Evening, I have a 1997 A25C articulating truck that has decided to stop shifting. I replaced the key barrel a month ago due to it having some issues with not going into gear. Didn’t use it much after that but it seemed to solve the issue. Was using it the other day, shifting fine working along. Put it in neutral got out. Got back in and then nothing. Doesn’t even try to go into gear. The back up beeper comes on when you put it in reverse I hear the relays clicking when I put it in reverse or drive. I have to wait until Tues to get a coupler to check the pressures I don’t have the type that on this. I’ve checked the alternator voltage that is 26 volts. Fluid looks good, I took a sample out of the bottom today it’s a little dark but no metal. I also tested the shifter that tested like it should. I’m thinking about draining the oil and checking the filter tomorrow just see if there is any metal in it.
I checked for power at the ecu plug had 24.2 volts on the 4 or 5 pins I don’t have a pin out for the plug so I’m not sure what numbers they were on
Drained the oil this morn not much in the filter little bit in the bottom of the cover, but doesn’t seem like anything out of the ordinary.
Dropped the pan, oil was a little dirty, but no metal or anything in it. Did find a bolt standing straight up in the pan when I dropped it. It’s the empty hole on the right. Someone has been in here before. Some different bolts in the pan and the valve body.
There is a cannon plug style connector that you have to pull up the floorboard in the cab to get at. It is down on the right hand side of the transmission. May want to check that as being tight and no wiring damage. The fact that you had a bolt fall out of the trans is somewhat alarming.....
I’m going to pull that plug tomorrow. I may get drop the valve body just to check whatever is going under there. I’m in this far now. I thought perhaps the bolt hole was stripped but it’s not. The bolt was standing upright in the pan just under hole. I checked the other ones they were all tight.are there any steel balls in the vale body like an automatic transmission in a truck or car?
Thanks for the information Slatco
Anyone have a pin out for the ecu plug?
This might seem a dumb question, but how do I know which side is the #1? Also thank you hou for that info
I didn’t see any numbers on the plug
Beautiful!!!!!! Thank you very much!!!
So, I pulled the harness plug off the transmission and have continuation all the wires except T on the round plug to #43 on the computer plug.
continuity
Never mind that one is good too.
Not really sure what to suggest you to do next. If you end up needing a trans it was cheaper for me to get a exchange one out of the USA even with shipping and currency conversion....
I found the testing procedure you posted for someone else, I’m going to run that today, before I put the pan back on so I can test the pressures. I did notice the plug from the machine to the transmission was a bit loose. It also looked to be kinda worn at the base. I’ll post a picture in a bit.
The one with the voltages and ohms for the solenoids.
Also, some people have mentioned in a couple of other posts about a “get you home “ ecu. What do they mean by that?
Here is the plug for the transmission
Not sure is that’s how those top holes are supposed to look or not.
I ohmed the output speed sensor and the turbine sensor and get 1.6 or so. Does seem odd they would both be bad? Or more likely cut wires?
I see where the output sensor is in this diagram but it doesn’t show the location of the turbine input speed sensor.
I ohmed the solenoids they were all in spec, ohmed the input sensor and the out put sensor at the computer plug almost zero resistance on both. I pulled the output sensor and ohmed it at the terminals to rule out the wiring in the transmission. It is bad only had 1.8 ohms. Where is the turbine input speed sensor?
Sorry about the extra posts
I found the input speed sensor thanks to SlatcoAu pictures of his valve body. I took it out just to check the ohms on it 1.05 seems they are both bad. Or they don’t meet the spec given in the testing procedure
Hey there, sorry been out in the bush. Hopefully the speed sensors worked. Do you have the contronic display?
No worries Slatco, no they didn’t work, I bought 2 new ones and figured I’d check them with the meter ended up getting a bunch of weird readings on the new ones. Turned out the meter was bad. I went and bought a Fluke checked them got the right reading on old ones and the new ones.
Don’t have the contronic screen in it. I broke down and am having Strongco out this week. I put the pan back on yesterday so could check the pressures but the hydraulic place sold me the wrong tema coupler. So I’ll have to pick up another Monday hopefully.
It had a contronic in it, the ecu is there for it and the wiring but the screen is not
I did the electrical tests you posted on another post, on test #5 from pin33-37 SW13 on (which I assume is the one on the dash) I have no voltage but should have 24v Test#7b pin33-37 SW25 on (which I assume is the pedal on the floor) I get 24v but should have 0v Test #27 pin 24-18 load sensor I’m getting 5.53 ohms on should have 50-2000
I tested the voltage to the load sensor that seems to be right about where it should be it says 5v I have 4.8v my plug is different than the one I found the test procedure for. But it seems to be ohming to high. Would a bad load sensor cause it not to shift?
I found some info, I had sw13 and sw25 backwards, I retested and that stuff all checks out. Everything but the load sensor. It is ohming too high and when do the test to see if the resistance changes I get nothing.
No change in resistance I should have said.
Lol I feel your pain. Try changing that load sensor? The get home fix is bypassing the one ECU and plugging into the other one.
Thank you Slatco, I appreciate site that. I’ve ordered a new load sensor. Bender sent me the trouble shooting chart that can be one of the causes to make it not shift. Everything electrical checks out good minus the load sensor.
Thanks again for your help. This site is a real benefit to people like myself.
Well, put the load sensor on, didn’t fix it. But the old one was bad. I tested them beside each other. I plugged in the get you home ECU and it worked right away. So I’m on the hunt for a TCU now. Oddly enough the engine ECU went in my 14 ton Volvo this season too.
Fantastic! TCU is a hell of a lot cheaper than a transmission!
Agreed! I’m just glad I know what it is.
Coldcreek, damn I knew that name was from somewhere, I just replied to your email to our company this morning about this ecu, as I am sure you are now aware the A25C ECU is rare old thing, but I've sent you a second email as I received a bit of new information.
Than you very much!
Thanks sfrs4 I appreciate it
hey guys, ive been using this thread is a bible as i think i have a very similar issue. ive done the resistance checks on everything and all looks good except my load sensor which is also very high, lke 700k. i have no data coming up on my display as well. im thinking the load sensor is no good but that wouldnt cause the display to show no data right? that would be the ecu?
I replaced the load sensor on mine before I realized I had the “get you home computer” do you have that in your unit?
The load sensor I had ohmed not in spec but so did the brand new one I replaced it with. Mine turned out to be the ECU which I sent out to be repaired, I just got word back last week it’s done.
I do have the get you home ecu, I’ve plugged it in and it seemed to work and all was good but I plugged it back in to the other just out of curiousity and it was working with that one as well. So figured it was a bad connection, tried to pull it outside and it stopped working again with both ecu’s. which lead me down the path of checking everything else. I think It was slatco that posted a transmission functions and checking guide on a different post that I’ve been using, everything checks out except the load sensor which was open.
What was doing before you had the issue?
Intermittent gear engagement?
When you first started it and built the air up the first time you put it in gear it would go but if you tried to put it back in neutral and select a gear it wouldn’t go. If you selected reverse it would put on the back up lights and beeper but not actually engage a gear. Now it wont even do that.
You have power in the places you need it?
Even if the load sensor were bad you should still get the reverse beeper and lights to come on.
So I’ve had a little development, was checking some voltages and what not, found ecu fuse blown, mustve blown recently. Fuse s24. I’ve got data on my display now and shifting ok, however I just pulled it outside and was in reverse and it just slowly felt like it disengaged then couldn’t shift again. I pulled that s24 fuse and put it back in and it jumped back into neutral and shifting fine. Back to square one
Trying to find relay #30 but it’s not in either fuse compartment. Need to do some more digging
Well, you are making progress. Have you tried wiggling the key in the key switch when it’s not shifting?
This is the most overlooked thing with the A25C when you have transmission problems, the ignition switch is involved in the operation of the transmission, and aftermarket switches just don't cut the mustard with them. For the money a genuine one costs, I'd replace that before doing anything else.
I have tried wiggling it, I will dive into that a bit more today. I found R30 (thank you slatco) and resistance on it is 217 ohms, so I’ll replace it as well. Would the ignition cause it to just sort of fall out of gear?
Well, I’ve gotten it narrowed down to something with the reverse circuit. I can reverse for about 30 seconds before it just disengages. Relay #30 gets pretty warm, if I put it in neutral and I pull the relay or the ecu fuse S24 then it pop back in it goes into neutral and away I go until the relay heats back up then I’m back to popping the fuse. Does anyone have any circuit diagrams for the reverse circuit?
Seemed to have things narrowed down. Everything works as it should besides when I reverse. Only lets me reverse for about 10-20 secs before it seems to disengage the gear, I have to pull ecu fuse (s24) or key relay (r30) to reset it and try again. I think I will order ignition switch and see if that is the culprit. I find it odd that everything seems to work fine driving forward though.
Received the new Volvo ignition switch this morning. I’ve come to learn it has a CAT or a generic switch in it now so there is no harness for the new switch. Does anyone have a wiring diagram for a Volvo switch?
try these fella.
I got the transmission controller back. Just finished putting it back in it’s shifting between drive and reverse. She’s got a flat currently so I can’t run it, once I get that sorted I’ll let you know how it worked out. Had the controller repaired at unitech electronics in Ontario.
How much did the repair of the TCU cost?
The ECU repair was 1850 or something like that.
Plus 50 ish for shipping