QuestionWell, I drove about a hundred miles and now the fuse is blowing again. It blows immediately when I start the van. I checked the resistance and it now measures .97 ohms. (It was 1.56 ohms when I first installed the TCM). Could something else be causing the TCM to go bad? I hate to buy a new one and have the same thing happen again.
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I have driven the van for a few days without any problems. It appears to be fixed. I still think that the corroded positve batery cable running to the PDC was part of the problem because I had replaced the TCM earlier and it still blew the fuse right away. One follow up question -- is there a way to "train" the new TCM without taking it into a repait garage? It drives ok but there is a delay in the PRNDL display when the transmission shifts and it sometimes acts wierd. i.e. when in low and 3rd it displays "D" and when you stop and shift into park it displays "R". It's not a big deal but I'd like to fix it if I can without an expensive trip to the repair shop.
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If you remember, earlier I drove the van with the instrument cluster disconnected and then with the TCM disconnected and the fuse blew both times. Today, when I drove it with them unplugged, it didn't blow. Then I checked the codes with the ignition key self read out and got 12, 66 and 55. But last night I had the battery disconnected for several hours because I had to charge it back up. (I think it needs to be replaced. It doesn't seem to hold a charge for very long.) When I disconnected that battery, the positive part of the cable going to the PDC fell apart. It was completed corroded through. After I fixed that cable, I decided to take some readings on the my TCM and compared them to the replacement TCM that I had. I found that on my TCM, pin 16 and pin 57 read 0L and on the replacement TCM it had a reading (I don’t remember what it was). I think pin 16 goes to the transmission relay in the PDC. So I put in the replacement TCM and took a reading on the output side on fuse #2 and it now reads 1.56 ohms. ( It still reads 0L when the TCM is unplugged) I have taken a couple of short trips and it has not blown yet but I’ve driven that far before and it eventually blew. So I am going to hold my breath for a few days. Do you think that the bad battery cable could be the reason that the replacement TCM blew the fuse when I tried it the first time? Also when I used the replacement TCM the first time, I did not remove the old one, I just laid the replacement one next to it and plugged it in. Should it have been installed to get a good ground?
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I have never worked on an electrical problem of this nature before so I probably am doing something wrong, so bear with me, I am going to explain in exactly how I am getting my measurements.
With the instrument cluster and TCM plugged in, the resistance from fuse #2 to the body ground is 1.1 ohms. When I unplug the instrument cluster, it still reads 1.1 ohms. When I unplug the TCM, the digital voltmeter reads 0L.
(One thing that I did notice, when I was getting the 0L reading. Without touching anything, I watched the meter for at least 3 or 4 minutes and I would occasionally get a reading for just a split second. But the readings were up and down all over the place.)
In case that I misunderstood you, I checked the resistance from pin 11 to pin 53 and 57 on both the plug end and also the TCM module itself. Both ways I got a reading of 0L.
Am I doing something wrong?
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Yes, I am using a digital voltmeter. When I checked the reading from pin 11 to pin 53 and 57 on the TCM plug, I still get "no reading". I double checked pin 11 continuity to the junction block and it is ok, and pin 53 and 57 are grounded.
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The resistance from the fuse socket to ground measures only 1.1 ohms. When I pull the plug from the instrument cluster, the reading remains the same. When I pull the plug from the TCM, I get no reading at all. I have disconnected the TCM and the cluster, and could not find a short at the red/white wire at the junction block. Should I remove the BCM, if so, what do I look for?
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I disconnected the TCM and then the instrument cluster and the fuse blew both times. I am not sure which gray and black plugs that you are talking about to test for a short. The four 40pin plugs on the top of the junction control block are all gray. Are these the ones?
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I could not determine the cause of the blown fuse after performing the tests that you suggested. I drove the van but could not tell which component was the cause.
Can I drive the van with the instrument cluster and TCM disconnected to eliminate either of these? And if there is a short in one of the wires, how do I track it down? Also,(I don't know if this has any bearing on the cause)but the last two mornings I had to jump the battery but I haven't been driving the van much since it has this problem.
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On my ’97 voyager, the 10A gauge fuse (fuse #2 in the fuse block) keeps burning out, the transmission goes into limp mode and the PRNDL lights are all selected. When I replace the fuse, everything works until I drive a couple of blocks and then the same thing happens.
I ran the diagnostic test of the instrument cluster and it checks out ok except for a 905 code - No CCD bus messages from TCM. My Actron OBDII scan tool reads P1698 - Manufacturer Control - Auxiliary inputs Auxiliary outputs. When I looked up P1698 for Chrysler on the internet, it gives a different message - No CCD bus messages from TCM. I switched out the TCM, the input and output sensors, and the transmission control relay in the PDC from another voyager which made no difference.
Can you help me?
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Hi Gary,
The fuse #2 provides power to three separate modules: the transmission module, the body control module, and the instrument cluster. Aside from the possibility of a short in one of those three lines, one of the modules is drawing too much current. The question then is which one and why?
The first step is to localize which cirucit is blowing the fuse.
I would begin by removing the fuse and turning the ignition switch to run and observing which side of the fuse socket it "hot". Then I would measure the resistance to ground from the other side of the fuse socket, which is attached to the three modules. It should read much more than 1.2 ohms (so that the draw is less than 10 amps). If it is not significantly more that 1.2 I would pull the red plug from the instrument cluster and see if that raised the resistance significantly, and also pull the transmission controller plug and see if that raised the resistance significantly. If neither raises the resistance then the body computer is drawing too much current or one of the 3 red/white wires to the 3 modules is shorted to ground. If the resistance is significantly more than 1.2 ohms then I would try driving the van with the fuse removed to see if the resistance drops to less than 1.2 ohms while you are driving which would be the point where the fuse would have blown if it were in the socket, and see if you can tell which of the 3 components might have asked for more current at that moment.
So give that approach a try and let me know what you observe. Use the "rate the expert" tab to get back to me if I am maxed out.
Roland
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Hi Gary,
The van should certainly be driveable with the instrument cluster disconnected, and if you drove with the TCM disconnected it would no doubt revert to limp-in, but if you tried both of those indepedently you might find that the fuse doesn't blow one way or the other which would help focus your attention. The short issue could be checked by disconnection the TCM and the cluster, and then check at pin 10 of the black plug to the junction block, and then check at pin 20 of the gray plug that has a red/white wire (there are three gray plugs so you will have to inspect for the wire color), after pulling the plugs and test to see if there is a short to ground from those pins. You might try shaking the harness from the plug to the module in question (The pin on the black plug goes to the instrument cluster, the pin of the gray plug goes to the TCM). I have heard that the harness to the TCM can be a problem because of its proximity to heat sources.
But in any case, try driving it first with the cluster disconnected and then with the TCM disconnected and see if the fuse doesn't blow in either of those modes. Then check the red/white wire for a short to ground, and shake the harness to try and generate an intermittent short.
I'm interested to know what you learn.
Roland
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Hi Gary,
The red/white wires from the fuse to the cluster and to the tcm are found in the upper left plug, pin 10 and the lower left plug, pin 20. Notice that these are 36 pin plugs, numbered left to right starting with the top row. But you should look for the red/white wires as your targets. If those wires don't appear to be shorted to ground when the TCM and PCM are unplugged (and of course the plugs have to be pulled from their sockets because they carry 12V from the fuse) then you may need to remove the body control module which is ganged with the junction block and investigate its wiring. It appears from the wiring diagrams to have some direct plug-in to the junction block interface but I haven't seen it personally. There is shown to be a branch of the red/white that plugs into an internal (non-plug?)connector of the body control module. You have demonstrated that the TCM and the instrument cluster themselves don't blow the fuse, so it either has to be the red/white wires that carry current from fuse #2 of the jucntion block that are shorted or the body control module at 'internal connection' #7 that is drawing too much current. I am working with the '98 diagrams, and rather than showing 4 gray plugs suggests that the the lower left plug is black rather than gray. But I think we are on the right track. What does the resting resistance that the fuse is 'looking at' appear to read?
Roland
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Hi Gary,
No, I think you have your answer. If by "no reading at all" and you are using a digital voltmeter, that means that by disconnecting the tcm the resistance has changed to being higher than full scale (which is what digital meters do when for whatever range you have the meter set at), e.g. the resistance in then ok and therefore the tcm is truly presenting too low a resistance (1.1 ohms) and that module appears to be faulty in some manner. I believe you said that the tcm was replaced, so maybe that is not a good tcm. Or try shaking around the plug to see if it might be faulty, and you could also check the reading from pin 11 to pin 53 and/or pin 57 (both of which are grounds) of the TCM proper. That would verify the problem if you get 1.1 ohm from that measurement because pin 11 is what the red/white wire attaches to.
Let me know if I misunderstand you, using the Rate the Expert tab if I am "maxed out".
Roland.
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Hi Gary,
I think we are misunderstanding oneanother. You told me that the resistance from the fuse #2 output side to ground was 1.1 ohms and then it became "no reading" when you disconnected the TCM plug. That has to mean that the TCM side of the interface at pin 11 has to read 1.1 ohms which is so low that it will take out the 10 amp fuse. I am not clear whether you have or have not measured that resistance at the TCM itself with the plug removed. Because you removed the plug you can't measure from 11 to ground you have to measure from 11 to 53 or 57 of the TCM itself and it should read 1.1 ohm or thereabout. Have you perhaps reversed the polarity of the meter leads? The - lead should go to 53 or 57 and the + lead to 11. If you don't get that 1.1 then I can't see how you will get 1.1 when measuring from the cold side of the fuse socket when you plug it back together. The only possibility is that the wiring changed between 97(your van) and 98 (my manual) but I don't see why that would have happened because in '94 it was that way and it still was in '98. So try it again with the above in mind.
Roland
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Hi Gary,
I don't know why you are getting this discrepency. If you have removed fuse #2 and looked at the resistance from the downstream socket of the that fuse, and you read 1.1 ohms then that of course means that the combination of the the instrument clusted, TCM, and body controller are going to draw 11 amps which of course blows the fuse. Now when you disconnect the cluster the resistance doesn't change. So either the TCM or the body controller is responsible for drawing too much current. Then you remove the TCM and the resistance to ground goes OL (if you raised the dial setting of the ohmmeter function you can find out exactly what is the resistance value, so try that just out of curiosity). To me that has to mean that the TCM is the unit that is overdrawning the fuse. I see no reason why when you then go back to the disconnected TCM it should not by itself read about 1.1 ohms EXCEPT it could be the case that what is different is that there is a second and third power supplies to the TCM on pins 15 and 56 and those are of course disconnected so the TCM unplugged may cause a different load on pin 11 than if the TCM were plugged in. So that may explain the discrepency. IN ANY CASE: it is clear that the fuse blowing has to depend upon the TCM and its function. You can verify this by driving (probably in limp-in mode) or at least running the engine with the TCM unplugged. I would predict that the fuse #2 will not blow. So all I can say is that the issue has to be with the TCM but without a manual about the TCM internal wiring I can't tell you why it is drawing too much current.
My only suggestion at this point would be to try and get a fault code from the system by either doing the ignition key self readout :"on-off-on-off-on and leave on" doing this in an elapsed time of 5 seconds or less. Then watch the check engine light to begin to flash, pause, flash, pause, etc. Count the number of flashes before each pause, then group them in pairs to form two digit fault codes. Write me back with any such codes and we'll go from there. You can get a more complete/specific list of code possibilities by attaching a code reader to the data link plug under the dash. Some autoparts stores like Autozone will do that for free, otherwise get it done at a shop and let me know the P +4 digit numbers. There may be a code that tells us something specific about the TCM or about the other circuits to the TCM but at the present it appears to me that the reason the fuse is blowing is the TCM is drawing too much current. So check it out at to whether you can drive without blowing fuse #2 and get the fault codes.
Roland
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Hi Gary,
I doubt that the corroded main battery cable would have contributed to the fuse blowing. Similarly, I doubt that not having the replacement TCM mounted should make a difference because it does have ground wires. I do still wonder, like you, if fuse #2 is not going to blow when it is delivering current into a resistance of 1.56 ohm, which should draw close to 10 amps which is the fuse limit. But I'll keep my fingers crossed.
By the way, when you get an 'OL' reading, try switching to the next higher range or resistance to get a reading.
Roland
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Hi Gary,
I don't believe that the shifter position indicator is "live" in the sense of telling you what internal gear the trans is using at that moment. Rather it simply indicates a certain program of gear selections at each position of the shift lever. I say this because the indicator lights are illuminated via switches that are attached to the vertical shift rod on the transmission which in turn is coupled to the shift lever that you move via a cable. So if the trans is behaving like it is in the OD mode of operation (not necessarily in the OD gear itself) and yet the OD light doesn't illuminate, then that is a problem in switch adjustments at the valve body in the solenoid box of the trans located at the bottom of the vertical rod, or possibly in the logic connecting those switch positions to the indicator lights. I don't think TCM programming has anything to do with that discrepency. The switch position data is sent to the body control module and the body control module tells the dash which light should be illuminated. It may be a problem in the body control logic rather than the switch positions. I don't think it has anything to do with the TCM.
If the trans isn't shifting in an optimum way, that would be a relevant issue for considering the TCM programming question. And my '98 manual says that if you change the TCM it needs to go thru a "quickk learn" procedure that does involve the use of the DRB III, which means at a dealer or shop with a DRB III and the knowhow to do a 'quick learn'.
I hope that the fuse blowing has stopped, but I have to say that I still don't understand why it was blowing and why it has stopped, but my understanding is at best second-hand.
Roland
AnswerHi Gary,
I thought this was not going to last, too close the limit of the fuse. I don't know what else could cause the TCM to draw too much current. The wiring diagrams show it as a black box so there is no way to understand what the current is used for. One thing you might want to do is readout the transmission control module memory to see if it has logged a fault code which might explain whether one of the ancillary modules that are powered by the controller is at fault. You might simply measure the input impedence at pin 11 (after removing the plug) to verifly it is 0.97 ohms or not, but if it was that would rule out an outside reason for the excess currrent draw and tell you that a new TCM is required. You could also see what happens (with the unit plugged in) to the impedence as seen at the fuse socket if you removed the trans control relay in the PDC as a test of whether that relay or its wiring may be the cause of the low impedence because the relay does draw on the 12V supply to activate the relay coil but I can't be sure it draw from fuse 2 or not
Those are the only things I can think of doing before getting another TCM.
Please let me know what happens.
Roland
