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
The cylinder balance test is an aid in finding a weak or noncontributing cylinder in engines equipped with sequential PFI fuel systems. The ECA shuts off the fuel supply to each injector and measures the RPM drop. It computes the variation between the cylinders and identifies any weak ones. This test mode is entered during the KOER Self-Test after all codes have been displayed. Within 2 minutes after the 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, the 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 will be reduced. Service codes displayed during this test correspond to cylinder number and indicate a weak or non-contributing cylinder. If Code 90 is displayed during this test, it indicates a pass. If Code 77 is displayed, repeat cylinder balance test. If throttle is moved during this test, Code 77 will appear, indicating that test was 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 |
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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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