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check engine light, no code

S

slow cruiser

Regular Contributor
2001 Crusader 8.1, engine starts, runs fine until @ 3,000 rpm or more the check engine light and buzzer turn on but does not register a diagnostic code. If I turn the engine off it starts right up and there is no warning light or buzzer until reaching 3000+ rpm again. Engine temp and oil pressure are fine, runs smooth even at speed.
Any ideas?:confused:
 
perhaps monitoring the sensor inputs to the fault condition with a scanner would help....so would checking the manual's description of the states that turn on the buzzer...and this assumes the buzzer referred to is the one driven by the ECU and NOT a stand alone (usually redundant) warning system....
 
I believe the buzzer is driven by the ECU, it goes on when the light does and is integral to the dash. I did run it with the scanner (TechMate) attached, the only item high was the IAC which I didn't think would trigger the alarm. I'll check the manual but I only remember the only reference to an alarm was the MIL light. The manual did note that a high temp alarm might not leave a code but the temp was 160*. I took it up to 3800 rpm and it ran fine except for the alarm.
 
"..the temp was 160*." - determined by the gauge or what the TechMate indicated?? Except for a fully integrated dash, most gauges use separate sending units from the ECU....and temp senders are known to produce "bad measurements" after some use...
 
TechMate. From what I've read the ECU uses the coolant sensor and the gauge uses the block sensor. The dash gauge reads higher than the scanner but not high enough to set a warning. Specs for the 8.1 is 220* as over heat
 
If its the integrated horn going off and you can't see anything out of spec with the TechMate, that's gonna be a tough nut to crack...may wanna check with crusader's tech support team...
 
If by manual you mean anything that came with the boat or engine, then these are pretty much useless. What you need (if you do not have) is the MEFI 4 (or possibly 3 in your case) Diagnostic Manual. Somewhere in the 200+ pages it may tell you how the alarm can be triggered without throwing a code. The manual is even more valuable than the TechMate and together they are really the nuts. Go to Pirate 4X4 and look for the diagnostic manual.
 
I couldn't find anything in the manual to give me direction. No help from the manufacturers. Did some PM, fuel filters, flame arrestor, cleaned corroded ground connections. Took it out for a trial run and NO ALARM. Runs great up to 4,000 rpm. I did not run after each action so I do not know which one helped.
 
slow cruiser said:
I couldn't find anything in the manual to give me direction. ...... cleaned corroded ground connections. I did not run after each action so I do not know which one helped.
Click to expand...

There's plenty in the manual; its rather generic in many cases though....the highlighted item is most likely to be the original root cause, especially if it any of them were dedicated grounds for the computer...
 
A little explanation, the main aid from the manual was how the system works and potential causes before getting into in depth diagnosis (check the basic items first). The scanner was a big help because without codes it showed what the problem wasn't-a HUGE help.
This is my first year with this boat and in spite of what the surveyor said and the service records show PM was not a concept this mechanic was accustomed to using.
 
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