94 Stuck in Self Test Mode

Hello all,

Great Forum site. Hope someone might have some advice on this issue.

I have been trouble shooting an irratic idle issue and CEL. Ford dealer was of no help and like a lot of others, I sunk a few c-notes into their services with no real improvement.

I learned how to do the self test and was able to read my codes. I did both the KOEO test and the KOER test.

Although I am still working through the primary issue, I have created another one that I was not able to find discussed on the forum anywhere.

Even though I have removed the jumper between the self test pin and the single wire pin, and have tried disconnecting the battery for over an hour, the self test mode is still activated.

The Explorer is still driveable, so I am not sure if the self test mode is causing problems while driving. After about 3-5 minutes of driving, the CEL comes on solid.

Does anyone have an idea on what might be causing this condition? If so, what can I do to get the computer out of this mode?

Thank you for your help.

John

My first thought is to look for a short to ground in teh STI circuit (between the self-test connector and the PCM).

Mr. Shorty,

Thank you for the response. I have done some checking as per your response and here are my findings.

With the battery disconnected, the STI pin (single wire) is open to the Signal Return Pin (i.e. not shorted). I checked this with a meter. I also did a visual inspection and no insulation damage is seen on any of the wires from the test connectors prior to where it goes under the harness covering.

With the battery installed and key on, the STI pin measures 0 Volts compared to vehicle ground. The Signal return pin measures .2 mV.

With the battery installed and key off, the following resistance measurments were taken: Signal Return Pin is shorted (0 Ohms) to vehicle ground. STI pin is completely open to ground (i.e. no short there).


By the way, the following items have been serviced and/or replaced in trying to deal with the original issue of rough idle, sluggish acceleration and CEL.

1. Checked for vacuum leaks, no obvious ones found. If vacuum leak is created at the vacuum hose connector assembly, then engine really starts to hack and cough. Replacing cap on unused port causes engine to go back to original condition.
2. Fuel filter changed. (by dealer)
3. Injector Ports cleaned (by dealer)
4. Battery terminals and termination points cleaned and checked.
5. Dealer recommended Right o2 sensor be replaced. I did this, no change in results (this is because one of the codes was for right side 02 indicating rich condition (code 173) You may want to check me on this one, I replaced the o2 sensor on the passanger side exhaust manafold. Hopefully that is the one considered the right side.
6. TPS replaced. This is because on start up, the engine was doing a fast idle, then faster, then down to 500 rpm. Parts store man thought this might be the trick (and it was fairly inexpensive). No change in status, and now I believe the erratic throttle operation is just part of the self test issue.
7. PCV valve checked and found ok.
8. MAF sensor assembly replaced (this was a cause of similar rough running issues when the Explorer was new, so after cleaning the existing one with no results, I thought to change it out. No change in operation.
9. ECC relay changed.

At this point I think it is going to be tough to solve any of the other issues until I get the self test issue fixed.

Please let me know if you have some further advice on how to proceed with this one.

Thank you,

John

The only reason I can think of for it to be stuck in self-test mode is if there's a short between STI and ground or STI and sig ret. If you can't find the short in the wiring harness between the self-test connectors and the PCM, perhaps it is inside the PCM.

One question -- have you counted the sequence of flashes you get to make sure it is in test mode? I can't tell from your post if you are familiar with the KOER test, but if you start the engine and it is stuck in test mode, you should see a sequence of meaningful flashes that would tell you if it is running the KOER test.

Mr. Shorty,

I see we have similar taste in vehicles. Like you, I have also have a suburban (97, K1500).

Back to the Explorer. Yes I am familiar with the test modes. I have the Haynes manual and had been using it to guide me through the self tests before finding this great forum. I have also seen Joe Dirt's video on doing the self test.

If I turn the key on, but not starting the car (KOEO test), you can hear various items being actuated (fuel pump, relays, etc) and then I only get the series of ones meaning everything is currently ok on what that is checking. Then I get the seperator code, then I get code 173 (twice), and on my most recent trip I am also getting 335 (twice). Code 173 is right o2 sensor reading rich. I believe the sensor is accuratly reporting that condition as I have changed that sensor (see my previous post, hope I changed the correct side). Code 335 states EGR sensor out of range. I haven't looked yet on how to tackle code 335 as that is a new one for me.

Anyway, I am confident in saying that the car is really in self test mode.

I am starting to wonder if the dealership had another way to get into self test that did not involve the standard connector, And that they forgot to undo whatever it is they may have done. Also, if this is set in the Keep Alive memory, how long would a person need to disconnect the battery before any information in that memory is reset?

Some more information:

At speed, the car runs well, except the CEL is on solid.

When cool, pretty rough idle when in gear. When warmed up, idle is much better.

If I start the car, then it gives the 3 flashes code for the engine (6 Cyl). I believe it is also manipulating the idle speed as part of its tests.

Mr. Shorty, I do appreciate your looking at this. I guess that this time I would like to take the PCM out and check the connectors. I will review these forums to see if there is advice on where the PCM is and how to remove it. If you have a favorite thread, can you post the link for me?

Thank you for your help. Also, if anyone else has had this issue with the self test (Am I really the only one), please add your thoughts and you will have my un-dying gratitude.

John

I see we have similar taste in vehicles. Like you, I have also have a suburban (97, K1500).

Click to expand...

Do you wake up at night and hear growls/snarls from the garage? It's kind of funny to run into someone with both a 1st gen Explorer and a late '90's Suburban like that.

I am starting to wonder if the dealership had another way to get into self test that did not involve the standard connector, And that they forgot to undo whatever it is they may have done. Also, if this is set in the Keep Alive memory, how long would a person need to disconnect the battery before any information in that memory is reset?

Click to expand...

I'm not aware of any alternative method for entering self-test mode. If you wanted to make sure KAM was clear, disconnect the battery for a couple of hours.

Mr. Shorty, I do appreciate your looking at this. I guess that this time I would like to take the PCM out and check the connectors. I will review these forums to see if there is advice on where the PCM is and how to remove it. If you have a favorite thread, can you post the link for me?

Click to expand...

I haven't seen a lot of discussion on the internals of the PCM. Some guys talk about it occasionally. PCM is located in front of the door, below the glove box, behind the kick panel there.

I think this is the first time I've heard of this problem you're having, so I hope you figure it out. When you do, be sure to tell us what the problem was and how you end up figuring it out.

Mr. Shorty,

I went to the local junk yard and they had just received a 94 XLT that was exactly like my wife's (same custom Boise River Festival decals and all). They sold the PCM to me for $65.00. Swap took all of about 10 minutes.

It is amazing, everything (except for the brake switch) is working like factory new (even the cruise control which has not worked for about 6-7 years). Anyway, too bad the PCM does not have a diagnostics code to identify itself as the culprit as that would have saved a lot of time and money. I’m also glad I didn’t let the local dealer continue on the course of action they laid out. They had a list over $1000 long that they wanted to try, and it did not include a new PCM. Working through the issues using this forum is definitely the answer.

I need to look for forum threads on the brake switch now. I fixed that with an Autozone part a few years ago, but it does not work very good. You really have to hit the brakes hard for the switch to activate. Anyway, once I get that issue fixed, the car will not have any outstanding issues that I am aware of (Yahoo).

Thank you for your support.

John

quick update:

Grabbed the break switch from the junk yard Explorer. That resolved the Brake Light issue. Its been three weeks since the PCM exchange and the Explorer is still running like new. Just amazing that it was the PCM.

1 year update

94 Explorer is still running like a champ with the replaced PCM. Just put some new rubber on. Tire Dealership said they couldn't do an alignment, as I had too much end-play (they wouldn't even try). They said I needed to have the bearings repacked ($100 a pop). I had trouble believing that, as I have always done my own repacks and do them by the book. I last repacked them about 3 months ago.

After looking at the forum on bearings and hubs (I have 4x4 with auto hubs, stock), I see that some say that some end play is normal.

Mr. Shorty, If you are still out there, can you comment on the adjustments of the wheel retaining nut. The proceedure I use is:

1. Tighten to 35 Ft-Lbs while spinning hub/rotor assy.
2. Loosen 1/4 turn.
3. Tighten to 16 inch-lb's.
4. If locking key does not go in, then tighten just a bit until it does (nut is still just finger tight at about 16 inch pounds).

If I want to get rid of the end play, then I need to leave the final adjustment at about 20 ft lbs, but I would think that would damage the bearings quickly.

Mr. Shorty, any advice?

Also, do you still own your Suburban? I still have both.

After looking at the forum on bearings and hubs (I have 4x4 with auto hubs, stock), I see that some say that some end play is normal.

Click to expand...

Some end play is normal for the rear axles, because the rear is a semi floating axle. There shouldn't be any end play in the front.

The procedure you are using to tighten the front bearings sounds like it comes straight out of a repair manual, so I think you are doing it right. If there is still looseness in the front wheels then:

1) Are we sure it is the bearings that are loose? Could the play be in the ball joints or the tie rods?
2) If it is in the bearings, then I would suspect some kind of wear in the bearings and/or races and/or spindle that is causing the looseness. I this case, a simple repack would not be enough -- likely need some new parts.

I don't know how thoroughly your shop inspected the front end before declaring it "unalignable." Whatever it ends up being, it sounds like the front end needs a thorough inspection.

An , yeah, I still have the Suburban. And the Chevy and the Ford still growl and snarl at each other in the garage

94 Explorer Hub End-Play issue/advice on getting hub nut key out.

Shorty,

The tire dealership said they inspected the ball joints and front end bushings. They said those looked great (they were replaced at about 100,000 Miles, 185K on the odometer now). They were pretty sure it was in the bearings (and by overtighting, it did remove the play).

All the bearings and races are less then a year old (Right side only about 3 months).

I am giving the car to my daughter for local commuting, so I probably won't sweat the alignment (although that may affect the tire mileage warranty, in 30 years of getting new tires, I have never had occasion to try to take advantage of that). It is driving perfectly straight down the road and handles well.

I am going to go back and reset the hub adjustment nut by the book again (instead of over tighting just to get the end play out).

Given that this is a 94, it looks and drives like about a three year old car (not new, but not close to being done either).

I appreciate the good work you do on the site.

Oh, and for anybody that has an issue getting the hub adjustment nut key out (first time for me took 2 hours), I have a handy hint. I can now get that sucker out in less then 30 seconds, every time!!!! Once you have accessed it by taking the cam off, use the hub nut socket to center the nut over the key. Then take a narrow air nozzel and direct compressed air to the side of the key. If the pressure from the nut is off, it will pop right out (keep a close eye on it and use safety glasses cause it comes out fast).

I think I have to change my user name now. It seeems like I only have to do work about every three months on the Explorer. Still the best new car I ever bought (Other one was an 88 Ford Ranger).

Now if I could ever get my 70 Chevelle SS (True SS) 396, Cowl Induction, 4-Speed back, I would be a very happy man.

John

Glad you got everything fixed.

Sure you may be sad to see it go, but at least it is still in the family

Been dealing with front end issues, bearings/spindle, on my explorer recently and never thought about using the air to help in releasing the key. Great tip, thank you and I will remember that for, tomorrow.

I'm sure my father would agree with you on the Chevelle comment. He sold his after wreaking it about, 20 years ago. But out of his 51 years I think he has owned every year Chevelle they ever produced and his tight self is still hanging on to original GM parts for a 70 SS. Fenders, hood, wind shield, sure there are more. Last time I seen them, 3 years ago, they still looked brand new with no rust all tucked in the warm basement and a four foot wide solid steel door protecting them.

Locking Key Tip

Currency,

Let me know how the tip worked. I reworked the front end again myself today. I found that I shouldn't have been packing the auto hubs with grease, so I took the opportunity while cleaning those up to inspect and repack the bearings. Once again, using a shot of air popped those locking keys right out (after centering the adjustment nut to relieve any pressure).

After repacking the bearings and adjusting the hub nut to specifications, I still find that I have a little end play. Once you get your bearing work done, let me know if you have any top/bottom end play (after you have the tire back on).

John