OBD-II trouble code
P0266: Cylinder 2 Contribution/Balance
SAE J2012 APR2002: cylinder 2 contribution/balance. A balance rate is not an injector-circuit fault. The printed pair is one injector after compression is ruled out.
Quick facts
- System
- Powertrain
- Category
- Fuel Injectors
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $768 – $953 (one fuel injector replacement, parts and labor, after 19-NA-232 relative compression does not show a mechanical fault; a charge-air leak and a compression repair are outside this pair)
- DIY difficulty
- Shop recommended
Browse every code in P0200–P0299, or start from the full code library.
What does P0266 mean?
SAE J2012 APR2002 names P0266 Cylinder 2 Contribution/Balance. It is not P0264, cylinder 2 injector circuit low, and it is not P0265, circuit high. A contribution code can set with the injector circuit electrically intact. A VAG-group code list prints 16650 P0266 as a deviation of fuel quantity injected on cylinder 2. That line is a label, not a pinpoint.
NHTSA service bulletin SB-10030789-2893 says balancing rates alone do not indicate a specific failure, and it says not to replace components solely based on balancing rate information. On that sheet a positive rate means fuel is being added and a negative rate means fuel is being removed. The monitor step reads cylinders 1 through 4, so cylinder 2 is inside it. The setup on that sheet is engine off for one minute, then idle for 2 minutes with engine temperature greater than 140°F, then rpm above 1500 for 30 seconds, then back to idle for one minute. Rates update below 1200 rpm. If a rate is high, the sheet sends you to injector flow-rate programming, exhaust-port temperature within ±20°F of the other ports, and a compression test. It does not name a millimetre limit. Use the service manual's value, which that step points at.
GM bulletin 19-NA-232, NHTSA MC-10168238, October 2019, lists P0266 among codes that can sit with P0300 through P0308 on 2017–2020 Silverado and Sierra trucks with the L5D and L5P, plus the cab-chassis years that bulletin lists. The causes it names are a fuel injector, an electrical issue, or loss of cylinder compression. The relative-compression setup pulls the fuel-pump control module B+ fuse so the engine cranks without fuel. Steps 3 through 5 connect the PicoScope across battery positive and battery negative and graph battery voltage. The downward dip is battery voltage dropping as the starter draws more current on a compression stroke. A passing voltage trace is not a reason to open the injector. A weak dip leaves the injector and goes to mechanical diagnosis.
Bulletin 17-NA-194, NHTSA MC-10166641, lists P0266 on 2016–2020 Colorado, Canyon, Express, and Savana vehicles with the LWN diesel, and the cause it names is an induction-system leak. The test it names is Charge Air Cooler Diagnosis, the full-system air leak test. That is not the L5P relative-compression crank, and it is not SB-10030789's balance-rate sheet.
ACDelco training reprint LBT-149 records Duramax balance rates for cylinders 1–8 and states a window of +4 mm³ to −4 mm³ in Neutral or Park and +6 mm³ to −6 mm³ in Drive, after coolant is above 82°C (180°F) and a 30-second idle. Do not judge a Drive reading on the Park window. Do not paste those millimetres onto SB-10030789, which does not print them. A spark plug is not the first part in any of these diesel documents.
Common causes
- On a 17-NA-194 LWN, an induction-system leak
- On a 19-NA-232 L5D or L5P, loss of cylinder compression
- A fuel injector or an electrical fault on that bulletin, once the battery-voltage trace is even
- Cylinder 2 fuel being added or removed on the SB-10030789 balance monitor, which that sheet then sends to flow programming, port temperature, or compression
- A Duramax cylinder 2 quantity outside +4 mm³ to −4 mm³ in Park or Neutral, or outside +6 mm³ to −6 mm³ in Drive, from LBT-149
Symptoms
- P0266 stored
- A balance rate the bulletin tells you not to treat as a parts order
- P0300 through P0308 on a 19-NA-232 truck, which adds the relative-compression path
- An LWN that also stores one of the other codes 17-NA-194 lists, which adds the charge-air test
- P0265 stored, which is the circuit-high code
Diagnostic steps
- 1.If P0264 or P0265 is stored, diagnose the circuit code. Contribution is the row that can remain after the circuit tests pass.
- 2.On SB-10030789, idle the engine through that sheet's temperature and rpm steps before reading cylinder 2. Do not replace a part on the rate alone. Positive means fuel added. Negative means fuel removed. A high rate goes to flow-rate programming, exhaust-port temperature within ±20°F, and compression.
- 3.On a 19-NA-232 L5D or L5P, pull the fuel-pump control module B+ fuse before the crank so no fuel is delivered. Graph battery voltage across the battery posts. A weak downward voltage dip, the starter drawing more current on a compression stroke, goes to mechanical diagnosis. A voltage trace that matches the others leaves compression and returns to the injector or the electrical path the bulletin names. Do not buy an injector from a balance rate alone. SB-10030789 forbids that.
- 4.On a 2016–2020 LWN named in 17-NA-194, run the full-system charge-air leak test before an injector is ordered. That bulletin's cause is an induction leak.
- 5.If the engine is the Duramax the LBT-149 reprint describes, compare Park or Neutral with +4 mm³ to −4 mm³ and Drive with +6 mm³ to −6 mm³. Do not use one window for the other gear.
- 6.Depressurize before an injector is opened. The printed pair is one injector after compression is not the cause. The charge-air repair and a compression repair are outside it.
- 7.Verify with the same balance reading, in the same gear the window required, or with the relative-compression trace on the bulletin's trucks.
Repair cost
$768 – $953 (one fuel injector replacement, parts and labor, after 19-NA-232 relative compression does not show a mechanical fault; a charge-air leak and a compression repair are outside this pair)
RepairPal's fuel injector replacement, updated 3 September 2026, is $768–$953 (labor $304–$446, parts $464–$507). The printed pair is that national average and matches the 19-NA-232 path that still has an injector after the no-fuel crank looks even. A fuel filter is $258–$322 nationally and is not the test SB-10030789 or 17-NA-194 names, so it stays outside. The Silverado 1500 filter line on that estimator is $290–$415 and is also outside. Diagnosis is $125–$183 labor and is separate. A charge-air repair and a compression repair were searched as their own totals and are not this pair. Other vehicle lines on the injector estimator, including the 2026 F-150 at $1,130–$1,415, are outside it.
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DIY vs shop
Leave this one to a qualified shop. The barrier here is high-pressure fuel components, where residual pressure remains after shutdown and escaping fuel can penetrate skin. DIY attempts often produce a more expensive problem than the original code.