a/c turns of SES??

Q: I have been chasing a canister purge solinoid code (26) for a while.
I had a bad Solinoid and some bad hoses -- all were leaking pretty
badly. Canister is okay. I checked my wiring and PCM -- all good. But
after ~30 seconds of running, the code reappears and the SES comes on.

Just out of dumb luck, I turned the A/C on. In about 5 seconds the SES
went out. I have found that if I leave the A/C on, I get no code. Any
explainations for that one?

Bill > wrote:
> Just out of dumb luck, I turned the A/C on. In about 5 seconds the SES
> went out. I have found that if I leave the A/C on, I get no code. Any
> explainations for that one?

The AC kicks the idle up a little bit. Maybe the increased idle
speed prevents whatever condition sets the code?

-DanD

--
# Dan Duncan (kd4igw) http://pcisys.net/~dand
# Of all the strange 'crimes' that human beings have legislated out of nothing,
# 'blasphemy' is the most amazing- with 'obscenity' and 'indecent exposure'
# fighting it out for second and third place. -Lazarus Long

I believe the A/C clutch driver is the same "quad driver" that can
cause EGR/canister purge solenoid/etc. SES codes. It's conceivable
that for example the canister purge solenoid is just barely out of spec
and the extra current draw of engaging the A/C masks this.

Tim.

I have a test PCM that I can use. I'll try to see if this makes a
differance.

Thanks!

Well, there should be nothing (EGR, Purge solinoid, etc) out of spec,
because I had to replace them all already. I'm pretty sure the problem
is in the PCM. I went and tried a test PCM and the code stayed away
with and without the a/c on. Previously, before replacing the purge
solinoid, both would code 26.

Tim, I think you are on to something. If there is an internal problem
with the "quad drive", this could explain it. I only had limited time
to test it, but I'm pretty sure the other PCM will be the cure.

Thanks!

> but I'm pretty sure the other PCM will be the cure

Don't neglect checking the wiring harnesses and grounding (battery to
frame and PCM to frame in particular). It'd be awful to buy a new PCM
when all you really needed was to clean up a few ground connections.

Tim.

Thanks for the info. I go down the road of bad grounds at my "real job"
quite a bit. It will cause some strange problems. The PCM actually cost
me a whole $28.00 plus shipping on Ebay.