P0272

P0272 means the ECM detected cylinder 4 contribution/balance fault — same diagnostic framework as the rest of the P0263/P0266/P0269/P0272 cylinder-balance family. The ECM monitors per-cylinder crankshaft acceleration and injector balance rate (mm^3/stroke deviation) and sets P0272 when cylinder 4 falls outside the calibration window — typically +/-8 to 15% contribution deviation or 2-5 mm^3/stroke balance error. Cheapest-first ladder: (1) scan-tool live-data the per-cylinder injector balance rate at warm idle — positive deviation greater than 4 mm^3/stroke means cylinder 4's injector is over-fueling (stuck/leaking), negative means under-fueling (clogged/worn nozzle). (2) Swap the cylinder 4 injector electrical connector with an adjacent cylinder, clear codes, and see if the fault follows the connector — this nails down electrical/wiring vs. mechanical/hydraulic in 10 minutes. (3) Return-flow test with calibrated bottles (look for less than 50-100mL/min per injector at idle; outliers point at stuck-open). (4) Relative compression test via scan-tool starter-current monitoring; greater than 15% variation indicates mechanical compression loss. (5) Verify injector trim/IQA codes match etched codes on the physical injector — a frequent overlooked source of balance faults. Cylinder 4 location matters: on a 4-cylinder diesel (VW TDI, Sprinter OM651 4-cyl) cylinder 4 is at the rear of the engine and runs hottest; on an inline-6 Cummins cylinder 4 is mid-aft and a common balance-code cylinder; on a V8 cylinder 4 is the rear-most cylinder on the right (passenger) bank in most North American configurations. Pull the FSM cylinder map before chasing. Expensive-misdiagnosis caveat: cylinder-balance codes paired with a hard miss can look like a bad injector when the real fault is a wiped cam lobe, a bent pushrod, or a hairline head-gasket leak between cylinders — confirm compression and return flow before quoting injector parts that may not fix the symptom.

Vehicle-specific patterns: 2001-2004 GM Duramax LB7 throws P0272 as part of the well-documented full-set injector failure under the valve covers — GM's extended warranty covered many through 200k miles. 2003-2007 Ford 6.0L Powerstroke throws P0272 from HEUI stiction or low HPOP; verify branch-tube integrity and ICP signal before condemning. 2008-2010 Ford 6.4L Powerstroke throws P0272 from piezo injector wear or CP3.3 starvation. 2011-2016 Ford 6.7L Powerstroke throws P0272 from CP4 contamination metal embedded in the cylinder 4 injector nozzle. 2003-2018 RAM Cummins 5.9L/6.7L throws P0272 from Bosch CR injector wear — at the inline-6's rear-mid position cylinder 4 is one of the hotter cylinders. 2007-2018 Mercedes Sprinter OM642 V6 and OM651 4-cyl throws P0272 from piezo injector wear; the OM651 four-cylinder puts cylinder 4 at the rear adjacent to the firewall where it gets the worst heat soak. 2009-2014 Audi/VW TDI 2.0L CR throws P0272 from injector nozzle wear, often as one of the first cylinders to show balance drift after a CP4 contamination event. Estimated repair: $400 to $7,500.