P0271Generic code

P0271 Code: Cylinder 4 Injector Circuit High

The P0271 code means the control circuit of the cylinder 4 fuel injector has a higher voltage than the computer expects, normally from an open circuit or a short to voltage. The injector does not open, so cylinder 4 gets no fuel. A disconnected connector is the most common cause.

Severity
Medium
Can I keep driving?
Yes, but with caution
Estimated cost
$20 to $600
Difficulty
Medium
System
Fuel Injection
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0271 code means

When the computer orders the injector to open, it connects the injector control wire to ground, and the voltage should fall to almost zero. If it stays high, either the circuit is open (the injector coil or the wire is cut) or the control wire is touching 12 volts. In that case the injector does not open and cylinder 4 is left without fuel.

The fastest test is to unplug injector 4 and plug in an injector test light (noid light) or an LED lamp in its place. While cranking the engine, it should blink. If it blinks, the wiring and the computer are working, and the problem is the injector or its connector. If it does not blink, follow the wire back to the computer.

Cylinder numbering depends on the manufacturer. On most inline engines, cylinder 1 is the one closest to the timing belt or chain. On V engines, the odd and even numbered cylinders are usually on different banks. Confirm the numbering in the service manual before you take anything apart. A P0271 code always points to this one cylinder.

P0271 code symptoms

  • Check engine light on.
  • Shaking engine or rough idle.
  • Loss of power.
  • Black or white smoke on a diesel, or misfires on a gasoline engine.
  • The engine may run on one cylinder less.

Likely causes of the P0271 code

  1. Injector 4 connector unplugged or broken. This is the most frequent cause.
  2. Injector 4 coil open, with infinite resistance.
  3. Control wire cut.
  4. Control wire shorted to 12 volts from rubbing against another wire.
  5. Computer driver open. This is uncommon.

How to diagnose the P0271 code step by step

  1. Confirm the cylinder with the scan tool, using misfire counters or, on a diesel, the fuel correction values per cylinder.
  2. Measure the resistance of injector 4 and compare it with the other injectors.
  3. Check the 12 volt supply at the connector with the key on.
  4. Check the control wire. Look for continuity back to the computer and for isolation from ground and from 12 volts.
  5. Use an injector test light (noid light) to see whether the computer is sending the command.
  6. Clear the codes and reproduce the condition to confirm the repair.

How to fix the P0271 code

  • Repair the damaged wire or connector.
  • Replace the injector if its coil is open or shorted.
  • Repair the power supply (fuse, relay, wire).
  • If the computer driver is damaged, replace the shorted injector first.
  • Clear the codes and confirm the repair with a road test.

Technical reference data

  • High impedance gasoline injector: 11 to 18 ohms.
  • Low impedance injector: 2 to 5 ohms.
  • Typical supply: 12 volts from a relay or from the computer. The computer switches the ground to open the injector.
  • Piezoelectric common rail diesel injectors are not tested with an ohmmeter in the same way. Follow the manufacturer procedure.
  • These are reference values only. Check the manufacturer data for your engine.

Brand-specific notes

On many vehicles the injector power shares a fuse with the ignition coils. If several codes show up at the same time, check that fuse first.

Frequently asked questions about P0271

Can I drive with a P0271 code?
With caution and only for a short time. A cylinder that adds nothing makes the engine shake and increases wear.
Which cylinder is number 4?
Cylinder numbering depends on the manufacturer. On most inline engines, cylinder 1 is the one closest to the timing belt or chain. On V engines, the odd and even cylinders are usually on different banks, so confirm the numbering in the manual before you take anything apart.
Do I have to replace the injector?
Only if the tests confirm it. In many cases the fault is in the wiring.
How much does it cost to fix P0271?
Between $20 and $600 on a gasoline engine. On a diesel, an injector can cost $150 to $800 plus coding.
What does the P0271 code mean?
The P0271 code is a generic OBD2 code. The control circuit of the cylinder 4 injector has a higher voltage than expected, which points to an open circuit or a short to voltage.

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