01 Surprising Test Results Show Which Budget Brake Pads Stop F… • 02 This Is How to Fix a Car That Won’t Start After Replacing t… • 03 From Slight Pause to Complete Failure: Understanding Transm… • 04 This Is How Mercedes Magic Body Control Scans The Road • 05 Bright Solutions: Resolving the Mystery of Dim Car Headligh… • 06 Understanding Canbus in Automotive: Enhancing Connectivity … • 07 How Long Can an Engine Run Without Coolant? • 08 This Is How Your Turbocharger Works And Why A Small Whistle… • 09 Why You Should Avoid Driving in Very Low RPMs on High Gear • 10 This Is Why Your Car’s CV Axle Is Failing •

DTC codes / P02xx · Fuel and air metering (injector circuits) / P026D

P026DFuel Injection Quantity A Higher Than Expected

P026D indicates that the engine control module (ECM) has detected a fuel injection quantity for a specific cylinder that is higher than the commanded or expected amount. The ECM monitors injector performance and calculates that more fuel is being delivered than the engine's operating conditions require, which can upset the air-fuel ratio and trigger the check engine light.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyProfessional
AreaFuel and air metering (injector circuits)

Symptoms you may notice

  • Illuminated check engine light, often with no other noticeable symptoms
  • Rough idle or engine misfire, especially when cold
  • Decreased fuel economy and a rich-running exhaust smell
  • Black smoke from the tailpipe under acceleration
  • Hesitation or stumble during acceleration
  • Elevated hydrocarbon (HC) and carbon monoxide (CO) emissions on an emissions test

Common causes, most likely first

  1. Faulty or sticking fuel injector for the affected cylinder
  2. Contaminated or degraded fuel causing injector imbalance
  3. Wiring harness damage or poor electrical connection to the injector
  4. Low fuel pressure or a weak fuel pump causing uneven delivery
  5. Engine control module (ECM) calibration issue or internal fault
  6. Mechanical engine problem such as low compression on that cylinder
  7. Leaking or restricted fuel return line affecting injector performance

How to diagnose and fix it

  1. Connect a scan tool and record freeze-frame data to identify the affected cylinder and operating conditions
  2. Inspect the injector wiring harness and connectors for corrosion, chafing, or loose pins
  3. Perform a fuel pressure test and compare with manufacturer specifications
  4. Run an injector balance test or cylinder contribution test to isolate the faulty injector
  5. Check for intake and exhaust leaks that could skew the ECM's fuel calculations
  6. Swap the suspect injector with a known-good one from another cylinder and recheck the code
  7. If the injector is faulty, replace it and clear the adaptive fuel trims before retesting

What the code does not always mean

  • A P026D code can be set by a simple electrical fault such as a corroded injector connector, so always inspect the harness before condemning the injector itself.
  • Low fuel pressure from a tired fuel pump can cause the ECM to command a longer injector pulse width, which may be misinterpreted as excess fuel delivery and set this code.
  • On some vehicles, a dirty mass airflow (MAF) sensor or a vacuum leak can skew fuel calculations enough to trigger P026D without any injector problem.
  • The code often appears alongside misfire codes like P0300 or P0301, but the misfire may be the root cause rather than a separate issue.
  • A sticking injector may only act up when the engine is cold or under specific load conditions, so intermittent symptoms should not be dismissed.

Can I keep driving with P026D?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy acceleration or towing because excess fuel can damage the catalytic converter and dilute engine oil. If the engine is misfiring badly or the check engine light is flashing, stop driving and have the vehicle towed.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage