Questions and Answers

Volkswagen Jetta DTC P0172 Q. Hello sir, How are you? I have a black Volkswagen Jetta GLS 2.0 liter and automatic transmission. I got a Check Engine Light awhile ago and brought my car to the dealer. They found the DTC P0172 (System Too Rich, Bank1) after scanning and suggested to change the Mass Air Flow Sensor (MAF). I noticed that the MIL light comes on when I was driving and a few minutes after I turned on A/C.

Could you please advise me if the MAF sensor is possibly the correct part to change in an effort to resolve the problem; or it is some other type of sensors that actually need to be replaced.

• 1999 Volkswagen Jetta GLS
• 2.0 liter
• Automatic transmission
• 46,000 miles
• Fuel Injection
• ABS brakes
• P/S, A/C, Cruise control
• Rack and pinion steering

Thank you very much for your time and insight.

A. DTC P0172 - Fuel Trim, Bank One System Too Rich means that to fuel mixture is so rich that the HO2S control cannot lean it out. This code does not necessarily mean the MAF sensor is bad. It can also be due to high fuel pressure, injectors that are leaking down into the engine, fuel contaminated engine oil or an exhaust leak between the cylinder head and catalytic converter.

There is a TSB on MAF codes so if they want to replace it under warranty, let them. If they want to charge you for it, tell them if they will take it back if it doesn't fix the problem.