95 Bronco Trans Question

[Pamm]

Sorry, I guess it wasn't clear:

"Vehicle Speed Sensor: This is the two-wire sensor in the differential housing"
Or more specifically, the two-wire sensor that mounts in the top of your rear end, like this here:


View attachment 29551


ATC = Automatic Transmission Controls, the multi-wire connector on side of transmission that @L\Bronco referenced after you asked.

Any luck yet?

I am just getting back on it again this week. Thank You for the pic. I will post answer when I try it

 

[Pamm]

That is actually a great idea. Help to hopefully narrow it down to electrical or mechanical.

Pass. Side reaf of trans, behind heat shield. The truck should still move in forward and reverse with this unplugged.

I will try this week and post, thanks

 

[Pamm]

Sorry, I guess it wasn't clear:

"Vehicle Speed Sensor: This is the two-wire sensor in the differential housing"
Or more specifically, the two-wire sensor that mounts in the top of your rear end, like this here:


View attachment 29551


ATC = Automatic Transmission Controls, the multi-wire connector on side of transmission that @L\Bronco referenced after you asked.

Any luck yet?

GREAT NEWS I HOPE..... I unplugged the vss and no change, it idles in r, l, n, but dies in D still. BUT then I started the motor first and then unplugged what i think is called the ATF the main transmission control connector looks like new switch on drivers side of trans with several wires and it did NOT die out while unplugged and put in drive. So now getting closer. So whats next???

 

[Tiha]

Interesting, but sounds like you made progress. Nice approach.

That switch is the neutral safety switch or transmission range sensor. I have never had any trouble with any of mine, but have heard they can go bad, some people find them full of water.

Good time to replace it maybe? I think they are fairly cheap. There is a process for properly setting them up. Maybe someone else can explain it. I just set it up so it starts in neutral and park like it is supposed to and that has always been good enough for me.

 

[Motech]

GREAT NEWS I HOPE..... I unplugged the vss and no change, it idles in r, l, n, but dies in D still. BUT then I started the motor first and then unplugged what i think is called the ATF the main transmission control connector looks like new switch on drivers side of trans with several wires and it did NOT die out while unplugged and put in drive. So now getting closer. So whats next???

Going back to my original post, you've eliminated half my input, yes!

FTR:
ATC is what I labeled the connector itself: The Automatic Transmission Controls connector.
ATF is Automatic Transmission Fluid, and is what I said can mess with the terminals inside that connector.

Two things commonly cause this symptom:

1. Vehicle Speed Sensor: This is the two-wire sensor in the differential housing. Sensor becomes very sensitive and will spike when driveshaft engages differential gears, sending a high speed signal to PCM causing shutdown.
2. ATF in the main transmission control connector: This will cause ATC circuits to short, often engaging the Torque Converter Lockup circuit causing a loaded stall in gear.

First try disconnecting VSS sensor at differential. If symptom goes away, there it is.
If no joy there, unplug ATC harness from transmission. If connector is dripping ATF, replace transmission controls sub harness (inside pan)

This probably means there is a short to ground at the TCC Solenoid circuit as I mentioned above, and as L\Bronco discussed when he supplied these excellent diagrams and connector views below.

Still sounds like the torque converter clutch is stuck on, (I'm sure that's what Tiha is getting at as well)
you could try unplugging the main connector at the transmission and see if it stops stalling.
It will be stuck in one gear with very high pressure, but it will rule out a few things. If it still stalls, the issue is likely in the valve body in the transmission. But if it doesn't stall unplugged, either the TCC control wire (pin 4 PPL\Yel) is shorted to ground, or the PCM is faulty.
Hope that helps.View attachment 29472 View attachment 29473

So when you unplugged that 12 pin, 9 wire connector, did ATF drool out of it? If so, get a can of brake cleaner and clean all that red fluid from both connectors, blow it out, reconnect and very quickly start and put in gear. If no stall, it's the fluid seeping through the transmission connector and shorting the wires inside, and it'll happen again real quick. You'll need a new solenoid pack.

From here, if no ATF bleeding out of connectors, it requires some simple electrical testing. Simple for trained technicians I should say, but foreign, enemy territory for most others.

I'll throw out a simple and effective test here while swiping L\Bronco's great connector view:

 

[Motech]

PS:

If neither of those tests produce light, turn key on and repeat first test. If it lights now, it's your PCM, and it will need to be replaced.

If that is the case, and you or a friend are confident enough to repair it with waterproof heat-shrink later, you can snip that purple w/ white stripe wire going into #4 terminal at least 3 inches up from connector (to make ample room for repair later) and drive it 'til you find your replacement PCM. Your converter clutch will not lock up when it should, and it may turn on the Check Engine light, but it should drive just fine, albeit with noticeably reduced fuel economy on longer highway drives.

(I totally expect some verbal spanking for this unorthodox, temporary band-aid, but if it truly is an internally-shorted TCC transistor inside your PCM, I stand behind it 100% to get you on the road)

 

[Pamm]

PS:

If neither of those tests produce light, turn key on and repeat first test. If it lights now, it's your PCM, and it will need to be replaced.

If that is the case, and you or a friend are confident enough to repair it with waterproof heat-shrink later, you can snip that purple w/ white stripe wire going into #4 terminal at least 3 inches up from connector (to make ample room for repair later) and drive it 'til you find your replacement PCM. Your converter clutch will not lock up when it should, and it may turn on the Check Engine light, but it should drive just fine, albeit with noticeably reduced fuel economy on longer highway drives.

(I totally expect some verbal spanking for this unorthodox, temporary band-aid, but if it truly is an internally-shorted TCC transistor inside your PCM, I stand behind it 100% to get you on the road)

Thank You, your pics and diagrams sure do help it make sense enough for me to test. Did I note that the trans man that said he replaced the trans put a new part on the side of the trans where that connector you speak of plugs in. If that switch is the neutral safety switch or transmission range sensor could it be out of adjustment? it does start ok in P or N. I will try to test the connector with a tester I know how to use after work if it don't rain, I am doing all this from just sliding under it on the ground. I usually get nasty on the front of my tee shirt due to close tight fit and things touching! A ramp would sure be nice.

 

[Pamm]

PS:

If neither of those tests produce light, turn key on and repeat first test. If it lights now, it's your PCM, and it will need to be replaced.

If that is the case, and you or a friend are confident enough to repair it with waterproof heat-shrink later, you can snip that purple w/ white stripe wire going into #4 terminal at least 3 inches up from connector (to make ample room for repair later) and drive it 'til you find your replacement PCM. Your converter clutch will not lock up when it should, and it may turn on the Check Engine light, but it should drive just fine, albeit with noticeably reduced fuel economy on longer highway drives.

(I totally expect some verbal spanking for this unorthodox, temporary band-aid, but if it truly is an internally-shorted TCC transistor inside your PCM, I stand behind it 100% to get you on the road)

(Noticeably reduced fuel economy on longer highway drives). It that because it cuts out overdrive or something?

 

[Motech]

A ramp would sure be nice.

Right? At least it's not a Mustang you have to crawl under.

Some answers in your quote:

Thank You, your pics and diagrams sure do help it make sense enough for me to test. Did I note that the trans man that said he replaced the trans put a new part on the side of the trans where that connector you speak of plugs in. If that switch is the neutral safety switch or transmission range sensor could it be out of adjustment? it does start ok in P or N. ​

​

No. Neutral Safety Switch/Range Selector switch is separate from ATC connector we're talking about. That is an "input" component that communicates information to the PCM, ie: it inputs gearshift selector position back to the PCM. If it was not adjusted right, your starter wouldn't crank in P or N properly.

The ATC connector we're playing with are "output" circuits. They connect components the PCM "outputs" commands to. In simpler terms, the solenoids are turned on and off with switches inside the PCM.​

​

I will try to test the connector with a tester I know how to use after work if it don't rain, I am doing all this from just sliding under it on the ground.​

​

Noticeably reduced fuel economy on longer highway drives). It that because it cuts out overdrive or something?​

​

Sort of, but not overdrive.
TCC = Torque Converter Clutch.
The torque converter is the direct connection between engine and transmission. It makes that connection through viscous hydraulic inertia instead of a mechanical clutch used on a stick shift.
Think of TCC as a mechanical bypass to that hydraulic connection. When PCM turns on TCC, the torque converter becomes mechanically locked to the engine, literally converting from auto to manual transmission. This removes the stress the engine needs to overcome that hydraulic inertia, the engine relaxes, and fuel economy improves dramatically.
"Clutch" is the key word in TCC, and "lockup" the key action the TCC Solenoid delivers.
The computer commands TCC on only at relaxed cruising speeds in third or fourth gear, relieving that stress and reducing engine RPM, which improves fuel economy.
From that context, that it converts an automatic to a stick shift, consider if it stayed locked on when you come to a stop. It would be just like rolling to a stop in a stick shift truck without pushing the clutch in. The engine would stall, right?
Your short circuit is substituting a full-time, constant command to the TCC lockup solenoid. When placed in gear, it's like dumping the clutch pedal in gear, at a stop with brake on. Instant stall.
With our tests, we're trying to figure out why your clutch isn't connected to the pedal anymore.

 

[Pamm]

Going back to my original post, you've eliminated half my input, yes!

FTR:
ATC is what I labeled the connector itself: The Automatic Transmission Controls connector.
ATF is Automatic Transmission Fluid, and is what I said can mess with the terminals inside that connector.



This probably means there is a short to ground at the TCC Solenoid circuit as I mentioned above, and as L\Bronco discussed when he supplied these excellent diagrams and connector views below.




So when you unplugged that 12 pin, 9 wire connector, did ATF drool out of it? If so, get a can of brake cleaner and clean all that red fluid from both connectors, blow it out, reconnect and very quickly start and put in gear. If no stall, it's the fluid seeping through the transmission connector and shorting the wires inside, and it'll happen again real quick. You'll need a new solenoid pack.

From here, if no ATF bleeding out of connectors, it requires some simple electrical testing. Simple for trained technicians I should say, but foreign, enemy territory for most others.

I'll throw out a simple and effective test here while swiping L\Bronco's great connector view:

I got under it with my tester but when I unplugged it. It did not match your Pic so I stopped. Here is my plug.

View attachment 29863

 

[Pamm]

 

[Pamm]

My plug has less holes in it , can i cut a wire on it?

 

[Tiha]

Wait, is that the neutral safety switch plug?

The diagram is for the solenoid pack plug.

 

[Motech]

My plug has less holes in it , can i cut a wire on it?

Tiha is correct. That looks like the Transmission Range Sensor, which incorporates the Neutral Safety and Backup light switches too. It's on the LH (driver) side of trans and mounts on the shifter shaft.

The connector in the diagrams above is for the solenoid pack on the RH (passenger) side of transmission.

 

[Pamm]

Oh Ok the plug behind the metal plate? Ill try again looking under plate on passenegr side of trans , thanks again

 

[Tiha]

Oh Ok the plug behind the metal plate? Ill try again looking under plate on passenegr side of trans , thanks again

Yes it probably had a heat shield over it.

 

[Motech]

Here's a photo of the shield protecting the plug. Usually 8mm (5/16") heads on the shield bolts.





Here's a shot of connector plugged in with shield removed:






Here's what that connection looks like on the transmission when ATF is seeping through





Here is what old harness connector wires typically look like after decades of service