Rick's Free Auto Repair Advice

P0133 P0139 P0170 P0173 P0171 P0174 P1136 P1138 P1141 P1143

Fix code P0133 P0139 P0170 P0173 P0171 P0174  P1136 P1138 P1141 P1143 AUDI, VOLKSWAGEN

If you own an Audi A4, A6, A8, or a Volkswagaen Golf, Jetta, Passat, and New Beetle
With 1.8T, 2.0, 2.8/3.2 VR-6, 2.8 V6 90° or 4.2 V8 engine and have any of the following codes:

P0133 P0139 P0170 P0173 P0171 P0174  P1136 P1138 P1141 P1143

P0133 Oxygen sensor: slow response Bank 1
P0139 O2 sensor: slow response, Bank 2
P0170 P0173 Fuel trim malfunction Bank 1/2
P0171 P0174 Bank 1/2 fuel trim lean
P1136 P1138 Bank 1/2 long term trim at lean limit
P1141 P1143 Load calculation cross-check limits

don’t start throwing parts at the problem. Keep this in mind. Every value the computer sees is run through a filter of a sort. For example, before the computer can even compute the air fuel mixture, it must know the outside temperature, the engine coolant temp sensor, the throttle position sensor and must have some indication of barometric pressure.

On older vehicles, the computer used a manifold absolute pressure (MAP) MAP sensorsensor to help it calculate barometric pressure. The computer would look at the reading as you turned the key to on—that would give it atmospheric baro pressure. Then, once the engine was started, it would measure engine vacuum. Since it knew the displacement of the engine, it could calculate absolute baro pressure.

But late model vehicles depend on a mass airflow sensor (MAF). The MAF MAF sensor cleaningconsists of a wire or plate that conducts an electrical current to heat up. Air flowing across the wire or plate cools it off and the computer measure how much current is required to maintain the wire or plate at a set temperature. Basically, the computer is calculating wind chill. So the computer now knows the temp of the air, the quantity of air, and the mass of the air. That allows it to calculate a much more accurate air/fuel mixture.

However, this all depends on getting an accurate reading from the MAF. Any debris that comes in contact with the MAF wire or hot plate can bake onto it and interfere with its accuracy. If you have a oiled racing filter, for example, the oily fibers from the filter can break away and bake onto the MAF. Even standard cellulose filters can shed fibers. Once the hot wire or hot plate are insulated, they provide inaccurate readings that are detected by the oxygen sensors. A contaminated MAF doesn’t set a check engine codes until the data goes outside a set range. But if the sensor stays within range, it can send faulty data all day long, making you think that the other trouble codes are causing the problem, when in fact, they’re just reporting a symptom of the problem.

So before you even think of replacing any sensors, clean the MAF. Click here for instructions on how to clean a MAF


© 2012 Rick Muscoplat

Posted on by Rick Muscoplat

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