My 1996 Mazda Protege check light has come on recently. I used my Actron OBDII which says the problem is the Baro Sensor Circuit. So, I check out my Haynes Repair Manual Schematic of the EFI (Electric Fuel Injection) system but I don't see the Baro Sensor Circuit anywhere in the book. Can anyone tell me, is there another name for the Baro Sensor Circuit? Also, where should I look for the item? Is this replacement easy to do?

Oh yeah, one more question, since the check light has come on I notice my car has a lower grumble coming from the muffler. In the past, whenever the car was in idle you could not tell if the car was running. It was quiet and smooth. Now, the car sounds like a Harley Davidson motorcycle and it idles roughly. Would a bad baro sensor circuit create a lower tone / grumble in the muffler and cause the car to idle badly? By the way, my Actron scanner showed the 02 htr with the arrow pointing.

Any response to these issues would be greatly appreciated.

 

The BARO sensor is built into the ECM. This is a semiconductor pressure sensor with properties which cause its electrical resistance to change when stress is applied to the sensor’s crystal (silicon) (piezoelectric effect). This sensor is used to detect the atmospheric (absolute) pressure and outputs corresponding electrical signals. Below schematic shows the BARO (Barometric Pressure) Sensor Circuit Diagram.

The BARO (Barometric Pressure) sensor is a variable capacitance sensor that when supplied with a 5 volt reference signal from the PCM produces a linear analog voltage signal that indicates barometric pressure.


Not my description as im not that technical - however cant see this causing your problem. Could be an o2 sensor but I would get your exhaust checked as it may be a collapsed / blocked cat at a guess

 

Well, I discovered I have a small hole about the size of a dime in pipe leading to muffler. I realize that is what has caused the increase in the noise from my muffler. Also, I located the Baro Sensor Circuit which was inside the PCM. However, I am unable to determine which circuit on the board needs replacing. I pretty much opened the PCM and then closed it. Just wondering, the fact that my car has over 200,000 miles, is it possible the engine light is programmed to go on as a default function by the manufacturer. Could this be the cause of the p1195 code getting triggered on my vehicle? Do you think I may have to replace the PCM? Can I use one from a junk yard? Must I use the PCM from a Mazda Protege or can I interchange PCM with another Mazda vehicle? Any response to these questions would be greatly appreciated.

 

So, I patched the dime size hole on the pipe leading to the muffler. After driving the car for a while, I thought I would use the Actron and try clearing the code again. The code p1195 and 02 htr with the arrow pointing up appeared on the Actron screen. So, I proceeded to clear the code and ..... viola, the check engine light disappeared. I went to put gas in the car and the check engine light remained off. So, now I will wait and see if the problem has been solved.

 

Great news mate gald t was something so simple. Sometime higher mileage cars can be more reliable than ultra low milegae cars - as the ultra low ones tend to get clogged up. Its a Mazda so wo knows how long it can go for - just keep her maintained

 

Thanks ggsumo for your feedback. So far, the engine light has not returned. However, I have noticed a small oil leak by the valve cover gasket. I had the gasket replaced a year ago, so I am stumped why it would be leaking again. I noticed oil caked on the front side (side facing the radiator) of the engine block and now there are small drops of oil appearing on the ground. So, I am now on a mission to resolve this issue. Again, thanks ggsumo for your insight.

 

no probs mate happy to help.

On the oil leak - i think the rocker (valve) cover gaskets are a simple low presure that dont need high torque on the bolts. What you may find is that somebodies done the bolts too tight when fitting and its compressed the gasket too much. For what they cost probably just need to replace again and check the bolt torque required. If i'm wrong hopefully someone with more experience of these engines can correct me.

 

I noticed my air intake hose and Resonance Chamber had oil in it. What would cause oil to get in these components?

 

not sure of your engine config mate but assume resonator box is where your air filter is. Just a guess but you will have a breather pipe off the crank or cam that runs either into the box or the link between the airbox and the inlet manifold. If your air filter gets blocked it can suck on the breather dragging oil into the box.

i would suggest clean the box out, replace your air filter and clean your plugs as if you are drawing oil into the air system they may be a little dirty.
Cant say for definite this is what it is but always try the cheap things first

 

Well, I its baaaaaaack ! That darn P1195 code.
Since the last time I post. I replaced the muffler with the hole in it.
I cleaned the oil out of the resonance chamber and air intake hose
and oil has not returned. Replaced air filter, EGR Valve, and replaced spark plugs.
Replaced boost sensor and check all the intake hoses. After resetting the
engine light with the OBDII Actron the light went out and returned again.
Good news the oil leak by the manifold stopped. Basically, I slightly tightened the
nut and it seemed to do the job.