P1775 on 2006-2012 Mitsubishi Eclipse 3.8L V6: Second Solenoid Valve Fault Guide

What's Unique About the 2006-2012 Mitsubishi Eclipse

The 2006-2012 Eclipse (4G) with the V6 engine uses a 5-speed automatic transmission (model F5A51). Unlike some other manufacturers where P1775 points to a notoriously high-failure part due to valve body wear (e.g., certain Chrysler/Dodge models), on this specific Eclipse, it is not a widely reported pattern of premature failure in owner forums. The issue is typically a straightforward electrical or mechanical fault of the solenoid itself, as outlined in the factory service manual, rather than a known design flaw in the valve body.

Symptoms You May Notice

• Check Engine Light is on
• Transmission is stuck in 3rd gear (fail-safe/limp mode)
• Flashing 'D' or gear position indicator light on the dashboard
• Harsh or failed shifting
• Inability to shift into certain gears
• Vehicle feels sluggish on acceleration from a stop

Most Likely Causes

1. Failed Second Shift Solenoid 🔴 High Probability → Shop Transmission Valve Body Solenoids are electro-mechanical parts with internal coils and moving plungers that can wear out or fail electrically over time due to heat cycles and vibration. In the F5A51 transmission, all the shift solenoids are identical and interchangeable.
   How to confirm: Perform a resistance test on the solenoid terminals after disconnecting it. The factory service manual specifies a resistance of 2.7 - 3.4 Ohms at 68°F (20°C). A reading outside this range, or an infinite reading (open circuit), indicates a failed solenoid.
   Typical fix: Replace the failed solenoid. While Mitsubishi sells individual solenoids, it is common practice and highly recommended to replace all shift solenoids as a complete aftermarket pack, as they have all experienced the same wear. This involves removing the transmission oil pan and valve body to access the solenoid pack.
   Est. part cost: $80-$250
2. Damaged Wiring Harness or Connectors 🟡 Medium Probability The wiring harness leading to the transmission can be exposed to heat, oil, and road debris, which can cause wires to become brittle, frayed, or shorted over time. The connector pins can also corrode.
   How to confirm: Visually inspect the external wiring harness for any signs of damage. Check for continuity and shorts to ground between the PCM connector, the A/T control relay, and the transmission solenoid connector. Fluid intrusion into the main connector is also a possibility.
   Typical fix: Repair the damaged section of the wiring harness or clean/replace the corroded connector.
   Est. part cost: $10-$100
3. Low or Dirty Transmission Fluid ⚪ Low Probability → Shop Transmission Assembly While not a direct cause of an electrical fault code, extremely low or contaminated fluid can cause solenoids to stick or operate erratically. Debris in the fluid can clog the small passages within the solenoid, preventing it from functioning.
   How to confirm: Check the transmission fluid level and condition. The fluid should be at the correct level, pink/red in color, and not have a burnt smell or contain excessive metallic particles.
   Typical fix: Perform a transmission fluid and filter change. If the fluid is heavily contaminated, it may indicate a more severe internal issue requiring further diagnosis.
   Est. part cost: $70-$150

Rare But Worth Checking

• Faulty Powertrain Control Module (PCM): → Shop Engine Control Module (ECM) This is the least likely cause and should only be considered after all other possibilities (solenoid, wiring) have been thoroughly ruled out. PCM failure is rare.
• Failed A/T Control Relay: The A/T control relay supplies battery voltage to all the transmission solenoids. If it fails, multiple solenoid codes, including P1775, may be set. The service manual suggests checking for DTC P1788 (A/T Control Relay Malfunction) as part of the diagnostic procedure for P1775.

Diagnosis Steps

1. Check for other transmission-related DTCs with a capable OBD-II scanner.
2. Check the transmission fluid level and condition. Ensure it is clean and at the proper level.
3. Using a bi-directional scan tool, perform an 'Actuator Test' on the Second Solenoid Valve. Listen for an audible click from the transmission pan area.
4. If the solenoid does not click, inspect the external transmission wiring harness and connectors for damage, corrosion, or loose pins.
5. If the wiring appears intact, drop the transmission oil pan to access the solenoids.
6. Disconnect the solenoid pack connector (B-111-2) and measure the resistance of the Second Solenoid. It should be between 2.7 and 3.4 Ohms at 20°C (68°F).
7. If the resistance is out of spec, the solenoid is bad. It is recommended to replace the entire solenoid pack.
8. If the resistance is within spec, the solenoid itself is likely okay electrically. Check the wiring between the solenoid connector and the PCM for opens or shorts.
9. If the solenoid and wiring are confirmed to be good, the issue may be a mechanical problem within the valve body or, in very rare cases, a faulty PCM.

Parts You'll Likely Need

• Transmission Solenoid Pack (OEM #MD758981 (for a single solenoid)) — This is the most common cause of failure. The 'Second Solenoid' is part of this assembly. While Mitsubishi sells them individually, aftermarket kits contain all 5 shift solenoids and are the recommended repair.
  Trusted brands: Rostra (P/N: 52-0487), Transtar, Sheng Hai
  OEM price range: $55-$140 per solenoid
  Aftermarket price range: $80-$250 for a full kit
• Automatic Transmission Fluid — The fluid must be drained to replace the solenoid and should be replaced with new fluid. Use a fluid that meets Mitsubishi Diamond SP-III specifications. Many owners successfully use compatible multi-vehicle synthetic ATFs.
  Trusted brands: Idemitsu SP-III, Valvoline MaxLife Multi-Vehicle ATF, Eneos ECO ATF
  OEM price range: $15-$25 per quart
  Aftermarket price range: $8-$15 per quart
• Transmission Pan Gasket (OEM #MD759234) — The gasket should always be replaced when the transmission pan is removed to prevent leaks. Some technicians prefer using a high-quality RTV sealant designed for transmission fluid.
  Trusted brands: Fel-Pro, Mahle, Permatex The Right Stuff
  OEM price range: $25-$40
  Aftermarket price range: $15-$25

Related Codes That Often Appear With This One

• P0700 — P0700 is a generic code that means the Transmission Control Module (TCM), which is part of the PCM in this vehicle, has stored a fault code. It is an informational code that tells you to look for more specific codes like P1775.
• P0732 — This code indicates 'Gear 2 Incorrect Ratio'. It can sometimes accompany a solenoid fault code like P1775 if the solenoid's failure to actuate prevents the transmission from properly engaging or holding second gear.
• P1788 — This code (equivalent to P1751) points to a malfunction in the A/T Control Relay System. Since this relay provides power to the second solenoid, its failure can trigger P1775.

Platform-Specific Known Issues

• On forums like club4g.org, owners discussing P1775 and related transmission issues confirm that replacing the solenoid pack is the standard, successful repair. There is little discussion of this being a 'pattern' failure, but rather a typical repair for a vehicle of this age and mileage.
• A user on a Mitsubishi forum with a 380 (Australian Galant) experienced repeat 6G75 engine failures due to stretched main bearing bolts under boosted conditions, highlighting a potential weakness for modified engines, though it is unrelated to the transmission code itself.

Mechanic-Grade Diagnostic Values

• Second Solenoid Valve Resistance — expected: 2.7 - 3.4 Ohms at 20°C (68°F). Failure: A resistance reading outside this range, or an infinite reading (open circuit), indicates a failed solenoid.
• Solenoid Voltage (monitored by PCM) — expected: Greater than 3.0 Volts when commanded ON. Failure: If the PCM detects solenoid voltage is 3.0 volts or less for 0.3 seconds when it should be high, it flags a fault.

Scan Tool Commands That Help

• Mitsubishi MUT-III (MB991958): Actuator Test Item 3: Second Solenoid Valve — This command is the first step in the factory diagnostic procedure. It allows the technician to directly command the solenoid on and off to check for a response (an audible click from the transmission pan) without having to drop the pan first.

Wiring & Ground Locations

• B-111 — Main A/T control solenoid valve assembly connector on the transmission case.. This is the primary external connector for the entire solenoid pack. Checking for corrosion or damage here is a key step before dropping the pan. The service manual references checking for opens/shorts between this connector and the PCM/relay.
• B-111-2 — Internal connector for the Second Solenoid valve itself, inside the transmission pan.. This is the connector that must be disconnected to perform a direct resistance test on the suspect solenoid.
• B-15X — Connector for the A/T control relay, located in the engine compartment relay box.. Terminal 4 of this connector supplies power to the solenoid assembly. A fault here can cut power to all solenoids.
• B-20 — Connector at the Powertrain Control Module (PCM).. This is the other end of the circuit. The PCM provides the ground signal to energize the solenoid. Wiring checks are performed between this connector and B-111.
• Transmission Ground — A large ground strap typically connects from the negative battery terminal to one of the transmission-to-engine mounting bolts.. A poor ground connection for the transmission case can cause a variety of electrical issues, including erratic solenoid behavior. Ensuring this connection is clean and tight is a fundamental electrical diagnostic step.

OEM Part Supersession History

• MD758981 → MD758981 is still the active part number for a single solenoid. — N/A
  Heads up: All shift solenoids for the F5A51 are physically identical and interchangeable. However, they are different from the TCC/EPC solenoids. When buying a kit, ensure it is for the shift solenoids.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Clear Coat / Paint Failure 🟠 Medium — Very common, especially on darker colors and cars exposed to high UV/sunlight. Peeling often starts on the hood, roof, and rear bumper.
• Cracked or Peeling Dashboard 🟠 Medium — Widespread issue where the dashboard material cracks, peels, or lifts near the windshield due to heat and sun exposure.
• Timing Belt Replacement 🔴 High — The 6G75 is an interference engine requiring timing belt replacement every 60,000-100,000 miles. Failure to do so will result in catastrophic engine damage. The water pump and hydraulic tensioner must be replaced at the same time.
• Valve Cover Gasket Oil Leaks 🟡 Low — A common issue for the 6G75 V6 is oil leaking from the valve cover gaskets. If left unaddressed, this oil can leak into the spark plug tubes and cause ignition coil failure.
• Main Bearing Bolt Stretch (Modified Engines) 🔴 High — In high-performance or boosted applications, there are reports of the center main bearing bolts stretching, leading to bearing failure. This is not a common issue on stock, naturally aspirated engines.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For this repair, a used solenoid pack from a junkyard is generally NOT recommended. Solenoids are wear items with a finite lifespan determined by heat cycles and usage. A used part may have significant wear and could fail shortly after installation, forcing you to do the labor-intensive job twice.

Donor-vehicle mileage cap: roughly under 60000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• If considering a used part, source it from a vehicle with the lowest possible mileage.
• Ask for the VIN of the donor car to verify it had the F5A51 transmission and wasn't involved in a severe front-end collision.
• Inspect the electrical connector pins for any signs of corrosion, moisture, or damage.
• Avoid any parts that appear to have been stored outdoors or exposed to the elements.

OEM-only on this vehicle (don't cheap out):

• No parts for this specific repair are strictly OEM-only. High-quality aftermarket solenoid kits are widely available and are the standard repair method.

Aftermarket brands forum-validated for this vehicle:

• Rostra: A well-known and reputable manufacturer of aftermarket transmission electronics.
• Transtar: A major supplier of transmission parts to the professional repair industry.

Brands owners have reported issues with on this vehicle:

• Be cautious of unbranded, generic solenoid kits from online marketplaces. While they may be significantly cheaper, their quality control and longevity can be inconsistent, leading to premature failure.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0700 — Transmission Control System (TCS) Malfunction. This is a general fault code indicating the TCM has stored a specific trouble code, like P1775. It often appears as a companion code to alert the technician that a transmission-specific fault exists.
• P1776 — Low/Reverse Brake Solenoid Circuit. This code points to another solenoid within the same pack. Since all shift solenoids in the F5A51 are identical and wear at a similar rate, a failure of one makes failure of another likely. The root cause is the same as P1775.
• P1777 — Underdrive Clutch Solenoid Circuit. Like P1776, this code indicates a fault with another identical solenoid in the transmission. The recommended repair for any of these solenoid codes is to replace the entire pack.
• P1778 — Overdrive Clutch Solenoid Circuit. This code is for another identical solenoid in the same assembly. It shares the same common cause of failure (age, heat cycles) and repair procedure as P1775.
• P0882 — TCM Power Input Signal Low. The diagnostic steps for P1775 include checking the A/T control relay. A fault in this relay or its wiring could cause low voltage to the TCM and solenoids, potentially triggering P0882 alongside specific solenoid circuit codes.

Frequently Asked Questions