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Mr. Anderson

4T60-E Solenoid Testing Question

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So on my 91, I have been dealing with a code 26 and poor drivability, and I believe that it is transmission related.

Now, I don't really know much about the 4T60-E transmission, but from what I have read online and in the service manual, it uses 4 solenoids to shift through the gears (solenoids A, B, PWM, and TCC if I am correct) and each solenoid can fail 'on' or 'off' with each failure mode resulting if different outcomes. The fluid in the trans. does not smell burnt, but it is in need of a change, as it is discolored.

My question is how can I test each individual solenoid for proper operation? Are any of these tests accessible through the diagnostic mode? I know it is a loaded question, but I really don't know much about this, and any help would be greatly appreciated. Thanks!

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Bret what is the symptoms of your transmission that leads you to think it is causing a code 26?

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Ronnie, I think that a solenoid has failed in it. It appears that it is starting in something other than first because when I pull it into OD the car will barely pull itself under its own power, but when I pull it into 2nd, the car responds fine. For example, the car wasn't able to drive up onto a trailer in OD but could easily in 2nd. The fluid is brown, but it isn't burnt, so I think the internals are ok.

I was also reading in the service manual that a failed solenoid will set a code 26, but I am not sure which one (or how many of them) has failed.

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Does your A/C compressor engage when turned on? I know it is an odd question, just answer it.

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I'm fairly sure it does, but it only blows out of the defrost vents. I will be back working at the car in an hour or so and I will be sure to verify then.

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Ronnie, I think that a solenoid has failed in it. It appears that it is starting in something other than first because when I pull it into OD the car will barely pull itself under its own power, but when I pull it into 2nd, the car responds fine. For example, the car wasn't able to drive up onto a trailer in OD but could easily in 2nd. The fluid is brown, but it isn't burnt, so I think the internals are ok.

I was also reading in the service manual that a failed solenoid will set a code 26, but I am not sure which one (or how many of them) has failed.

What happens when you try starting out with the shifter pulled down in 1st gear?

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What happens when you try starting out with the shifter pulled down in 1st gear?

Ronnie, I finally got around to trying this, and when I did, the car quickly went into first without any problems. It was the quickest shift out of park I had ever experienced in a car!

TexasJonh55 – I haven't got to checking the a/c compressor yet, I had a window regulator problem pop up suddenly that jammed the driver window. I will check on this soon.

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... It was the quickest shift out of park I had ever experienced in a car! ...

Huh? Sorry, I don't know what you are trying to tell me.

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Brett, if you have low gear, my question is probably irrelevant. Be advised that your trans will default to "limp mode" if you blow the fuse or lose power to the transmission. Limp mode will be evident by the trans only having 2nd and 3rd gear, no low gear or drive, but will start off in 2nd and will shift to 3rd but will not shift hi gear. The most noticeable symptom will be that it is sluggish taking off from standstill because it is 2nd gear and will give the impression that it is slipping until you get rolling good. It would have same symptom whether in Drive/OD on take off.

If you have a wiring schematic, it will show the wiring designation of each wire at the trans connector. Using that, you may be able to momentarily power each solenoid and listen for the click. Your first post requested info on testing solenoids and no one has addressed that yet. I have not personally done that so I waited for some one more knowleadgeable to step in. John

To test trans solenoids, you would need an identical connector from salvage yard car that you could plug into your trans and have access to power each circuit as desired.

I don't know for sure if '91 used 12v dc for powering solenoids or whether it may be using PWM drivers. Be advised that if they are PULSE WIDTH MODULATED solenoids, continous 12v direct current will smoke the solenoid in seconds! IT WILL ACT LIKE A DIRECT SHORT!

Edited by TexasJohn55 (see edit history)

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Oh sorry, my bad Ronnie. What I mean by this is that there was no delay from park to drive like there is in my other buicks. In my LeSabre for example, it takes about a second for the transmission to engage into drive when I shift out of park.

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Oh sorry, my bad Ronnie. What I mean by this is that there was no delay from park to drive like there is in my other buicks. In my LeSabre for example, it takes about a second for the transmission to engage into drive when I shift out of park.
John pretty much covered what my line of thought was when I asked about low gear. I would follow up on his suggestion to check the AC fuse as it can prevent the '91 E transmission from shifting properly.

I don't have access to a '91 FSM so I can't help much with troubleshooting the solenoids. If I were you I would drive the car, starting out in low gear, and see how many of the gears you can shift through manually. If it starts out in low and shifts through the gears manually but will not start out in low gear if you put the shifter in Drive, I would think the transmission clutches etc. are good and the problems is electrical.

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Great information, thank you so much! I will follow up on this in the next few days.

Quickly looking at the FSM on my phone, the 91 book doesn't show the A / C fuse connected to the solenoids, at least directly in section 8a... I am seeing the PCM fuse 7 in the interior relay center controlling these solenoids. Am I in the right area here?

post-91942-143143107306_thumb.png

Posting from my phone, sorry, the quality may not be as great.

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Ok, so from the looks of the wiring schematic (posted below) it appears that I will be working with terminals E and F, but primarily terminal F as that connects directly to the suspect solenoid. Am I right in saying that I will have to give this terminal 12 volts in order to activate the solenoid?

Sorry for the persistent questions, I am not too good with electronics and this is something that I don't want to mess up.

post-91942-143143107369_thumb.png

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From looking at these wiring diagrams it appears that the ECM is switching ground connections to the solenoids. The Reds are all common and should have 12 volts on them with key on and brake not activated. I would use a meter to make sure the reds all have 12 volts present. If not you will need to resolve why no power to them. If all the reds have 12 volt power, then to activate the solenoids ground is supplied on the other colored wires controlled by ECM. I know when I wired TCC lockups on my early 90's Chevy trucks I supplied a ground to active the TCC.

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Like he said, check for power on wire A and E with key on, this will resolve questions of trans being powered up. Other terminals are momentarily grounded to click solenoids.

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You should test the solenoids from proper resistance, for a ground or open circuit before testing them as described below. If you have an FSM is should have the electrical specs for the solenoids in it somewhere.

*The other guys covered this already but since I had most of this written when I saw their post I'll give you my version of answering your question:

To activate the solenoid the ECM grounds terminal F. Terminal E is hot anytime the key is on.

I assume you are going to unplug the connector at the transmission to test the solenoids. You will have to run a jumper wire from the hot side of the battery to terminal E on the transmission connector to supply power to the solenoid. Then run a jumper wire from a ground to terminal F to activate the solenoid. I don't know if you will be able to hear the solenoid click to know it is working or not.

Be sure you work with the connector on the transmission and NOT the one that plugs into it.

Take lots of care to keep from shorting out the jumper wires. Serious damage could happen to the car and you could be injured by the wire turning red hot and melting in your hand.

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Like he said, check for power on wire A and E with key on, this will resolve questions of trans being powered up. Other terminals are momentarily grounded to click solenoids. The white wire, terminal B shows to be a PWM circuit, be careful not to ground it more than momentarily, it will smoke. You could check the circuits resistance first before you try to power check any solenoids. The pwm solenoid will show shorted with a reading of less than 1 ohm, there may be specs in your book for checked solenoids.

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So I have finally got around to testing the solenoids in the transmission.

 

Using the service manual, I started by making sure that power was getting to the transmission, and it was.

Next, I checked the voltage at terminals A and E to ensure a proper voltage, and it was good at 11.5-12 volts.

Next, I took an ohmmeter and checked for continuity of the wires inside the transmission. The pins that led to the solenoids proved to be good and continuous.

I then went into diagnostics to test to see that the solenoids would click. On a 91, the ECM Outputs EO07 through EO10 are reserved for the transmission solenoids. EO07 is TCC, EO08 is PWM, EO09 is A, EO10 is B. After cycling through these tests in diagnostics, I could hear each solenoid click, and concluded that they were all working.

 

Unfortunately, this does not help my problem at all.  :unsure: Right now I am not sure what direction that I can go here. I figure that I will take and change the fluid and filter to see if that helps, and if not, then I suppose the next step is to rebuild it.

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Just to post a resolution to this. I got to take the car out today for a drive to check the transmission out. I am happy to report that everything is working perfectly! Everything was shifting right and there was no check engine light. I'm not sure why it decided to start working today, but I'm not complaining at all, lol!

I'm guessing that the main problem was that it was sitting for so long that the connection wasn't very solid at the transmission. Just to be safe, I will still do a fluid and filter change because I'm sure that it needs it.

Just goes to show that when a car sits for some time, stuff really does stop working.

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Glad to hear it's shifting properly! I was amazed recently to find that disconnecting and reconnecting relays on my Rx7 a lot of non functioning features came back. Sitting does weird things to a car.

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Just goes to show that when a car sits for some time, stuff really does stop working.

 

This applies not only to cars. Remember this when you get "old".

Many octogenarians/centenarians when asked what the secret is to living a long life, 9 times out of 10 of them will say "just keep moving!"

 

Just sitting around just don't get it.

 

John F.

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