Dear Doctor: My dad recently purchased a used 2002 Nissan Sentra. The "check engine" light came and he brought it to the local garage. They diagnosed it to be the catalytic converter, so they unplugged the decoder and the "check engine" light went out. What's your opinion on this? -- Mike
Dear Mike: Have the shop monitor the rear oxygen sensor and see if the value stays around 1/2 volt. If the rear oxygen sensor is changing like the front oxygen sensor, then there is a problem in the catalytic converter. There have been some oil consumption problems with some Nissan four-cylinder engines. The oil being burned does contaminate the catalytic converter. You can check with the dealer to see if this car was under any extended recalls. They can run the VIN number at no charge to you.
Dear Doctor: I need your advice on a transmission issue with my 2003 Volvo S80 T6. With a tight budget, what would be the most advantageous thing to do: rebuild it or buy a used transmission? I've seen used transmissions come with a one-year warranty. -- Guy
Dear Guy: I would consult with the shop that is going to work on the car. We use a lot of used transmissions, and yes, they do come with a warranty. The warranty coverage will vary. The salvage company we use offers anything from a 30-day to one-year warranty, parts only and parts plus labor. The used units are usually half the cost of a rebuilt unit. This decision will be up to you and the shop technician.
Dear Doctor: I own a 2010 Honda Accord four-cylinder that has been serviced by the dealer since new. The service advisor says that to keep the car in warranty I must continue all services at the dealer. Every time I go in for the oil change special, there is always much more service than just a simple oil change. I think I am being oversold. What you think? -- Debbie
Dear Debbie: The required services can be done by anyone qualified to perform the service. You must follow the owner's maintenance manual as for recommended service intervals. You must use the correct oil and fluids that meet or exceed the factory oil and fluids to maintain the warranty. You must also keep all receipts with mileage and dates and all services performed. In some cases, not all, sometimes additional services not in the manual may be required. This does not give the dealer or an independent an open check book to oversell you on services that you do not need.
Dear Doctor: I own a 1997 Dodge Caravan 3.3-liter V-6. The "check engine" light came and the code was P0401 Low EGR Flow. The mechanic replaced the parts in the EGR system and said the system is working as designed. He said the computer may have to be reprogrammed. What are your thoughts? -- Martin
Dear Martin: I see this problem often. Just because there's a fault code for a particular system does not necessarily mean the problem is in that circuit or system. In your case, the problem could be a slow (lazy) front oxygen sensor. A normal operating oxygen sensor voltage will change as soon as the EGR opens and closes. A lazy front oxygen sensor is operating fast enough not to set an oxygen sensor code, but not fast enough to see the EGR valve opening and closing as it should.
Dear Doctor: I bought a used 2010 Mitsubishi Outlander that did not come equipped with heated seats. Do you consider the aftermarket installations for heated seats to be reliable and do they function as well as original equipment? -- Doug
Dear Doug: Aftermarket heated seat elements have been around for years. I've been installing them for 22-plus years. We use a very reliable product from a company called Check Chart. I would recommend the Hi and Low model, not the Multi-temperature units. I've never had a failure with this brand. The cost for two seats should be less than $500 installed. In some vehicles the seats don't have to be removed. Just pull back on both the seat back and bottom, install the heating elements, mount the small round rocker style switch in the plastic seat trim, run a power and ground wire to a key on power supply and the job is done. -- Junior Damato, Motor Matters
Junior Damato is an ASE-certified Master Technician. Email questions to firstname.lastname@example.org. Mail questions to: Auto Doctor, 3 Court Circle, Lakeville, MA 02347