Vehicle specs below. Steady CEL for five years straight. Codes 34 & 35 (egr and purge control solenoids). Here's the sequence:

1. Carefully place a piece of handcrafted black electrical tape over the CEL. Do nothing for the next few years.

2. Get ambitious: Do a full Seafoam treatment (thru PCV, some in gas, some in oil). This caused CEL to become intermittant (on at cold or hot start, then goes off at hot engine).

3. Get more ambitious: Clean electrical contacts at non-functioning solenoids, and at Air Control Valve. Understandably, this accomplishes apparently nothing (but you feel better for having done it). CEL remains intermittant.

4. Adjust idle by closing completely (clockwise), then opening screw exactly one full turn (counterclockwise).

5. Here's the key: Remove breather hose from Air Control Valve (mounted on the front of your throttle body), spray in about a teaspoon of brake cleaner. Let some of it evaporate for about 3 minutes. Replace hose. Drive around. CEL has stayed off for a week - first time in five years.

My mechanic told me a cheep way to fix that but you need a volt meter. If you can find out how many volts it is signaling when it works you could put in a resistor that lets the same amount of volt through and fake out the computer.

 

I'm not so electorically inclinded to have figured it out yet. So I use the electical tape method.