Replace the input speed sensor (ISS/TSS) on the 6R80 automatic transmission to restore proper speedometer and transmission shift operation.

Warnings

Tools required

Parts

• Input Speed Sensor (TSS) × 1 — Motorcraft DY1189 or equivalent
• Sensor O-ring × 1 — Usually included with sensor

Fluids

• Motorcraft MERCON LV ATF — 2 qt

Preparation

1. Park vehicle on level surface and apply parking brake firmly
2. Place wheel chocks behind rear wheels
3. Allow transmission to cool to ambient temperature if recently driven
4. Raise front of vehicle and secure on jack stands at frame contact points
5. Remove plastic engine undershield if equipped to access transmission

Procedure

1. 1

   Locate the input speed sensor
   The input speed sensor is located on the driver's side of the transmission case, approximately mid-body of the transmission bell housing. It is positioned above the transmission pan and below the transmission cooler lines. The sensor has a gray or black electrical connector with a sliding lock tab.
2. 2

   Disconnect the sensor electrical connector
   Press the sliding lock tab on the electrical connector toward the sensor body, then depress the release tab while pulling the connector straight away from the sensor. Do not pull on the wiring harness. If connector is difficult to remove, use a small flathead screwdriver to assist with the release tab.
3. 3

   Position drain pan
   Place a drain pan directly beneath the input speed sensor location. Ensure the pan has at least 2 gallon capacity and is positioned to catch fluid that will flow from the sensor bore when removed. Transmission fluid level sits above the sensor mounting point.
4. 4

   Remove sensor mounting bolt
   Using a 10mm socket, remove the single bolt securing the input speed sensor to the transmission case. Keep the bolt in a clean location for reinstallation. The bolt may have thread sealant residue on it.
   Torque spec

   Sensor Bolts12 Nm (9 lb-ft)
5. 5

   Extract the sensor
   Grasp the sensor body firmly and pull straight out from the transmission case with steady pressure. Avoid twisting or rocking the sensor during removal. Transmission fluid will begin flowing from the bore immediately. Allow fluid to drain into the pan for 30-60 seconds until flow reduces to a drip.
   ⚠Transmission fluid may still be warm. Avoid contact with skin and eyes.
6. 6

   Inspect sensor bore and old sensor
   Examine the transmission case bore for metal debris or damage. Use a shop rag to clean the sealing surface around the bore opening. Inspect the old sensor O-ring for cuts, deterioration, or deformation. Check the old sensor reluctor wheel (visible at tip) for damage or metal buildup.
7. 7

   Prepare new sensor
   Remove the new input speed sensor from packaging. Verify the new O-ring is properly seated in the groove on the sensor body. Lightly lubricate the O-ring with clean MERCON LV transmission fluid. Do not use petroleum-based lubricants or grease.
8. 8

   Install new sensor
   Align the sensor with the bore and insert straight into the transmission case until the sensor body contacts the mounting surface. Ensure the sensor is fully seated and the mounting hole aligns with the threaded bore in the case. There should be no gap between the sensor flange and transmission case.
9. 9

   Install and torque mounting bolt
   Thread the 10mm mounting bolt by hand into the transmission case through the sensor mounting flange. Ensure bolt threads engage smoothly without cross-threading. Using a torque wrench, tighten the bolt to specification in a single smooth pull. Do not overtighten as this can damage the sensor housing or strip the aluminum transmission case threads.
   Torque spec

   Sensor Bolts12 Nm (9 lb-ft)
10. 10

    Reconnect electrical connector
    Push the electrical connector straight onto the sensor until it clicks into place. Slide the connector lock tab to the locked position. Gently tug on the connector to verify it is securely latched and will not pull free.
11. 11

    Refill transmission fluid
    Locate the transmission fluid dipstick on the passenger side of the engine bay. With the transmission still at ambient temperature, add approximately 1.5-2.0 quarts of Motorcraft MERCON LV ATF through the dipstick tube using a funnel. Do not overfill at this stage; final level check will be performed with engine running.
12. 12

    Reinstall undershield and lower vehicle
    Reinstall the plastic engine undershield if it was removed. Lower the vehicle from jack stands to the ground. Remove wheel chocks.

Reassembly

1. Ensure electrical connector lock tab is fully engaged in locked position
2. Verify no tools or rags were left in the engine compartment or under the vehicle
3. Check that drain pan has been removed from under vehicle before starting engine

Verification

• Start the engine and allow it to reach normal operating temperature while monitoring for fluid leaks at the sensor location
• With engine running and transmission in Park, check transmission fluid level using the dipstick and add fluid as needed to bring to the correct operating range
• Shift transmission through all gear ranges (P-R-N-D-L) while holding brake pedal, pausing 2-3 seconds in each position
• Using an OBD-II scanner, verify that no speed sensor diagnostic trouble codes are present (P0715, P0717, P0722 specifically)
• Test drive the vehicle and verify speedometer operation and normal transmission shift points through all gears
• After test drive, recheck transmission fluid level and inspect sensor area for any fluid seepage

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