2002 Chrysler Town and Country Town and Country not shifting

Tiny
TIM BAKER
  • MEMBER
  • 2002 CHRYSLER TOWN AND COUNTRY
  • 3.3L
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 230,000 MILES
My 2002 Town and Country will not shift out of 2nd and is stuck in limp mode. I replaced the TCM, input, output sensors but still nothing. With the neg cable off the battery I tested the relay and with my test light hooked to negative battery terminal, I get power from socket 87 Fuse B, 86 Trans. Control and 85 ground. When I hook up the negative cable to the battery I get power to 87 only. I also tested it with the relay half out and get the same reading. According to the diagram 86 and 87 are the load sides and should be hot all the time.
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Monday, September 21st, 2015 AT 2:23 PM

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Tiny
CARADIODOC
  • EXPERT
The first thing you need to do is have the diagnostic fault codes read and recorded to know which circuit needs further diagnosis. That information was lost when you disconnected the Transmission Computer, but since the problem is still there with the new computer, it should have set the same code(s). You may be able to read them yourself as you can with engine codes. Cycle the ignition switch from "off" to "run" three times within five seconds without cranking the engine, then watch the code numbers show up in the odometer display.
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Monday, September 21st, 2015 AT 8:47 PM
Tiny
TIM BAKER
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The trouble code is P1768 I also tested by removing the positive cable and touching the tip of my test light to the battery positive post and the clip to the battery positive cable and came up with a dim light which from what Ive read means a small short and bright light means dead short. I removed the wiring plug directly under the Auto shutdown relay on the fuse box and the light went out. As far as I can see its the harness to either the TCM or the solenoid the 2 are taped together I didn't have time Friday to check by wire colors as to where it goes.
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Saturday, September 26th, 2015 AT 1:17 PM
Tiny
CARADIODOC
  • EXPERT
Your test method is valid, if the vehicle was from the 1980s or before. For a 2002 model you're going about this all wrong. There is going to be a small current drain of as much as 35 milliamps all the time to keep the many computer memory circuits alive. When you disconnected the battery, the diagnostic fault codes, fuel metering data, and transmission clutch volume data were lost. Now you're going to have engine performance and transmission shift quality problems until that data is relearned.

More importantly, some computers need up to 20 minutes to go to "sleep" mode after the ignition switch is turned off. During that time it is common to find up to three amps for current draw. You can't measure current with a test light. All you can see is if you have enough current to make the light bright enough to see. The resistance of the bulb also reduces current flow to the point where a computer may never get to sleep mode.

If you're going to pursue this line of troubleshooting, you need an amp meter, but you have to start out on a scale high enough to read at least three amps. On most digital meters, that means moving the positive lead to a special jack. Once you see current drop after 20 minutes, you need to move the lead to the standard jack and lower scale to get more accuracy. Doing that creates an open circuit while the lead is disconnected. That wakes the computers up again and the 20-minute cycle starts all over. Most digital meters have a 2-amp scale and an internal 2-amp fuse. That fuse will blow due to the three amps the computers are trying to draw.

The next problem is you'll want to switch to the 200 milliamp scale for even more accuracy. All digital meters use a "break-before-make" range switch. That means as you turn it, the switch breaks the contact to one scale, then, as you turn it further, it makes the contact to the next scale. That momentary break is enough to wake up the computers again.

You need to insure there is never a break in that circuit when you do any switching. That is easy to do by connecting a small jumper wire from the battery's post to the cable clamp when any switching is done. We always do this with the negative cable. Once you're on the scale you want, remove the jumper wire so current goes through the meter.

As for code 1768, there is no real good description for it but it is related to the transmission relay. Typically you're going to find a broken ground wire for that relay, or damaged wires near the transmission or left inner fender.
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Saturday, September 26th, 2015 AT 3:28 PM
Tiny
TIM BAKER
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Thanks for the fast detailed reply, I'll have to try the amp meter. Can I rule out the solenoid pack on thebtransmission? I plan to get a closer look at the wires by the transmission.
Thanks for steeeing me in the right direction.
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Saturday, September 26th, 2015 AT 6:34 PM
Tiny
CARADIODOC
  • EXPERT
Yup. There's three ways a solenoid pack can have a problem. The first is if the assembly is leaking, and that's usually a gasket problem. That is found strictly by observation. The second way is to have an electrical problem, which is almost always due to a break in one of the circuits. That can be a corroded terminal in a connector, a cut wire, a wire rubbed bare and touching ground, or less commonly, a break inside the solenoid's winding. The third way is to have a good circuit, but when it's energized, no fluid flows so no pressure increase is detected or the clutch pack doesn't engage. That is a mechanical problem related to operation of an electrical circuit. The last two defects will be detected by the computer which will set appropriate diagnostic fault codes.
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Monday, September 28th, 2015 AT 2:40 PM
Tiny
TIM BAKER
  • MEMBER
With a multi tester I got the following readings in the Etax relay socket
W/o negative cable hooked up and the negative test meter lead on the neg battery terminal.
Pin 86 - 11.12 volts pin 30 - 11.40 volts
pin 87 - 11.82 volts pin 85 - (ground?) 11.59

With negative battery terminal hooked up and negative test lead on negative battery post
Pin 86 - 0 volts Pin 30 - 0 volts
Pin 87 - 11.76 volts Pin 85 - 0 volts

I've heard of the power distribution centers going bad could this be it? I looked at all connections and wires and cant see anything wrong.
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Tuesday, September 29th, 2015 AT 12:44 PM
Tiny
CARADIODOC
  • EXPERT
I'm not sure what you're testing, but how do you get any voltage anywhere with the battery cable disconnected?

Wait a minute, I see the problem. Your positive probe is taking a reading related to a reference point, which commonly is ground, which is the negative battery post, but you removed that. This is like trying to measure barometric pressure with the gauge sitting in a jar pumped into a vacuum. There is some circuitry that is allowing the tiniest trickle of current through your meter, and that is what is allowing it to pick something up. You can prove this by measuring any of those voltages, then place a test light across the same two points. You'll see the test light doesn't light up and your voltmeter will go to 0.0 volts.

The only valid voltage readings are those taken with the battery connected. The battery does need to be disconnected to take some resistance readings unless the circuit can be made dead some other way, as in turning off a switch or pulling a fuse. Voltage in a circuit will cause totally incorrect resistance readings.

Terminals 30 and 87 are the contacts that are switched on and off. 12 volts on terminal 87 all the time is correct. That 12 volts will show up on terminal 30 when the relay is energized. Terminal 85 or 86 will have 12 volts when the ignition switch is turned on. I can never remember which one. If you have the relay plugged in and are able to reach the terminals with the meter probe, you'll find 12 volts on both 85 and 86. 12 volts is getting to the second terminal through the coil of wire in the relay. One of them gets grounded by the Engine Computer for one second after you turn on the ignition switch. It gets grounded again anytime the computer sees engine rotation, meaning cranking or running.

All of the testing you've done so far can be summed up with a single voltage reading. The relay has to be plugged in so you might have to fashion a thin piece of wire if necessary to reach the terminal. Measure the voltage on terminal 30. A test light works much better for this test for two reasons. First, most digital meters don't respond fast enough to catch quick pulses. Second, think of a compressed air line. All you need is a tiny pinhole through what is otherwise total blockage of the pipe, and you'll have full pressure on a gauge at the end of the line, but you'll never be able to get enough volume through there to run a tool. Similarly, all you need is any circuitry with really high resistance to let a teeny dribble of current through and the meter will pick that up as a voltage, but you'll never be able to get enough current through that resistance to do any useful work. A test light has very low resistance so it's going to draw relatively high current through the circuit. It can only do that and light up if the circuit is working properly. Also, we don't need to know the exact voltage at terminal 30. The test light is going to be off, (0.0 volts), dim, (insufficient voltage, but something), or bright, (enough voltage to prove the circuit is working).

There's two parts to this test. With the test light connected to terminal 30, it should be off. Now turn the ignition switch on. You should see a bright test light for one second, then it will go back off. You might hear the fuel pump's hum at the same time. That has just proven the circuit is okay and the Engine Computer has control over the relay. Next, crank the engine. The test light should turn on anytime the engine is rotating. If it does, move on to something else.

The only time a mechanic would do this test is if there was a fault code related to the "switched 12 volts is missing" and he wanted to verify that or see if the 12 volts was making it as far as the relay. That would instantly tell him if there could be a break in the circuit before terminal 87 or after terminal 30.
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Tuesday, September 29th, 2015 AT 9:22 PM
Tiny
TIM BAKER
  • MEMBER
I did the test on the fuse box plug in for the Etax relay. What I dont understand is why is there power to 30 and 86 with the negative battery cable off and the multi meter black touching the negative on the battery and Red lead probing the female terminals on the fuse box, however when I do the same test with the cable hooked back up and the multi meter black to the battery negative once again I get completely different readings from 12 volts to zero. Im gonna give your test a try and see what results I get. Can I do this with the relay lifted enough to get the test lead on it? I seen a vid on youtube that showed this but just want to make sure.
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Tuesday, September 29th, 2015 AT 10:48 PM
Tiny
CARADIODOC
  • EXPERT
This is real hard for me to explain better without having a marker board to draw on. A better example might be to think about when you remove a battery cable to insert an amp meter. How can you get a reading of any current unless it is able to find a path through some circuitry on the car. Okay, now that we know there's some circuitry there, you're putting one meter probe on the battery's negative post, then the other probe on the negative cable that is attached to that circuitry and goes all the way around and back to the positive cable and battery post. In effect, you're measuring right across the battery, but with a pile of circuitry in between.

For all practical purposes, the voltmeter has extremely high resistance so it just measures electrical pressure, (voltage). No current actually flows through it. No air flows through a pressure gauge on a compressed air line. That's why it can measure full pressure when there's just that little pinhole in the blockage in the pipe.

If you tried to measure volume of air flow, you couldn't get any because of that blockage. You would not be able to run an air tool. The test light is that air tool. It needs current flow through it to make the filament light up. The circuitry in the car has way too much resistance to let enough current flow. That 's why where the voltmeter is showing 12 volts, the test light will show 0 volts. When you have the voltmeter connected and you're watching that voltage, it will drop to 0 volts when you put the test light across it.

You're right about lifting the relay out of the socket part way. All that's important is the terminals remain in contact with the terminals in the socket, otherwise it can't work. If you see the 12 volts show up on terminal 30, that can only happen if everything related to that relay is working. You can also stick a piece of wire in the terminal but you have to watch that it doesn't stretch the female terminal and cause an intermittent connection. That's a big issue with '90s GM relay sockets. Poking terminals with meter probes can cause the same problem.
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Tuesday, September 29th, 2015 AT 11:50 PM
Tiny
TIM BAKER
  • MEMBER
On my fuse box there is a small hole next to the relay socket that works great for testing I can fit a test probe in it so it should fit a small piece of wire or even a piece of bent paper clip to make contact. I have to wait for it to warm up a tad before venturing out (33F here) and do your test before I get anymore confused. Lol!
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Wednesday, September 30th, 2015 AT 6:08 AM
Tiny
TIM BAKER
  • MEMBER
I hooked a small jumper wire into socket 30 replaced the relay turned on the key and it lit for about 3 seconds and went out however there is no light when it started. It did one time after a couple tries light for a split second and then lit when cranking and running though after that I only get the light on turning the key and nothing when running.
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Wednesday, September 30th, 2015 AT 10:10 AM
Tiny
TIM BAKER
  • MEMBER
I tested socket 86 and got the same result as 30 a light for 3 sec and no light when cranking or running. Socket 87 is hot all the time and 35 I got nothing so I assume this is ground?
After re-scanning I got codes P0755 Shift solenoid A p0750 Shift solenoid B also P1768 Refer to service manual.
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Wednesday, September 30th, 2015 AT 11:31 AM
Tiny
CARADIODOC
  • EXPERT
First try swapping the relay with one of the other ones like it.

Next, what you described as intermittent operation suggests three likely possibilities. One is arced or pitted contacts in the relay. The next is intermittent loss of voltage feeding the coil of the relay. That is a Transmission Computer or wire issue. You said you replaced the computer already. The last suspect is the ground wire which seems like the best one.

Remove the relay, then use your ohm meter to measure the resistance between terminal 85 and ground. It should be real low, as in no more than a few ohms. If that appears to be okay, rig up your wire to measure the voltage on terminal 86 the way you did on terminal 30. This time it's a good idea to use the voltmeter instead of the test light. This is a very low-current circuit, and the driver transistor inside the computer may not appreciate being forced to pass enough current to run the test light.

For the moment we can assume the wire between the computer and terminal 86 is okay because you consistently saw the relay get turned on for a few seconds each time you turned on the ignition switch. What we want to see now is if that 12 volts stays there once the engine is running. Whether it stays or drops out will tell us which way to go next.
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Wednesday, September 30th, 2015 AT 8:11 PM
Tiny
TIM BAKER
  • MEMBER
I did swap relays, I figured since it starts great I would use the relay for the fuel pump and got the same results and it still fired right up.I'm going to try the next test tomorrow.
Who would have thought being so confused could be so much fun! LOL!
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Wednesday, September 30th, 2015 AT 11:04 PM
Tiny
TIM BAKER
  • MEMBER
I went out and tried the next test here is what I found

Socket 85 I have to insert the black probe in the socket and the red to the ground and all I get is a negative reading when it should read zero like when I tested it before hooking it up; If I hook it up the other way, I get nothing. Most likely my cheap digital tester soon to be replaced.

Socket 86 Key off 0.0, key on 10.5 volts dropping off to 0.1 engine started around 2 volts
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Thursday, October 1st, 2015 AT 6:33 AM
Tiny
TIM BAKER
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I bought another tester and here are the results
Battery voltage 11.89
RELAY IN KEY OFF
Socket 30 ---0.00
Socket 86--- 0.00
Socket 87 --- 11.8

RELAY IN KEY ON
Socket 30 ---11.8 dropping to zero and zero when running
Socket 86---- 10.5 Dropping off to 0.00 and zero when ruinning
Socket 87 --- 1.88

RELAY OUT KEY OFF
Socket 30 --- 0.00
Socket 86----0.00
Socket 87 ---11.8

RELAY OUT KEY ON

Socket 30-- 0.01
Socket 86---0.00
Socket 87 ---11.8
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Thursday, October 1st, 2015 AT 1:35 PM
Tiny
TIM BAKER
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I also checked the continuity from socket 30 to the body and got 0.00 right away and the multi meter alarm went off so can I assume the ground is good?
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Thursday, October 1st, 2015 AT 7:05 PM
Tiny
CARADIODOC
  • EXPERT
I think we're making some progress. Terminal 86 jumps to 10.5 volts, then drops to essentially 0 volts, which is correct, but it should go back up with the engine running. We have a problem there when it stays at 2 volts. It could be the computer is detecting a problem and is turning that voltage off on purpose to turn the relay off.

Terminal 87 must have 12 volts all the time. That comes right from fuse 15, a 20 amp, in the same computer module / fuse box as the transmission control relay. You posted:

RELAY IN KEY ON
Socket 30 ---11.8 dropping to zero and zero when running
Socket 86---- 10.5 Dropping off to 0.00 and zero when ruinning
Socket 87 --- 1.88

Unless you mistyped, you can't have only 1.88 volts on that terminal. The only thing that can cause that voltage when current is trying to flow is high resistance in that circuit. That would be like stepping on a garden hose a partially blocking it. As long as the nozzle is closed, you'll still have full pressure there. When you open the nozzle to turn on current (water) flow, the pressure, (voltage) will drop off. This is where a test light is more accurate. It needs current flow to operate where a voltmeter doesn't. Do this test again on terminal 87 with a test light. No matter what you do with the ignition switch, that test light should never go out. If it does, find that fuse 15 and test the voltage on it the same way. There will be two tiny holes on top for taking the readings.
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Thursday, October 1st, 2015 AT 7:47 PM
Tiny
TIM BAKER
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Sorry it should have read 11.8 on socket 87 I will try the next test in the morning.
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Thursday, October 1st, 2015 AT 8:00 PM
Tiny
CARADIODOC
  • EXPERT
Okay, terminal 87 is fine. It doesn't have a problem. The question now is why is terminal 86 dropping to 0 volts? My only guess at this time is the computer isn't happy about something so it's turning the relay off. What I would do next is remove the relay, leave the ignition switch off, then jump terminal 87 to 30. Listen for any clicking which would indicate there's nothing shorted in that circuit and things are trying to work. If you hear that, that's a good sign. If you don't hear anything, that's not a bad sign. If something is shorted, the 15 amp fuse is in there to protect the wiring.

If nothing goes up in smoke, remove the jumper, start the engine, then put the jumper back in. Along with all the other circuits that relay feeds, one line goes right back to the computer as its way of verifying the relay turned on when it expected it to, but it also wants to see it goes off when it's supposed to. If you leave the jumper in while you're cranking the engine, I suspect the computer will detect that, as far as it knows, the relay is stuck on, and therefore it has no control over it. By waiting to reinstall the jumper until after the engine is running, that will be avoided.

If everything seems to be okay, try driving the van to see if it shifts. With luck some other diagnostic fault code will pop up that may provide a clue as to where to look next.
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Thursday, October 1st, 2015 AT 9:17 PM

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