Toyota Repair: Check Engine Light Stays On, oil pressure gauge, oil pressure sending unit

Question
Mr. Ted,

My Check Engine light on my 1997 Toyota Avalon comes on and goes out from time to time. This has been occurring since last DEC.

Just a little history, the miles display is 300,300 miles and I have had major services done every 60,000 with the last one being preformed at 280,000 miles.

As for the performance, there has not been any changes (negative) in the performance or the gas mileage. On my most recent road trip from Central AL to Dallas, TX, I averaged 25 MPG. However, when I departed AL, the light on but it went out within the first two hundred miles of the trip and remained out until I got back to AL four days ago. However, I drove to Atlanta, GA today, 24 January and during this trip, the light went on within the first 50 miles and remained off until I came back this afternoon and it is still on.

My problem appears to be related to the temperature as during the past two trips, I started out in the early A.M. when the Temp is lower than it is during the middle of the day.

Thanks and any Intel you can provide on this problem would be appreciated,

Karl

Answer
Hello, there are two reasons for the oil warning light to turn on, a defective oil pressure sending unit or the oil pressure is actually low at times, the oil pressure should be tested using an external oil pressure gauge and if normal replacing the sending switch may cure this problem.