From 2010, CARB requires diesel engines to detect when the commanded injection quantity is not delivered. The module estimates the fuel actually burned from airflow and the measured lambda (from the NOx or oxygen sensor) and corrects the quantity; if that correction passes a limit, the code sets. P026D means the engine gets more fuel than commanded. GM's LML diesel sets it at idle at a correction of +16 to +35 mm³ per stroke for 12 s, two trips. Volvo trucks detect it as too little oxygen at the NOx sensors for the fuel flow and point to boost sensor, EGR valve and sensor, wrong injectors, turbo vanes and intake leaks. On GM's 2.8 litre diesel vans of 2020–2022 it could also be a software anomaly without driving problems. Symptoms are black smoke and more frequent filter regeneration.
Low severity. Can I keep driving?You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.
Symptoms
- Check engine light on
- Black smoke, higher soot load, more frequent filter regeneration
- Rough running or idle
- Often nothing noticeable while driving
Most likely causes
- Injector dripping or worn, or wrong injector type fitted
- EGR valve not closing or EGR differential pressure sensor wrong
- Boost sensor or turbo vanes faulty, intake leak
- NOx or oxygen sensor reading wrong
- Software
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: hard
- It affects emissions.
What each character of P026D means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 2: Fuel injection
- 6D: Specific fault in that system
Frequently asked questions
Can I keep driving with code P026D?
You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.
What causes code P026D?
The most common causes are: injector dripping or worn, or wrong injector type fitted; eGR valve not closing or EGR differential pressure sensor wrong; boost sensor or turbo vanes faulty, intake leak.
Related codes
- P026CFuel Injection Quantity A Lower Than Expected
- P027FCold Start Fuel Injection Quantity A Higher Than Expected
- P0263Cylinder 1 Contribution/Balance
- P020ACylinder 1 Injection Timing
- P026BInjection Timing Performance
- P0087Fuel Rail/System Pressure - Too Low
Sources
- law.cornell.edu: 13 CCR 1968.2
- gsi.ext.gm.com: 14OBDG10 Engine Diagnostics
- gsi.ext.gm.com: 18OBDG04 Engine Diagnostics
- static.nhtsa.gov: MC 10215342 0001
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.