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The oil light being on is strange. The p2188 is a system too rich code, which could be any number of things. I attached a diagnostic sheet from suzuki to give you an idea of possible causes, but the oil light has me thrown a little. There isn't anything common that would cause low oil pressure and a rich condition. Does the engine sound like it lacks oil pressure? Drive-train rattle or noise?
Between 40 (when cold) and 60 (when hot) PSI.
That sounds a little high, but not terrible. It might be just enough to trigger the rich code though. The only regulator in this system is inside the fuel pump so you need to be sure it's not something else or you will waste time and money on the fuel pump.
I think I would probably run some concentrated fuel system cleaner through the system (lucas fuel injector cleaner works well) and see if one of the injectors is just stuck open causing the rich condition.
If that doesn't improve it, then I would go after the fuel pump.
This is all that Suzki publishes on their oxygen sensors on this vehicle:
"If the catalyst is operating efficiently, the HO2S1 sensor signals will be more active than the signals produced by the HO2S2 sensor. The catalyst monitor sensors operate the same way as the fuel control sensors. The sensor's main function is catalyst monitoring, but they also have a limited role in fuel control. If a sensor output indicates a voltage either above or below the 450 mV bias voltage for an extended period of time, the ECM will make a slight adjustment to fuel trim to ensure that fuel delivery is correct for catalyst monitoring."
I can't find a data table anywhere. You pretty much need to look for a lower voltage signal on the second sensor because the cat should be cleaning up the exhaust content.
The down stream sensor seems kind of flat. It should rise and fall a little more. That sensor may be dead or dying.
Please don't forget to rate. They don't pay us if we don't get a positive rating.
What have you done since we last spoke a few weeks ago? Any work on the O2 sensors?
I guess at this point the next thing to look at is a PCM. I would probably go through all of the connectors and grounds and make sure everything looks ok first. If it got better for a little while and then came back I would definitely be suspicious of a bad PCM.
Is it the same trouble code?
Fuel pressure is still above 60 at the fuel rail when cold?
I hate throwing parts at this thing, but maybe it's time for a fuel pump. The pressure is regulated at the pump, controlled by the PCM. You replaced the PCM, so now the only thing left is the pump.
Just the one on the pump.
It is part of the fuel pump assembly. You can't replace just the pump portion of the assembly. Well, I guess you could, but it won't fix the problem you are having here. The regulator is part of the assembly, not part of the pump portion.
This is what you need
Sorry, we are having internet troubles here at the shop.
The parameters are flashed into the PCM. You replaced the PCM already. Was it programmed from the dealer?
Where did it come from?
I'm pretty sure it will need to be flashed by the dealer to get it to work correctly. You might have to call the suzuki dealer to verify.
Would you like me to opt out and see if someone else has any insights?
We've been working on this for a month now and I hate to keep you going without being able to fix it.
I haven't received a rating yet so I don't want to waste either your or my time.