P0270Generic code

P0270 Code: Cylinder 4 Injector Circuit Low

The P0270 code means the control circuit of the cylinder 4 fuel injector has a lower voltage than the computer expects, normally from a short to ground or a lack of power. A control wire shorted to ground can hold the injector open and flood the cylinder. Look into it soon.

Severity
High
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 P0270 code means

With the injector closed, its control wire should sit at about 12 volts, which is the supply that reaches it through the coil. If the computer sees a low voltage at that moment, it concludes that the wire is shorted to ground or that no power is arriving. A control wire shorted to ground can keep the injector open all the time and flood cylinder 4, so this is a fault to deal with right away.

To confirm it without special tools, unplug injector 4 with the key off and measure resistance between the control wire (the computer side) and ground. It should be very high. A reading near zero confirms a short in the wiring. If the wiring is good, measure the injector coil. A resistance far below that of the other injectors points to an internal short.

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. Any P0270 code diagnosis starts with that.

P0270 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.
  • High fuel use or a smell of fuel.

Likely causes of the P0270 code

  1. Control wire shorted to ground from rubbing on the engine.
  2. 12 volt supply interrupted: the fuse, the relay or the supply wire.
  3. Injector 4 shorted inside, with a very low resistance.
  4. Connector with water or corrosion.
  5. Damaged computer driver. This is uncommon.

How to diagnose the P0270 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 P0270 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 P0270

Can I drive with a P0270 code?
With caution and only for a short time. An injector that stays open can dilute the oil with fuel and damage the engine.
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 P0270?
Between $20 and $600 on a gasoline engine. On a diesel, an injector can cost $150 to $800 plus coding.
What does the P0270 code mean?
The P0270 code is a generic OBD2 code. The control circuit of the cylinder 4 injector has a lower voltage than expected, which points to a short to ground or a lack of power.

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