P0271: Cylinder 3 Contribution/Balance Fault - Causes, Fixes & Cost [2026]
What is P0271? P0271 means cylinder 3 is the weak cylinder in the PCM balance check. Most root causes match P0263 but on cylinder 3 - dirty injector, low compression, or weak ignition. Bank/cylinder layout varies by engine; verify the cyl 3 location before disassembly.
🎯 Top 3 Causes Ranked by Probability
47%
#1 - Most Likely
Weak or Clogged Injector (Cyl 3)
Cyl 3 injector flow is below spec. Cleaning or replacement is the usual fix.
🔨 Part
$80-$500
👨🔧 Labor
$100-$350
⚡ DIY
Medium
28%
#2 - Check First
Low Compression on Cyl 3
Worn rings, burnt exhaust valve, or a head gasket leak between cyl 3 and an adjacent cylinder.
🔨 Part
$200-$2000
👨🔧 Labor
$400-$1500
⚡ DIY
Hard
25%
#3 - Less Common
Ignition Component (gas engines)
Worn plug, cracked boot, or weak coil on cyl 3. Easy to swap-test.
🔨 Part
$15-$120
👨🔧 Labor
$50-$200
⚡ DIY
Easy
🔧 Step-by-Step Diagnosis
- Locate cylinder 3 - on most V engines it is on bank 1 (driver side on Fords/GM, passenger side on most imports). Verify before testing.
- Compression test cyl 3 against the rest of the engine. Variance over 10% confirms a mechanical issue.
- Swap the cyl 3 plug and coil with cyl 1. If P0263 appears next, the ignition part is at fault.
- Run an injector balance test or pull the cyl 3 injector and have it bench-tested for flow.
- If everything tests good, borescope the cyl 3 valves and check for carbon buildup or burnt seats.
🚗 Most Affected Vehicles
🚫 Is It Safe to Drive with P0271?
Short term yes, but expect rough idle and bad fuel economy. Fix before extended driving to protect the catalyst.
❓ Frequently Asked Questions
Which cylinder is cylinder 3?
Engine layout varies. On a Ford 5.4L V8, cyl 3 is on the driver-side bank, second from the front. On a Cummins straight-6, cyl 3 is the third from the front. Always check your engine diagram.
Is a P0271 dangerous to drive with?
It will not strand you immediately, but raw fuel from a weak cylinder can damage the catalytic converter or DPF in extended use.
Can I clear P0271 and watch for return?
Yes, but if you have a balance fault it usually returns within a single drive cycle. Use the clear-and-recheck as a confirmation step, not a fix.
How do I run an injector balance test?
Most professional scan tools (Snap-on, Autel, OEM tools) have a built-in injector balance test under Engine -> Functional Tests. Follow the on-screen prompts.
Will an engine flush fix P0271?
Sometimes, if a dirty injector is the cause. A quality fuel system cleaner is worth trying before mechanical repairs.