Wire problem could have multiple symptoms

Jul 09, 2023

Q. I have a 2005 Chrysler with about 50,000 miles on it. After driving for about an hour and a half on the highway, the low-fuel light came on and the gas gauge dropped to empty. I went to a gas station, where they put in some gas and the gas gauge went back to fuel and the low-fuel light went out. Then after a little bit of driving I noticed the car would not go above 48 miles per hour. I had the car towed to a repair shop where they kept the car for two days and couldn't find anything wrong. It hasn't happened again. Do you have any idea what was wrong?

A. Assuming that the repair shop checked for codes and didn't find any, I would suspect an intermittent wiring problem, most likely a faulty ground circuit. This same circuit could be affecting a number of systems, the fuel gauge and one of the car's computer circuits or sensors. I would start at the very beginning to make sure the battery connections are clean and tight. The first area that I look at with these cars when they lose power and go into "limp-mode" is the crank shaft and camshaft sensors and related wiring.

Battery mystery

Q. I had a problem with my car. The battery was going dead, even though I replaced it about a year ago. I had the car looked at, and the shop told me the alternator was weak. I replaced the alternator with a 96-amp alternator, but the battery is still dying. One shop told me to start the car and disconnect the battery, and if the car stalls the alternator is bad. Some other people tell me this isn't a good idea. What should I do?

A. I would start by finding a new repair shop. Disconnecting the battery on a car with an alternator will cause high voltage spikes and can damage the alternator and other sensitive electronics. Find a competent repair shop (for a listing go to aaa.com) and have a complete electrical system test performed, including a test of parasitic drain. It is possible the alternator is working properly, but there is an electrical drain causing the battery to become discharged.

Sensor to blame?

Q. I have a 2009 Buick with 90,000 miles on it. The only real work that was done is replacement of the front oxygen sensor. Now, occasionally, the car hesitates when the engine is cold and getting up to normal temperature. This did not happen until I replaced the oxygen sensor. Could the new part be defective? The check engine light was cleared and has stayed off, and there are no codes in the computer, but I don't like this hesitation.

A. It is possible that the aftermarket oxygen sensor isn't performing correctly. A technician with a quality scan tool may be able to watch the oxygen sensor voltage as the engine is warming up and see something out of the ordinary. I have seen many aftermarket sensors that just don't perform as well as the factory part. I have also seen many aftermarket parts outperform the factory part. Since the issue didn't happen until the sensor was replaced, logic indicates it could be a faulty sensor.

Security reset

Q. I own a 1999 Chevy pickup truck that I purchased used about seven years ago, and I use it for trips to the home improvement store. To me it seems as though if you own a house you need a truck. After dealing with several relatively minor issues at the beginning, the truck has been operating wonderfully, except for one annoyance: every once in a while (every month or two), I cannot keep the engine running at startup, and the dashboard light shows "SECURITY." I have found that if I try to start the truck and then wait for about 10 minutes, the engine starts and stays running. What do you think?

A. The problem is most likely with the ignition switch. The switch incorporates part of the security system of the truck. Before spending money on the switch, try a different ignition key. Sometimes a key that is not worn will solve the problem. You can also try resetting the truck's security system; this typically involves leaving the key in the on position for 10 minutes, and then cycling the key to off and back to on. You could also bypass the security system altogether— there are several bypass modules available for GM products.

— John Paul is the AAA Northeast Car Doctor. He has over 30 years of experience in the automobile industry and is an ASE-Certified Master Technician. Write to John Paul The Car Doctor at 110 Royal Little Drive, Providence, RI 02904. Or email [email protected] and put "Car Doctor" in the subject field. Saturday mornings at 8:30, tune into John Paul The Car Doctor at wrolradio.com. Follow him on Twitter @johnfpaul or facebook.com/Mrjohnfpaul.