Cylinder Balance Test

WARNING: This page does not describe the selected car, but rather 12 other vehicles, including the 1993 Mercury Tracer, 1993 Mercury Topaz, 1993 Mercury Sable, 1993 Mercury Grand Marquis, and 1993 Mercury Cougar. However, it is still accessible from the selected car via links, so may be relevant.

This test helps identify a weak or non-contributing cylinder in engines with sequential PFI fuel systems. PCM shuts off fuel supply to each injector and measures RPM drop. It computes variation between cylinders and identifies weak ones.

This test mode is entered from 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, PCM will activate test procedure.

Test will be repeated if throttle is depressed within 2 minutes of final code output. During second and third test sequences, percentage of allowable variation between cylinders is reduced. Service codes displayed during this test identify weak or non-contributing cylinder. See CYLINDER BALANCE TEST SERVICE CODES table. If Code 90 is displayed during this test, system has passed test. If Code 77 is displayed, repeat cylinder balance test. If throttle is moved during this test, Code 77 will appear, indicating test is not completed. Total test time is about 3 minutes.

CYLINDER BALANCE TEST SERVICE CODES

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