What Does P0284 Mean?
The ECM has detected a cylinder 8 contribution or balance fault, indicating that cylinder 8 is producing less torque than expected during its power stroke. Found on V8+ engines, this is determined by crankshaft speed variation analysis. The driver will notice rough idle, vibration, reduced engine power, and the sensation of a misfire, particularly at lower RPMs where the imbalance is more perceptible.
Common Causes
35%
Cylinder 8 fuel injector with degraded flow, restricted nozzle, or poor spray
25%
Low compression on cylinder 8 — piston ring wear, burnt valve, or head gasket leak
20%
Injector wiring or ECM driver fault reducing fuel pulse delivery to cylinder 8
12%
Intake manifold restriction or gasket leak at cylinder 8
8%
Glow plug or ignition component failure on cylinder 8
Diagnostic Steps
1
Review live data for cylinder 8 contribution rate — compare to all other cylinders, particularly those on the same bank, to confirm cylinder 8 is the underperformer.
2
Perform a compression test across all 8 cylinders — cylinder 8 should be within 10% of the highest reading. A low reading necessitates a leak-down test to isolate the leak path.
3
On diesel engines, perform an injector return flow test — measure the fuel returned from each injector at idle. Cylinder 8 showing excessive return flow points to a worn injector.
4
Check cylinder 8 injector correction values in the ECM adaptation data — large positive corrections confirm the ECM is compensating for reduced injector performance.
5
Swap the cylinder 8 injector with another cylinder, clear adaptations and codes, then drive — this definitively determines if the injector or the cylinder itself is at fault.
Estimated Repair Cost
$150 - $1,500
Parts + labor, varies by vehicle and location
The ECM has detected a cylinder 8 contribution or balance fault, indicating that cylinder 8 is producing less torque than expected during its power stroke. Found on V8+ engines, this is determined by crankshaft speed variation analysis. The driver will notice rough idle, vibration, reduced engine po...
The most common cause of P0284 (Cylinder 8 Contribution/Balance Fault) is: Cylinder 8 fuel injector with degraded flow, restricted nozzle, or poor spray
Typical repair costs for P0284 range from $150 to $1,500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The vehicle can be driven at reduced load for short trips. Persistent cylinder 8 imbalance on a V8 will increase exhaust temperatures on that bank, risking catalytic converter or turbo damage. Diagnose within a few days.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0284 to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel Injection / Engine Mechanical
Difficulty
Type
Generic (SAE)
Recommended Tools
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