Q: I own a 2000 Nissan Maxima and my "check engine" lamp came on. My local auto parts store plugged in a scan tool and found code P0325, which refers to the knock sensor. They said the knock sensor is probably faulty and needs replacement. Do you know where it's located on my engine, and do you think I could replace it myself? -- G.L., Oak Lawn

A: G.L., the knock sensor in your Maxima is located on the engine block in an area known as the "valley", which is located under the intake manifold. The labor/time guide lists the replacement time at 3.5 hours. If you're a novice, I wouldn't recommend tackling it yourself. I'd leave the repairs to a professional.

Q: I was searching online for what a Chrysler dealer who repaired my Jeep said was a "crash book" in which he based the hours needed to repair my Jeep and came across your postings. I have a 2004 Jeep Grand Cherokee with dual zone climate control and the passenger side was blowing just cold air. The dealer charged me $145 to hook up a scan tool to my Jeep and tell me that the passenger side blend door was broken. They told me the part would cost $59 and the labor ($75/hour) would be three hours.

I dropped the vehicle off at the appointed time and 4-1/2 hours later the steering column was sitting on the front seat, and they had it all torn apart and said, "we don't know how much longer it will take." In the end the head person called me "to explain the bill" and said they used a "crash book" that indicated the job should take 9.5 hours labor and so that is what I had to pay to get my vehicle out of the repair shop. Do you know what "crash book" they would have been referring to? Any Chrysler dealer would have all kinds of access to know how long this would have taken. Any suggestions would be appreciated. -- S.H., e-mail

I'm going into winter with heating costs for the home. If I knew the bill would have been $910 vs. $300, I would have told my passenger to turn the heated seat on and close the vents from the cold air!

A: S.H., I have never heard of a "crash book" for determining labor hours. To repair your Jeep's passenger side blend door/actuator, the dashboard needs to be removed. According to Alldata's labor/time guide, the repair hours listed to perform this repair is 4.6 hours. By the way, these actuators are problematic and there is a service bulletin (24-001-04) that lists subassemblies that can be installed to improve component reliability.

Once you've been quoted a price to perform repairs and both parties have agreed to the repair cost, the dealer cannot simply raise the price without your authorization. Sometimes, when making a repair, the technician finds more things that need to be replaced. When this happens, the dealer must contact you and get your authorization before completing the repairs. That does not appear to have happened here. It seems that the repairs took the technician longer than what you were quoted and the dealer wanted to pass those costs onto you. But that's not acceptable business practice.

See if anyone at the dealer, like the general manager, or dealer principal, will credit you the difference of what you were charged and what you were originally quoted. If not, contact the Better Business Bureau and report them.

Questions for Ira Siegel? Call the Auto Adviser Hotline at 708-633-6839 or e-mail Autoadvisr@aol.com AutoAdviser: Ira Siegel is an Automotive Instructor and ASE Certified Master Auto Technician