OBD-II Code · Fuel & Air
P0271
Cylinder 4 Injector Circuit High
Severity
high
Left alone, this one tends to take other parts with it.
Can you drive it
Not for long
Driving on this one risks further damage. Get it to a shop rather than carrying on with it.
Indicative cost (USD)
$100–$500
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
Cyl 4 injector high voltage.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Misfire cyl 4
- Check engine light
Likely causes
- Failed injectorMost common
- Wiring short
Read the full diagnostic procedureP0271 sets when the cylinder 4 injector driver circuit is detected at high voltage when it should be pulled low during the injection pulse, mechanica…
P0271 sets when the cylinder 4 injector driver circuit is detected at high voltage when it should be pulled low during the injection pulse, mechanically identical to P0262/P0265/P0268 but on cylinder 4, which on inline-4 engines is the cylinder closest to the firewall and on most V6/V8 platforms is on the passenger bank.
The diagnostic ladder starts cheap
- ohm the injector at the connector (11.4-18 ohms PFI, 1.5-4 ohms GDI), verify 12V on the supply side with key-on, then scope the driver line for the inductive flyback spike on the trailing edge of the pulse.
- If the injector ohms in spec but the harness shows open, perform a wiggle-test along the loom and inspect for chafe at any bracket pass-through or exhaust-adjacent run.
- Pin-drag test the connector terminals, terminal back-out from worn retention tabs is a high-frequency root cause on engines with 150K+ miles.
- Expensive misdiagnosis: on transverse 4-cylinder platforms cylinder 4 is the firewall-side cylinder and replacement requires either pulling the intake or working blind around the bulkhead, do not pull the intake until you have positively confirmed the injector itself is the fault by ohming it out of the harness, because the actual cause on aged vehicles is more often a corroded connector pigtail than a failed injector.
Vehicle-specific patterns2002-2006 Nissan Altima/Sentra 2.5L QR25DE has a chronic cylinder 4 injector pigtail problem where heat soak from the rear exhaust manifold cracks th…
- 2002-2006Nissan Altima/Sentra 2.5L QR25DE has a chronic cylinder 4 injector pigtail problem where heat soak from the rear exhaust manifold cracks the connector body;
- 2007-2012Mazda CX-7 2.3L DISI throws P0271 when the direct-injection high-pressure injector solenoid opens internally, the injectors are not individually serviceable on early units;
- 2010-2015VW/Audi 2.0L TSI (EA888) sees cylinder 4 injector failures from carbon buildup loading the winding and from harness chafe at the firewall pass-through, TPI 2026975 documents the replacement procedure.
Estimated repair$240 to $1,300.
Look up another code
P0271 — frequently asked
What does a P0271 code mean?
Cyl 4 injector high voltage.
What causes a P0271 code?
Common causes: Failed injector; Wiring short.
What are the symptoms of a P0271 code?
Typical symptoms: Misfire cyl 4; Check engine light.
Is it safe to drive with a P0271 code?
Not for long. Driving on this one risks further damage. Get it to a shop rather than carrying on with it. Estimated repair: $100-$500.
How do I diagnose a P0271 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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