What the Audi A6 C6 Fuel Pump Control Module Does When It Fails
The fuel pump control module on the Audi A6 C6 is a small power electronics unit mounted inside or directly on top of the in-tank fuel pump assembly. Its job is to regulate the voltage and current supplied to the fuel pump motor, adjusting delivery pressure to match engine load. When this module develops a fault, the fuel pump either runs at a fixed low speed, cuts out intermittently, or stops responding altogether — producing symptoms that closely mimic injector, pressure regulator or sensor faults.
How the Module Works and Why This Makes Diagnosis Harder
Unlike older vehicles where the fuel pump ran at a constant 12V from a relay, the C6 A6 uses a pulse-width modulated signal from the engine control unit to tell the fuel pump control module how hard to run the pump. Under light load the pump runs slowly and quietly. Under wide-open throttle or during cold start priming it ramps up. The module handles the high-current switching to achieve this. Because the ECU governs the demand signal separately, a failed pump module can produce fault codes that point toward the ECU output circuit or the fuel pressure sensor rather than the module itself. Many shops replace fuel pressure sensors or clean injectors before the actual module is considered.
The C6 chassis was produced from 2004 to 2011, covering the 2.0 TDI, 2.7 TDI, 3.0 TDI, 2.4 FSI, 2.8 FSI and 3.2 FSI variants among others. The fuel pump control module variant differs between petrol and diesel, and sometimes between early and late production years. This matters enormously when sourcing a replacement. For comparison, see Как модулът за управление на горивната помпа на Audi A6 C6 причинява проблеми при стартиране.
Symptoms When the Module Is Failing
- Hard cold start followed by normal running: The module may fail to ramp up pressure correctly during the priming phase, causing a long crank before the engine catches.
- Stalling under load or at junctions: At idle or low-speed deceleration the pump runs slowly. If the module cannot sustain even that reduced demand, the engine starves briefly and stalls.
- Intermittent power loss at motorway speed: The module works correctly at partial load but fails when asked to sustain high pump speed, cutting fuel delivery during overtaking or long highway gradients.
- Engine cuts out without warning and restarts after a short wait: Heat is a common trigger. The module has had time to cool before the restart attempt succeeds.
- Audible pump tone changes: The pump may sound louder or inconsistent if the module is sending unregulated voltage rather than a controlled PWM signal.
Fault Codes Connected to This Module
The following fault codes are commonly logged on C6 A6 vehicles when the fuel pump control module is at fault. Code presence alone does not confirm the module; they must be read in context with live fuel pressure data.
| Код | Описание |
|---|---|
| P0087 | Fuel rail/system pressure too low — common first entry when pump output drops |
| P0628 | Fuel pump control circuit low — indicates the ECU output signal is not being responded to correctly |
| P0629 | Fuel pump control circuit high — module or wiring sending back unexpected voltage |
| 16890 / P0506 | Idle control system RPM lower than expected — secondary code when fuel starvation causes idle instability |
| 00668 | Supply voltage terminal 30 — can appear when the module draws abnormal current on startup |
It is worth noting that P0087 by itself is a broad code. Before condemning the pump module, a technician should check actual rail pressure with a gauge or via live data in VCDS or ODIS. If pressure builds correctly when the pump is bypassed to full 12V directly, the control module is the most likely culprit rather than the pump motor itself.
OEM Part Numbers to Know
The pump control module for the C6 A6 is typically integrated into the sender unit assembly. The numbers below refer to the control module or complete pump assembly units that contain it. Always cross-reference with the sticker on your existing unit before ordering a replacement, because fuel tank geometry, flange diameter and electrical connector type varied by body style and engine variant.
- 4F0 919 087 — Fuel pump sender unit including control electronics, petrol engines, early C6
- 4F0 919 087 B — Revised version for mid-production petrol variants
- 4F0 919 051 C — Used on some 3.0 TDI and 2.7 TDI diesel C6 applications
- 8E0 906 087 M — Bosch pump control module carried over from B7 platform, applicable to some early C6 engines
- Bosch 0 580 303 065 — Bosch reference number for the pump regulator module found on FSI-engined C6 variants
Exact number matching is strongly recommended. A unit from a diesel variant will not function correctly in a petrol application and vice versa. Even within petrol variants, the FSI high-pressure supplement means the low-pressure circuit is calibrated differently from earlier naturally aspirated engines.
Affected Vehicles and Variants
The Audi A6 C6 was sold in saloon and Avant (estate) body styles from 2004 through to the 2011 facelift model. All fuel-injected variants — including the FSI, TFSI and common-rail TDI engines — use a variable-speed pump circuit governed by this control module. The Audi Allroad on the C6 platform shares the same system architecture. The A6 C6 Quattro and front-wheel-drive variants use the same pump electronics, though the tank sender geometry may differ between them. A related diagnostic guide is Какво прави сензорът за ъгъла на завиване на Audi A6 C6, когато откаже.
The 2.0 TFSI is probably the most frequently seen variant in independent workshops dealing with this fault, partly due to its volume but also because that engine demands precise fuel pressure during direct injection operation. Any deviation in pump output is quickly flagged.
Testing Before Replacement
Measuring actual fuel rail pressure during cold cranking is the most useful diagnostic step. On FSI and TFSI engines, the low-pressure pump supplies the high-pressure pump, so a weak module will show immediately as low pre-supply pressure in live data. If the ECU signal wire to the pump module carries the correct PWM signal but rail pressure is still low, and the pump motor itself is mechanically sound, the module is the logical replacement. A used OEM module from a matching C6 variant is a practical solution provided the part number is confirmed and the unit has been tested before dispatch.
Често задавани въпроси
Can the Audi A6 C6 fuel pump control module be repaired rather than replaced?
Some specialist electronics repairers can replace failed MOSFETs or driver ICs within the module. However, the module sits inside the fuel tank in a humid, temperature-cycling environment, and resoldered joints in that location tend to fail again. For long-term reliability, replacing with a tested OEM unit is the more practical choice for most owners.
Does the replacement fuel pump module need coding on the A6 C6?
The pump control module itself does not require VIN-specific coding in the same way that an ECU or instrument cluster does. However, if the replacement comes as part of a complete sender unit assembly, any fuel level sender calibration in the instrument cluster should be checked. The pump module is essentially plug-and-play provided the part number matches the original. For additional context, read Как модулът на електронното паркиране на Audi A6 C6 отказва.
How do I know whether the pump motor or the control module is the failed component?
The clearest test is to supply the pump motor directly with controlled 12V and measure its current draw and pressure output. If the motor performs correctly under direct power but fails when driven through the control module, the module is the fault. If the motor draws excessive current or produces no pressure even on direct supply, the motor itself is defective.
Is this fault more common on high-mileage C6 A6 models?
The control module does not appear to have a sharp mileage cliff. Failures have been reported from under 100,000 km on some examples. Heat cycling, particularly on vehicles that do frequent short runs where the tank never cools fully between trips, appears to accelerate module degradation more than mileage alone.
Can a faulty fuel pump module on the C6 A6 cause the engine to run rich or lean?
Yes, indirectly. If rail pressure is chronically low, the ECU will attempt to compensate by extending injector open time, which shifts fuel trim toward positive (richer commanded). Conversely, if pressure is erratic, the ECU may log lean faults during the dips. This can lead to unnecessary replacement of injectors or oxygen sensors before the actual cause is traced to pump output.
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