Fuel Level Sensor

Remove and replace the fuel level sensor assembly located in the fuel tank. Requires lowering or partially dropping the fuel tank for access.

Warnings

Tools required

Parts

• Fuel level sensor assembly × 1 — Use OEM specification
• Fuel pump access plate O-ring/seal × 1 — Use OEM specification
• Fuel line O-rings × 4 — Use OEM specification
• Fuel tank strap hardware (if corroded) × 1 — Use OEM specification

Preparation

1. Park vehicle on level surface in well-ventilated area away from ignition sources
2. Disconnect negative battery terminal and secure cable away from battery post
3. Remove fuel filler cap to vent tank pressure
4. Relieve fuel system pressure: Remove fuel pump fuse (fuse box location varies; consult fuse diagram), start engine and allow it to run until it stalls, then crank for 5 seconds to ensure pressure is released
5. If possible, drive vehicle until fuel level is at 1/4 tank or less to minimize fuel removal
6. Raise vehicle on lift or securely support on jack stands at all four corners, ensuring adequate working clearance underneath
7. Place absorbent pads and drain container beneath fuel tank area

Procedure

1. 1

   Remove rear underbody panels and heat shields
   Access to the fuel tank requires removal of underbody protection panels. Remove the rear underbody cover panels secured by Torx fasteners around the perimeter. Remove exhaust heat shields in the fuel tank area if present; verify the fastener type and size on your vehicle before removal. Set aside all fasteners organized by location. Note: Remove exhaust heat shields in the fuel tank area if present; note and verify the fastener type and size as you remove them, as they may vary from the Torx sizes commonly assumed.
2. 2

   Drain fuel tank
   Using a hand siphon pump or fuel transfer pump, drain as much fuel as practical from the tank through the fuel filler neck. Transfer fuel to approved fuel-safe containers. Drain fuel only via a hand siphon or fuel transfer pump through the filler neck or an accessible line; do not energize the in-tank fuel pump to drain the tank, as this risks running the pump dry and creates a fire/arc hazard. Drain until tank is as empty as possible. Note: Drain fuel using a hand siphon/transfer pump only. Note the DB9 uses a saddle (twin-chamber) tank with separate pump/sender modules; draining via the fuel pump may not empty both chambers and is not recommended. Note: Draining is best performed via hand siphon or fuel transfer pump through the filler neck; do not attempt to drain using the vehicle fuel pump as this risks running the pump dry. Note: Fuel tank capacity is approximately 85 liters (about 22 US gallons); verify exact capacity against factory documentation. Drain fuel as appropriate for the service method used. If the access-panel-from-above method applies, full tank removal may not be required; verify the correct procedure before committing to lowering the tank.
3. 3

   Disconnect fuel filler neck and vent lines
   Locate the fuel filler neck connection at the tank. Loosen the hose clamp securing the filler neck hose to the tank inlet using a flat-blade screwdriver or socket. Slide clamp back and twist/pull filler neck hose off tank inlet. Disconnect the evaporative emissions vent lines from the tank; these are typically quick-disconnect fittings. Press the release tabs and pull lines free. Cap or plug open fittings to prevent contamination.
4. 4

   Disconnect fuel supply and return lines
   Locate the fuel supply and return lines at the tank connections. These are quick-disconnect fittings. Use the appropriate fuel line disconnect tool for the fitting size; insert tool into the fitting, press to release the locking mechanism, and pull the line free from the tank fitting. Expect residual fuel spillage; catch in absorbent pads. Inspect O-rings in the fittings and replace if damaged. Cap or plug all open fuel line ends to prevent contamination.
5. 5

   Disconnect fuel tank electrical connectors
   Locate the electrical connector(s) for the fuel pump and fuel level sensor assembly on top of the tank. Press the release tab(s) and disconnect the connector(s). On some configurations, there may be one large multi-pin connector or separate connectors for pump and sensor. Secure connectors away from the work area to prevent damage during tank lowering.
6. 6

   Support fuel tank with transmission jack
   Position a transmission jack or suitable adjustable jack with a wide wooden block on the saddle directly under the center of the fuel tank. Raise the jack until it just contacts the tank bottom and provides firm support, but does not lift the tank. The tank must be securely supported before removing straps.
7. 7

   Remove fuel tank retaining straps
   Locate the fuel tank retaining hardware; the number and configuration of straps or mounting fasteners must be verified against factory documentation for the 2009 DB9, as the saddle-type tank may not use conventional cross straps. The strap fastener head size must be verified against the Aston Martin workshop manual before beginning (do not assume 13mm/15mm). Support the strap end with one hand while removing the fastener with the other to prevent the strap from falling. Remove fasteners from both ends of each strap and remove the straps. Lower the jack slowly and carefully, controlling the tank descent. Lower the tank approximately 150-200mm to gain access to the top of the tank where the fuel pump/sensor assembly is mounted. Note: The strap fastener size must be verified against factory documentation for the 2009 DB9 before selecting a socket. Note: The fastener size and type are unverified for this platform; confirm against Aston Martin workshop documentation before beginning. Note: If the tank is strap-mounted, locate the fuel tank retaining straps and note their quantity and fastening; confirm the exact configuration against Aston Martin workshop documentation, as the number and type of straps for this platform is unverified. Note: Strap count/configuration unverified — verify against the Aston Martin workshop manual; the saddle-type tank may not use conventional cross straps. Note: Fastener size unverified — obtain exact strap fastener size and type from the Aston Martin workshop manual for the 2009 DB9 before selecting a socket.
8. 8

   Access and remove fuel level sensor assembly
   With the tank lowered, access the top of the tank. Locate the fuel level sensor assembly access cover or the fuel pump module that includes the sensor. The retention method for the fuel level sensor/pump module (locking ring versus retaining bolts, and exact bolt count) must be verified against factory documentation for the 2009 DB9 before attempting removal. If a locking ring is used, use a large adjustable spanner, locking ring tool, or carefully tap counterclockwise with a brass punch and hammer to loosen. If bolts are used, remove them in a cross-pattern to release tension evenly. Carefully lift the sensor assembly upward and out of the tank opening. The float arm will need to be maneuvered through the opening; tilt assembly as needed. Expect residual fuel in the assembly; drain back into tank or into container. Note: The retention method (locking/retaining ring vs. bolts) and exact fastener count must be verified against the Aston Martin workshop manual for this specific tank before proceeding. Note: The assembly retention method (locking ring, bayonet ring, or bolt circle) is unverified for this platform; confirm against Aston Martin workshop documentation before attempting removal. Note: Retention method and fastener count unverified — verify (locking ring vs. bolts, and exact count) against the Aston Martin workshop manual for the 2009 DB9.
9. 9

   Inspect tank opening and clean sealing surface
   With the sensor assembly removed, inspect the tank opening and sealing surface. Remove the old O-ring or gasket from the tank flange. Clean the sealing surface thoroughly with a clean, lint-free cloth; remove any debris, old gasket material, or corrosion. Inspect the inside of the tank opening for debris or contamination; if visible debris is present, use a flexible grabber or magnet tool to remove it, being careful not to drop anything into the tank.
10. 10

    Install new fuel level sensor assembly
    Install the new O-ring or gasket onto the new fuel level sensor assembly or into the groove on the tank opening, as designed. Ensure the O-ring is properly seated and not twisted. Carefully lower the new sensor assembly into the tank opening, maneuvering the float arm through the opening. Align the assembly to its correct orientation; there is typically an alignment tab or mark to ensure proper orientation. If using a locking ring, thread it clockwise and hand-tighten, then torque to the manufacturer specification using the locking ring tool. Do not assume a value; obtain the exact torque or index/rotational-stop position from factory documentation for the 2009 DB9. Note that plastic retaining rings commonly require far less torque than metal fittings and may use a defined rotational stop rather than a torque figure. If using bolts, install them and torque in a cross-pattern to ensure even sealing pressure. Ensure the assembly is fully seated and sealed. Note: If using a locking ring, thread it and tighten per the Aston Martin workshop manual torque specification using the correct locking-ring tool (do not apply an assumed torque value — many plastic retaining rings require far less torque than torque value unverified — obtain exact torque or rotational-stop/index position from factory documentation; do not apply an assumed 40-60 Nm value to plastic retaining rings or use a defined rotational stop). Note: If using a locking ring, install it per its design (threaded or bayonet) and torque to the manufacturer specification; the correct torque value for this platform is unverified and must be obtained from Aston Martin workshop documentation.
11. 11

    Reconnect electrical connectors
    Reconnect the electrical connector(s) to the fuel level sensor and fuel pump assembly. Ensure connectors are fully seated and the locking tabs click into place.
12. 12

    Raise and secure fuel tank
    Using the transmission jack, carefully raise the fuel tank back into its mounting position in the vehicle. Align the tank with the mounting points and ensure no wires or hoses are pinched. Reinstall the fuel tank retaining straps, positioning them correctly over the tank. Install the fasteners at both ends of each strap and torque to the Aston Martin workshop manual specification (do not use an assumed value). Remove the transmission jack once straps are secured. Note: Install the fasteners at both ends of each strap and torque to the manufacturer specification. Obtain the exact torque value from factory documentation for the 2009 DB9; do not assume a value. Note: If strap-mounted, install the fasteners and torque to the manufacturer specification; the correct torque value for this platform is unverified and must be obtained from Aston Martin workshop documentation. Note: torque value unverified — obtain exact strap fastener torque from the Aston Martin workshop manual for the 2009 DB9
13. 13

    Reconnect fuel lines
    Reconnect the fuel supply and return lines to the tank fittings. Install new O-rings on the line ends before connecting. Push each line firmly onto its fitting until you hear or feel a click indicating the locking mechanism has engaged. Tug on each line to verify it is securely locked. If threaded fittings are used on any connections, torque to specification.
    Torque spec

    Fuel Line Fittings25 Nm (18 lb-ft)
14. 14

    Reconnect filler neck and vent lines
    Reconnect the fuel filler neck hose to the tank inlet. Slide the hose fully onto the inlet pipe and position the hose clamp over the connection area. Tighten the clamp securely, but avoid overtightening which can damage the hose. Reconnect the evaporative emissions vent lines to their fittings on the tank; ensure quick-disconnect fittings click into place.
    Torque spec

    Hose Clamps3 Nm (2 lb-ft)
15. 15

    Reinstall underbody panels and heat shields
    Reinstall all exhaust heat shields and underbody cover panels removed in Step 1. Install all Torx fasteners and torque appropriately for trim fasteners (typically hand-tight plus small additional torque; avoid overtightening plastic-retained panels).
16. 16

    Refill fuel tank and reconnect battery
    Lower vehicle to ground. Reconnect the negative battery terminal. Add a known, sufficient quantity of fresh fuel (enough to register in both tank chambers given the DB9 saddle-tank design) through the filler neck to allow proper fuel gauge/sensor verification. Reinstall fuel filler cap. Note: Add fresh fuel to the tank through the filler neck to ensure adequate fuel for testing; on a saddle-type tank add enough to reach both tank halves so sender operation can be verified across its range.

Reassembly

1. Ensure all fuel line connections are secure and fully locked before pressurizing the system
2. Verify all electrical connectors are fully seated and latched
3. Double-check that fuel tank straps are torqued and tank is stable in its mounts
4. Confirm no tools or parts have been left in the underbody area before lowering vehicle

Verification

• Reinstall the fuel pump fuse. Turn the ignition key to the ON position (do not start engine) to activate the fuel pump and pressurize the system. Listen for the pump to run for 2-3 seconds
• Inspect all fuel line connections at the tank for leaks while system is pressurized. Look for wet spots or fuel odor. If any leaks are found, immediately turn off ignition, relieve pressure, and correct the connection
• Start the engine and allow it to idle. Monitor for fuel leaks and listen for unusual fuel pump noise
• Verify the fuel gauge on the instrument cluster is reading accurately. With the known amount of fuel added, the gauge should reflect the approximate level. Drive the vehicle through a range of fuel levels to confirm sensor operation through its full range
• Check for diagnostic trouble codes related to fuel level sensor circuit; clear any codes that were set during the procedure if sensor is now functioning correctly
• Perform a final visual inspection underneath the vehicle for any fuel leaks or loose components after test drive

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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