Cylinder-Balance Case Analysis: Why a Large Fuel Correction Does Not Automatically Identify a Faulty Injector

Case Type: Technical Diagnostic Case Analysis
Application: Electronic Diesel Engine Management
Diagnostic Focus: Cylinder Correction / Contribution Analysis

A cylinder showing a large ECU fuel correction can quickly become the suspected injector.

That is only one possible explanation.

Correction Is a Response

The ECU is compensating for a cylinder contribution difference.

It does not directly identify why the difference exists.

Check Mechanical Condition

Before condemning the injector, diagnosis may include:

• compression;
• valve condition;
• cylinder cut-out response;
• injector electrical behavior;
• fuel delivery.

Why Parts Swapping Can Be Misleading

If the cylinder has a mechanical compression problem, replacing the injector will not normalize combustion contribution.

For the broader interpretation method, see Technical Insight: Why Diesel Cylinder Correction Values Should Not Be Used as a Standalone Injector Test.

Case Takeaway

Cylinder correction should be treated as directional diagnostic data, not as a standalone injector verdict.