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Discussion Starter #1
Guys you have to be patient w me on this !! I previously posted about my TC locking up intermittently. I was given several ideas on what to check but honestly I'm not a very good trouble shooter. After driving it for a few weeks now this is what I have discovered. When I first crank it and leave in the morning or after it has set for a long time the TC will lock up every time. However when I slow and it unlocks or I come to a stop it won't lock in again. It's like after it warms up it quits working. Is this indicative of a bad solenoid? I think I could change that out if that's the problem. I just don't know how to trouble shoot electrical problems. Ohmns and stuff. (The code was a PO740 TC solenoid open circuit).
 

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Why are you not going after the shop that supposedly rebuilt it?

The solenoid is bad. Make him replace it!
 

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Discussion Starter #3
Colonelhogan I can take it back to him. I took him the tranny because he had to put a bell housing on it. He said the bell housing was part of the pump. I just told him to do whatever he thought the tranny needed. Replace what it needed and leave what was good. He ended up doing the pump and a new T C. He only charged me $120. He said the bands or clutches whatever they are called looked good. So maybe he thought he was saving me some money by not doing the solenoid. I have talked to him and he said he would replace the solenoid but he wasnt sure that was the problem.
I was told in my previous post that he could be a short in the wiring,but the way it's consistently doing the same thing I think eliminates that.
 

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Running wires to a bulb in your cab, as per Aqua's post in your last thread, is easy to do. If you wire this to the TCC relay by your battery, you will see whether the relay is working or not, and sending it's signal. This will confirm the relay portion of this circuit, as well as the ECU. If the light comes on at the appropriate speed, it's easy to see. If so, the next step is to test the white wire going from the relay to the solenoid for continuity. If this tests ok, then you need to test the solenoid with 12v to it, to see if it's working or not - you need to drop the pan for that. No way around testing the portions of this circuit to see where your problem lies.
And advise which car you're talking about. 96 or 98?? In reading through the info for the solenoid, at some point in 1996 they removed the pressure switch which would activate the solenoid.
 

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The TSB has the pressure switch being kicked to the curb anyway.

So when you replace the solenoid, you basically re-wire the circuit. If you can't use a mutimeter (or don't have the desire to take the 2 minutes to figure it out) then just don't bother even trying to replace the solenoid. Just take it somewhere. If you actually want help from this community, you'll need to be willing to learn. This is a DIY bunch.
 

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Discussion Starter #6
98 model 3spd Bex. I think I could run a wire from the relay. Ill look under the hood and see if I can see which relay it is. I understand the principle of it lighting up at 47 mph. I just need the light hooked to the post on the relay that gets voltage at that speed.
Colonel it's not that I'm not willing to learn. It's understanding what I'm doing that's the problem lol. I have a volt meter and I know how to ohm something. Mine beeps if it has continuity.
Ill try the relay first. Ill look at them by my battery. Thanks.
 

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If you look in the engine compartment, just next to your battery, on the passenger side fender, is the fusible link box, which is 4 large fuses that run the car. The relay is there, and I believe 4 wires come out of it - white/red, blue/black, white/yellow and white. The white wire will be energized (light up your bulb) when the switch in the relay closes. You run your light from this wire, (by backprobing into the pin where this wire is attached, and a ground.
And I imagine that it's easier/safer to run the light into the cab, rather than try to install it on the wipers somewhere, as you have to go 47 mph for the light to go on - your bulb will be smashing into the windshield or similar.
 

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Discussion Starter #8
If you look in the engine compartment, just next to your battery, on the passenger side fender, is the fusible link box, which is 4 large fuses that run the car. The relay is there, and I believe 4 wires come out of it - white/red, blue/black, white/yellow and white. The white wire will be energized (light up your bulb) when the switch in the relay closes. You run your light from this wire, (by backprobing into the pin where this wire is attached, and a ground.
And I imagine that it's easier/safer to run the light into the cab, rather than try to install it on the wipers somewhere, as you have to go 47 mph for the light to go on - your bulb will be smashing into the windshield or similar.
Ok Bex found them. My colors don't match yours. 2 of them have heavy gauge wires and the other two have smaller wires. Here's a pic of them.
 

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Discussion Starter #9
I just spoke to a guy at the chevy dealership and he said that's those four relays were for
Fuel injection
ECM
Headlights
Lights
He did say the part number for the TC relay was #30019347.
 

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Discussion Starter #10
Is there no way you can trace the wire from the transmission to the right relay. I have a 98 FSM in front of me...the wire colors are blu/blk from main relay...wht/yel to the PCM. Now the wire that enerjises the TCC is white that's the one you want to put your test light on. There's one more wire on the relay blk/white that should be hot all the time.
Big Ed I may have found it. One of them has a blue/black,white,white/yellow,black/white. In a small gauge wire. That's probably it.
 

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Discussion Starter #11
Thank you Ed. I really don think it's a short because it so consistent. But I'll see thanks again.
 

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If you want to properly diagnose the transmission, you need to do the following:

1.) Crawl under the car and check to make sure the ground strap from tranny to the bean is intact, tight, and not corroded. If it is, move on. If it is missing, replace it. If it is loose or corroded, clean up and re-tighten.

2.) Probe from the wire that goes to the solenoid from the relay to a ground point (black lead on ground, red lead jammed into the back of the relay harness -- it should show approximately 25 ohms if the solenoid coils are at least somewhat intact

3.) If the 25 ohms is seen, do the light test. If the solenoid shows an open circuit, replace the solenoid. If the light test shows lockup, the solenoid is probably intermittently bad and/or the pressure switch needs to be removed.

This is all assuming that the fluid is new, the correct spec and the transmission is otherwise functioning properly.
 

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I just spoke to a guy at the chevy dealership and he said that's those four relays were for
Fuel injection
ECM
Headlights
Lights
He did say the part number for the TC relay was #30019347.
I don't get it, unless, this is just another example of why you NEVER talk to a chevy dealer about these cars. They don't have a clue. We don't have headlight relays....????

Anyway, glad you finally found the relay. Normally the procedure is to test the relay, before heading on to the solenoid. The relay should close at 47mph - your test light will indicate whether it does or not. If the relay passes, then test for ohms at the solenoid connector - as Colonel say, about 20 ohms is ok. There is also a test for testing the wiring from the relay to the solenoid, as well, as this can also be part of the problem. No sense dropping the pan and replacing the solenoid before you confirm that this is the problem....which it may very well be, anyway....;)

Edit: And despite impatience, I do think it is far safer to run that test light into your passenger compartment - just a bit more wire (run it through the window, you are not trying for a permanent install here. I cannot envision a test light outside the cab, when you have to drive the car at a speed of 47 miles per hour, for the test to work - now, that would have to be a 'permanent' install! ;)
 

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Discussion Starter #14
Ok guys thanks so much. It will be the square plug on the drivers side of the tranny right?
 

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What plug? Anyway, I think that the connectors at the tranny are all on the passenger (right) side.
 

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Discussion Starter #16
Bex it has a square plug on the driver side of the tranny right above the pan.
 

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Discussion Starter #17
Ok guys. The light comes on every time I hit 47. I can press my brake and light goes off like its supposed to. Solenoid bad? I don't think it's a continuity issued because it locks in every time when I first drive it. I drove it awhile ago after its been sitting about 8 hrs and it locked in. I touched my brake about five times and it locked/ unlocked every time. However when I came to my first complete stop it never locked in again even though the light came on.
 

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bad solenoid. The pressure switch was not included after 1995, IIRC. Check when you drop the pan to replace the solenoid.
 

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You may want to check the wiring from the relay to the solenoid first for continuity.
 
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