, Salem, MA

August 24, 2013

Auto Scanner: Are bad oxygen sensors to blame?

Auto Scanner
Larry Rubenstein

---- — Q: I have a check-engine light that comes on after 50 miles or so and the fault code is 44 — that is bad oxygen sensor. I have changed both sensors, but the check engine light comes on with the same fault code. I have had the dealer look at this problem and no one can find a solution. I hope you can help.

A: I believe that you changed two oxygen sensors and it didn’t resolve the problem. I can’t, however, believe a competent repair shop with access to a good diagnostic chart cannot resolve the problem. Let’s start at the beginning. Code 44 is not a trouble code that says you should change the oxygen sensors. Code 44 means the following: There is a problem in the oxygen sensor circuit on the right side cylinder head. The oxygen sensor receives 12 volts for the heater from the fuel pump relay; this wire may be chafed, or the relay may not be functioning properly. Also, the ground circuit for the oxygen sensor needs to be checked with a digital voltage ohm meter. By any chance do you still have your receipt for the parts you bought to use as diagnostic tools? If so, you may want to return them and reinstall your old sensors. If the sensor has more than 60,000 miles on it, you may have just done some good maintenance by updating the sensors. Make sure the shop you are working with has a good understanding of what a Code 44 actually is.

Q: have an 2007 Ford Explorer, 4.6 V8, 6-speed automatic, with 41,000 miles. Over the past three weeks the car has stalled three times — once while taking a left turn, once while stopped at a light, once while approaching a light at 10 mph. No codes are showing, the dealer has no clue, and I’m fearful of a serious accident. Would greatly appreciate your trusted advice.

A: I have to agree with the dealer on this one. There are no factory service bulletins concerning this problem. There is not a check-engine light leaving the technician with a path to follow. The problem has happened only once a week on average. One of the rules in my business is “in order to fix the problem, we have to be able to duplicate the problem.” I do apologize; I know this is not what you wanted to hear, but it’s the way it is. I would ask the dealer if he has a recording device you can plug into your car’s computer port to record all driving events. If the dealer has this available, he will be able to look at the recording to see exactly what was happening at the time of the stall.

Car Care Tip: When going through a car wash, ask for a receipt. If, after you get home, you find the car is not satisfactory, a return pass through the wash tunnel should be no charge to you, as long as you have a receipt to show.

Larry Rubenstein is a master technician who owns a North Shore service station. His column appears every Saturday. Write to Larry at The Salem News, c/o Auto Scanner, 32 Dunham Road, Beverly, MA 01915, or send an email to