Trouble Code 14 Mercruiser 7.4 MPI

[451stroker]

Hello,

I have a 2000 7.4 Mercruiser MPI with the alarm sounding at about 3000 RPM. I read the trouble codes and the only code is 14, which indicates that temperature sensor voltage is low. I already replaced the 2 wire temperature sensor, but the alarm still goes off. I would greatly appreciate any advice on what the next step should be in troubleshooting the problem.

Thanks!

 

[Bt Doctur]

put a resistor in the circuit and pay attention to the analog temp gauge

 

[451stroker]

put a resistor in the circuit and pay attention to the analog temp gauge

Do you mean put a resistor in to permanently defeat the ECT and just rely on the analog gauge from here forward, or would I be doing it as a troubleshooting procedure?

 

[Bt Doctur]

I am currently working on a test jig for the water pressure sensor that is really not needed if you do the required service at the required intervals.
Almost all of these circuits rely on a 5 volt source for the ecm to read.Corrosion and water create havoc with the plugs.
We never had these sensors with older motors and we got along just fine.
Does your analog temp gauge stay stable at the correct temp?
Has the impeller been replaced?
Have you verified the temp with a laser?

 

[451stroker]

Do you mean the out drive water pump impeller? Yes, it has about 4 hours on it and I also just replaced the engine water pump. Today, I replaced the 5 year old ECT sensor, but the alarm is still going off.

Also, based on your last response:
1. What resistor value should I put in the circuit?
2. Will a resistor cause the engine to run lean on cold start up because the computer is fooled into thinking that the engine is already warmed up?
3. I measured a steady 5 volts across the ECT plug with my VOM. Could the plug still be at fault?

Thanks!

 

[451stroker]

Something I should mention is that the temperature gauge reads at 170 degrees, but when I hit rough water, the gauge fluctuates between 100 degrees and 170 degrees. That's usually when the alarm goes off. I figured it was a separate problem since the gauge and temp sender are not part of the ECT circuit and are not read by the ECM. Now I'm wondering, is there some way the engine temperature is actually fluctuating and momentarily dropping to 100 degrees under load and causing the alarm to off? If so, what could cause the temperature to fluctuate and actually make the engine run too cool? Code 14 indicates that temperature is too low.

Thanks!

 

[Bt Doctur]

use a laser to verify the hot temps first, then try changing the thermostat