No overdrive

[rodb]

Can someone please direct me to the correct pcm printout for my 1991 4.0, I only find the 202 print but don't think that is the right one. Thanks

 

[MrShorty]

For these circuits, I found that even the wiring diagrams in Chilton's are adequate for identifying the pinouts. If you register with Autozone's (autozone.com) website, they offer free "vehicle repair guides" that are essentially an electronic version of the Chilton's DIY manuals, including wiring diagrams.

 

[FR-425]

Can someone please direct me to the correct pcm printout for my 1991 4.0, I only find the 202 print but don't think that is the right one. Thanks

http://www.auto-diagnostics.info/ford_eec_iv

 

[rodb]

http://www.auto-diagnostics.info/ford_eec_iv

I don't see the 3-4 shift solenoid circuit pin there.

 

[rodb]

I also registered at Auto Zone, they do not have the pinout either.

 

[MrShorty]

I also registered at Auto Zone, they do not have the pinout either.

It's still there for me. Login -> make sure your Explorer is chosen as "my vehicle" -> Click "Repair Help -> Click "Vehicle repair guides" -> Click "Chassis Electrical" -> Click "Wiring diagrams" in the left menu -> Find the "engine wiring" diagram for your year/engine (It looks like Fig 7 is the '91 Explorer engine wiring diagram).

 

[FR-425]

found this for 1994 should be the same as 91??

Looks like pin 51 Orange/Yellow for 3/4 solinoid

http://www.explorerforum.com/forums/showthread.php?t=232576&page=2

 

[rodb]

Thank you MrShorty and FR-425, now we are making progress

 

[rodb]

found this for 1994 should be the same as 91??

Looks like pin 51 Orange/Yellow for 3/4 solinoid

http://www.explorerforum.com/forums/showthread.php?t=232576&page=2

Mine is not the same, looks like the '94 was different.

 

[rodb]

On mine the orange/yellow is pin 52, I probed the wire and at idle up to about 45mph it read 14 volts, above 45mph it drops to around .42 volts, is this normal ?

 

[FR-425]

Any reason you haven't tested the 3-4 solenoid yet?

 

[rodb]

It was suggested to make sure the shift solenoid was being energized first, which the results I previously posted. So I need to drop the pan next ?

 

[MrShorty]

On mine the orange/yellow is pin 52, I probed the wire and at idle up to about 45mph it read 14 volts, above 45mph it drops to around .42 volts, is this normal ?

Yes, that sounds normal. If you study the circuit, you can see that the 3/4 solenoid is continuously powered from the EEC relay, and the PCM acts as a ground side switch to complete the circuit when it wants the transmission to upshift to 4th gear.

Did the transmission upshift when the voltage dropped? If the transmission upshifted, then the 3-4 shift is working correctly. If the transmission did not upshift, then something hydraulic/mechanical inside of the transmission is preventing the shift from responding.

 

[rodb]

The overdrive does not work, so have I eliminated the PCM as the problem? If so do I need to replace the solenoid in the trans?

I dropped the pan, everything looked ok, no metal shavings, now how do I check the 3/4 shift solenoid ?

 

[FR-425]

The overdrive does not work, so have I eliminated the PCM as the problem? If so do I need to replace the solenoid in the trans?

I dropped the pan, everything looked ok, no metal shavings, now how do I check the 3/4 shift solenoid ?

Test resistance. 26-40 ohms.

There are 3 wires going to the tranny to get the resistance..

Purple/Yellow (Tcc), Orange/Yellow (4th gear) and Red (12v)

Resistance between the Purple/Yellow wire and the red wire.. And the same for the Orange/Yellow to red wire...

You can actually do this in the engine bay.. Find the connector (drivers side) that has those 3 wires.. disconnect the connector then check the resistance between the wires...

12v on the Red at all times when key is on. The striped wires are the grounds and go to the PCM. PCM makes the ground on demand for shift.

If all this checks out manually ground the solenoid, you will here it click, if no click it is stuck. Pull it out and clean it. Once you have it out you can bench test it off the battery or a battery charger.

Still no click? Replace solenoid.

 

[rodb]

Looks like that plug is attached to fender well and is a 5 wire black plug. The two additional colors are green/yellow and blue/purple. The red wire is 12v with key on. With key off I probed the inside off plug (female side). Both purple/yellow and orange/yellow read 103 ohms when connected to red wire.

You said it should read 26-40 ohms, am I doing something wrong?

The shift solenoid itself read 27 ohms.

How do I remove the 3/4 solenoid ? Removed the two bolts but there is also tabs that hold it in on both sides.

 

[Gadget X]

You'll have to drop the valve body to remove the solenoid. Make sure you get new gaskets before reassembly, though. Good luck with it!

 

[rodb]

Still waiting on response from my previous post, not sure if the solenoid is bad according to the readings I have taken so far.

 

[Gadget X]

Gotcha. Yeah, I was having similar issues with mine. Had no OD and couldn't figure out why. Replaced the solenoids, even though everything tested "good", but still no OD on mine. So I just gutted the whole thing and changed it over to a manual! Good luck with it, hopefully yours will be a "simple" fix!

 

[rodb]

Thanks for all that have helped, but can someone respond back to me regarding my readings in post #36 .