What does P0172 and P0175 mean for 2000 Toyota Echo?

Answer 1

If your O2 sensors are old (more than 100,000 miles) I recommend replacing them both. Use ONLY genuine Denso replacement sensors (solder in ones can cost as little as $35 shipped). Change the air filter ($10) and if the problem doesn't go away, clean or replace the MAF. If the problem still doesn't go away, have the fuel pump tested or if it has more than 100,000 miles just replace it (replace fuel filter at the same time, each can be found for as little as $25 although its a somewhat difficult job to do yourself).

• The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters can cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
• There could be a vacuum leak.
• There could be a fuel pressure or delivery problem

Possible SolutionsPossible solutions include:

• Inspect all vacuum and PCV hoses, replace if necessary
• Cleanthe MAF sensor. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
• Inspect fuel lines for cracks, leaks, or pinches
• Check the fuel pressure at the fuel rail
• Check the fuel injectors, they may be dirty. Use fuel injector cleaner or get them professionally cleaned/replaced.
• Check for an exhaust leak before the first oxygen sensor (this is unlikely to cause the problem, but it is possible)