P2699: Exhaust Aftertreatment Fuel Injector A Circuit Low
What to do
Expect the particulate filter warning to appear sooner or later, and possibly nothing else at first.
One thing overrides everything else here: if you can smell unburnt diesel from the exhaust, or there is unusual heat from under the vehicle, stop and get it recovered. This fault can hold the injector open, and raw fuel running continuously into a hot exhaust can destroy the particulate filter and is a fire risk.
Otherwise this is a wiring repair. Ask for the loom to be rerouted or re-sleeved away from the exhaust rather than just repaired in place — it runs alongside hot metal and under the vehicle, and a patched wire left in the same position cooks through again in the same spot.
What this code means
The exhaust fuel injector's control circuit reads below its valid range — a short to ground, or a module output that has failed low.
The injector's purpose is at P2697 and the over-delivery hazard at P2698.
A short to ground on this circuit deserves the caution that any high-current fault in a fuel-carrying system deserves, and here there is an additional consideration: the fault could hold the injector open. An electrically stuck-open dosing injector is the leaking-injector case from P2698 arriving by a different route — continuous raw fuel into a hot exhaust — so a short here is not merely a circuit to repair at leisure.
That is why the practical advice is the same as at P2698: a fuel smell from the exhaust or unusual heat underneath means stop, regardless of which code is stored.
Where the damage usually is follows from where the wiring runs. This loom reaches an injector mounted on the exhaust, so it passes close to hot metal and under the vehicle: heat-hardened insulation cracking against a grounded exhaust component, and chafing where the loom crosses a bracket or heat shield, account for most of these. A repair that simply replaces a length of wire without rerouting or re-sleeving it away from the heat will fail again in the same place.
Likely causes
Start here
- Wiring shorted to ground · moderate
- Heat damage to sensor or wiring · moderate
- Damaged wiring harness · moderate
Less common
- Faulty exhaust aftertreatment fuel injector · moderate
- Control module driver failure · specialist
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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