Engine Light keeps coming on

I have a 2005 Jeep Grand Cherokee with 120,000 miles. The engine light came on and I took it in for service. The catalytic converter was defective and replaced. After service and 30 miles the light came back on. They erased the memory. After 35 miles the light came back on. So far I have returned 4 times and they cannot find the problem. Have any other owners experienced this?

The paperwork from the shop should indicate what Dignostic Trouble Codes were recorded. This may show up as a DTC and starting with a “P”.

That’s the info we need.


When the CEL comes on, trouble codes are recorded in the cars computer. We need to know the codes that are causing your CEL to turn on…Most autoparts stores will read the codes for you for free…

Perhaps the oxygen sensors were the real problem . . .

Agree with db4690. The only way the computer knows that the catalytic converter might be bad is if the oxygen sensors say so. But if the oxygen sensors themselves have gone bad, their report will be wrong.

Most likely your shop should have tested and replaced the oxygen sensor(s), not the cat.

Is there a leak on the gas filler cap or not going back on properly or even a tiny hole in a gas pipe… the engine light can come on if the pressure on the gas inlets are down. I had the light come on for ages because the gas filler cap wasn’t on properly.


In your case, you had a gross evap leak code

OP most likely had a P0420 catalyst efficiency code

The MIL was on for a different reason in your case