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Old 05-07-2009, 10:25 PM
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Join Date: May 2009
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Default P0400 97 Mazda Protege

HI First post here.

Its my grandma's car to start with. It has a EGR Valve code showing up. I have already replaced that plugs, plug wires, egr valve, and both o2 sensors as I was getting 2 misfire codes, an o2 code and the egr one. So everything was groovy replaced everything and cleared the cel, so then she tells me it came back on. What do I do? This car has to pass emissions by about the 15th of June to get the tags. Friggin CA emissions won't pass it with CEL on.

1997 Protege LX Special Edition
260k Original Miles
2nd Tranny and Clutch- Pilot shaft disintegrated.
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Old 05-08-2009, 08:03 AM
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Join Date: Mar 2009
Posts: 466

The cel doesn't just come on all by itself. There are codes behind it, but an Autozone type of OBD read might not pick them all up.
When you replaced the EGR valve, did you clean out all the ports at the same time?
Mazda EGRs have been problematic because the plumbing carrying exhaust in to the valve gets sludged up and the stuff hardens and chokes off the flow. They have to be cleaned with carb cleaner and have the crud reamed out (Mazda had to provide an extended warranty and completely redesign the EGRs for Canadian cars incorporating a hot water jacket in them to prevent premature failure). Another frequent source of cel is intake air leak downstream of the MAF.
Search for a forum topic by Adam S dated 04.20.2009 starting "I have a 2000 Mazda Protege, 1,8L with 5 speed manual transmission @ 190,000 kms" and follow the threads to the oldeng thread dated 04-13-2009, 10:06 PM. and follow through the technical stuff in that that thread.
Pop the air filter and look very carefully and flex the air intake duct look very carefully for cracks/ splits especially in the corrugations near the engine end, be thorough, (they are hard to locate and can close up so well with the engine stopped or idling that they produce no symptoms).
Check your PCV too, just yank it out and shake it: if it rattles, it's OK.
Check all of your plumbing around there for leaks too.
For the EVAP sytem, you'll find a map of it under the hood which will help in finding what goes where; usually you just pull a pipe and use your thumb to test for good vacuum. Another test for vacuum is your cruise control; it's a good sign if it's working normally and speed stability is good.
Sounds dumb, I know, but just having a loose or worn gas tank cap can cause an EVAP fail, which will set the cel on.
This post was a bit Protege specific, but the key points apply for the most part to Mazdas in general of that era.
Don't spend big bucks on hardware replacement until your certain that the problem is not elsewhere.

Keep us posted on your progress.
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Old 12-08-2009, 11:16 PM
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Join Date: Dec 2009
Posts: 1
Default P1525. P1540 and P0400 - Mazda Mellenia 2001

Hi -

I am having a similar problem and don't know where to begin. I am getting three codes, P1525. P1540 and P0400. What I don't understand is that why i'm getting all three codes. MY mechanic told me that I don't need to worry about these as they will not impact my driving, but I don't feel comfortable driving with three codes popping up.

Any suggestions??
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Old 12-09-2009, 04:40 AM
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2004 Mazda Mazda3
Join Date: Mar 2007
Location: Manor, TX (Outside of Austin)
Posts: 8,581

Yes! First off, find a new mechanic. He obviously knows less than I do about modern cars and is too lazy to find out.

OK, some quick research has revealed that the two main codes indicate an air leak somewhere. Based on what I have read about Protégé's, I would think the best place to start is by looking at the intake tube between the filter box and throttle body. See if there are any cracks in it. That seems to be a common affliction.

Of course I am only guessing.... :/

edit: This might be helpful too: http://forums.mazdaworld.org/index.php?showtopic=18936


"There is no tool you can buy that will replace experience." - Josh Mills, C.K.DeLuxe/Koolhouse Publishing

Last edited by virgin1; 12-09-2009 at 04:45 AM.
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