OBD-II Diagnostic Trouble Code
P0268 — Cylinder 3 Injector Circuit High
P0268 means the ECM detected a high voltage or open condition in the cylinder 3 injector control circuit. The driver sees no normal current flow, typically from an open wire, unplugged connector, open coil or short to voltage, and usually shuts the injector off.
Severity 4/5
Truck-relevant
Stop within 50 mi
Severity
Stop within 50 mi
Cylinder 3 Injector Circuit High
Code
P0268
Category
Powertrain
Subsystem
Fuel
Truck-relevant
Yes
What this means for truckers
P0268 (Cylinder 3 Injector Circuit High) — same path.
Before you replace parts — try this first
P0268 on the Fuel system is most often open or disconnected cylinder 3 injector wiring or connector — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
A dead cylinder 3 produces a steady miss, rough idle, vibration and power loss, sometimes with smoke and a derate. Misfire or balance codes often set too.
Common causes
- CommonOpen or disconnected cylinder 3 injector wiring or connector ($100–$700)
- CommonOpen cylinder 3 injector coil ($400–$2500)
- OccasionalCircuit shorted to battery voltage ($150–$700)
- RareECM injector driver failure ($1200–$3500)
How to fix
Check that the cylinder 3 injector connector is fully seated.
When to use: First, especially after recent engine work.
Measure injector resistance through the harness and at the injector.
When to use: To locate the open.
Check for short to battery voltage.
When to use: When resistance is normal.
Repair the wiring or replace the injector and program trim codes.
When to use: Once the fault is located.
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → P0200 — Injector Circuit Malfunction
- → P0201 — Injector Circuit Malfunction - Cylinder 1
- → P0202 — Injector Circuit Malfunction - Cylinder 2
- → P0203 — Injector Circuit Malfunction - Cylinder 3
- → P0204 — Injector Circuit Malfunction - Cylinder 4
Frequently Asked Questions
Can I drive with code P0268?
Drive with caution. P0268 is severity 4 — stop within ~50 miles. Most commercial diesel codes at this severity (turbo, fuel rail, transmission solenoid) can damage adjacent expensive components if left unrepaired. Get to a service location before highway-speed loads.
How much does it cost to fix P0268 on a commercial truck?
Total repair cost ranges $100–$3500 depending on the root cause. The cheapest fix is usually the first one listed below — Open or disconnected cylinder 3 injector wiring or connector — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will P0268 fail a DOT inspection?
P0268 itself doesn't automatically fail an inspection, but if the truck is in reduced-power mode (limp mode) at the time of inspection, it WILL be flagged. Most inspectors will note the check engine light but pass the truck if it's running and performance is normal. Fix it before a Level 1 inspection regardless.
What's the difference between P0268 and related codes?
P0268 is closely related to: P0200 (Injector Circuit Malfunction), P0201 (Injector Circuit Malfunction - Cylinder 1), P0202 (Injector Circuit Malfunction - Cylinder 2), P0203 (Injector Circuit Malfunction - Cylinder 3). These codes share the same subsystem (fuel) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only P0268 is set without the companions, the issue is more isolated.
How do I prevent P0268 from coming back after a repair?
For P0268 (Cylinder 3 Injector Circuit High), prevention centers on the fuel system. Replace fuel filters at the OEM interval — don't stretch them. Use only diesel from high-volume fuel stops (avoid bottom-of-tank fuel at low-traffic stations). Add a water separator if you don't have one. After repair, prime the fuel system per the engine manual.