Q: I have a problem with my Dodge Durango's 4WD system. It won't shift into 4WD HI. I've replaced the transfer case motor already, with no luck. I can't afford going to a shop for the repairs so I'm trying to do it myself. I need to know what to do next to solve my problem. Can you offer any tips? -- A.R., e-mail

A: A.R., the shifting of your Durango's transfer case into 4WD HI is likely controlled by a microprocessor known as the Transfer Case Control Module (TCCM). Of course, that depends on what year your Durango is.

I wouldn't suggest throwing any more parts at your Durango in an attempt to fix the problem. Instead, see if any of your local auto parts stores provide a free service of reading diagnostic trouble codes. They'll need a scan tool that can read codes from the TCCM. If there are any codes stored in the TCCM that come back after clearing them out, you'll need to follow a diagnostic procedure (also known as a flowchart) to pinpoint the trouble.

You'll need to be skilled in using a digital multimeter to make voltage and resistance checks. And, of course, you'll need to have access to the proper diagnostic procedures for your vehicle. It's possible you're your problem could be caused by poor electrical connection or by a faulty sensor or switch.

Q: I own a '98 Chevrolet Express 2500 Van with approximately 70,000 miles. It has a 350 cu. in. engine and a 30-gallon fuel tank. When starting, the fuel gauge goes way past full instantly, then returns to the correct fuel level. Then, the needle on the gauge vibrates rapidly about 1/32". It appears that it is indicating the correct amount of fuel, though. Do you know what could cause a problem like this? -- R.R., Evergreen Park

A: R.R., according to the wiring diagram for your Van's fuel gauge, a component called the Vehicle Control Module (VCM) controls the operation of the fuel gauge by monitoring the in-tank fuel level sending unit. The sending unit is a variable resistor that changes resistance as the level of fuel in the tank changes. The sending unit should have about 40 ohms of resistance with an "Empty" tank and about 250 ohms of resistance with a "Full" tank.

One of the things a technician can do to test operation of the fuel gauge is to disconnect the in-tank sending unit back by the fuel tank and temporarily install a "known-good" sending unit or resistor (40 ohms for "Empty" and 250 ohms for "Full"). Rarely do gauges go bad, but they should be tested to see if they operate properly.

It's more likely that the sending unit is faulty, though. If the gauge operates normally with a "known good" sending unit or resistor installed, the sending unit in the fuel tank will need to be replaced. If the gauge doesn't operate properly with the test unit or resistor installed, the wiring and VCM should be checked before condemning the fuel gauge.

Q: Does my 2000 Daewoo Leganza have a timing belt or timing chain? If it has a belt, at what mileage should it be replaced? -- D.N., Chicago

A: D.N., It has a belt and according to service information it should be changed every 72,000 miles.

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