I retrieved the codes from the engine service lights.The codes retrieved are as follows 12,21,21,55.What does the codes mean ?

It means that there is a malfunction with the engine control system which is most likely related to the emission control system, the computer stores some diagnostic trouble codes that should be retrieved, the trouble code numbers will help to find where the problem may be. The way to get the trouble codes is by putting a jumper wire in the diagnostic connector under the hood between the terminals TE1 and E1 with the key on the check engine light will blink the code, for example a code 24 would be two blinks followed by four and so on. Once the codes are known you can reply back to me and I can help further.

That the engine computer has recieved information from a sensor/s that is not correct, could be a bad sensor or other issues with the engine. I would take the car to Auto Zone and they will use an OBD II scan tool to retrieve the code/s, which will tell you where to check for the problem.

The Check Engine Light (CEL) is a warning indicator—it means your vehicle's computer has determined that a component or system in your emission control system is not working properly. When the light comes on, one or more diagnostic trouble codes (DTC) are stored in the Engine Control Module. These DTCs remain even if the light goes out. To address a Check Engine Light problem, the DTCs are retrieved and the appropriate troubleshooting information is followed in order to determine the problem.

Don't confuse the Check Engine Light with the maintenance or service light. These lights illuminate when a routine service is due. They are usually triggered by mileage, gallons of gasoline consumed, or some other type of vehicle-use measurement.

Visit one autozone for scanning and knowed the foult code is there.

Good luck (remember rated this post).

it is flashing the codes if you got the sequence right it is codes 12,21,55 what engine? 12 battery disconnect,21 isO2S shorted to voltage, and 55 is MIL may not come on

If the light was flashing when it came on, then it means your engine is misfiring.

A solid light can mean anything from a loose/faulty gas cap to a transmission issue.

This light comes on when the computer detects a fault of some sort in its diagnostic tests. If it keeps detecting this issue, the light will remain on. If the light turns off, then it has detected that the issue may no longer be present.

In order to find out what the exact reason was for your light, You need to have your car computer scanned to retrieve the code that the computer would have stored when the light triggered. Most garages will do this free of charge. The code will tell you what may have caused the light to initially turn on.

The codes can be retrieved by turning your ignition switch on and off three time quickly and watch your service engine light. It will flash once pause then flash twice then it will begin to give any fault codes that have been stored. It will flash once or twice then pause then flash in concession again then pause and start another code if any. When you have retrieved all the codes available it will flash 5 times pause then flash 5 times which means it has finished. There are several sites on the net that will explain what each code stands for and which circuit needs your attention.

The engine control codes need to be known to go further The codes can be retrieved at most auto parts stores as they can sell you the parts recommended to fix the cat they usually don't charge to retrieve the codes and then the parts lookup computer can make some recomendations on the repairs needed. The transmission codes might not be retrieved this way and this is only giong to give you an idea of whats wrong and not a for sure. Following though on engine control codes is best left to a pro and the parts guy can probly tell you a shop the fixes cadillacs regully and buys the kind of parts that yours might end up needing

you have to have the code read at a garage equiped with scanner to retrieve and eventually erase the code your car is running on safe mode not the best setup

i would say it is just reminding you to to get the vehicle serviced its not major but most vehicles need to be serviced on a regular basis i think every 5000 km

3 times ..turn the key > off on off on off on .> then count the flashes of the light , flash flash pause flash flash , = 22 , pause , i think when you see 5 flashes pause 5 flashes , that means end of list . there might be multiple codes , have a note pad , you have to do it twice to be sure of the code(s) .