• Support M247: Allow Ads or Register (fewer ads)

P0090 - Pressure regulator control circuit

I am at my end with this car. 181k miles. When driving (when taking turns), the car will start bucking and then turn off, this is incredibly dangerous as the steering becomes damn near impossible which is scary when in the middle of a turn.

I have replaced the prc control solenoid, and switched it with one of the other similar sensors, still got the problem. Disconnected and reconnected the ECU and still got the problem. I even installed a new pressure regulator and tried to look at the fuel pump and make sure that is fine even though I knew that shouldn't have anything to do with a p0090 code. I took it to Mazda in hopes they would be able to do something but the only new info they had that could possibly help is some sort of fuel flow issue in the fuel rail but they don't make that part anymore apparently so they couldn't do anything about it.

Protege5 p0090 This is what it looks like at idle when trying to recreate, if I was moving when taking this video it would've broken down. The problem is hard to recreate and gives zero warning beforehand.

Has anyone had any experience similar to this?
 

pcb

The Diagram Dude
:
2002 MP5
I think that you may have a clogged fuel filter and maybe a failing fuel pump.

Did Mazda do a fuel pressure and flow test on your car ?

Screenshot_20210815-123043_Acrobat for Samsung.jpg


Screenshot_20210815-122124_Brave.jpg



Inadequate fuel pressure could possibly throw a PRC code.


A new fuel filter is relatively cheap and may fix your problem.

Here's a how-to about replacing it...


Thread 'How To Change Your Fuel Filter (lots of pics)' How To Change Your Fuel Filter (lots of pics)
 

pcb

The Diagram Dude
:
2002 MP5
Keep in mind that when the battery is disconnected, the ECU needs to relearn how to idle the car.
The idle will bounce around and the car may stall during the relearning process.
It takes about 100 miles of driving for the idle to stabilize.


Thread 'P5 rough idle... Help!' P5 rough idle... Help!
 

pcb

The Diagram Dude
:
2002 MP5
I watched your video again more closely, and that is looking really strange.

The idle relearning thing only applies to the idle, and once the throttle brings the rpms above idle, the bouncing rpms normally stops.

It looks like you fixed your code, because the CEL isn't on.

I know the cell will flicker when the rpms drop too low, and that could be why it is coming on.

Your tachometer isn't just bouncing, it's Really flickering around.


It's as though the engine is continuously stalling and starting again.
Your battery light is even flashing.

It's almost like there is a broken ignition wire that is intermittently disconnecting ?

I suppose that inadequate fuel pressure or a flow issue could show the symptoms that you have?

The fuel rail is available.
Those Mazda guys don't know what they're talking about.

I have no idea if that will fix your problem , but you can get the part...

Screenshot_20210815-134700_Brave.jpg
 

pcb

The Diagram Dude
:
2002 MP5
Another thing to look at...

Inspect your crank sensor wires.

Some guys had their wires rubbing on the engine somewhere and it wore through the insulation and was shorting out.

The ECU shuts down the engine the instant that it doesn't receive crank info.

Check your crank sensor for contamination and the gap and make sure that your toothed sprocket is still connected to the crank pulley.

They have been know to slip and break free.

20210815_141018.jpg


20210815_141050.jpg
 

pcb

The Diagram Dude
:
2002 MP5
Check your cam sensor wires too, but the engine will run with bad or no cam sensor information and you'll get a code.

There is a code for the crank sensor but I don't know of anyone that has popped that code even when they had crank sensor issues.

It looks like the ECU shuts down the engine so fast, that it doesn't have time to register that code.


You may have disturbed the crank sensor wire when you replaced your PRC solenoid, causing your issues.
 

pcb

The Diagram Dude
:
2002 MP5
What a useless code...


20210815_144426.jpg



You will pop this code if your ECU doesn't receive data for 4.2 seconds, but the ECU shuts down the engine in a millisecond if it doesn't receive crank sensor data, so you will never pop this code. Lol
 
:
2003 protege 5
With 180k on it has the fuel pump ever been changed? I had the issue with the crank sensor wiring. It never threw a code. Either while driving and it just shut off or whenever trying to start. I would inspect the wiring to it. Especially where it routes behind the ps unit. Thats where mine wore down. If you have the money and are willing to tackle it i would replace the fuel pump. You can buy the one with a new pick up filter too so youre assured its getting proper flow.
Another thing to check is under the hood in the fuse box. The fuel pump relay. Ive seen some that have started to arc and short out.
 

pcb

The Diagram Dude
:
2002 MP5
... If you have the money and are willing to tackle it i would replace the fuel pump. You can buy the one with a new pick up filter too so youre assured its getting proper flow.


It's not too much money...

Here's what you need...

Screenshot_20210815-193918_Brave.jpg


Screenshot_20210815-193956_Brave.jpg


Screenshot_20210815-194058_Brave.jpg


Screenshot_20210815-194033_Brave.jpg


And this...
A JIS screwdriver.

Screenshot_20210815-194651_Brave.jpg




Thread 'PSA: Know your screws! JIS vs Phillips (IAC valve, etc...)' PSA: Know your screws! JIS vs Phillips (IAC valve, etc...)




Another thing to check is under the hood in the fuse box. The fuel pump relay. Ive seen some that have started to arc and short out.


Thread 'P5 Won't Start & Rough Idle' P5 Won't Start & Rough Idle



20210815_200021.jpg




20210815_201154.jpg




I like rockauto.com

Their stuff always fits and works.

Amazon and eBay can be sketchy.


Remember too that I live in Canada.
You guys would pay about ten bucks for everything. Lol
 
Last edited:
I watched your video again more closely, and that is looking really strange.

The idle relearning thing only applies to the idle, and once the throttle brings the rpms above idle, the bouncing rpms normally stops.

It looks like you fixed your code, because the CEL isn't on.

I know the cell will flicker when the rpms drop too low, and that could be why it is coming on.

Your tachometer isn't just bouncing, it's Really flickering around.
The CEL never turned on when driving UNTIL it happened, it wouldn't come on before which is annoying., the problem happens with no warning. And in the video I am actually putting down power but I'm in park, not at idle (although it has happened at idle). Going to take a look at everything.
 
Take a good look at your crank sensor wires..

Maybe even remove it to check it.
The top had some exposed material, looks like the insulation just gave up due to heat/age on the top, haven't got a look at the bottom. Going to be ordering a new one and I'll see if that fixes anything, for now, electrical tape.
 

pcb

The Diagram Dude
:
2002 MP5
The top had some exposed material, looks like the insulation just gave up due to heat/age on the top, haven't got a look at the bottom. Going to be ordering a new one and I'll see if that fixes anything, for now, electrical tape.
Cool!
You may very well have found the problem.
Keep in mind that the wires have have metal shielding around them (like cable TV wire) and you don't want the shielding to be touching the wires inside if the insulation is worn through to the wires inside.

Screenshot_20210816-160228_Acrobat for Samsung.jpg
 
:
2003 protege 5
Pcb is awesome!! Def the guy with links and pics! You can try to tape up the crank sensor wiring sheathing and see if that fixes it as long as the wires inside arent damaged. Also check the relay. Open the lid and it will show you which relay is which. If its burnt looking, corrosion on the plugs, or even the surrounding plastic looks melted that might be the issue. At the very least you can glob some dielectric grease on it and plug it back in if it looks ok.
 
Updating in case anyone has a similar issue. Been one week since I taped it up and I replaced the crank position sensor with a new one and its been fine up until now where the problem just happened again on a turn. Back to square one possibly.
 

pcb

The Diagram Dude
:
2002 MP5
Well that sucks.

The fuel pump and relay would be good things to inspect next.

It sucks to spend time and money chasing a Gremlin.


Did you inspect your toothed ring and check the air gap ?

Keep us informed, it helps us keep our cars going.
 

pcb

The Diagram Dude
:
2002 MP5
I took it to Mazda in hopes they would be able to do something but the only new info they had that could possibly help is some sort of fuel flow issue in the fuel rail but they don't make that part anymore apparently so they couldn't do anything about it.


Did the Mazda technicians do a fuel flow and pressure test ?

Was the car misbehaving while they were inspecting it ?
 
Did the Mazda technicians do a fuel flow and pressure test ?

Was the car misbehaving while they were inspecting it ?
They did not, and they were not able to get the car to misbehave at all.

I am replacing the fuel pump relay and the alternator soon, I noticed either smoke or steam coming from that side of the car and the drive belt is worn a lot. I think it's weird how it has only died while turning so I am opening up my repairs to more wide reaching areas.