P020B – Injector Circuit/Open – Cylinder 11

P020B is an OBD-II trouble code that points to a problem with one specific fuel injector circuit, usually labeled as “Injector B.” When this code sets, your engine computer (ECU) has detected an electrical fault in that injector’s control circuit, which can lead to rough running, misfires, and poor fuel economy. You might notice a check engine light, loss of power, or hard starting. This guide walks you through what P020B means, common causes, symptoms, how a mechanic diagnoses it, possible repairs, and whether it’s safe to keep driving.

What Does P020B Mean?

P020B stands for “Injector Circuit / Open – Cylinder 2” or “Injector B Circuit Range/Performance,” depending on manufacturer terminology. In simple terms, the ECU sees something wrong with the voltage or current going to one injector in the bank, often the second cylinder or the injector labeled “B.”

The ECU constantly monitors injector control signals. If it detects an open circuit, short to power, short to ground, or an abnormal resistance or current pattern on that injector, it stores P020B and usually turns on the check engine light. On many vehicles, it may also disable that injector to protect the engine and wiring.

Quick Reference

• Code: P020B
• Meaning: Injector “B” / Cylinder 2 injector circuit fault (range, performance, or open)
• Severity: Moderate to high – can cause misfire and drivability issues
• Typical causes: Bad injector, wiring damage, poor connector contact, ECU driver fault
• Primary symptoms: Rough idle, misfire, low power, poor fuel economy, MIL on

Real-World Example / Field Notes

In the shop, I often see P020B show up on trucks and SUVs that have a slight misfire at idle but seem “okay” at highway speeds. One recent case was a direct-injected V6 where cylinder 2 kept dropping out intermittently. Scan data showed that injector pulse width for that cylinder was commanded, but current ramp was flat. A quick wiggle test on the injector harness made the engine stumble worse. Pulling back the loom revealed a partially broken wire right at the injector connector from years of vibration. A simple pigtail repair and clearing codes fixed the issue completely.

Symptoms of P020B

• Check engine light (MIL) on – P020B is usually stored as a confirmed fault and may be accompanied by misfire codes.
• Rough idle – The engine may shake or feel uneven, especially when stopped in gear.
• Engine misfire – You may feel hesitation, stumble, or a “skip” under load or acceleration.
• Loss of power – With one injector not working correctly, overall engine power drops noticeably.
• Poor fuel economy – Misfires and incorrect fueling can cause higher fuel consumption.
• Hard starting – Extended cranking or needing to press the accelerator to start in some cases.
• Fuel smell or exhaust issues – Raw fuel odor, rough exhaust note, or in severe cases, backfiring.
• Possible limp mode – Some vehicles reduce power to protect the engine and catalytic converter.

Common Causes of P020B

Most Common Causes

• Faulty fuel injector (Injector B / Cylinder 2) – Internal coil failure, shorted or open windings, or mechanical sticking can trigger the code.
• Damaged injector wiring – Broken, chafed, or corroded wires between the ECU and the injector are very common, especially near the connector or where the harness bends.
• Poor injector connector contact – Loose terminals, bent pins, or corrosion in the connector can create intermittent open-circuit conditions.
• Short to power or ground – The injector control wire rubbing against metal or another wire can cause a short, upsetting the ECU’s expected current draw.
• Previous engine work – After head gasket, intake, or injector replacement, harness routing errors or pinched wires often lead to P020B.

Less Common Causes

• ECU (PCM) driver failure – The transistor inside the ECU that controls the injector can fail, though this is less frequent than wiring or injector faults.
• Low system voltage – Weak battery, poor grounds, or charging issues can cause injector circuit monitoring to behave erratically.
• Aftermarket modifications – Poor-quality performance injectors, tuning, or splice-in harnesses can create resistance or current anomalies.
• Connector contamination – Oil, coolant, or fuel intrusion into the injector or ECU connectors can affect electrical signals.
• Internal engine damage – Rarely, severe mechanical problems can change load and feedback enough to confuse diagnostics, usually with other codes present.

Diagnosis: Step-by-Step Guide

To properly diagnose P020B, you ideally want a scan tool with live data, a digital multimeter, and, if possible, a noid light or injector test light. Access to wiring diagrams and Mode $06 data is very helpful. If you’re not comfortable working around fuel and electrical systems, this is a good time to involve a professional.

1. Confirm the code and check for related DTCs
   Connect a scan tool, read all stored and pending codes, and note freeze-frame data. Look for misfire codes (P0302, P0300) or other injector circuit codes that might point to a pattern.
2. Visual inspection of injector and harness
   With the engine off, locate the “B” or cylinder 2 injector. Inspect the connector for broken locks, corrosion, or pushed-back terminals. Follow the harness a few inches in each direction, looking for rub-through, cuts, or melted insulation.
3. Wiggle test while monitoring data
   Start the engine and watch live data for misfire counts or injector status. Gently move the harness and connector. If the engine stumbles or data changes when you move a certain spot, you likely have an intermittent wiring or connector issue.
4. Check injector resistance
   With the key off, disconnect the injector connector. Use a multimeter to measure resistance across the injector terminals. Compare to factory specs and to another known-good injector. An open circuit (infinite resistance) or a reading far off from the others indicates a bad injector.
5. Test power supply to the injector
   With key on, back-probe the injector connector to verify that you have proper battery voltage on the supply side (usually one wire is common power, the other is ECU-controlled ground). No power points to a blown fuse, relay issue, or upstream wiring fault.
6. Check injector control (ground) from ECU
   Use a noid light or test light connected to the injector control circuit. Crank or run the engine. The light should flash, showing the ECU is pulsing the injector. No pulse suggests a wiring break between ECU and injector or a failed ECU driver.
7. Continuity and short tests on wiring
   With the battery disconnected, check continuity from the injector connector back to the ECU pins using a wiring diagram. Also test for shorts to ground and shorts to power. Any abnormal reading means the harness needs repair.
8. Swap test (when practical)
   On some engines, you can swap the suspect injector with another cylinder. If the code and misfire move to the new cylinder, the injector itself is faulty. If P020B stays on the same cylinder, the problem is more likely wiring or ECU.
9. Review Mode $06 and freeze-frame
   Advanced scan tools let you look at Mode $06 injector and misfire data. This can confirm that cylinder 2 / Injector B is the only one out of range and help rule out broader fuel system issues.
10. ECU evaluation
    Only after power, ground, injector, and wiring have been verified should you suspect the ECU. In many cases, a specialist can bench-test or rebuild the ECU if the injector driver is bad.

Pro tip: Always disconnect the battery or pull the injector fuse before doing resistance or continuity checks. Testing live circuits can damage your meter, the ECU, or the injector driver.

Possible Fixes & Repair Costs

Fixing P020B usually involves addressing the specific injector circuit fault. The most common repairs include:

• Replacing the faulty fuel injector for cylinder 2 / Injector B
• Repairing or replacing damaged injector wiring or connectors
• Cleaning and tightening corroded terminals
• Replacing blown fuses or faulty injector relay (if applicable)
• In rare cases, repairing or replacing the ECU

Typical repair costs vary widely. An injector replacement on most gasoline engines runs about $200–$500 parts and labor. Harness or connector repairs can range from $100–$350 depending on access and how much wiring needs to be replaced. If the ECU is at fault, you may be looking at $500–$1,200 or more, especially on newer vehicles. Labor rates, engine layout, and whether multiple injectors are serviced at once all affect the final bill.

Can I Still Drive With P020B?

You can sometimes drive with P020B, but it’s not recommended for long. If the injector is not firing, that cylinder is effectively dead, which can cause rough running and poor power. Raw fuel may enter the exhaust, risking catalytic converter damage and higher emissions. Short trips to get home or to a shop are usually okay if the engine still runs reasonably, but if you have severe misfire, flashing check engine light, fuel smell, or stalling, you should stop driving and have the vehicle towed.

What Happens If You Ignore P020B?

Ignoring P020B can lead to long-term damage. Continuous misfires can overheat and melt the catalytic converter, wash down cylinder walls with fuel, contaminate engine oil, and in extreme cases, damage pistons or valves. What starts as a relatively simple injector or wiring repair can turn into a very expensive engine or exhaust repair if left unchecked.

Last updated: January 22, 2026

Vehicles Commonly Affected by P020B

P020B shows up most often on modern fuel-injected vehicles from manufacturers like Ford, GM (Chevrolet, GMC, Cadillac), Chrysler/Dodge/Ram, Toyota, Nissan, and Honda. It’s especially common on V6 and V8 engines where injector harnesses run along the intake and are exposed to heat and vibration. You’ll see it frequently on pickup trucks, SUVs, and vans that see heavy use, towing, or off-road driving, but it can affect passenger cars and crossovers just as easily.