Shift Solenoid - Single

Replace a single shift solenoid in the 722.9 7-speed automatic transmission (7G-TRONIC) by removing the transmission oil pan, valve body cover, and accessing the solenoid pack.

Warnings

Tools required

Parts

• Shift solenoid (Y3/6y1-Y3/6y7 as identified by diagnostics) × 1 — A2212770497, A2212770597, or specific solenoid per fault code
• Transmission oil pan gasket × 1 — Use OEM specification
• Valve body cover gasket/seal × 1 — Use OEM specification
• Transmission drain plug crush washer × 1 — Use OEM specification
• Transmission filter (recommended) × 1 — Use OEM specification

Fluids

• Mercedes-Benz ATF 134 — 10 qt

Preparation

1. Retrieve diagnostic trouble codes using Star Diagnostics to identify which specific solenoid has failed (Y3/6y1 through Y3/6y7)
2. Ensure vehicle is on level ground and completely cooled (minimum 2 hours after driving)
3. Raise vehicle on lift or secure on jack stands with all four wheels off ground for clearance
4. Remove engine undertray and transmission protective panels
5. Disconnect negative battery terminal and wait 10 minutes for system shutdown
6. Place large drain pan under transmission oil pan
7. Prepare clean workspace with magnetic trays for organizing small bolts and components

Procedure

1. 1

   Drain transmission fluid
   Locate the transmission drain plug on the bottom of the pan. Using appropriate socket, slowly loosen the drain plug while maintaining pressure to control fluid release. Remove plug completely and allow all fluid to drain into pan (expect 8-10 quarts). Inspect drained fluid for metal particles or debris which may indicate additional transmission problems. Once drained, clean drain plug and install with new crush washer.
   Torque spec

   Transmission Drain Plug30 Nm (22 lb-ft)
2. 2

   Remove transmission oil pan
   Remove all transmission pan bolts in a criss-cross pattern, starting from the center and working outward. Note that some residual fluid will remain in pan. Carefully lower the pan, keeping it level to avoid spilling remaining fluid. Remove and discard old pan gasket. Inspect interior of pan for metal shavings or clutch material. Clean pan thoroughly with lint-free towels and brake cleaner. If replacing filter, remove old filter by pulling straight down from valve body.
   Torque spec

   Pan Bolts22 Nm (16 lb-ft)
3. 3

   Remove valve body cover
   With pan removed, you will see the valve body cover (sometimes called conductor plate or mechatronic sleeve). Remove all cover screws in sequence, keeping track of different screw lengths if applicable. Carefully lower the cover to expose the valve body and solenoid pack. Inspect and remove the cover gasket/seal. Do not allow any debris to fall into the exposed valve body.
   ⚠Keep the work area extremely clean. A single piece of debris in the valve body can cause catastrophic transmission failure.
   Torque spec

   Cover Screws15 Nm (11 lb-ft)
4. 4

   Identify and access target solenoid
   The 722.9 transmission contains 7 shift solenoids arranged in the solenoid pack on the valve body. Using your diagnostic codes, identify the exact solenoid position (Y3/6y1 through Y3/6y7). The solenoids are typically arranged in a row and held by individual retaining clips or a common retaining plate. Reference your diagnostic information or service documentation to confirm exact position before removal.
   ℹ️Take photos before disassembly to document wire harness routing and solenoid positions. Incorrect reassembly will cause transmission malfunction.
5. 5

   Remove electrical connections
   Locate the wire harness connector for the faulty solenoid. Press the retaining clip and carefully disconnect the electrical connector. Note the exact routing of the wire harness. Some solenoids may have individual connectors while others share a common connector block. Handle connectors carefully to avoid damaging pins.
   ⚠Do not force connectors. Mercedes electrical connectors use specific release mechanisms that can break if forced.
6. 6

   Remove faulty solenoid
   Remove the retaining clip or plate securing the target solenoid. This may be a spring clip, bolt, or locking tab depending on position. Grasp the solenoid body firmly and pull straight out from the valve body. Do not twist or rock the solenoid. Inspect the solenoid bore in the valve body for debris or damage. Check the O-rings on the removed solenoid for wear patterns that might indicate installation issues.
   ⚠The solenoid must be pulled straight out to avoid damaging the valve body bore. Any scratches or damage to the bore will require valve body replacement.
7. 7

   Install new solenoid
   Verify the new solenoid matches the removed part exactly. Lubricate the new solenoid O-rings lightly with clean ATF 134. Carefully align the solenoid with the valve body bore and push straight in until fully seated. The solenoid should slide in smoothly without force. Install the retaining clip or plate, ensuring it is fully engaged. Reconnect the electrical connector, listening for the click of the locking tab.
   ⚠A solenoid that does not slide in smoothly is either misaligned or the wrong part. Do not force it or you will damage both the solenoid and valve body.
8. 8

   Inspect and prepare valve body cover
   Clean the valve body cover mating surface thoroughly. Install new gasket/seal onto the cover, ensuring it is properly seated in all grooves. Verify all magnets in the cover (if equipped) are clean and secure. Check that no debris has fallen into the valve body during the repair.
9. 9

   Reinstall valve body cover
   Carefully position the valve body cover back onto the transmission, ensuring the gasket remains properly positioned. Start all cover screws by hand to ensure proper thread engagement. Tighten cover screws in a criss-cross pattern from center outward to ensure even gasket compression and proper sealing.
   Torque spec

   Cover Screws15 Nm (11 lb-ft)
10. 10

    Install filter and prepare pan
    If replacing the transmission filter, install the new filter by pushing it straight up into the valve body until it clicks into place. Clean the transmission pan mating surface on the transmission case thoroughly. Install new pan gasket onto the pan, using a small amount of gasket adhesive if needed to hold it in position during installation.
11. 11

    Reinstall transmission pan
    Carefully lift the pan with new gasket into position, ensuring gasket remains aligned. Start all pan bolts by hand before tightening any. Once all bolts are started, tighten in a criss-cross pattern from the center outward to ensure even gasket compression and prevent leaks.
    Torque spec

    Pan Bolts22 Nm (16 lb-ft)
12. 12

    Refill transmission fluid
    Connect transmission fluid pump to the fill port on the side of the transmission (not through dipstick tube - this transmission has no dipstick). Fill with approximately 7-8 quarts of MB ATF 134 initially. The exact amount will be determined during the fluid level setting procedure using Star Diagnostics. Do not overfill at this stage.
    ⚠Only use genuine Mercedes-Benz ATF 134. Using incorrect fluid will cause immediate shifting problems and long-term transmission damage.
13. 13

    Reconnect battery and clear codes
    Reconnect the negative battery terminal. Connect Star Diagnostics system to vehicle. Clear all stored fault codes related to the transmission and solenoid. Navigate to the transmission control module and prepare for the fluid level setting procedure.
14. 14

    Set transmission fluid level
    Using Star Diagnostics, initiate the transmission fluid level setting procedure. Start the engine and follow the on-screen prompts to cycle through all gears while monitoring transmission temperature. When fluid reaches 40°C (104°F), check and adjust fluid level per Star Diagnostics instructions by adding or removing fluid as needed. Continue until proper level is achieved at operating temperature (80-100°C/176-212°F). The system will indicate when proper level is reached.
    ⚠️Transmission fluid level MUST be set using Star Diagnostics at proper temperature. Incorrect fluid level will cause shifting problems, slippage, or transmission failure.

Reassembly

1. Reinstall all transmission protective panels and engine undertray with proper fasteners
2. Lower vehicle to ground and perform final visual inspection for any fluid leaks around pan gasket
3. Allow vehicle to reach full operating temperature and recheck for leaks with Star Diagnostics connected
4. Verify no new fault codes have been generated after repair

Verification

• Connect Star Diagnostics and verify the specific solenoid fault code has cleared and does not return
• Perform a test drive including all gear ranges (P, R, N, D, manual mode) and verify smooth shifting with no harsh engagements or slipping
• Monitor transmission temperature and ensure it reaches and maintains normal operating range (80-100°C)
• Perform Star Diagnostics transmission adaptation reset if required per service procedures
• Recheck fluid level after test drive at operating temperature to confirm proper fill
• Verify no fluid leaks from pan gasket, drain plug, or fill port after test drive
• Check for any new diagnostic trouble codes after test drive and verify transmission control module shows no faults

Related trouble codes on this vehicle

Codes that commonly send this job to the bay — tap one for symptoms, causes, and diagnostic steps.

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