spooledUP7

I'm looking to find someone that is an expert in 2nd gens to help me solve some strange happenings on a '90 GTU non turbo.

Here is a list of problems:

Check Engine light with codes 9 and 33 (Water thermosensor, and port air solenoid switch)

I tested the thermosensor and it appears to react well within the range of resistance specs, however it still appears to as a code.

I pulled the port air assembly off and found broken fragments of a once bad airpump's apex seal stuck within the air bypass valve. This was no big surprise since the old air pump really sounded crappy before replacing it.
There was no real damage to the assembly and I was able to remove the apex seal chunks.

I first tested the port valve solenoid according to mazda testing procedures and I found that voltage at idle was 12-13 volts (The proper voltage for a less than 20K miles car, but the car has 160K on it) instead of the 2 volts that it needs to be.

I could get 2 volts if I were to not ground the "L" wire and simply connect the multimeter to both the contacts, but when I revved the motor the volts did not rise to 12 volts like it should.

I checked the continuity between the harness and the ECU and I found a high level of resistance but nevertheless continuity. It was like that for both wires. Is this normal, or should it zero out?

The solenoid continuity checked out to be 31ohms (Identical to the split valve solenoid which leads me to believe that the port air solenoid is fine) and applied 12 volts to the solenoid to see if the plunger would retract. It did.

The big dilemma is that even after clearing the codes, (according to some people on the forum by pulling the ground terminal and waiting between a period of 10 seconds to 10 minutes.) the codes will still reoccur within a minute of driving the car. The car will also act very sluggish as if it is in limp mode, which I am guessing it is.

I have also tried resetting the ECU by applying the brake pedal as you would with a third gen, but the codes seemingly remain within the system.

My questions are:
Is there a method of completely clearing the codes of memory residing errors, and is there a method of determining why I am seeing 12+ volts on the port air solenoid harness when it should be 2 volts?

Is it possible that the ECU thinks that it is still a 20,000 mile car that is stuck in Safe mode?

I would appreciate any assistance in the problem.

Thanks in advance.

mazdaspeed7

Hmmm...It could be some wires within the harness touching and shorting each other out, or it could be bad wires, but that is a real pain to find/fix. Check the plugs for the water temp sensor and the port air solenoid. You said the resistance of the solenoid was 31 ohms? I had similar problems a while ago, and when I checked the resistance, I remember it being closer to 35 ohm. My solenoid worked, but a few wires in the harness were bad. I ended up pulling the engine harness from my parts car, and putting it into my car, and everything worked great after that.

A new harness is insanely expensive, like $1200-1500 depending on where yu get it. You might want to pull your engine wiring harness out, and pull all of the tape off and check all the wires. If you find any bad wires, replace the individual wire. Just be sure to solder any connections. You wouldnt want to have this problem again just because you didnt want to take the extra time to do it right the first time.