P020F – Injector Circuit/Open – Cylinder 15

P020F is an OBD-II trouble code that points to a problem with the fuel injector circuit on cylinder 6. When this code sets, your engine computer has detected an electrical fault that can affect how that cylinder fires. You might notice rough running, poor fuel economy, or a flashing check engine light. Left alone, it can lead to internal engine damage or a no-start condition. This guide walks you through what P020F means, common causes, symptoms, and how you or your mechanic can diagnose and repair it correctly.

What Does P020F Mean?

P020F stands for “Injector Circuit/Open – Cylinder 6.” Your ECU (engine control unit) constantly monitors the voltage and current going to each fuel injector. If it sees an open circuit, short, or abnormal electrical signal on the injector for cylinder 6, it sets P020F and usually turns on the check engine light.

In simple terms, the ECU is telling you that cylinder 6’s injector is not being controlled properly. That can be due to a bad injector, damaged wiring, a poor connector, or in rarer cases, a fault inside the ECU itself.

Quick Reference

• Code: P020F – Injector Circuit/Open – Cylinder 6
• Type: Fuel injection / electrical fault
• Severity: Moderate to severe (can damage engine if ignored)
• Common causes: Bad injector, wiring damage, loose connector, ECU driver fault
• Typical symptoms: Misfire, rough idle, reduced power, poor fuel economy

Real-World Example / Field Notes

I’ve seen P020F show up many times on V6 and V8 engines where cylinder 6 is buried near the firewall. One case was a pickup that came in with a rough idle and a flashing check engine light under load. The owner had already replaced spark plugs and coils with no improvement. A quick check with a multimeter showed no injector pulse at cylinder 6. After peeling back the harness tape, I found a broken wire where the loom rubbed on a bracket. A simple wire repair and harness re-routing fixed the issue and the truck ran like new.

Symptoms of P020F

• Check engine light on: Often steady at first, may flash during heavy acceleration or uphill driving.
• Rough idle: Engine may shake or feel like it is “skipping” at stoplights.
• Misfire under load: Hesitation, jerking, or lack of power when you accelerate.
• Poor fuel economy: You may notice more frequent fuel stops or a drop in MPG.
• Hard starting: Extended cranking or needing to press the gas pedal to start in some cases.
• Fuel smell or rich running: Unburned fuel from the misfiring cylinder can cause a raw fuel odor from the exhaust.
• Engine protection mode: Some vehicles may limit power or disable the injector to protect the catalytic converter.

Common Causes of P020F

Most Common Causes

• Faulty fuel injector (cylinder 6): The internal coil in the injector can open or short, causing incorrect resistance and loss of control by the ECU.
• Damaged wiring harness: Chafed, broken, or corroded wires between the ECU and injector 6 are extremely common, especially near the back of the engine.
• Loose or corroded injector connector: Heat and vibration can loosen terminals; moisture can corrode them and create an intermittent open circuit.
• Poor ground or power feed: If the injector power supply or shared ground circuit is weak, the ECU may see an injector circuit fault on that cylinder.
• Previous engine work: Harnesses pinched or stretched after intake manifold, head, or valve cover repairs can lead to injector circuit issues.

Less Common Causes

• ECU driver failure: The internal injector driver for cylinder 6 can fail, especially if a shorted injector has overloaded it over time.
• Connector pin damage at ECU: Bent, backed-out, or corroded pins at the ECU plug can disrupt the signal to injector 6.
• Aftermarket modifications: Poor-quality remote start, performance tunes, or wiring add-ons spliced into the injector harness can cause intermittent faults.
• Rodent damage: Mice and other critters love chewing injector wiring looms, particularly on vehicles parked outdoors.
• Internal engine issues: Rarely, a severe mechanical problem (burned valve, low compression) can coexist with an injector code, confusing diagnosis if not tested properly.

Diagnosis: Step-by-Step Guide

To diagnose P020F correctly, you’ll want a basic scan tool, a digital multimeter, and ideally a noid light or an oscilloscope. Access to a wiring diagram and service information for your specific vehicle makes the job much easier. If you’re not comfortable with electrical testing, this is a good time to involve a professional, because guessing and parts-swapping gets expensive fast.

1. Confirm the code and check for companions. Use a scan tool to read all stored and pending codes. Look for related misfire codes (like P0306) or other injector circuit codes that might point to a shared power issue.
2. Inspect cylinder numbering. Verify which cylinder is number 6 for your engine layout. Many DIYers test the wrong injector because cylinder numbering differs between manufacturers.
3. Visual inspection of injector 6 and harness. With the engine off, inspect the injector connector and wiring. Look for broken clips, oil saturation, melted insulation, or obvious rubbing points against brackets or the intake manifold.
4. Check injector resistance. Unplug injector 6 and measure resistance across its two terminals with a multimeter. Compare to spec and to a known good injector. An open circuit (infinite resistance) or a reading far from spec points to a bad injector.
5. Verify power supply to the injector. With key on (engine off), use the multimeter or a test light to check for 12V (or system voltage) at one of the injector terminals, usually the common power feed. If multiple injectors share this feed, compare readings to another cylinder.
6. Check injector pulse (control side). Use a noid light or scope on the control wire while cranking or running the engine. You should see a pulsing signal. No pulse on cylinder 6 but good pulse on others suggests a wiring or ECU driver issue.
7. Wiggle test the harness. While monitoring injector pulse or resistance, gently move the harness around cylinder 6 and along the route to the ECU. If the signal cuts in and out, you’ve likely found a broken or internally corroded wire.
8. Continuity test from injector to ECU. With the battery disconnected and ECU unplugged, check continuity and resistance of the injector 6 control wire from the connector to the ECU pin. Also check for shorts to power, ground, or adjacent wires.
9. Check Mode $06 data (if available). Some scan tools can access Mode $06 to show misfire and injector performance counts by cylinder. This can confirm that cylinder 6 is the only one affected.
10. Evaluate ECU only after wiring and injector pass. If injector resistance, power, ground, and wiring continuity are all good, and there is still no control signal, the ECU driver may be faulty. At this point, professional testing or ECU replacement/programming may be required.

Pro tip: Before replacing the injector, swap cylinder 6’s injector with another cylinder (if access allows) and see if the code or misfire follows the injector. If P020F moves to the other cylinder (for example, becomes P0202 for cylinder 2), you’ve confirmed a bad injector.

Possible Fixes & Repair Costs

Repairs for P020F depend on what you find during diagnosis. In many cases, replacing the cylinder 6 injector and repairing any wiring damage solves the problem. Costs vary widely by vehicle, engine layout, and labor rates, but here are typical ranges and what affects them.

• Replace fuel injector (cylinder 6): $150–$450 parts and labor, depending on engine design and whether the intake manifold must be removed.
• Repair or replace wiring/connectors: $100–$350 for harness repairs, more if a large section of the loom or a pigtail connector needs replacement.
• Clean and tighten injector connector terminals: $50–$150 if corrosion is minor and no parts are needed beyond contact cleaner and dielectric grease.
• ECU repair or replacement: $400–$1,200+ including programming, usually only after all other causes are ruled out.
• Related maintenance (plugs, coils, fuel system cleaning): Often recommended while you’re in there, adding $100–$300 depending on parts and access.

Factors that affect cost include how hard cylinder 6 is to reach, local labor rates, whether you use OEM or aftermarket injectors, and if additional components (gaskets, fuel rails, intake manifold seals) must be removed and replaced during the repair.

Can I Still Drive With P020F?

You might be able to drive for a short distance with P020F, but it’s not recommended. A misfiring or non-firing cylinder can dump raw fuel into the exhaust, overheating and damaging the catalytic converter. The engine may run rough, stall at idle, or struggle under load, which can be dangerous in traffic or on the highway. If the check engine light is flashing, that’s a clear sign of an active misfire, and you should avoid driving except to get the vehicle safely to a repair shop.

What Happens If You Ignore P020F?

Ignoring P020F can turn a relatively simple electrical or injector repair into a much bigger bill. Prolonged misfiring can melt the catalytic converter, foul spark plugs, contaminate engine oil with fuel, and in extreme cases damage pistons or valves from uneven combustion. Fuel economy will suffer, and the vehicle may eventually fail emissions testing or become difficult to start and keep running.

Last updated: January 22, 2026

Vehicles Commonly Affected by P020F

P020F can show up on almost any OBD-II vehicle, but it’s more frequently seen on V6 and V8 engines where cylinder 6 is harder to access and wiring is tightly packed. Common platforms include domestic trucks and SUVs from Ford, Chevrolet, GMC, Dodge, and Ram, as well as V6 sedans and crossovers from Toyota, Nissan, Honda, and Hyundai. Many European models from BMW, Mercedes-Benz, and Volkswagen with V6 or inline-6 engines can also trigger this code, especially as wiring ages and heat cycles take their toll.