Failed your emission smog test? Can you afford to pay the repairs?

By: Richard Trent | Posted: 05th October 2006

Everybody knows for a fact that one of the requirements of driving in city streets is

passing the emission smog test. We do this so as not to pollute our atmosphere

besides helping us to conserve fuel. However, one of the nightmares that drivers have

is the cost involved in passing such test. When this problem occur, our vehicle must

be either brought to a garage or you can try to fix it yourself. The first one is not

a problem if you have money set aside for this situation but what happen if you

decide to do this yourself? How do you begin? What tools do you need? Where do you

get the info to fix this problem?

If you have not done any repairs in your vehicle, this is scary situation but if you

bring your vehicle to a shop, here is what you are up against:

scanning for codes including one hour diagnosis to find the problem...$100-$150

depending on the type of vehicle you have

And then another $100 per hour as soon as the mechanic starts working on your

vehicle. The final cost can easily run you from $300-$800 just to fix just one

problem. And assuming the mechanic find another code or sensor that can cause another

smog failure, which will be extra.

So why not try to do it yourself? An example is shown below on how a smart driver

will fix his own smog problem using the check engine light from the dash panel.

Here it goes...


My 2001 Ford F150 Pick up truck has failed the smog test and this code P0402 (EGR

flow high) came on the other day on my vehicle. I tried to fix this myself and when I

introduced vacuum to the egr valve port at idle, the engine quit which tells me that

the valve is OK. The engine seems to run OK except this nagging light that will

surely fail my smog test. Is there a common fix for this code so I can pass emission

test?

Note: Here are his initial expenses: getting the code is free using my blog info (see

below) and the vacuum pump is about $20.

Looking at my files about this vehicle, this problem is indeed common and here is

what I told him:

There is a common fix for this and most of the time it needs the replacement of the

DPFE sensor. This sensor looks like a small box with 2 ports coming from the exhaust.

The sensor is located between the valve cove and throttle body with tubes running

from it. This sensor measures the exhaust back pressure when the EGR valve is

activated. The passages (tubes) for this sensor can get cracked and leak to trip the

code but there has been a lot of failure on the sensor itself. Also, if the tube has

a build up of carbon and restrict the flow; the code can be set too. To check,

measure the signal voltage of the sensor using a wiring diagram. Max reading is about

0.9 volt and any reading higher means you have to replace the sensor.

Note: The final fix for this was the replacement of DPFE sensor which can be bought

from any parts store at discounted price. A digital voltmeter was also used which can

be bought for around $50-$100. If you add the cost of other common hand tools, he

might end up spending the same amount of money if he brought it to a garage. However,

this is the biggest difference, he kept the tools and gained his confidence, self

worth and next time a code comes around he's ready for it!

Does this approach make sense to you?

For more info about checking your engine using check engine lights codes, please read

my blog.

Thanks!

Richard Trent


This article written for Richard Trent's blog for vehicle owners who want to save

money on car repairs. For more info, please check this blog at "http://www.check-engine-light-codes.blogspot.com" title="check engine light">check

engine light
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Tags: money, failure, blog, atmosphere, mechanic, diagnosis, ford, ford f150, scary situation, nightmares, vacuum, city streets, initial expenses