What Does the 'Service Engine Soon' Light Mean on a 2008 Ford F650 with a Cummins Engine?

It sounds like you're dealing with a few trouble codes on your 2008 Ford F650 with a Cummins ISB 240 engine. The codes you've mentioned indicate several potential issues. For instance, the `1868` code points to a failure in the transmission automatic 4-wheel drive indicator circuit, while `0197` suggests a low signal voltage from the engine oil temperature sensor, which could be due to a faulty sensor or poor electrical connections. The `2448` and `2449` codes relate to the secondary air injection system, indicating possible leaks or disconnections in the air outlet hose. The `2387` code indicates a problem with the variable geometry turbo (VGT) actuator driver circuit, which may not be responding correctly. Lastly, `1899` suggests that the park/neutral switch might be stuck. To start troubleshooting, I recommend disconnecting the positive battery terminal for about five minutes. This can sometimes reset the system and turn off the service engine soon light. After reconnecting, check if the light remains off. Regarding the `2387` code, it’s crucial to inspect the charge-air cooler, hoses, and piping for any leaks or damage. Even if everything looks good, sometimes the mechanical system can be out of adjustment, so it’s worth checking the turbo's gear for any broken teeth. If you've cleaned the EGR system and the control motor is making a humming noise when the key is on, that’s typically normal. However, if the truck runs rough and the service light stays on, it may indicate a deeper issue, possibly with the engine control module (ECM). If you continue to see multiple codes, it might be worth considering the possibility of a failing ECM, as it can sometimes communicate with sensors but still have underlying issues. If you need further assistance with specific repairs for each code, feel free to reach out.