OBD-II Code P0268 — What It Means & How to Fix It

What Does This Error Mean?

P0268 means the Cylinder 3 fuel injector circuit is reading too high. The engine computer detected excess voltage on the circuit controlling Cylinder 3's injector. This usually means a short to power in the wiring, or the injector coil has shorted internally. Cylinder 3 may be over-fueling, causing rich exhaust, rough running, and increased fuel consumption. A shorted injector also risks damaging the ECM's injector driver circuit.

Affected Models

All vehicles 1996+
Common in Ford, GM, Toyota, Honda V6 and V8
Common after wiring harness damage near cylinder 3
Seen in vehicles with heat-damaged wiring near exhaust
Common in direct injection engines

Common Causes

Short to power in the cylinder 3 injector control wiring
Cylinder 3 injector coil shorted internally — near-zero resistance
Bridged connector pins at the injector connector
Damaged wiring harness touching a battery positive source near Cylinder 3
ECM driver output failure sending excess voltage to Cylinder 3

How to Fix It

Pull all codes. If P0303 (Cylinder 3 misfire) accompanies P0268, the over-fueling is causing combustion problems. Additional injector high codes on multiple cylinders suggest a shared wiring harness problem.

A single-cylinder fault is more likely an injector or localized wiring issue than a shared-circuit problem.
Inspect the Cylinder 3 injector wiring harness for sections touching power wires or battery cables. Look especially near the fuse box, alternator wiring, and any recently repaired areas of the harness.

A wire that's been repaired with electrical tape and is now touching a power source is a common cause of this fault.
Measure the resistance of the Cylinder 3 injector. Disconnect it from the harness first. If it reads near zero ohms (shorted coil), the injector must be replaced before anything else.

A shorted injector can damage the ECM. Fix the injector before worrying about whether the ECM was affected.
Measure the voltage on the injector signal wire at the Cylinder 3 connector with the key on. If you read battery voltage (12V) on the signal wire, you have a confirmed short to power in the harness.

The signal wire for fuel injectors should only see brief switching pulses — not continuous battery voltage.
After replacing the injector or repairing the wiring, clear codes and use a live scanner to monitor Cylinder 3 injector pulse width. It should match the pulse width of the other cylinders at idle.

If the pulse width is still irregular after repairs, have a shop check the ECM driver circuit with an oscilloscope.

When to Call a Professional

A persistent high-circuit code that remains after wiring repair points to an ECM driver failure. ECM driver diagnosis requires an oscilloscope and professional-level equipment. Never replace the ECM without first verifying the wiring harness is clean — a shorted harness will destroy a new ECM. Shops that specialize in automotive electronics are the best choice for ECM-related faults.

Frequently Asked Questions

What happens if I keep driving with P0268?

If Cylinder 3 is over-fueling, unburned or partially-burned fuel enters the exhaust. This overloads the catalytic converter and can permanently damage it in a matter of days. A ruined catalytic converter costs $500–$2,000+ to replace. Fix the injector fault first — it's far cheaper.

Could the ECM have caused P0268 without a shorted injector?

It's possible but uncommon. The ECM's driver circuit for Cylinder 3 could fail in a way that sends too much voltage. However, a shorted injector or wiring short is far more common. Always check the injector resistance and wiring before suspecting the ECM. A shorted injector that isn't replaced will destroy a replacement ECM too.

How much does it cost to fix P0268?

Injector replacement (single): $150–$400 installed. Wiring repair: $100–$350. Connector replacement: $50–$200. ECM driver repair: $300–$1,200. Always start with the injector and wiring before moving to ECM repairs.