2000 Toyota Echo - running rich

Hello group.

I'm new here, so far the little Echo has been running fine, giving me no reason to inquire. However, some time ago the MIL light went on and wouldn't go out. I bought a code reader and it gave me P0172 - system too rich (bank 1).

Can anyone interpret this? Where do I go from there? Shoud I suspect the oxygen sensor or the mass air flow sensor? There seem to be no air leaks along the intake.

Any help will be appreciated. TIA

Radek in Ottawa, Canada

Reply to
Radek
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I would check the air filter, mass air flow sensor, and the oxygen sensor mounted ahead of the catalytic converter, in that order. You can get access to the factory service manual at techinfo.toyota.com for $10 U.S. per day for the factory's procedure for diagnosing the trouble code and for checking those components. You can try GENTLY cleaning the wire on the mass air flow sensor with some rubbing alcohol and a cotton cloth or q-tip.

Reply to
Ray O

Thanks Ray;

I replaced the filter already so now I will start with cleaning the wire. Would you know where to get a complete service manual and how much would it cost? One that would for example give resistance values for testing a sensor? I've drifted from the VW/Audi world, where a Bentley manual contains nearly all you need to know. What would be the counterpart of Bentley in the Toyota world? Thanks again.

Radek.

Reply to
Radek

You can order a factory service manual from your local Toyota dealer. Toyota Motor Sales U.S.A. allows consumers to order directly from their Material Distribution Center, I would imagine that Toyota Canada has a similar arrangement. The best manual for a Toyota is Toyota's factory service manual. It has the most complete information of all the manuals I've seen. There are a few shortcomings to the factory service manual - their completeness means that they are about the size of a big city phone book, and you sometimes have to order several volumes at close to $150 U.S. each; they assume that the user is a professional technician so some do-it-yourselfers do not understand some procedures, like taking a voltage reading; and the troubleshooting matrices do not always seem logical.

The other alternative is to pay $10 U.S. per day for on line access to the factory service manuals at techinfo.toyota.com or subscribe to Alldata, which a lot of independent shops use for diagnosis.

Reply to
Ray O

Thanks again Ray.

I cleaned the wire but the code is back. I guess I should now replace the front oxygen sensor. Why are there two of these, anyway? Cheers.

Radek.

Reply to
Radek

I would not replace the O2 sensor without first checking it. The procedure for checking the O2 sensor will pretty much be the same as for a VW.

The MAF measures air flow, and the ECM determines how much fuel to mix with the air. Once everything is warmed up, the O2 sensors measure O2 content in the exhaust and "fine tunes" injector pulse duration. Under certain conditions like wide open throttle, the ECM ignores the O2 sensor output and uses the pre-set values.

The second O2 sensor monitors the exhaust after the catalytic converter and monitors catalytic converter performance. The ECM compares the signal from the second O2 sensor with the signal from the first O2 sensor. If the cat is doing its job, the signal from the second O2 sensor should detect a cleaner exhaust. If the quality of the exhaust coming out of the cat is the same as what is going into the cat, then the ECM assumes that the cat is bad.

Reply to
Ray O

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