Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Cylinder Balance Test: Description
The cylinder balance test is designed to aid in the detection of a non-contributing cylinder. The cylinder balance test first reads engine RPM, with all injectors activated. Next each injector is turned "off and on", one at a time. The RPM drop that results, if any, is then read. These two RPM's are compared to verify that the RPM drop was greater than a calibrated level.
The cylinder balance test has the capability of comparing RPM drop of each cylinder against three different calibrated levels. the first level checks for gross errors (electrical opens, shorts, etc). The second and third levels check for partially contributing cylinders. If the appropriate RPM drop is not achieved at any levels, then a service code corresponding to that cylinder will be set. For the cylinder balance test codes see SERVICE TEST CODE TABLE.
| Service Code | Description | ||
|---|---|---|---|
| 10 | Cylinder No. 1 Problem | ||
| 20 | Cylinder No. 2 Problem | ||
| 30 | Cylinder No. 3 Problem | ||
| 40 | Cylinder No. 4 Problem | ||
| 50 | Cylinder No. 5 Problem | ||
| 60 | Cylinder No. 6 Problem | ||
| 70 | Cylinder No. 7 Problem | ||
| 77 (1) | Rerun Test | ||
| 80 | Cylinder No. 8 Problem | ||
| 90 | No Problems Encountered | ||
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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