P2689: Fuel Supply Heater Control Circuit High
What to do
Nothing to feel, particularly in warm weather — but see P2687 for why it should not wait until winter.
Two questions worth answering before paying for any diagnosis, and both are about the fuel filter:
- When was it last changed? The heater's connector has to be unplugged to change the filter on most vehicles, and it gets reconnected by feel in a tight, fuel-covered space. A plug left half-latched is one of the commonest causes of this code and free to fix.
- What was fitted? On some vehicles the heater is part of the filter assembly, so a cheaper pattern filter can leave it out altogether. The filter fits, the engine runs perfectly, and this code is the only indication that a function has quietly gone missing.
If the answer to either is yes, start there rather than with a new heater.
What this code means
The fuel supply heater's control circuit reads above its valid range — an open circuit, a disconnected connector, or a short to supply.
The heater's purpose and the seasonal argument for fixing it promptly are at P2687.
An open circuit here has a cause that is worth naming because it is a maintenance item rather than a failure: the fuel filter change. On most vehicles the heater is built into the filter housing or its cap, and its connector has to come off every time the filter is replaced. That plug is then reconnected by feel, in a tight space, often with fuel on everything — so a connector left unmated, only half-latched, or with its locking clip broken is one of the commonest causes of this code, and it dates precisely from the last service.
On some vehicles the heater is part of the filter assembly rather than a separate part, which means a filter fitted without its heater element, or a cheaper pattern filter that omits the heater entirely, produces this code on a vehicle where nothing has failed at all. That is worth knowing before a diagnosis is paid for: an aftermarket filter that fits and works perfectly can still be missing this function, and the code is the only sign.
So the first two questions are when the fuel filter was last changed, and what was fitted.
Likely causes
Start here
- Disconnected sensor connector · easy
- Open circuit in heater wiring · moderate
- Corroded or loose connector · easy
- Faulty fuel supply heater · moderate
Less common
- Incorrect replacement filter fitted · easy
- Wiring shorted to voltage · moderate
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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