Engine High Temp and Low Oil Pressure Alarm Does Not Work At All

[Halligan693]

I have a 2000 5.7L GSI. Recently repowered which was much needed before but due to an overheat from the high temp alarm not sounding while underway caused major damage to the heads, which lead me to just repower. The repower was a basically a brand new long block from Michigan Motors (not a reman) which was dressed with the original intake and engine harness (including ecu.) New oem manifolds/risers, bell housing & coupler, raw and fresh water pumps and a whole bunch more new parts. That was 2 summers ago. The motor purrs like a kitten.

The issue is the high temp and low oil pressure alarm still to this day do not function. Everything else works fine. Engine is not throwing codes. Runs like a champ both idle and underway.

My marine mechanic said it has to do with an aged engine harness and possibly some corrosion in the main connector. He said we can either replace the entire harness, which including labor and parts would be close to $3000 if not more if issues come up, which they always do with boats... The other option would be to bypass the entire main connectors, basically cut the wires on both sides and splice them together. Or purchase an aftermarket kit and install a new sender and run a wire to the helm.

Oh and I had the alarm speaker replaced and it works if you put power to the leads.

My main question is what could prevent the audible alarm from sounding? If it is in fact the engine harness does anyone know what wires specifically to splice? I would like to do this myself.

Anyone have any ideas?

JR

 

[dypcdiver]

Sounds like a common feed that might not be working, have you checked that they are powered?

 

[Halligan693]

Hey thx for the reply. What do you mean by common feed? I looked at a wiring schematic and I can't seem to make heads or tails of it. Looks like the senders go to the Ecu and the speaker is fed from the ecu. The senders work cuz they are new and the mechanic tested them with a multimeter. Sounds like a connection from the Ecu to the speaker. I just don't know where to look.

 

[dypcdiver]

As far as I can make out the connections for the high oil/temp alarms feed into the ECU on wires that are coded tan/black. The switched supply to the horn is also tan/black and from my diagrams is a single wire common to both alarms. On both of my diagrams it shows the tan/black wire to be on pin No 4 on the main connector ie. the big round one. Check the supply to the horn (No 17) purple wire from the ignition switch (No 20) and also the ground (black wire)

View attachment Helm.pdf

Best of luck.