This procedure covers the removal and replacement of the output speed sensor on the electric drive unit (EDU) transmission of the 2023 Chevrolet Bolt EUV.

Warnings

Tools required

Parts

• Output speed sensor × 1 — GM Part 24278867 or equivalent
• Speed sensor O-ring seal × 1 — Use OEM specification
• Transmission drain plug crush washer × 1 — Use OEM specification
• ACDelco Dexron VI ATF × 2 — ACDelco 10-9395

Fluids

• ACDelco Dexron VI ATF — 2 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Disconnect the 12V battery negative terminal and wait 5 minutes
3. Verify high-voltage system is de-energized per manufacturer safety procedures
4. Raise vehicle on lift or support securely on jack stands at manufacturer lift points
5. Remove plastic underbody panels/shields to access transmission area
6. Allow transmission to cool to safe working temperature if recently operated
7. Clean area around transmission drain plug and sensor location to prevent contamination

Procedure

1. 1

   Drain transmission fluid
   Position drain pan beneath transmission drain plug. Using appropriate socket, carefully loosen and remove the transmission drain plug. Allow fluid to drain completely (approximately 2-3 quarts will drain). Inspect drain plug crush washer and replace if damaged. Reinstall drain plug with new crush washer.
   Torque spec

   Drain Plug34 Nm (25 lb-ft)
2. 2

   Locate output speed sensor
   The output speed sensor is mounted on the driver's side of the electric drive unit, near the output shaft/halfshaft area. It will have an electrical connector with a locking tab. Clean the area around the sensor thoroughly with brake cleaner to prevent debris from entering the transmission.
3. 3

   Disconnect electrical connector
   Press the locking tab on the sensor electrical connector and carefully pull the connector straight away from the sensor. Inspect connector pins for corrosion or damage. If connector is difficult to access, it may be necessary to remove nearby brackets or harness clips.
4. 4

   Remove speed sensor retaining bolt
   Using the appropriate socket, remove the single sensor retaining bolt. Keep the bolt clean and inspect threads for damage. If the bolt shows signs of corrosion or thread damage, replace it.
   Torque spec

   Sensor Bolts11 Nm (8 lb-ft)
5. 5

   Extract speed sensor
   Carefully pull the speed sensor straight out from the transmission case. Some resistance is normal due to the O-ring seal. Do not pry against the transmission case. If sensor is stuck, gently rotate while pulling. Expect a small amount of residual fluid to leak when sensor is removed.
6. 6

   Inspect and clean sensor bore
   Inspect the sensor bore in the transmission case for debris, metal shavings, or damage. Clean the bore thoroughly with a lint-free cloth. Do not allow any debris to enter the transmission. Remove the old O-ring from the sensor bore using a small pick, being careful not to scratch the sealing surface.
7. 7

   Prepare new sensor
   Remove new output speed sensor from packaging. Install the new O-ring seal onto the sensor body. Lubricate the O-ring lightly with clean Dexron VI ATF to ease installation and prevent seal damage. Verify the sensor reluctor/pickup area is clean and undamaged.
8. 8

   Install new speed sensor
   Carefully insert the new speed sensor straight into the transmission bore, ensuring the O-ring does not roll or pinch. Push sensor fully into place until it seats completely against the transmission case. The sensor should sit flush with the mounting surface.
9. 9

   Install and torque sensor bolt
   Install the sensor retaining bolt and tighten by hand until snug. Using a torque wrench, tighten the sensor bolt to specification. Do not over-torque as this can damage the sensor housing or transmission case threads.
   Torque spec

   Sensor Bolts11 Nm (8 lb-ft)
10. 10

    Reconnect electrical connector
    Reconnect the electrical connector to the speed sensor, ensuring it clicks securely into place. Verify the locking tab is fully engaged. Gently tug on the connector to confirm it is properly seated.
11. 11

    Refill transmission fluid
    Using the fill plug location (or through dipstick tube if equipped), refill the transmission with the appropriate amount of ACDelco Dexron VI ATF to replace what was drained (approximately 2 quarts). Use a fluid transfer pump for accurate filling. Check fluid level per manufacturer specification.
12. 12

    Reinstall underbody panels
    Reinstall all underbody shields and plastic panels that were removed for access. Ensure all clips and fasteners are properly secured.
13. 13

    Reconnect battery and clear codes
    Reconnect the 12V battery negative terminal. Using a scan tool, clear any diagnostic trouble codes related to the speed sensor. The vehicle may need to relearn certain parameters.

Reassembly

1. Verify all electrical connectors are properly seated and locked
2. Ensure transmission drain plug is torqued to specification with new washer installed
3. Confirm transmission fluid level is correct per manufacturer procedure
4. Verify all underbody panels and shields are reinstalled
5. Check for any fluid leaks around sensor and drain plug before lowering vehicle

Verification

• Start the vehicle and verify no warning lights are illuminated on the instrument cluster
• Using a scan tool, verify the output speed sensor is providing a signal and reading correctly
• Perform a short test drive and monitor for any transmission-related warning lights or messages
• Verify speedometer operation is accurate
• After test drive, inspect sensor area and drain plug for any fluid leaks
• Re-scan for diagnostic codes to confirm no speed sensor faults are present
• Verify transmission shifts smoothly and operates normally

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