Korey

Just helped my friend get a '92 2WD extended cab with 102k miles on it and no rust. It runs great and has no engine codes. However, when left in drive, it starts in what I think is 3rd gear and will not shift into overdrive or downshift when you press on the gas. When shifted manually into L, it goes into 1st gear fine, shifting into the 2 position seems to put it in third, and then shifting in to D seems to put it into overdrive, just like the FSM says its supposed to when the solenoid wire is disconnected. However, after about 20 min of driving around and shifting back and fourth, the flashing O/D light goes away and it shifts perfectly. It is showing a code 62 which is a severed or short in the #1 solenoid and I am puzzled as to what would cause the solenoid to act like it was disconnected for the first 20 minutes. The wire is obviously not severed, and if it was shorted, I don't think it would work at all, so what would cause the solenoid to not work until well after the truck is warmed up?

I've tried another battery and getting a jump from another running vehicle to see if maybe there wasn't enough power reaching the solenoid to no avail. I'd like to narrow the causes down before I open up the transmission pan. Any ideas or experiences are greatly appreciated. I have not needed to post much here because of the invaluable info that has already been posted which has saved me hundreds, if not thousands of dollars in work.

scope103

"Obviously" because you can see the outside of part of the wire? Or because it eventually works after heat and vibration gets to it?

Since you a) have a code saying the ECM can't communicate with solenoid 1 and b) the drive test confirms that, I would go next to a direct test of the solenoid. http://www.ncttora.com/fsm/1990-1995...1/troubles.pdf page 39. Be aware that you might have a broken conductor inside a "good-looking" wire that makes/breaks intermittently (try wiggling the harness). Also, you could have an "open" in the solenoid itself that makes contact after heat and vibration (test resistance at the transmission as well as at the ECM.)

Let us know.

Korey

Thanks for the link. Obviously as in the wire is not completely severed, but it could be worn enough to cause the problem. I'd have to trace it tomorrow when my friend comes over and test the resistance in the ECM. If I don't find anything, then I will proceed to take off the transmission pan to check the wires and solenoid.

Korey

Working on the truck now and looking through the fsm you showed me, but I'm not very good with a multimeter. I have the ohms section set at 200, however I'm not getting any readings when I test the resistance at the connecter terminals whenI have the negative probe in S1 and positive probe in S2 and S3. Also the FSM says to apply battery positive voltage to each terminal to listen for solenoid operation, which i did with the multimeter since the ohm setting puts out battery voltage, but it doesn't seem to do anything. Am I doing this wrong?

Pardon the noobiness, but even though I am good at fixing things mechanically, I'm not as good with the multimeter.

scope103

1. When you use a multimeter, it is impossible to "not get[] any readings." You can get zero resistance or infinite resistance or overrange or 12.6 volts or lots of other readings. You cannot get "no reading." (Don't feel bad, lots of folks claim they "get no reading." They're just wrong.)

2. When the FSM says to apply "Battery voltage," they mean the "truck battery." You don't have to use the actual battery, but you need 12volts. The battery in your ohmmeter is what? 1 AA battery with about 1.5volts?

3. When you say you're testing "S1," is that at the ECM? Is the connector to the ECM connected? What I think you want to do is test the solenoid circuit. To do that, you disconnect the connector, and on the solenoid side you test for continuity ("very low resistance") to ground (not to S2 or S3). Infinite resistance means that the wire is not connected through the solenoid, or the solenoid itself has an "open." (Broken wire.)

For a very general introduction, try http://www.autoshop101.com/, Technical Articles, Analog v. Digital meters.

Korey

Sorry I should have said I was getting a reading of 1, which I assume is infinity. Was just trying to do the fsm step by step which said to check resistance of No. 1 solenoid valve at the ECM connector, which I was doing, so yes I was testing S1 at the ECM, but at the connector.

When you say to disconnect the connector, are you referring to the connector that goes into the transmission and testing that connector for continuity cuz I did that as well and am getting an infinite amount in 4 of the 10 terminals.


Checked ECM connection again and am getting infinite for S1 and S2, and 4.2 for SL.

scope103

Did you put the probes on S1 and S2? That doesn't measure the resistance TO GROUND. Put one probe on S1, and the other to some metal of the truck (you can use the E1 terminal on the connector, but the solenoids ground through the case of the transmission, so the truck body should be a good ground.)

If you do this test by "back-probing" the connector at the ECM while it is still plugged into the ECM, you don't know if you're measuring the resistance of the solenoid circuit, or inside the ECM itself. But if you get infinite resistance on S1, it doesn't matter. You have an open in the S1 circuit. You still don't know if it is in the wiring to the transmission, or in the solenoid itself, but it is probably the solenoid. I'd go ahead with the disassembly, but once I removed the solenoid I'd test it again. If the solenoid is good you might have a wiring problem.

(By the way, your probes are "plus and minus" when you're measuring voltage or current, but it's not so clear when you're measuring resistance. It's covered in the article I referred you to. But unless you're checking diodes (you're not here), it doesn't matter.)

Korey

I had the negative probe grounded while I used the positive in the connectors. The transmission pan is now out and i am about to pull the solenoids to test em.

scope103

Pictures would be good; most of us never go that far into the depths of the transmission.

Korey

Just checked the #1 solenoid and it's engaging and I also ran air through the solenoid and checked it again. Works fine although I am not sure how to check for leaks?

Korey

The transmission I'm working on is very similar to the one in these pics https://www.yotatech.com/forums/f116...riteup-208821/

Or would you like to see pics of the trans that I am working on?

Korey

Now I'm baffled. Solenoid #1 was working fine, then I tested #2 and it was sparking without engagement, so I tried #1 again which produced sparks which didn't happen the first time and is not working now.


After some manipulating with the cables, they both seem to be working without much sparking.

scope103

Obviously, sparking is very bad. Glad to hear you got ahead of it. If manipulating the cables got them working, perhaps you have a bad wire somewhere? I would do my best to find it; whatever you did to get the copper to connect inside the wire will be instantly undone once the truck vibrates in the least.

Korey

I had to keep the positive cable away from the body of the solenoid and the teeth on the terminal to keep it from sparking. It does take some manipulation to get the solenoids to engage sometimes, though and since I checked the voltage which read about 8.4 at the connections that plug into the solenoids, it looks like the solenoids may be going. I found a set of new ones for under $140/free shipping here: http://www.transmissionpartsusa.com/...-00094393a.htm.

What do you think? Does the voltage sound about right?

scope103

Doesn't that sound like bad insulation on the wire? The body of the solenoid is grounded, so if you have bad insulation on the cable it could arc to the body of the solenoid.

If that's the case, replacing the solenoid will get you nowhere (in fact, the solenoids may be good -- if the power wire is shorting out, of course they won't actuate).

But I'm not there, and you are. Before I ordered new solenoids, I'd remove one of the suspect ones, and carefully set it up so you can test it away from the suspect harness. (There's a bolt hole in the frame just forward of the battery; bolt the solenoid there and use a good piece of wire to jump to the battery.) If the solenoid tests good, my money is on a bad harness.

8.4 volts sounds low, if that's with the solenoid operating, it means you're dropping 4 volts through the harness. But it may be okay.

Korey

What i actually did was take em out of the truck, hook the positive and negative terminals to the battery, and the other positive to the solenoid terminal, then the other negative to the bracket where the bolt goes through on the solenoid. I think they are supposed to be tested individually from the truck as it looks like in the FSM. I didn't even test em with the wiring connected.

While the solenoids were out, I tested the wires that connect to the solenoids and got 8.4 on all of em, and I also tested the wiring connection to the harness and got the same results. This time, I had the multimeter on 20 V== rather than 200 ohm. So it's actually supposed to read about 12 volts then?

Wonder what I am doing wrong here. I didn't order new solenoids, but I am off to Bob's auto parts for trans fluid and filter as well as Permatex Right Stuff. If you notice in the pics of the link above, you will see some magnets and the ones here are coated in metallic colored fluid while the rest of the pan is pretty much pinkish with a little bit of brown. The fluid was grey when I wiped my finger on one of the magnets, so it's pretty neat how much wear those magnets are saving the transmission from.

Hopefully when I return, you would have figured out what the heck it is I'm doing wrong here. LOL.

scope103

You're now beyond my personal experience. The manual http://www.ncttora.com/fsm/1990-1995...2/troubles.pdf (page 38) gives 9-14v as "okay" for S1. Why it would be different than battery voltage (around 12. 6 -- whatever you measure at the battery) is not clear to me, but 8.4v sounds pretty close to the 9-14v range. What does NOT sound right is getting 8.4v on lines to the other solenoids (S2 and SL). Those should be zero.

Other than that, your described test procedure sounds really good. I don't think I can help you much more.

By the way, Permatex Right Stuff sets really quickly. Excellent if you're charging by the hour (like a real mechanic). Not as good if you're a duffer like me. I use RTV blue, but as long as you remember that you don't get much "open time," Right Stuff is really good.

Korey

Just got back from the parts run. Going to go over the harness again before I seal everything back up. When I pulled the solenoids, some black fluid came out which was most likely metal build up in the fluid. Gonna go over the FSM and harness once again.

Korey

Ok. I must have had a brain fart all day yesterday. I did it right this time. Here are the results:

ECM connector resistance: S1- 13.6 OHMS, S2- Infinity, SL- 4.0
Solenoid resistance: 13.6 OHMS for all
Wiring voltage@ solenoid connectors- 8-8.6 Volts for all

Ok, so here I am with a code 62 which is a fault in the #1 solenoid circuit and I am getting perfect readings for that solenoid of 13.6 volts, yet #2 is showing an open reading at the ECM connector and the lockup solenoid is showing 4.0. What the heck? LOL.

scope103

When you measured the resistance at the ECM connector, was it still connected to the ECM? If not, you're measuring the resistance of the solenoid and harness, which would be useful. And zero ohms for S2 would be bad. If still connected, you are also measuring the "resistance" looking into the ECM, in parallel with the solenoid. I don't think the manual gives any standard values for that.

Did you measure the voltage at the ECM connector as described in the manual? (Note that has the connector plugged in). What concerns me is that you are getting voltage on S2 and SL (at the transmission) when you should get zero. If you get the same voltages at the ECM, unplug it and try to measure the voltages at the ECM without the plug. It you get voltage/0/0 on S1/S2/SL then, you have a short in the harness.

Last, you can disconnect the harness at each end and ohm out each wire (zero resistance end to end, infinite from one wire to the next). This is tedious (you might need a helper), but some of your results sound like a bad harness.