Steve Collison

Yesterday, I wrote about how you can manually test your A604 transmission by engaging the solenoids directly – bypassing the transmission’s control module and possibly faulty wiring issues.

It is important to note that if your solenoid pack is bad, this test will fail. Here’s how my testing went:

Notes: I jacked up the van and put the front end on jack stands. I stuck bricks either side of the rear wheels and pushed on the emergency brake. I actually cut the solenoid connector end of the harness and wired my wires directly through that. I did resistance tests between wires 4-5, 4-6, 4-7 and 4-8 to make sure that I had connectivity with the solenoid pack.

I started the engine, and put the van into drive. It engaged nice and quickly, so I gave the engine a rev. My van shook like crazy. When looking beneath the van, I noticed I have a slightly bent drive shaft! But that’s a problem for another time, when I have the transmission repaired…

With the transmission now running, I started my test. First I engaged solenoids 7 and 8 – this should engage the clutch for the 1st gear. It didn’t. I had 1st gear before I started this test, so I was a little confused.

(I left it for a little at this point, and went and played with my old solenoid pack. I dismantled it and actually removed the four individual solenoids. I found that the solenoids made no noise (or basically did nothing) when I applied voltage to them directly. Interesting for sure.)

I went back to the vehicle and decided that I’d try to engage 4th gear. I engaged solenoids 5 and 6 as documented in the previous entry. The strangest thing happened, the vehicle started to slip and lost all speed. When I released the solenoids, it jumped back into 2nd gear.

Testing of these solenoids individually showed than solenoid 5 directly caused this and solenoid 6 actually did nothing. At this point, I’m starting to wonder whether THIS solenoid pack is actually any good. I bought it for $60 on eBay from a dealer that supposedly refurbishes and tests them.

I took the solenoid pack off the vehicle, and dismantled it. Solenoid 5 engages. Solenoid 6 and 7 make noise when you shake them up and down, but they don’t engage. Solenoid 8 is stuck and makes no noise when you shake it up and down.

I conclude from this that I have a bad ‘guaranteed working’ solenoid pack.

Friday will be the next day I can actually do anything. I’m going to go to the scrap yard and find myself another solenoid pack to test.

To note, when you don’t change your fluid it starts to gum up and this can cause solenoids to get plugged up. Therefore, this places even more importance on changing your fluid!

I have a hunch that the transmission is mechanically okay, given my lack of working solenoid packs. But only time and testing will tell. I am glad to say thought that my method of testing as shown in the previous entry officially works!

My 1996 Plymouth Voyager developed a problem many months ago where it wouldn’t engage 3rd gear (or 4th, from what I could tell). Instead the transmission would fly into neutral, and when the revs & speedometer came back down, the transmission would engage 2nd gear indefinitely – more commonly known as limp mode. Turning the engine off and on would bring it back to life, only to go through the same process and ultimately end up in limp mode again.

Since then I’ve been fiddling with the van to try to figure out what is wrong. Dodge vans are notorious for electrical problems. Frankly, I’m tired of wasting my time, I need to work out if the issue is mechanical or electrical, to do this I need to be able to engage the solenoids manually which in turn will allow me to change gears manually.

This will involve creating a custom wiring harness for the solenoid pack. This bypasses the TCM completely.

Disclaimer: This is by no means a permanent fix. I DO NOT recommend driving the van this way, as the clutch engagement will be very rough. With the van on jack stands, there will be barely any load on the clutches. This is ONLY for testing purposes.

Additional note: This test will FAIL if the solenoid pack does not work properly. If the test does fail, I recommend testing the solenoid pack outside of the vehicle. Check that you can hear or feel each solenoid engage.

What I intend to do is this:

1. Wire a 12V feed to the solenoid pack on pin 4.
2. Connect switches to pins 5, 6, 7 and 8.
3. Connect the other end of all switches to ground.

With the van on jack stands, the engine running and the transmission in drive, I will test the solenoid as follows:

1. To begin with, no switches will be engaged. The transmission will be in 2nd gear.
2. Pressing switches 7 & 8 should engage 1st gear.
3. Pressing switches 6 & 8 should engage 3rd gear.
4. Pressing switches 5 & 6 should engage 4th gear.

If all gears engage successfully, I will assume the problem is electrical. Otherwise, my transmission is probably due a rebuild. (assuming of course that the solenoid pack is good)

And so we do begin to celebrate the birth of a new category – the 1996 Plymouth Voyager. A van that could only be described as Satan’s larger blue sister (and by Satan, I am of course referring to the seldom missed 1992 Saturn SL).

When I bought the Plymouth Voyager, I thought to myself – at last, a decent vehicle. And then everyone told me that a Plymouth is in fact a Dodge, and that Dodge has a reputation for its unreliable transmissions. Strange, no one ever speaks up before I sign up.

It wasn’t long before the power steering pump exploded, and I spent more than $150 replacing components only to find the rack and pinion also leaks and will need replacing – but not before the mighty transmission problem is solved!

Yes, the Saturn has sent its sister to ruin my life. On a trip home from a gig one night, I came off the highway to a stop sign. I was on the phone with my wife at the time, I pulled out and started accelerating… 1st… 2nd… neutral — wait, that’s not right? CLUNK! And we’re back in 2nd, and apparently 2nd is the only gear my transmission has now.

After much research, it has become apparent that when this transmission is stuck in 2nd gear, it generally means it is in limp mode – or limp home mode as some people have dubbed it. Limp home mode is meant to give you just enough power to push the van over the side of a cliff with yourself in it.

On comes the diagnostics. Like a fool, I bought a solenoid pack without really diagnosing things properly. Replacing the solenoid pack made no difference. The truth is, although I tested the original relay pack, I did the test with an analog multimeter which incorrectly lead me to believe that the solenoid circuits had shorted out when in fact they hadn’t, they just have naturally low resistance. So, now I have two working solenoid packs.

I decided to re-start with a circuit diagram, with the helpful aid of a skilled electrical technician over at geometroforum.com (thanks mwebb). I found that the ground wire on the input sensor had no continuity, and of course this means that the input sensor circuit is broken. I repaired this – and suddenly the van would rev up in 1st gear and clunk into 2nd. Previously it would go from 1st to 2nd to neutral and then clunk into 2nd. PROGRESS! I’m not sure if I’ve progressed forwards or backwards at this point.

Anyway, I picked myself up a pair of sensors (both the input and output sensors) from a junk yard. I plugged these in, and the same problem persists.

I intend to spend no more money on this transmission, instead I am going to start seriously testing it.

One thing I’m going to try before testing it – purely out of curiousity involving what I read somewhere – is splicing the +12v supply to the solenoids and providing power to it directly from the battery. Apparently, when the TCM (Transmission Control Module) activates limp mode, it de-activates the transmission by shutting off the relay that provides +12v to the solenoids. I read somewhere that splicing this wire and bypassing the relay will make the transmission work again. Although, obviously, if it does work I still haven’t solved the underlying electrical cause, but I would be able to at least confirm that my transmission mechanically functions!

My plan over the next few days:

1. Put the van on jack stands so I can accelerate but not have to chase the van down the road with a multimeter in one hand and my will in the other.
2. Test the input sensor’s voltage to make sure that it corresponds nicely to the engine speed.
3. Test the output sensor’s voltage to make sure that it corresponds nicely to the vehicle’s speed.
4. Test both sensors again, but while wiggling the connectors on the sensors to see if I lose connectivity.
5. Wire up test lights to all four solenoids on the solenoid pack, so I can see what (and/or) if the transmission is trying to engage.
6. Replace the ‘overdrive’ wire on the solenoid pack’s harness connector, as this is the single wire responsible for activating the solenoid that engages 3rd gear. I have already tested continuity on this wire, but it became apparent that the wire could still be damaged despite having continuity and therefore might not be capable of carrying the amps required to engage the solenoid.

Beyond this, I’ll have to come up with another course of action. This is a test that I’ll be taking pictures of, and posting more posts about.

If I can repair the transmission successfully, I’ll be removing and rebuilding the rack & pinion in another post.