1993 80 Series A442F Stuck in Overdrive When in "D" (2 Viewers)

[Fzj80 1997]

EDIT: The circuit boards for the TCM’s on both the original and the one I swapped in were messed up in different areas. My buddy with a 93 came over and we swapped his TCM in and it fixed my issues.


I bought a 93 FZJ80 equipped with a A442F transmission the other week. The truck had been giving the previous owner issues with the transmission and he had replaced all of the solenoids twice already with Izusu units. The previous owner also tried cleaning out the transmission connector near the starter. The connector broke and he repaired all of the wires by soldering and heat shrinking them back together. I saw this and immediately thought this was the issue, but after going through the wires and putting in new connectors, things are unchanged. When I received the truck, it would immediately die when putting it in drive. I swapped the transmission computer with another truck and that seemed to have fixed that issue, but the "stuck in overdrive" issue persists. swapped the ECU out with another 94 model and have driven the truck 100 miles. Check engine light has not come back on. According to the carfax, the owner prior to the guy I bought it from took the truck to midas to have its rear main seal replaced.

What the truck is doing:

When the gear selector is in "D", the transmission is stuck in overdrive. It drives fine, but obviously very low on power starting off. If you put the selector in "L" first gear is engaged and the truck can start off fine and you can move up to third by manually shifting through "L", "2", and "D" . On the highway stomping on the accelerator does not make the transmission downshift and when pressing the "overdrive off" button, the light illuminates, but nothing happens. The truck does NOT get a flashing OD light.

I had read a few threads on mud and a few people who have had the exact same issue resolved by cleaning out the transmission electrical connector near the starter, but as mentioned, I have had no such luck.

What I have done:
-Replaced the ECU with one out of a 94
-Replaced the transmission computer
-Rewired the connector for the transmission
-Replaced the neutral safety switch
-Made sure the fluid level is correct

It definitely seems the issue I am having is electrical related. I do not have an A442F transmission FSM. Any input is greatly appreciated.

 

[Mark W]

Check the ground cable at the back of the intake manifold.

Mark...

 

[use2bn83]

You have no coms between the TCM/ECU.

Take a look over this. I’d start with verifying that source power exists at the TCU and verify those circuits. After that start figuring out why the ES circuits are communicating with the ECU

 

[PIP]

When the shift solenoids fail it can act like that. That's the first thing I replace.

 

[Fzj80 1997]

Check the ground cable at the back of the intake manifold.

Mark...

I took a quick look at it earlier from the top. The ground cable is definitely bolted to back of the intake manifold. I'll take a closer look at it tomorrow.

You have no coms between the TCM/ECU.

Take a look over this. I’d start with verifying that source power exists at the TCU and verify those circuits. After that start figuring out why the ES circuits are communicating with the ECU

Funny thing is, I just drove it for 25 miles and the check engine light has not come on since installing a different ECU. Shifting symptoms are still messed up in the exact same way.

When the shift solenoids fail it can act like that. That's the first thing I replace.

The previous owner said they did it twice with Isuzu solenoids. It's possible the incorrect parts were installed or the solenoids were installed incorrectly. This will probably be the next step before dropping the transmission to check all the wiring.

 

[PIP]

I took a quick look at it earlier from the top. The ground cable is definitely bolted to back of the intake manifold. I'll take a closer look at it tomorrow.


Funny thing is, I just drove it for 25 miles and the check engine light has not come on since installing a different ECU. Shifting symptoms are still messed up in the exact same way.


The previous owner said they did it twice with Isuzu solenoids. It's possible the incorrect parts were installed or the solenoids were installed incorrectly. This will probably be the next step before dropping the transmission to check all the wiring.

442 solenoids seem fragile. Some cruisers go through them again and again. If it has a track record for eating shift solenoids that'd be the first thing I check.

 

[Fzj80 1997]

442 solenoids seem fragile. Some cruisers go through them again and again. If it has a track record for eating shift solenoids that'd be the first thing I check.

I don't think the truck has been driven more than 50 miles since having them replaced for the second time.

 

[PIP]

I don't think the truck has been driven more than 50 miles since having them replaced for the second time.

Did it sit unused?

 

[Fzj80 1997]

Did it sit unused?

I think it may have sat for a few months, but it's been driven pretty regularly.

 

[PIP]

I think it may have sat for a few months, but it's been driven pretty regularly.

I've noticed a pattern where some 442 solenoids go out within a week of starting to drive them after sitting. But that's been more than a few months in all cases I've seen.

 

[Pericles]

Check your TPS. Inexpensive check and it can cause those codes and transmission issues because it tells the ECU whether the engine is in an idle state. There's a post somewhere on here about it.

 

[ThreeEyedBandit]

Dumb question, does the D light illuminate in drive?

 

[Fzj80 1997]

Dumb question, does the D light illuminate in drive?

It does not. The other lights were also not consistently lighting up so I replaced the neutral safety switch and now all the lights light up consistently besides the D light. I assume the bulb is just burnt out. The only thing that has changed since swapping out the NSS is the lights now light up consistently.

 

[ThreeEyedBandit]

It does not. The other lights were also not consistently lighting up so I replaced the neutral safety switch and now all the lights light up consistently besides the D light. I assume the bulb is just burnt out. The only thing that has changed since swapping out the NSS is the lights now light up consistently.

Forgot that the TCU doesn't get a 'D' signal, sorry for the pointless test.

While in 'D' see if you have power to the S1 solenoid, start at the TCU since it is the easiest.

Also check resistance at the TCU for S1 and S2 to ground with the connector unplugged at the TCU

Being stuck in O/D(can feel like 3rd) while in D indicates either S1 and S2 died, TCU doesn't know that it is in 'D', or wiring problem from the TCU to the solenoids. This is irrelevant of the O/D switch position.

Here is some reading for you.

 

[ThreeEyedBandit]

Also, can you confirm that it is in

1st in L
2nd(not third) in 2
3rd(not O/D) in D?

Being stuck in a tall gear in D usually indicates neither solenoid or wiring is correct, and the failsafe for that is being in OD in D.

Check page AT-20 from the troubleshooting above.

 

[Fzj80 1997]

I will look into everything that has been mentioned in this thread over the weekend and report back. Thanks for all the info

 

[Fzj80 1997]

Also, can you confirm that it is in

1st in L
2nd(not third) in 2
3rd(not O/D) in D?

Being stuck in a tall gear in D usually indicates neither solenoid or wiring is correct, and the failsafe for that is being in OD in D.

Check page AT-20 from the troubleshooting above.

I think that you’re correct with it being in 4th/OD when in “D”. I have edited the title and original post to reflect this

 

[Fzj80 1997]

Messed around with a voltmeter following the “Trouble No.1 No shifting” flow chart in the FSM pg. AT-31 and am not getting any change in voltage regarding the throttle position sensor signal when opening and closing the throttle. Just a steady 7.5V. Went to step 2 in the flow chart and tested terminal BK for the TCM and the voltages for the brake switch checked out so I guess my options now are either messed up Tt data link wire or the TPS is messed up. I tested the TPS via the FSM on pg. AT-39, and was able to get the proper readings according to the fsm

 

[Fzj80 1997]

Forgot that the TCU doesn't get a 'D' signal, sorry for the pointless test.

While in 'D' see if you have power to the S1 solenoid, start at the TCU since it is the easiest.
View attachment 3542472
Also check resistance at the TCU for S1 and S2 to ground with the connector unplugged at the TCU

Being stuck in O/D(can feel like 3rd) while in D indicates either S1 and S2 died, TCU doesn't know that it is in 'D', or wiring problem from the TCU to the solenoids. This is irrelevant of the O/D switch position.

Here is some reading for you.

Tested S1 and there is no power to when in neutral or drive With the ignition turned on.

When I’m probing this stuff should the connectors be connected to the TCU and backprobed, or is it ok to have the connectors disconnected and tested from the front? I have been doing the latter.

 

[Fzj80 1997]

When I was messing around with the truck yesterday I started it up without any of the connectors plugged in for the tcm and it acted just like it would have with the replacement tcm I robbed from a 94 that has been sitting for almost a decade. I then plugged the original one in and it died almost immediately when putting it into drive and letting go of the brake just like it had before I swapped out the TCM originally. Could it be that the replacement I put in was completely dead and that the original TCM is working fine and is just going off a faulty reading from a sensor and causing the truck to die ?

Update on this: I plugged in the smaller TCM connector into the original TCM and the truck did not die and it started out in first gear, but would not upshift. I then tried to plug in the larger connector into the TCM and as soon as contact was made, the truck died. I then tried it the other way around with the large connector plugged in and the smaller one unplugged. The truck did not die, but it started out like it did with the replacement TCM or with both plugs unplugged. As soon as I plugged in the smaller connector, the truck died. There are also a lot of clicking noises when the original TCM is plugged in and the truck is running in park from what I can assume are the solenoids. Reverse is also really messy with it idling rough and going into neutral and dropping into gear with the original TCM

My buddy with a 93 is coming over tonight. I'm going to swap the TCM's and see how the truck behaves