Holy codes...please help!

Chief115 · Aug 24, 2014

So taking the dash apart yesterday revealed that the check engine light was not on because it was missing. Turns out it has 5 codes
P0753
Shift solenoid "a" electrical
P0300
Multi cyl misfire
P0304
Cyl 4 misfire
P0308
Cyl 8 Misfire
P1765
Transmission 12v supply relay

Now I have the codes, and understand what they mean. My question is what causes these codes?

Merc225hp · Aug 24, 2014

Misfire could be anything from bad spark plugs to cylinders with low compression. I would start by doing a comp test before you spend a dime on parts. For the tranny solenoides they just go bad over time, to change these you will have to drop the tranny pan.

Chief115 · Aug 24, 2014

So I did a compression test. All were very close to 150 psi. All build and hold pressure. I retested cyl 1 and on the second test and on it was barley 100 psi. Weird but idk if that's relevant. Main point is the 2 cyl it says it's misfiring have compression. So the only thing I can think to do (which I was going to do anyway) is plugs wires, rotor and cap, and coils

Holy codes...please help!

Chief115

Senior Member

Merc225hp

Senior Member

Chief115

Senior Member

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