P0285 Cylinder 9 Injector Circuit Low

P0285 points to a low injector circuit on cylinder 9. The injector 9 electrical path is grounded, missing voltage, or below expected current.

Code details

Generic OBD-II · P0

System: Injector
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not replace injector 9 before tracing the low circuit through wiring and driver control.

Symptoms of P0285

Check-engine light, often with a misfire feel from one cylinder.
Rough idle, hesitation, or a slight loss of power.
Higher fuel use, or in some cases a fuel smell.

Common causes of P0285

A stuck, leaking, clogged, or electrically failed injector.
Injector wiring, connector, or driver-circuit faults.
Low fuel pressure or contamination affecting injector behaviour.

Useful checks before replacing parts

Measure cylinder 9 injector feed, control voltage, resistance, and current while checking for short-to-ground faults.
Compare cylinder 9 misfire counters, contribution data, injector pulse, fuel trims, and freeze-frame operating conditions.
Inspect connector terminals, harness routing to cylinder 9, shared injector feed, moisture, oil intrusion, and rubbed insulation.

Related OBD-II codes

These nearby injector entries can help compare wording and pin down the fault area.