Powertrain, generic · Fuel and air metering (injector circuit)

P026C Fuel Injection Quantity A Lower Than Expected

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

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. P026C means the engine gets less fuel than commanded. GM's 6.6 litre LML diesel checks it at idle with the vehicle stationary and the engine warm, setting it at a correction of −20 to −35 mm³ per stroke for 12 s; later GM diesels use the learned correction value (10 of 20 samples); both need two trips. FCA lists it with an injector cleaning procedure for deposits. Ford diesels do not use it. Typical causes are coked injectors, wrong airflow or lambda measurement and weak fuel supply.

Likely causes

Injectors coked or clogged (too little flow)
Airflow or boost measurement wrong, NOx sensor lambda inaccurate
Weak low- or high-pressure supply (filter, pump, rail pressure)
Fuel quality or contamination
Software

Symptoms

  • Check engine light on
  • Lack of power
  • Rough running or idle

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–4,000
Time0.5–6 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

fuel injectorsmass air flow sensornox sensor

Related codes

P026DP027EP0263P020AP026BP0087

References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov.