Transmission Range Sensor

Replace the transmission range sensor (also known as neutral safety switch or inhibitor switch) on the Mercedes-Benz 722.6 5-speed automatic transmission, restoring proper gear position detection and starting safety function.

Warnings

Tools required

Parts

• Transmission range sensor × 1 — A0005427418 or equivalent
• Transmission range sensor seal/O-ring × 1 — Typically included with sensor
• Red ATF for 722.6 5G-Tronic × 1 — MB 236.10 specification

Fluids

• transmission_auto — 1.5 qt

Preparation

1. Park vehicle on level ground and engage parking brake firmly
2. Ensure transmission selector is in Park position
3. Allow transmission to cool if recently driven (fluid may be hot)
4. Disconnect negative battery terminal to prevent fault codes during sensor disconnection
5. Raise vehicle using jack and support securely on jack stands rated for vehicle weight
6. Remove transmission splash shield or undertray if equipped using Torx fasteners

Procedure

1. 1

   Locate and access transmission range sensor
   From underneath the vehicle on the driver side, locate the transmission range sensor mounted on the left side of the transmission case near the shift linkage connection point. The sensor is a round electronic component approximately 3 inches in diameter with an electrical connector on top and mounted flush to the transmission case. Clean the area around the sensor with a wire brush to remove accumulated road debris and dirt.
2. 2

   Position fluid catch pan
   Place a fluid catch pan with at least 2-3 quart capacity directly beneath the transmission range sensor. When the sensor is removed, transmission fluid will drain from the opening at a moderate rate. Position the pan to capture fluid without spillage onto the ground or crossmember.
3. 3

   Disconnect electrical connector
   Locate the electrical connector attached to the top of the transmission range sensor. Press the locking tab on the connector and pull straight up to disconnect. Some connectors may have a secondary safety clip that must be released first. Inspect the connector pins for corrosion or damage and clean with electrical contact cleaner if needed.
4. 4

   Remove sensor mounting fasteners
   The transmission range sensor is secured by 2 Torx bolts accessible from the front. Using a T30 Torx driver, remove both mounting bolts completely and set aside. These bolts are approximately 25-30mm in length. Note the position of any alignment dowel pins if present.
5. 5

   Remove transmission range sensor
   Carefully pull the sensor straight out from the transmission case using steady pressure. Fluid will immediately begin draining from the opening once the sensor is withdrawn. Allow fluid to drain into the catch pan for 30-60 seconds. Remove and discard the old O-ring seal from the sensor mounting surface or from the sensor itself.
6. 6

   Clean mounting surface
   Using a plastic scraper or clean rag, thoroughly clean the transmission case mounting surface where the sensor seals. Remove all traces of old gasket material, debris, or transmission fluid residue. Do not allow debris to enter the transmission opening. The mounting surface must be completely clean and dry for proper seal.
7. 7

   Prepare new sensor for installation
   Inspect the new transmission range sensor and verify it matches the original part. Install the new O-ring seal onto the sensor body, ensuring it seats properly in the groove. Lightly lubricate the O-ring with clean ATF to ease installation and prevent seal damage. Verify any alignment pins or tabs on the sensor body are intact.
8. 8

   Install new transmission range sensor
   Align the sensor with the transmission case opening, ensuring any alignment dowels or tabs engage properly. Push the sensor firmly into the transmission case until it seats flush against the mounting surface. The sensor should sit completely flat with no gaps between the sensor body and transmission case.
9. 9

   Install and torque sensor mounting bolts
   Install both Torx mounting bolts and hand-tighten initially to ensure proper alignment. Using a torque wrench and T30 Torx socket, tighten both bolts in a cross pattern to specification. Verify the sensor remains flush to the transmission case during tightening.
10. 10

    Reconnect electrical connector
    Push the electrical connector firmly onto the transmission range sensor until it clicks into place. Ensure the locking tab engages fully. Gently tug on the connector to verify it is secure and will not pull free. If equipped with a secondary safety clip, engage it to lock the connector.
11. 11

    Add transmission fluid
    Using the transmission dipstick tube as a fill point, add approximately 1.5 quarts of MB 236.10 specification ATF to replace the fluid lost during sensor replacement. Use a long-neck funnel and add fluid slowly to prevent overflow. The exact amount will vary based on fluid loss during removal.
12. 12

    Reinstall splash shield and lower vehicle
    Reinstall the transmission undertray or splash shield using the original Torx fasteners. Tighten securely but do not overtighten plastic mounting points. Remove jack stands and carefully lower the vehicle to the ground. Reconnect the negative battery terminal.

Reassembly

1. Installation follows removal in reverse order
2. Always use a new O-ring seal with the replacement sensor
3. Torque sensor mounting bolts in cross pattern to prevent case distortion
4. Check transmission fluid level with engine running and transmission at operating temperature after test drive

Verification

• With brake pedal depressed, verify engine starts in Park and Neutral positions only
• Verify engine does not start in Drive, Reverse, or any other gear position
• Check instrument cluster for correct gear position display in all selector positions
• Scan for diagnostic trouble codes using a scan tool - no transmission range sensor codes should be present
• Test drive vehicle and verify smooth shifting through all gears with no delayed engagement
• Verify backup lights illuminate when transmission is shifted into Reverse
• Recheck transmission fluid level after test drive with engine running, transmission in Park, at operating temperature. Fluid should be in the hot range on dipstick
• Inspect underneath vehicle for any transmission fluid leaks around sensor mounting area after test drive

Related trouble codes on this vehicle

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