Al4 Transmission Solenoid Valve
Fix Harsh Shifts and Limp Mode with the AL4 Transmission Solenoid Valve If your Renault, Peugeot, or Citroën suddenly feels stuck in third gear, flashes a snowflake or “S” on the dash, or jerks between gears, the internal hydraulic control has likely failed. The usual culprit is a worn AL4 transmission solenoid valve. Flying Bull offers a direct-fit replacement for AL4 and DP0 gearboxes, designed to bring back original shifting quality. This automatic transmission solenoid valve manages oil flow inside the valve body. It opens and closes in milliseconds, controlling clutch engagement and shift timing. When the original part wears out from heat, debris, or age, the transmission control unit (TCU) sees incorrect pressure readings. In response, the TCU activates a protection program – locking the gearbox in third gear. You will notice high engine speed at cruising, weak acceleration from a stop, and repeated lock-ups even after restarting. Flying Bull’s AL4 solenoid valve matches OEM specifications closely. It features a corrosion-resistant steel body, high-temperature sealing rings, and precision-wound coils. The resistance (typically 4–8 ohms) and flow curve are calibrated so the TCU reads signals correctly without new error codes. Each unit is tested for leaks under pressure cycles from 0 to 20 bar. Key benefits of this transmission shift solenoid: Direct replacement for AL4 / DP0 transmissions – no modifications needed. Smoother shifts and reduced shift shock. Stops the flashing snowflake or “S” light. Operating voltage: 12V DC. Temperature range: -40°C to 150°C. A common failure symptom on Citroen C4 or C5 (and similar models) is a pressure regulation fault code. Using a scanner, you may see a difference between rated pressure (e.g., 3.0 bar) and actual pressure (e.g., 2.4–2.5 bar). That difference triggers the emergency program. Replacing the main pressure solenoid on the valve body and using fresh transmission fluid usually solves the problem. For workshop mechanics and DIY owners, swapping this solenoid is straightforward after removing the transmission oil pan. For best long-term results, replace all three solenoids on the AL4 valve body at the same time and always use clean, manufacturer-recommended ATF. Keep your gearbox shifting like new – choose the AL4 transmission solenoid valve from Flying Bull.
Product Introduction
Products Description
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OE NO.: DPO AL4 257416 2574.16 |
Car Model: for Renault |
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Car Fitment: Renault |
Size: Standard |
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Warranty: 1 YEAR |
Condition: New, 100% Brand-new |
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Place of Origin: Zhejiang, China |
Type: Transmission Assembly |
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Brand Name: FLYING BULL |
Transmission Model: AL4 dpo |
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Delivery: 5-7 Working Days |
Product name: EPC Solenoid |
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OEM NO: 257416 |
Quality: High-Quality |
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Supply Ability: 10000 Piece/Pieces per Day |
Shipping: DHL UPS EMS FEDEX OCEAN |
AL4 transmission solenoid valve failure cause analysis:
Citroen Sega is equipped with AL4 transmission solenoid valve, OE: 257416, 4-speed transmission, the transmission oil pressure solenoid valve is easy to damage, when AL4 transmission solenoid valve is worn and the pressure is insufficient, the actual oil pressure and the oil pressure specified by the computer reach a certain error in high-speed driving. The pressure transmission computer will start the protection program, that is, the emergency program to lock the gear and not shift. At this time, the gearbox is locked in the third gear at high speed, the engine speed is particularly high, and then start after pulling over, the vehicle starts in third gear, acceleration is weak, the engine is turned off and restarted, and the fault disappears, but the gearbox may still have a lock failure if it continues to drive.
Citroen Sega Gearbox fault repair process:
① First, the computer detects the transmission system fault code, showing the difference in pressure regulation or setting temporary faults.
② According to the fault code, we can know that this is caused by the deviation of the actual oil pressure and rated pressure after the main pressure solenoid valve is worn. Reading the data stream, we found that idle driving, idle gear, standard pressure 3.0, actual pressure 2.4~2.5 back and forth changes, the oil pressure difference is large.
③ Release transmission oil, transmission oil is particularly black.
④ Remove the gearbox, the oil pan exposed is the gearbox valve body.
⑤ Take out the transmission valve body and replace the main pressure solenoid valve on the right side of the transmission valve body.
After installing the solenoid valve, reinstall the valve body and oil pan, and fill the Citroen special automatic transmission oil. Test check the data flow, idling into the forward gear, the actual oil pressure is 3.0, the rated oil pressure is between 2.95 and 3.05, the fluctuation is completely in the normal range, high-speed test and real-time check the oil pressure, the actual oil pressure and rated pressure have been maintained in a certain range, the Sega transmission solenoid valve failure has been successfully solved.
Company Introduction
Frequently Asked Questions (FAQ)
1. Which vehicle models use this AL4 transmission solenoid valve?
This solenoid fits all AL4 and DP0 automatic transmissions. You will find these gearboxes in Renault (Laguna, Megane, Scenic), Peugeot (206, 307, 407), Citroën (C4, C5, Xsara), and some Nissan or Suzuki models. Always check your transmission code before ordering – not just the car model.
2. What are the most common symptoms of a failing AL4 solenoid?
The clearest sign is the transmission locking in third gear (limp mode) with a flashing snowflake or "S" on the dashboard. You may also experience harsh upshifts or downshifts, delayed engagement, or unexpected shifting. Fault codes like P0750, P0753, or P1167 are typical.
3. Why does the transmission lock in third gear when the solenoid fails?
The TCU compares the rated oil pressure (set by the computer) with the actual pressure reading. When a worn solenoid causes a large difference – for example, 3.0 bar rated versus 2.4–2.5 bar actual – the TCU activates an emergency protection program. It locks the gearbox in third gear to prevent further damage.
4. Is this solenoid a direct replacement for the original part?
Yes. The dimensions, bolt pattern, connector shape, and hydraulic ports match the original. No cutting, wiring changes, or adapters are required. Remove the old unit and install this one with a new seal ring.
5. Should I replace just one solenoid or all three at once?
You can replace only the failed unit, but we recommend replacing all three solenoids on the AL4 valve body together. The older units may fail soon after, and the labor to open the pan and remove the valve body is the same. Doing all three at once saves time and repeat repair costs.
6. What fluid and post-installation steps are required?
Use the recommended ATF for your AL4 transmission – usually Dexron III or a compatible synthetic fluid. After installing the new solenoid, refill with fresh ATF, warm up the gearbox, and check the fluid level with the engine running. Also reset the TCU adaptation values using a diagnostic scanner for best shift learning.
7. Does this solenoid valve come with a warranty?
Yes. Flying Bull provides a 1‑year warranty against manufacturing defects. Normal wear from contaminated fluid or electrical issues outside the solenoid is not covered. Always use a clean filter and fresh ATF when installing.
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