4-speed electronic trans: range sensor tests

Question

QUESTION: 1999 Dodge Grand Caravan 170K 4-speed transmission

I am asking a new question as the limit for follow-up questions was reached for my first thread of questions.

I believe it is something with the transmission back-up lamp/range sensor as I noticed that the fuse is now gonig out while shifting the gear. I have a multimeter but the intermittant nature of the problem is not letting me use it. I have following three questions:

The rear fog lamps are not working (as per your last answer these are with the back-up lights and might be connected to the problem. I am unable find a fuse for these; I can see a fuse for Front Fog Lamps under dash but no fuse for rear fog lamps. Can you help me locate the fuse for rear fog lamps (I will open up the rear lights to see inside tomorrow as it was raining today).

I believe I have a 4speed transmission. Can you help me locate this 10-pin connector on the transmission?

If the transmission range sensor is bad then I will have to get it replaced from a transmission shop. Is there a way for me to be sure if this sensor is bad? Will it come up in a code reading?

ANSWER: Hi Shafique, The 3-speed trans shift lever choices are D,2,1 while the 4-speed are OD,3,L. which do you have? Then we can proceed to check out the reverse switch pins. The rear fog lamps appear to be for vans that were sold outside the U.S. (export versions). Is yours of that type? It appears that the rear fog lamps are tied into the back-up lamps on the same circuit, so maybe those bulbs are burned out? Did they ever work when you were going forward or just when in reverse? You can check the bulbs with your multi-meter. The way to check out the range sensor circuit is with your multimeter, but lets define which transmission you have, and then consider what to do. It may not be the sensor but rather the associated wiring.

Roland

---------- FOLLOW-UP ----------

QUESTION: Yes, my van is a middle east model. I checked the rear fog lamps six years ago when I bought this van and these were working fine while van was in P. I never used and checked these again! I will check the rear lights unit tomorrow.

The transmission is 4-speed. Ofcourse the work at the tranmission shop will be expensive and I want to be dead sure that the range sensor is bad.

Thanks for your help!

ANSWER: Hi Shafique, It may be that one of the fog lamp bulbs is shorted to ground, or the same could be true for the back-up lamp bulbs. So you could remove all those bulbs and see if the fuse still blows or not. The range sensor plug is on the side of the transmission that faces the front of the vehicle, and at the very far end of it. It is the only plug with 10 pins I believe. So check out the wire colors as I described. Basically you should find 12v on white wire of the plug on pin 1 which comes from fuse 12 when you have the key in the 'run' position. And then see if the socket into which pin 1 fits shows continuity to pin 6 socket when trans is put in reverse, and also verify that neither pin 1 socket nor pin 6 socket is shorted to ground (should show infinite resistance to ground when the plug is removed from the socket. If you have continuity and no short to ground then the range sensor is OK. Then you would need to check the resistance to ground of the violet/black pin 6 of the plug and it should not be shorted to ground either (but could have a resistance of a few ohms, but not 0 ohms thereabout. Please 'rate' my answer. Thanks, Roland

---------- FOLLOW-UP ----------

QUESTION: Thanks for your help. It is a difficult problem to diagnose at hand.

I have checked rear lights assembly. It seems that nothing is wrong there with the rear fog bulbs etc. One fuse blew even when both rear lights assembly were completely disconnected, which means that short is not from rear light assembly. The rear fog lamps are not working probably because of a problem in headlight switch. I cleaned the headlight switch last week as it was not making proper connections. Now, when I check the headlight switch terminal connectivity, I am not getting 5.2 ohms between 2 & 1 when the switch is off and continuity between 2 & 3 when front fog lamps are on. I have no idea what should be the terminal contiuity when rear fog lamps are on.

Now back to transmission problem: I told you that sometimes back-up lights are on even when not in R. I noticed that the fuse is blowing when this happens and I move the selector from N to R!!! At that time, I was able to get short between voilet/blank wire (at rear lights assembly) and ground for some time. Then everything was fine. It appears that the short does not stay for long time (I do not know if I will get any thing when I check the transmission range sensor as it might be working fine at that time). Once I put a new fuse, every thing is just like normal until the back-up lights stay on and then it blows again. I am starting to believe it is from the range sensor as a short between wires should be permanent, am I right?

I noticed something else today: I could start the van in R (but not in D) although the R gear actually kicks in after like half a second after starting.

Thanks again for your help on this difficult issue!

Answer

Hi Shafique, Here are the continuity test for the range sensor: Park: Pins 5,8,9 grounded Reverse:9 grounded, pin 6 connected to pin 1, make certain that pin 6 is NOT shorted to ground. Neutral: 5,7,9 grounded Low: 7,8,9 grounded 3: 6 grounded Overdrive: 7 grounded Ignore pins 3 and 4. "Ground" is the surface of the transmission. I also suggest that before you do the continuity testing that you adjust the gear shift cable that connects between the shift lever in the cabin and the shift lever on the transmission: Put the shift lever in the cabin in P, set the parking brake, remove the key. At the transmission loosen the adjustment screw where the cable attaches to the lever. Pull the lever fully forward to the park position detent. Release the park brake and test that the park position lock is still holding the park wheels. Reset the park brake, Tighten the adustment screw. We will deal with the headlamp switch later. Roland