2012 Mercury Black Scorpion 350 Cat/O2 sensor delete
 

I just acquired a 2012 Supreme V226 that has been throwing a O2 sensor code, it apparently is a somewhat common problem on the Black Scorpions that had the emission garbage on them. I was curious how to tell if the motor is a Scorpion ES DTC, or a Scorpion DTS? I have been looking to possibly delete the CAT system and have found some tuners at will bypass the O2 sensors like this one

https://www.magnumtuning.com/en/deta...ect-box-anchor

Or this one

https://www.cpperformance.com/p-1670...-computer.aspx

Also are there just resistors I can put in place of the O2 sensors?

The boat has been throwing the same O2 sensor code for years apparently and the boat runs fun and never goes into a limp mode. It has been to a very reputable Merc shop locally and they are stumped... I know they can’t delete but I sure can.


Thanks!

pull the serial number off the engine. run it through their database. Mercs are fun to identify!

It is a DTS motor, now off to discover what the voltage is for possibly putting in a resistor to mock signal to the ecm from the o2 sensors

never heard of this approach to fixing a sensor. they can't be that $$$.

if you want to go this route, is there another you can pull to test voltage?

.

Maybe I left a bit out, it had all new o2 sensors, it’s running rich and when the mechanic adds vacuum it gets proper fuel pressure. It’s getting like 45psi fuel pressure and it should be less like 40ish. It runs fine but throws a code for being rich. It doesn’t go into gurdian mode but beeps every 2 minutes. Possibly map sensor or tps sensors?

Interested to see anyones thoughts this.
I have the same motor which seems to go thru rear(after cat) sensors regularly. It throws the code and then does the 2 minute warning. Runs fine with code but it is set to run very rich when the code is thrown which is not great.
If the CP performance system bypasses the rear sensor and keeps the fuel mix correct then I would be keen on this as the code throwing and sensor changing is annoying and actually really expensive.

Ya it sounds like similar issues, the mechanic is going to try one last thing this weekend and will lake test. Have you tried changing the iac or tps sensors? Also are your four sensors all the same or are the two before the cat a different type of sensor than the down stream ones that keep throwing codes? There are a few ways to “trick” the downn streams or post cats. Do you reset the code on your own or does it go away when you replace the o2 sensor?

I think the sensors are all the same. I think older systems you could trick the controller to think it was getting a reading but I think these 4 wire sensors do actually read and adjust fuel mix based on the before and after readings. So if you bypass the rear sensor with a resister or some such then the fuel mix is likely to be wrong.
The code needs to be reset by diagnostic program.

Would it be worth it to take to a knowledgeable car shop to have a custom tune made for the ECM that simply turns off/ignores those sensors?

I have a heavily customized car that I had 3 tunes made for it. 1 tune for pump gas, 1 for racing fuel, and a final tune for when I have to get a yearly state inspection. The first 2 tunes ignore all of these dumb sensors that are all over new motors so it's not constantly throwing codes. The last inspection tune has them all turned on so I can pass an inspection. The tunes I had made cost less than $100 a piece and then a handheld tuner for $150 or so.

I’m pretty sure if the ecm is bring told it’s getting a good signal/tricked it will send the proper fuel air mix. I have a rinda scanner, just don’t want to be popping codes all summer, I’ll let you guys know what I figure out.

Pretty sure that is what the magnum scanner is above. They also have just a modular that allows you to send a heated adjustable signal to the sensors for 110$.. I may try that first

So doing some more home work apparently the boat is runny no too rich. The shop replaced the fuel regulator and checked for the infamous paint peeling inside the fuel rail. I have purchased a Ronda code reader and will give it some more time once the weather clears up. The boat is at 46 psi which is considered too high, the tech stated once given vaccum it drops the fuel pressure to the proper 42-40.... anyone heard of this? I will pull the regulator and inspect for debris.

I would think that the command for the injectors wouldn’t cause the few pounds over of fuel pressure to cause a rich issue. The injector command should lessen once seeing the rich fuel curves in the O2’s I would think.

Ya I agree seems like a cat issue would lean it out, MAP sensor maybe?? But that’s more bad idle issues typically

So low engine vacuum or a restricted fuel return line

What would cause low vaccum? Possible leak?

Low compression an/or timing. Ignition timing is easy to check/set, cam timing, not so easy. Low vacuum can be tested with a simple vacuum gauge and a restricted return line can be temporally bypassed and recheck fuel pressure.

I have a timing light, hope it’s not a cam ha ha. I may just do a really good vaccum check with some smoke, I have a fuel and vaccum gauge, would I check at the fuel booster or up top?

Would a 350 DTS time just like the old rigs? Just put the light on the notch and advance/retard like normal ?

I also have a rinda scab tool but haven’t had to use it, does it have a service mode to time ? I haven’t even figured out how to get the boat to rev without going into gear, I literally just got her.

Since you know that applying proper vacuum to the pressure regulator with a manual pump, lowers the fuel pressure, take that vacuum hose off the regulator and plug it into your manual vacuum gauge.

Not sure what the smoke is for, you need a gauge to measure engine vacuum, and then another for compression.

That engine likely has an electronic means to put it in base timing mode. The scan tool may do it, but also a plug to disconnect to connector to jump. Just note, ignition timing will never compensate for cam timing. A worn timing chain would need to be fixed first.

They checked compression and said it was good

Ya I think I’ve read up on a purple wire somewhere that I will ground out and it will go into base timing mode

After doing some more homework on timing of these things I’ve found I can’t really adjust it, ecm does. Also there are some gremlins that mercurcybcan possibly fix with a re flash of the ecm

The Smartcraft gauge alarm is showing fault “48 and 50 fuel system”

Stinger, what codes does yours throw?

Was this conclusion from the same crews that cant resolve high fuel pressure?

There are two layers to a compression test. How even they are, which is usually the most important factor, as we are typically looking to resolve a cylinder misfire. The next aspect is what is the overall PSI level. Yes, they may all be even, but are they really low? This is the number(s) we would look at if we were looking for, say, weak vacuum.

Yes, the ECM does control the timing, but if this is a distributor engine with electronic ignition, it should have a base timing setting procedure. if its got a coil pack, or is CNP or COP ignition, there is no base timing setting. Cam timing can still be retarded.

My code is always:
Sys Fault 48
<Fuel System>
It occurs because the rear co2 sensor fails. No other issues.
It seems to happen more than it should and requires replacement of the rear co2 sensor which is a pain and not particularly cheap.
I have no other issues and the motor runs perfectly.
My only interest was whether the CP performance thing would delete the need for a working rear co2 sensor

It would I believe, I spoke with them and it’s basically designed for mercy with the 4 four pin style sensors is what I was told. Lots of guys use them on the bigger Mercs they said. They recommend leaving the cat in if I wasn’t looking for more top speed just code clearing issues. Sounds like we maybe similar issues. I won’t lie I haven’t even started this boat I bought it with the owner just running for literally years with the check engine code and the shop wasn’t able to solve. Thanks chphrl for all the help man, I have a Rinda in the mail will clear the 50 and 48 and see for my self how rich it’s running. I have a fuel gauge just need a vaccum now. I also will look into checking the timing. I found some info I’ll post a link later it ways for a Mag 350 with the dts system. Can’t find the actual scorpion online for timing procedures

Yes on the crew, but they didn’t dig too deep into it. I may just chck l timing and go from there, I owe you some beer

When it says “stbd engine” is it actually the starboard side or is the motor just listed as such in the smartcraft due to the system being capable of 2 engine setups.? Are you thinking about trying the max volt?

I'm thinking stbd side. In a twin setup, each engine will have its diagnostics port.

Stinger are you going to try that max volt kit?

Was yours stbd side rear o2 when it had code 48?

So I was on another forum and have my rich condition more diagnosed and narrowed down. I purchased a rinda scanner and have actual faults of 322 cylinder bank stbd fuel trim low, 321 same but port side and 129 tps failure on shut down, I turned the key to the ign on without batter hooked up and the smart craft threw some codes that all went away. I’m suspecting 129 won’t come back now that I’ve cleared them.

I believe that a bad o2 sensor is causing the rich conditions. Motor is at 100% on power and didn’t ever go into gurdiIan. I found a good deal on 02 sensors and had two leftover new ones from my old boat. I will update once those are in and on the fake lake.

Next is I am doing new plugs and a good oil change before start up and make sure that the water temp and plenum air temp sensor are good. If the motor always thinks it’s cold it can also cause rich conditions. Anyone have experience checking the manifold, thermostat and plenum temp sensors current for a good circuit to make sure it’s putting out the right resistance?

I also noticed on the rinda I think I can see the 4 o2 sensors and they have numerical values accounted with them but didn’t look into it too much, maybe I can find the bad sensor with the scanner??

A faulty or accurate o2 is easy to see with a scanner. If the engine is running rich yet the o2 still indicates lean, its an issue with the o2 or its circuit. If the engine is running rich and the o2 value reflects that, then the o2 is telling the truth.

Remember, you have already indicated a fuel pressure issue that would create a rich engine. You need to solve that first. IMO, changing the o2 is part swapping.

Ya having it running at operating temp on the fake lake is next, seeing what water and air temps I’m getting, also going to check the poppet to make sure water isn’t passing at idle coursing the engine to think it’s “cold”

Also wouldn’t the codes I have above indicate just that? I am indicating fuel trim low and the engine is running rich? 321 and 322....I need a damn service manual but can’t find one anywhere

The purpose of the code is to not condemn the sensor related to it, but to let you know the sensor is showing a reading thats out of its programmed limits. Yes, the sensor can be faulty, but it can also be telling the truth.

I keep going back to the high fuel pressure. Solve that first. You know its an issue. Patient is bleeding from a compound fracture, no need to test his cholesterol yet. Fix what you know is an issue.

The codes maybe searchable without the numerical factor through an automotive shop. If they could look up the fuel trim description you could get some Mitchell1 description for diag.

I agree the rich fuel is the problem and I found a Merc manual that addresses the rich environment and it could be o2 sensors etc etc the code I get is addressed on page 6of the manual for the rich conditions http://download.brunswick-marine.com...0086113_2b.pdf
Under “fuel systems monitor”

Any of the four ITerm faults—319 O2Control_ITermHighPort, 320 O2Control_ITermLowPort, 321 O2Control_ITermHighStbd, or 322 O2Control_ITermLowStbd—may be triggered by issues with:
• Injectors
• Spark plugs
• Spark plug wires
• Coils
• O2 sensors
• Voltage irregularity
• High or low fuel pressure
• Wiring harness
• Stuck thermostat
• Bad sensors
• Bad fuel
• Leaky exhaust
• Blocked exhaust
• Other

I will hopefully get to some good weather soon and get it on the fake lake and when the code pops up I can get the freeze frame of engine readings if/when the code pops

Oh!!!! Very good point!
I’ve seen a lot in the auto world of people putting 160 degree stats and not tuning their car to it. Well that causes the fuel trim to stay in open loop and dump more fuel trying to get the engine to warm up. If you have a bad thermostat then your engine maybe running slightly too cold, not enough to see on the gauge, and be dumping fuel!!! Put a thermostat in it first and then fake a lake!!!
The “hotrod youngsters” are guilty of this more often then none....

Ha ha ya a t stat is cheap and easy

So I cleared the codes with the rinda scanner, and threw on 4 new o2 sensors, I could tell two of them were the originals, and new plugs. Not codes on the fake lake for a 30 minute run up to about 2500 rpms and it was going into “closed loop” on the DTS emissions cycle once the motor was warmed up. Fingers crossed it’s good to go, I don’t know how many starts, RPM range etc for the emissions to be full cycled to not throw a code again, but it’s looking better than before for sure. I did not check fuel pressure because the plenum is so hard to get my hand under to put the gauge on.

So what fixed the high fuel pressure?

I’m guessing the o2 sensor, guessing it was getting false readings and creating a rich environment

The 02 sensor does not control fuel pressure, but high duel pressure will cause a rich condition and ruin O2's. Odds are, you "fixed" the symptom, not the root cause.

Maybe a bad plug, pretty sure the codes I had were showing it being rich 322 and 321 and that list of possibilities did include plugs. I’ll def be putting the gauge on it when I lake test, it’s just such a bitch to get to under that plenum.