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
This test helps identify a weak or noncontributing cylinder in engines with sequential PFI fuel systems. The ECA shuts off fuel supply to each injector and measures RPM drop. It computes the variation between cylinders and identifies the weak ones. This test mode is entered from the KOER SELF-TEST, after all codes have been displayed. Within 2 minutes after codes have been displayed, lightly depress throttle (a 2-3 degree throttle angle is required, NOT a wide open throttle). After a brief stabilizing period, ECA will activate the test procedure. The test will be repeated if the throttle is depressed within 2 minutes of the final code output. During the 2nd and 3rd test sequence, the percentage of allowable variation between cylinders is reduced. Service codes displayed during this test identify the weak or non-contributing cylinder. See CYLINDER BALANCE TEST SERVICE CODES table to identify the cylinder number corresponding to the service code displayed. If Code 90 is displayed during this test, it indicates a passing result. If Code 77 is displayed, repeat cylinder balance test. If throttle is moved during this test, Code 77 will appear, indicating that test is not completed. Total test time is about 3 minutes.
| Service Code | Application |
|---|---|
| 90 | Pass |
| 10 | Cylinder No. 1 |
| 20 | Cylinder No. 2 |
| 30 | Cylinder No. 3 |
| 40 | Cylinder No. 4 |
| 50 | Cylinder No. 5 |
| 60 | Cylinder No. 6 |
| 70 | Cylinder No. 7 |
| 80 | Cylinder No. 8 |
| 77 | Retest |
NO RELATED
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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.