OBD-II trouble code
P0278: Cylinder 6 Contribution/Balance
SAE J2012 APR2002: cylinder 6 contribution/balance. Both GM diesel bulletins list it. The four-cylinder balance sheet does not measure it. The printed pair is one injector after the crank is even.
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 shows even compression spikes; the LWN charge-air repair is outside this pair)
- DIY difficulty
- Shop recommended
Browse every code in P0200–P0299, or start from the full code library.
What does P0278 mean?
SAE J2012 APR2002 names P0278 Cylinder 6 Contribution/Balance. P0276 and P0277 are the circuit codes. A VAG-group list prints 16662 P0278 as a fuel-injection quantity deviation on cylinder 6.
Two NHTSA-hosted GM bulletins name this code, and they do not describe the same test. 19-NA-232 (MC-10168238, October 2019) puts P0278 on 2017–2020 Silverado and Sierra trucks with the L5D and L5P, and the cab-chassis years in that header, next to misfire codes P0300 through P0308. The causes it allows are a fuel injector, an electrical issue, or loss of cylinder compression. The procedure pulls the fuel-pump control module B+ fuse so the crank delivers no fuel, then graphs battery voltage with the PicoScope across battery positive and battery negative. The downward dip is battery voltage dropping as the starter draws more current on a compression stroke. An even voltage trace is the bulletin's pass. A weak dip is mechanical and leaves the injector alone.
17-NA-194 (MC-10166641) puts P0278 on 2016–2020 Colorado, Canyon, Express, and Savana with the LWN diesel. The cause sentence is an induction-system leak. The test sentence is the full-system charge-air leak test. That is not a balance rate and not a relative-compression crank.
SB-10030789-2893 monitors cylinders 1 through 4 only. Cylinder 6 is not in that instruction, so its positive-means-fuel-added language is not a cylinder 6 measurement. LBT-149 does record cylinders 1–8 on the Duramax it describes, with +4 mm³ to −4 mm³ in Park or Neutral and +6 mm³ to −6 mm³ in Drive, after 82°C and 30 seconds of idle. If a DTC other than P0300–P0308 is already set, that reprint sends you to the DTC list before the balance test. PIP5537, for 2017–2018 L5P misfires, says not to replace fuel injectors for the concern it describes and does not list P0278. It does not cancel 19-NA-232.
Common causes
- On a 19-NA-232 truck, loss of compression at cylinder 6
- A fuel injector or an electrical fault on that bulletin once the battery-voltage dips match
- On a 17-NA-194 LWN, an induction-system leak
- A Duramax cylinder 6 quantity outside the Park window or the Drive window in LBT-149
Symptoms
- P0278 stored
- P0300 through P0308 on an L5D or L5P that 19-NA-232 covers
- A second code from the 17-NA-194 list on an LWN
- A Park reading and a Drive reading that are not the same window
- P0277 stored, the circuit-high code
Diagnostic steps
- 1.Finish P0276 or P0277 first if one of them is stored.
- 2.Do not apply SB-10030789's cylinders-1-through-4 step to cylinder 6.
- 3.On a listed L5P or L5D, pull the FPCM B+ fuse, crank two to three seconds, save the battery-voltage waveform, refit the fuse, clear fuse-out codes. A weak downward voltage dip is mechanical. Even dips: compression is off the list. Do not read cylinder 6 on the sheet that stops at cylinder 4.
- 4.On a listed LWN, run the full-system charge-air test before an injector quote. The bulletin names an induction leak.
- 5.On the Duramax in LBT-149, record all eight cylinders. Park or Neutral uses +4 mm³ to −4 mm³. Drive, brake held, uses +6 mm³ to −6 mm³. Other non-misfire DTCs go to the DTC list first.
- 6.PIP5537's instruction not to replace injectors applies to the misfire concern that bulletin describes. It does not list P0278.
- 7.Depressurize before an injector is opened. The printed pair is one injector after compression is not the cause.
Repair cost
$768 – $953 (one fuel injector replacement, parts and labor, after 19-NA-232 shows even compression spikes; the LWN charge-air repair is outside this pair)
RepairPal's fuel injector replacement, updated 3 September 2026, totals $768–$953 nationally (labor $304–$446, parts $464–$507). The printed pair is that job when 19-NA-232 leaves an injector in play. The charge-air repair was searched and is not priced here. Diagnosis is $125–$183 labor, separate. A fuel filter at the national $258–$322 is not a step in either bulletin. The 2026 Tucson injector line, $456–$604, is outside the national pair.
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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.