I'm sure most guys know how to check codes on their trucks by cycling the key from off to on without starting three times. On the third turn of the key you will see the odometer readout change and display any codes that have tripped. Another interesting way to read them and I'm not sure it covers all, is to first hold down the trip odometer reset button. Then turn the key without starting and all your dash gauges and lights will come to life and perform a test run to the limits of their ranges. Got a big kick out of watching the speedo max out. Use the Search function on this web site and you'll find a explanation for the codes. I printed it and keep it in the glove box.........Great Stuff