Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that a part in the car that helps change gears isn't working properly. It's like if your bicycle chain wasn't moving smoothly when you try to change gears.
The transmission control module (TCM) has detected that the pressure control solenoid 'E' is not allowing enough hydraulic pressure to facilitate proper gear shifts.
The pressure control solenoid 'E' is responsible for regulating the hydraulic pressure needed for gear shifts in the transmission. If the solenoid is not functioning correctly, it can result in insufficient pressure, causing delayed or harsh shifts. The TCM monitors this and sets the P1904 code when it detects a deviation from expected pressure levels.
• Harsh or delayed gear shifts
• Transmission slipping
• Check Engine Light illuminated
• Faulty pressure control solenoid 'E'
• Wiring issues such as shorts or open circuits
• Transmission fluid contamination or low levels
Transmission Control Module (TCM): An electronic device that manages the operation of the transmission.
Solenoid: An electromechanical device used to control the flow of fluid in the transmission.
• Scan the vehicle with an OBD-II scanner to confirm the code.
• Inspect the transmission fluid level and quality.
• Check the wiring and connectors to the pressure control solenoid 'E'.
• Replace the faulty pressure control solenoid 'E'.
• Repair or replace damaged wiring or connectors.
• Flush and replace the transmission fluid.
• OBD-II scanner
• Multimeter
• Transmission fluid pump
$200 - $600
Moderate
• Ford F-150
• Chevrolet Silverado
• Toyota Camry
• Regularly check and maintain transmission fluid levels.
• Schedule regular transmission service.
• Inspect wiring and connectors periodically.
Transmission Issue
• Avoid driving aggressively until the issue is resolved.
• Have the transmission system inspected by a professional.
• Monitor for any changes in vehicle performance.
Check with your vehicle's manufacturer for warranty coverage on transmission components.
This code has been associated with vehicles that have experienced transmission wear and tear, especially those with high mileage.
Moderate – It's important to address this issue soon to avoid further transmission damage.
Ignoring transmission issues can lead to safety hazards on the road. Always address Check Engine Light warnings promptly.
• Vehicle at operating temperature
• Vehicle in motion
The pressure control solenoid 'E' is located within the transmission valve body.
Q: Can I drive with a P1904 code?
A: It's not recommended to drive for extended periods with this code as it can lead to further transmission damage.
Q: How often should I check my transmission fluid?
A: It's good practice to check your transmission fluid every 30,000 to 60,000 miles, or as recommended by your vehicle's manufacturer.
High-End · Full-system diagnostics
A full-system bidirectional platform aimed at advanced DIY users and professional diagnostic workflows.
Network faults often require full-system access instead of a generic code reader alone.
View on Amazon
Universal · Digital multimeter
A solid entry-level multimeter for voltage, continuity, resistance, and basic electrical troubleshooting.
Helpful for checking voltage drops, grounds, and basic circuit health when modules are not communicating.
View on Amazon
Universal · Wire connectors and repair kit
Useful when diagnosis points toward damaged wiring, corroded terminals, or connector repairs.
Useful if diagnosis points toward damaged connectors, wiring, or terminal repairs.
View on AmazonThese are optional diagnostic tools, not guaranteed fixes. As an Amazon Associate I earn from qualifying purchases.