Transmission Speed Sensor - Input

This procedure removes and replaces the input speed sensor on the ZF 6-speed automatic transmission of a 2009 Aston Martin DB9, requiring under-vehicle access and partial transmission pan work.

Warnings

Tools required

Parts

• Transmission input speed sensor × 1 — Use OEM Aston Martin specification
• Transmission pan gasket × 1 — ZF 6HP26 pan gasket
• O-ring for speed sensor (if not included with sensor) × 1 — Check sensor kit contents

Fluids

• transmission_auto — 3 qt

Preparation

1. Park vehicle on level surface and engage parking brake.
2. Disconnect negative battery terminal and wait 5 minutes for system capacitor discharge.
3. Raise vehicle on lift or secure on jack stands rated for vehicle weight, ensuring stability.
4. Remove undertray panels securing with Torx fasteners (typically T25 or T30) to access transmission from below.
5. Place large drain pan beneath transmission pan area.
6. Verify transmission fluid is cool to touch before proceeding.

Procedure

1. 1

   Locate Input Speed Sensor
   From underneath the vehicle, identify the transmission input (turbine) speed sensor. On the ZF 6HP26 the input (turbine) speed sensor is integrated into the internal mechatronic (valve body) unit and is NOT an independently serviceable threaded component; the sensor is part of the mechatronic assembly, which is serviced/replaced as a unit. Confirm serviceability and the correct repair strategy against Aston Martin service documentation before proceeding. Confirm the exact sensor location and serviceability against Aston Martin service documentation before proceeding, as access requires removing the transmission pan and may require mechatronic unit service. The sensor is a cylindrical component approximately 40mm in length with an electrical connector on the outboard end. Trace the wiring harness to confirm identification before proceeding. Note: identify the input speed sensor, which on the ZF 6HP26 is integrated into the internal mechatronic (valve body) module and is NOT an externally threaded case-mounted sensor — pan removal and mechatronic access is required; confirm sensor location against Aston Martin service documentation before proceeding
2. 2

   Disconnect Sensor Electrical Connector
   Depress the locking tab on the sensor electrical connector and carefully pull the connector straight away from the sensor body. Do not twist or bend the connector housing. Inspect connector pins for corrosion or damage and clean if necessary with electrical contact cleaner. Secure the harness out of the work area to prevent fluid contamination.
3. 3

   Assess Sensor Access Requirements
   Determine if the sensor can be removed with sufficient working clearance. On the DB9 ZF installation, the input speed sensor on the ZF 6HP26 is internal to the mechatronic module; the transmission pan must be fully removed (not merely lowered) to access the internal sensor/mechatronic assembly. Proceed to Step 4.. If pan removal is necessary, proceed to Step 4. If direct access is sufficient and sensor area is clean and accessible, skip to Step 6.
4. 4

   Loosen Transmission Pan Bolts
   Using appropriate Torx or E-Torx sockets, loosen all transmission pan bolts in a criss-cross pattern, starting from the center and working outward. Count and note bolt quantity and locations as some installations may have different length bolts in specific positions. Loosen bolts gradually and evenly to prevent warping the pan flange. Leave two bolts at opposite corners finger-tight to maintain pan position. Note: VERIFY bolt count and fastener type against Aston Martin/ZF documentation — VERIFY bolt count and fastener type (Torx vs E-Torx and size) against Aston Martin/ZF documentation before proceeding — do not assume a specific count or drive type, as the ZF 6HP26 uses an integrated filter/pan assembly whose fastener specification must be confirmed
5. 5

   Partially Lower Transmission Pan
   With drain pan positioned to catch fluid, carefully remove the two remaining pan bolts. Allow the pan to lower 15-20mm while keeping it supported and level to minimize fluid spillage. Use additional support (wire or bungee cord from crossmember) to maintain this position. Approximately 1-2 quarts of ATF will drain during this operation. Allow fluid to drain completely before proceeding.
6. 6

   Remove Input Speed Sensor
   Per Aston Martin / ZF 6HP26 service procedure, the input (turbine) speed sensor is part of the internal mechatronic unit. Remove the transmission pan, then service the sensor as specified by the manufacturer (sensor is typically clipped/integrated into the mechatronic unit rather than threaded into the case). Verify the exact removal method against factory documentation before proceeding. The input speed sensor is integral to the mechatronic unit and is not a threaded component; do not attempt to unthread or apply penetrating oil. Follow the Aston Martin/ZF mechatronic service procedure to release/service the sensor module, taking care not to damage the valve body. Remove sensor completely and allow residual fluid to drain into collection pan. Note: Access the input speed sensor on the mechatronic module after pan removal. The ZF 6HP26 input speed sensor is not a case-threaded hex component; removal follows mechatronic/sensor module service per Aston Martin documentation. VERIFY correct procedure and fasteners before proceeding. Note: no hex removal socket applies — the sensor is integral to the mechatronic unit; use the Aston Martin/ZF-specified mechatronic service procedure and tooling (verify against factory documentation)
7. 7

   Inspect Sensor Mounting Bore
   With the sensor removed, inspect the threaded bore in the transmission case for debris, metal particles, or gasket material. Use a non-metallic wire brush to clean the threads and sealing surface. Wipe clean with lint-free shop towels. Check the condition of the O-ring groove for damage or scoring. Any metal debris found may indicate internal transmission wear requiring further diagnosis. Note: With the mechatronic unit accessible, inspect the sensor mounting area and sealing surfaces for debris, metal particles, or contamination. Wipe clean with lint-free shop towels. Any metal debris found may indicate internal transmission wear requiring further diagnosis.
8. 8

   Inspect Old Sensor and Compare
   Examine the removed sensor for metal contamination on the magnetic pickup tip, physical damage to the sensor body or threads, or O-ring deterioration. Compare the old sensor/module to the new part to verify correct replacement, confirming connector type, body configuration, and mounting/seal position match exactly.
9. 9

   Prepare New Sensor for Installation
   Install the new O-ring onto the new sensor body, ensuring it is properly seated in the O-ring groove. Lightly lubricate the O-ring (if used) with clean ZF-approved ATF (ZF LifeguardFluid 6 / ZF LT 71141) to ease installation and prevent O-ring damage during assembly. Do not use petroleum-based lubricants. Verify the sensor tip is clean and free from protective coating or debris. Do not use petroleum-based lubricants. Verify the sensor tip is clean and free from protective coating or debris. Note: Lightly lubricate the O-ring with clean ZF-specified ATF (ZF Lifeguard 6 / Aston Martin specified transmission fluid) to ease installation and prevent O-ring damage during threading. Note: Lightly lubricate the O-ring with clean ZF-specified ATF (ZF LifeguardFluid 6 / Aston Martin-approved spec) to ease installation and prevent O-ring damage during threading.
10. 10

    Install New Input Speed Sensor
    Install the sensor/mechatronic module per the Aston Martin/ZF service procedure. The input speed sensor is not threaded into the case; seat the sensor/module and ensure any retaining clips fully engage. Install the sensor per the manufacturer's specified method. If the sensor is clip-retained in the mechatronic unit, seat it until the retaining clip fully engages (no thread torque applies). If it is a threaded sensor, torque to the exact ZF/Aston Martin specification verified from factory documentation. Do not over-tighten. Do not over-tighten as this can damage the sensor body or transmission case threads. Verify the sensor is fully seated against the mounting surface. Note: VERIFY torque from Aston Martin/ZF documentation — discrete sensor torque unconfirmed as the sensor is integral to the mechatronic module Note: no discrete sensor torque applies — the sensor is integral to the mechatronic module; follow mechatronic/valve-body fastener torque per Aston Martin/ZF documentation
11. 11

    Reinstall Transmission Pan (if removed)
    If the transmission pan was lowered in Step 5, clean the pan sealing surface and transmission case mating surface with solvent and lint-free towels. Remove all old gasket material completely. Install new transmission pan gasket according to manufacturer instructions (some are reusable silicone, others are one-time paper). Lift the pan into position and hand-start all pan bolts. Tighten bolts in a criss-cross pattern starting from the center outward to the specified torque.
    Torque spec

    Transmission Pan Bolts12 Nm (9 lb-ft)
12. 12

    Reconnect Sensor Electrical Connector
    Align the electrical connector with the sensor terminal pins and push firmly until the locking tab clicks into place. Gently tug the connector to verify it is fully seated and locked. Ensure the wiring harness is routed away from heat sources, sharp edges, and moving components, matching the original routing path.
13. 13

    Refill Transmission Fluid
    Locate the transmission fill/level plug on the bottom of the transmission pan (the ZF 6HP26 uses a pan-mounted fill plug with an internal overflow standpipe for level setting). Using a fluid transfer pump and funnel with filter screen, add ZF-approved ATF (ZF LifeguardFluid 6 / ZF LT 71141) to replace the fluid lost during service — note that full pan removal for mechatronic access can drain significantly more than 2-3 quarts; measure the drained volume and refill accordingly, then set final level via the level-plug procedure in Step 15. The exact quantity depends on how much fluid was drained. Fluid level will be verified in Step 15 during the checking procedure. Note: Using a fluid transfer pump, add ZF-specified ATF (ZF Lifeguard 6 / Aston Martin specified fluid) through the fill plug. Add fluid to replace the amount lost, then set the final level using the level-plug procedure at the specified fluid temperature as described in Step 15. Note: Using a fluid transfer pump, add approximately 2-3 quarts of ZF-specified ATF (ZF LifeguardFluid 6 / Aston Martin-approved spec) through the fill/level plug to replace the fluid lost during service.
14. 14

    Reinstall Undertray Panels
    Reinstall all undertray panels and secure with original Torx fasteners. Verify all panels are properly aligned and all fasteners are installed. Lower vehicle from lift or jack stands. Reconnect negative battery terminal.
15. 15

    Check Transmission Fluid Level and Test
    Start the engine and allow it to reach normal operating temperature (approximately 10 minutes of idling). With the engine running and vehicle on level ground, With the engine running, check and set the transmission fluid level using the ZF 6HP26 overflow/level plug procedure at the specified fluid temperature window (typically approx. 30-50°C); fluid level is temperature-dependent and must be verified per Aston Martin/ZF procedure. Cycle through gear positions as directed by the service procedure before setting level.. Check transmission fluid level according to the ZF/Aston Martin procedure: this is a sealed transmission with no dipstick, so level is set via the overflow standpipe/level plug with fluid at the specified temperature window (typically 30-50C). Add fluid as necessary to achieve proper level. Monitor for leaks around the sensor installation point and transmission pan gasket. Note: Check transmission fluid level using the ZF 6HP26 level-plug (overflow) procedure. This transmission has no dipstick; with the engine running and fluid at the specified temperature (typically 30-50°C), remove the level plug and add fluid until it just overflows, then reinstall the plug.

Reassembly

1. Installation follows removal in reverse order with the following notes:
2. Always use a new transmission pan gasket if the pan was removed or disturbed.
3. New O-ring for speed sensor is included with most replacement sensors but verify before installation.
4. All Torx fasteners should be inspected for wear and replaced if threads show damage.
5. Transmission fluid level must be checked at operating temperature with engine running to ensure accurate reading.

Verification

• Start engine and verify no warning lights related to transmission appear on instrument cluster.
• Use scan tool to verify input speed sensor signal is present and reading appropriately (should show RPM signal corresponding to engine speed when in Park).
• Road test vehicle through all gears, confirming smooth shifts and proper transmission operation.
• Verify no fluid leaks are present around sensor installation point or transmission pan after road test.
• Re-check fluid level after road test and top off if necessary.

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