Intermittent "Test Bulb" Display

If the test bulb illuminates intermitently but a trouble code cannot be obtained, check the following:

NOTE: If the engine rpm drops below 200 rpm for any reason, the test bulb will illuminate until engine rpm exceeds 200 rpm.

1. Poor connection in circuit from distributor tach terminal to ECM terminal A, ignition terminal 1 to ECM, and ECM terminal T to ground.
2. Tach filter resistance should be 14,000 to 18,000 ohms between distributor and ECM terminals (with one end disconnected) and an open circuit to ground.
3. Battery voltage under 9 volts.
4. Loss of long term memory. Momentarily grounding dwell lead with engine idling should cause trouble code 23 to flash, which should be retained after engine is stopped and restarted. If voltage is present at the long term memory lead but the code was not flashed, the ECM is defective.