If you have the three function gauge it should be telling you something when the horn sounds.
low oil - 4 beeps every two minutes and resets with engine/oil light illuminated
overheat - continuous beep with key on until temperature drops below preset level/temp light illuminated
over-speed - beeping sounds with reduced ignition timing/temp and oil lights flash alternately.
electrical sensor-TPS or engine temp sensor not functioning/temp and oil lights flashing alternately.
water seperating fuel filter sensor full of water- series of four beeps 2 minutes apart/fuel light illuminating constantly. Tested by removing from sensor and holding to ground for approx 30 seconds to hear the audible alarm
No knock sensor or O2 sensor on the 1998 EFI. But, there is a map sensor, air temp, TPS, engine head temp sensors.
The book says:
Rough Idle, Acceleration OK, Full Throttle Ok:
Improper EFI setup -- Unlikely as it is easy on the EFI
Failed Map Sensor
Coolant Sensor Fail
Broken Reed - Unlikely as the reed is in no way attached to the buzzer
Hope this helps. If you need any additional info let me know I have a book right here..Sensor testing is straight forward.. Dare I say easy.
