Doug McAllister/Under the Hood: Gas gauge fails

Q. I own a 2002 Buick Rendezvous with approximately 102,000 miles. About six months ago the gas gauge started to improperly sense the fuel level. I checked that the fuel tank cap was tight. I have been able to get a reasonable reading by putting the car in park/neutral and checking the reading.

I had the car scoped by the mechanic who does all of the work on my car. I’ve been told that the fuel gauge and the fuel pump are all in “one package” and very expensive (approximately $900) to repair.

I’m retired and would like to avoid this costly repair if possible. I’ve been keeping track of my mileage to know when to buy gas. Otherwise the car runs well.

A. So, here’s the deal with your Buick … your mechanic is correct in that the fuel sender is part of the fuel pump, so if you want it repaired you will have to replace the whole unit. Though inconvenient, you can continue to keep track of your fuel mileage if that is what you want to do.

If this is a car you want to keep for a while, I would recommend you make the investment in the repair. Here’s why: The fuel pump will not last forever and it generally will not give you any warning when it is going to fail. The car will just not start one day. It has already gone 102,000 miles; how much farther it will go is a guess.

If you replace it now with a good-quality fuel pump, you will kill two birds with one stone.

Q. I have a 2005 GMC Sierra that failed the emissions test. They were unable to get any information. It runs fine so I know there’s no problem with the truck.

I checked the 15 amp fuse that shows for the ECM. Is there any other reason that there’s no information where they plug in? It looks like just four wires to the plug.

A. The connector that you are referring to is called the ALDL. This is the communication port where you retrieve data from the vehicle’s computer.

Occasionally the pins in that connector get loose or pushed back so that no contact is made when you plug into the connector. If this is the case you can just repair the connector.

We’ve also seen this problem if the fuse to the cigarette lighter is blown. One of the pins in the ALDL is powered off that fuse.

Good luck … hopefully it will be one of these easy fixes.

Ÿ Douglas Automotive is at 312 S. Hager Ave., Barrington, (847) 381-0454, and 7218B Virginia Road, Crystal Lake, (815) 356-0440. For information, visit douglasautomotive.com. Send questions to underthehood@dailyherald.com.