P1904: Kickdown Solenoid Circuit High Voltage
The P1904 code indicates that the Powertrain Control Module (PCM) has detected a voltage higher than the specified range in the kickdown solenoid circuit. The kickdown solenoid is responsible for downshifting the transmission when the accelerator is fully depressed. A high voltage condition typically points to a short to power, a faulty solenoid, or a wiring issue. This can cause erratic transmission behavior, including harsh shifts or failure to downshift properly.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission fails to downshift when accelerating hard
- Harsh or delayed shifting
- Reduced fuel economy
- Transmission stuck in a single gear
2. Most Common Causes
- Open or broken wiring in the ground return circuit
- Corroded, damaged, or loose terminals in the transfer case sensor connector
- Faulty transfer case contact plate (position sensor)
- Internal mechanical damage in the transfer case preventing physical sensor contact
- Poor ground connection at the chassis or main harness
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 kickdown solenoid wiring and connectors for damage, corrosion, or shorts.
Step 3: Test the kickdown solenoid resistance with a multimeter; compare to manufacturer specs.
Step 4: Check for voltage at the solenoid connector with the key on; if voltage is higher than specified, trace the short to power.
Step 5: If wiring and solenoid are okay, test the PCM output; if faulty, replace PCM.
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 unpredictable transmission behavior, potentially leading to unsafe driving conditions or further transmission damage.
How much does it cost to fix?▼
The cost to fix P1904 typically ranges from $50 to $150 for parts and labor, depending on whether the issue is a simple wiring repair or solenoid replacement.
5. Commonly Affected Makes
This is a manufacturer-specific code. The exact manufacturer is not confirmed in our current database.