Jim Grant's Tech Tips

‘96 Dodge Caravan, Service Engine Soon Light
Q: The Service Engine Soon Light in my ‘96 Dodge Caravan constantly shows up. I have taken my car to a Dodge dealer who ran a complete diagnostic on the car, and he tells me that the car was misfiring due to having wrong spark plugs. After having the dealer replace the spark plugs the service light turned off for about a week. But it reappeared while waiting for a light. I have taken the car in for tune ups and oil changes and each time the mechanic resets the service light; three days later it shows up again. What could be wrong with my Caravan?......Sam

A: When you have the light turned off, does the technician check the computer to find out why the light came on? Your vehicle has a new generation computer that has some pretty neat features including a darn good history file. When a system failure occurs, the computer takes a snap-shot of the sensor’s values at the time of the failure and records and stores them in a history file. And of course, turns on the Malfunction Indicator Light (MIL) which, in your case, is a Service Engine Soon light. With the correct equipment a technician can connect to the vehicle’s computer diagnostic port and call the history files up for reviewing. It’s a great diagnostic tool for those of us that deal with such problems. If the MIL light is on there’s a reason and the computer has a diagnostic trouble code (DTC) on file to tell you why. Before the MIL light is turned off again you want to know what DTC turned that light on! The MIL light is telling you that an important part of your vehicle’s operating system is malfunctioning! Don’t settle for just having the light turned off. Have the cause identified and repaired.