most Common Causes
- Faulty kick down switch
- Short to power in the kick down switch circuit
- Damaged wiring or connector
- Corrosion or poor electrical connection
- Faulty PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission does not downshift when accelerator is floored
- Unexpected or harsh downshifts
- Reduced acceleration performance
- Transmission stuck in a single gear
03. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for additional 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; it should show continuity when depressed and open when released.
Step 4: Check for voltage at the switch connector; with key on, there should be 5V reference signal. If voltage is higher, suspect a short to power.
Step 5: If wiring and switch are okay, test the PCM input/output signals to rule out a faulty PCM.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code as it can cause unpredictable transmission behavior, potentially leading to unsafe driving conditions or transmission damage.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on whether the switch or wiring needs replacement.