Check Engine Light on 2000 Mazda Protege LX 1.6 Liter?

Question

Hello,
The "check engine light" came on yesterday. Had it looked by a mechanic and he said there are 2 diagnostic codes that came up: P0171 and P0402.
Any ideas as to what the problem could be? Is there a common problem that people have faced with this car, and a replacement?
Thanks.

Forgot to mention: Car has 90,000 miles on it.

I had a mechanic tell me the 2 codes. I am wondering if there is a common problem with this car, so that i wont have to send it to a dealer and have them spend 8 hours looking to diagnose the problem.

Answer 1

171 means your o2 sensor is reporting a lean mixture. a common culprit is the Mass Air Flow sensor (MAF). if the MAF is dirty it won't give your computer an accurate reading of the outside air pressure. as a result that the air/fuel mixture will be incorrect, which is why your o2 sensor is reporting back a lean mixture.

solution.. get a spray can of MAF cleaner from the parts store and clean that thing. it's right inside the air filter box. if you can't find it now's a good time to invest in a chilton's repair manual. chilton's are the best you can buy for 15$. haynes is all right but not for diagnosing electrical problems.


code 402 means excessive exhaust gas recirculation detected.
most likely is a faulty DPFE (differential pressure sensor), a cracked/loose vacuum hose, or possibly the Exhaust Gas Recirculation (egr) valve itself. check your vacuum hoses, and buy that chilton's repair book so you can test the EGR and the DPFE. you'll need a voltage meter (10-20 bucks) and a vacuum gauge (25-35 bucks) as well but they're a good investment. taking it to a mechanic every time gets expensive.

Answer 2

This Site Might Help You.

RE:
Check Engine Light on 2000 Mazda Protege LX 1.6 Liter?
Hello,
The "check engine light" came on yesterday. Had it looked by a mechanic and he said there are 2 diagnostic codes that came up: P0171 and P0402.
Any ideas as to what the problem could be? Is there a common problem that people have faced with this car, and a replacement?
Thanks.

Answer 3

According to Mazda the possible causes of P0171 are a maulfunction in one (or more) of the following;

Fuel injector, fuel pump, fuel filter, fuel hose, pressure regulator, purge solenoid valve, pulsation damper, coil, ignition wires, spark plugs, intake leak, oil pan leak, poor compression, MAF sensor, ECT sensor, throttle position sensor, front O2 sensor, vehicle speed sensor, open or short in wiring harness or poor connection, vacuum hoses.

Hope that narrows it down for ya :)

To diagnose it properly you need to access the freeze-frame data from the moment the code was stored to compare those readings with the specs. You'll need a serious scan tool for that. That's just where you start. There are about 20 steps beyond that - which ones you do depend of what the freeze frame data tells you.

P0402 is set usually due to a faulty EGR gasket or a problem with the PCM. The former is not so bad, the latter is bad. Fix P0171 first, clear the codes and see if this one comes back.

Answer 4

P0171 System too Lean (Bank 1)
P0402 Exhaust Gas Recirculation Flow Excessive Detected

Answer 5

How many miles are on the car engine? probably the catalytic converter needs replacing if over 80-90,000 miles. if under, possibly the O2 sensor is bad. I had that problem with my 1997 Mazda Protege with California emissions package ,and it cost me $820 to replace the converter and O2 sensor, which was necessary to pass Texas state inspection.

Good luck

Answer 6

P0171 Fuel trim system (RH) too lean ON 2 Fuel

P0402 EGR flow excessive detected ON 2 EGR

Needs to go to the shop, problems are probably related. There are allot of service bulletins on this car.

Answer 7

2000 Mazda Protege Lx Specs