2004 Jeep 4.7 liter engine lite stays on had tranny flushed and serviced. The light came shortly after has stayed on. Took it back to service rep he made go off for a short while. Gas c?

The check engine light (CEL) staying on in your 2004 Jeep with a 4.7L engine, even after a transmission service, suggests a problem unrelated to the transmission itself. The fact that the service rep temporarily got it to go off hints at an intermittent issue, possibly a loose connection or a sensor problem. The "gas c?" in your question suggests a possible fuel-related concern, but it's not definitive.

Here's what could be causing the CEL:

* Intermittent Sensor Issue: Many sensors in the engine control system can cause the CEL to illuminate. These include the oxygen sensors, mass airflow sensor (MAF), crankshaft position sensor (CKP), camshaft position sensor (CMP), and throttle position sensor (TPS). An intermittent problem with one of these means it might work fine sometimes and fail at other times.

* Loose Connection: A loose or corroded connection in the wiring harness can also trigger the CEL. Heat, vibration, and age can cause these issues.

* Evaporative Emission System (EVAP) Leak: A leak in the EVAP system, which controls fuel vapor emissions, will trigger the CEL. This is a common problem, and could be related to a gas cap issue (although usually the gas cap light is specific).

* Other Engine Issues: While less likely given the timing, problems like a failing catalytic converter, a misfire, or low engine coolant could also trigger the CEL.

What to Do:

1. Get a Diagnostic Code Read: The most important step is to use an OBD-II code reader to retrieve the diagnostic trouble codes (DTCs) stored by the vehicle's computer. These codes provide clues to pinpoint the problem. Auto parts stores often offer free code reading services.

2. Inspect the Gas Cap: While unlikely to be the sole cause given the mechanic's involvement, ensure your gas cap is securely tightened. A loose or faulty gas cap can cause an EVAP system fault.

3. Check for Loose Connections: If you're mechanically inclined and comfortable working under the hood, you could visually inspect connectors for corrosion or looseness. However, this requires some knowledge and caution.

4. Return to the Mechanic: Go back to the service representative and explain that the light is still on. Provide them with the diagnostic trouble codes. This is crucial as they should have the proper equipment to address the problem.

Do *not* ignore the CEL. Driving with a malfunctioning engine system can lead to further damage. Get the codes read and have the issue diagnosed properly.