I have a 96 Rodeo (4WD if it matters) and I have been getting error codes saying that its running rich. Usually I'd adjust the timing, check the distributor cap and rotor... but all the ignition is electronic so now I'm not sure what to check. I bought some new spark plugs, but it can't be that, can it?
How would you guys go about fixing this problem?

 

I have been getting error codes saying that its running rich. Usually I'd adjust the timing, check the distributor cap and rotor.