It's not a vehicle we service in the US but the "check engine" light is an indicator for a system that monitors many electronic functions in the system, also called the "malfunction indicator lamp" (MIL). It can come on for any of hundreds of different causes from any of the systems that the computer monitors. Some are very important and can lead to further component or engine damage and some are emissions related not as serious but still a problem and need to be repaired.
Your first step is to have the computer scanned to retrieve the trouble codes that were set when the check engine light came on. Those codes will give you specific information about what the computer saw and will get you pointed in the right direction to find your problem.
June, 22, 2011 AT 1:38 PM
There was no 6cyl Turbo diesel Holden Rodeo, (Isuzu). Your 2004 Rodeo either has a 2.8 or 3.0 litre 4cyl diesel engine, unless it has been highly modified.
If the lack of power produces more exhaust smoke than normal, (black smoke), then I would firstly check the Exhaust Gas Recirculation, (EGR), system. Most common cause of the symptom/s you describe on this model.
June, 23, 2011 AT 3:49 AM
I have had the EGR vavle replaced and the Fuel tank drained didn't do anythingat all now looking at replacing the injector pump and injectors at a cost of about 5k