A christmas tree of codes-2000 5.0

[Dono]

So, I filled up with gas, and very quickly had stumbling, trans codes, and all 4 o2 sensors firing codes.
Immediately, I felt it must be bad gas. I syphoned it out, and refilled. Within 2 miles the truck ran great. I was sure it was the gas. 2 days later its coming back, intermittently.

I did a code check and I have these codes, although the check engine light hasn't come on yet.
P1747 Pressure control solenoid A short circuit (see P092)
P0750 Shift solenoid A
P0755 Shift solenoid B
P0743 Torque converter clutch electrical circuit
P1451 Evaporative Emission system vent control circuit

I found this thread that seems very similar to what I am seeing:
http://www.explorerforum.com/forums/showthread.php?t=392916&highlight=p0750

With me, the issue is intermittent, suggesting a wiring issue. I'm not convinced bad gas caused this anymore. What's with the P1451?

Its interesting that before draining and refilling the gas tank I had O2 sensor short codes on all 4 o2 sensors, but those codes didn't show up this time (yet, anyway).



I'm starting to think I have a wiring issue. Intermittent..

 

[Dono]

I'll have to climb underneath and inspect the o2 wiring and make sure it isn't resting on an exhaust pipe and melting. [MENTION=111113]2000StreetRod[/MENTION] helped me already by posting that the O2 sensors are a part of the transmission circuit. I'm wondering if the o2 codes will come back as they did when this whole fiasco started.

Fuse 13 cant be blown, since the issue is intermittent.

Every thread on here about this seems to be a dead end. Lets hope mine doesn't end up in a dead end also.

I pulled fuse 13 (Under the hood, drivers side at firewall), checked for corrosion, cleaned, used a bit of di-electric grease, and re-seated it. Time will tell if its that easy. Its so cold here right now, I'm not in a real hurry to be rolling around inspecting wiring harness under there. Very good chance that's what I'll be doing though.

 

[vroomzoomboom]

that MAF wouldnt be playing games again would it?

 

[Dono]

No idea. Its all pretty dry and clean in that area.
Connectors are dry and tight.

 

[4pointslow]

codes

I have been very sick since last Sunday, Yesterday I must not have see this update due to my cough medicine induced hallucinations. Sorry to hear you are still having problems.
That other thread you posted, the guy stated that it started after refueling just like yours. Maybe you could try to check the resistance of the Canister Vent Solenoid. It only closes when the system tries to test the fuel tank,canister, and lines for leaks. There could also be high resistance in the power cicruit so that when there is a load on the circuit the voltage drops to an unsatisfactory lower voltage that makes thing go haywire. Thanks for posting the codes, I will check some wiring diagrams to see if there is anything else to be learned from them.

The fuse may have been just loose causing high resistance.

 

[Dono]

Sorry to hear of your illness, although drug induced hallucinations can ease the misery.

The fault has not come back since reseating the fuse. Tough to know since it seems to be intermittent.

The gas company insists on taking a sample of gas to have it tested. I was surprised, since I called head office when it happened and didn't have my call returned for days. When the call came, I explained that I felt it might not be the gas, but they want to test it anyway.

It was also explained to me that there is no mid-grade 'tank'. Mid grade is a mix of premium and regular that is done within valving at the station.

I really doubt this is gas, but instead a crazy coincidence. It will still be interesting to hear how the gas tests though.

 

[4pointslow]

Codes

Check out where the Canister vent shows up in the wiring. If the resistance was the fuse being loose that would make sense, the voltage would drop when all or some of the components were turned on by the PCM(grounded by PCM). For instance a loose fuse may allow the voltage to stay around 12 volts with all the O2 heaters being on and maybe a shift solenoid or two. Now add the Evap Canister Vent solenoid and that voltage may drop to 8 or something, and everything or somethings on that circuit stop working.

Another possibility is the windings in the Evap Canister Vent solenoid are starting to short which would drop the voltage when the PCM tries to ground it, causing a short to ground only when the PCM is grounding the vent solenoid. If the shorted solenoid still has a little resistance the fuse would not blow but the voltage would drop, if the solenoid has no resistance or a perfect short to ground condition it would blow the fuse. The latter would not be your problem since no blown fuse.
I will look for the specs on the solenoid just in case.

Let us know if it happens again.

 

[4pointslow]

Canister Vent Solenoid

The solenoid should be 48-65 ohms.

 

[Dono]

Thanks, Any idea how to get to the connector?
I don't really have a clue where that even runs. If you don't know off the top of your head, don't worry about it.

Im guessing that the canister is the one that is up above where the spare tire goes. I know there is another one drivers front, under the hood. I get them both mixed up.

 

[4pointslow]

vent

The vent is the one above the spare tire.
Probably have to drop the spare down, may be able to go through wheel well.

 

[Dono]

Thanks,
Should be reasonably easy, other than being cold on the floor.
The turbo occupies that area now, so as long as its not in the way I'm laughing.