QuestionQUESTION: Hello-I have 1 1992 Chrysler Lebaron LX Convertible that I've owned for 4-5 years. It has the digital dashboard, and in a nutshell here is my problem: the dashboard was dark when I bought the car-the local Chrysler dealer got it to light up, but ever since, the speedometer, tachometer & volt meter do not work (the odometer, oil pressure & temp gauge do work) I had a rebuilt transmission put in 2+ years ago-I was told the original one failed because the transmission computer has to read from the speedometer when to shift gears. I have been told by various repair shops the problem is the dashboard and/or the engine control module. I have since acquired 5-6 dashboards & 3 engine control modules (the ECM's are the correct one for the 1992 Lebaron-the number's are correct)but I've tried every one & the problem is the same. Last year I bought a 1990 Lebaron Convertible with a digital dashboard for parts & when I put the ECM in my 1992 the engine feels like it's missing-but all the gauges work, including the speedometer?!? It's been suggested I put the engine harness from the 1990 into the 1992, but the 1992 has antilock brakes & the fuse/relay panel is under the hood also, so I don't think this is a practical solution. Do you have any suggestions?? Any help would be GREATLY appreciated because right now I have a car I can only drive around town. Thanks much, Terry.
ANSWER: Hi Terry,
I am assuming that you have stuck to ecm's which are for the engine that you have, which I also assume is a 3.0L V-6.
Between 90 and 92 some of the fine points of engine fuel and timing settings may have changes which would explain why the missing is occuring. I am not certain I believe that the ecm is the problem however. I can't quite believe that only one ecm is working properly to "drive" your cluster. And at the same time, I can't believe that only one of the 5-6 clusters will work. The only wires that transmitt the cluster reading information from the ecm to the cluster are the digital data bus wires, on pins 7 and 8 on the blue plug and which go to pins 26 and 46 of the ecm plug. I would check the continuity of those wires and flex them to see if one might be flakey along the harness or at the plug. Because some of the data is there and others are not it is a tough issue, unless for some reason the signals that generate that data are compromised, but then you would think that the engine/trans wouldn't run right. One of the other possibilities is that there are circuit board trace cracks/solder breaks, but then why would all the dashes behave the same as your original one? I have to believe that there is a loose connection and that you just by chance got one ecm and one dash to work and all the others to not work in any combination. It is more likely such an intermittant or noisey connection that just happened to work with that '90 ecm to original '92 cluster by chance.
I can't see reason other than that.
Please let me know if you make some progress on this one.
You might also want to take a look at the body computer located on the right side cowl (kick panel). That is other major module that shares that digital data bus. Because of leaks that occur around the windshield of convertibles it is often the case that water drips down on the top of the body computer and causes shorts at random pins on the two plugs. If one or both data bus pins at the body computer were so-compromised it might interrupt some of the data that is not getting to the cluster. They are on pins 5 and 20 of the black plug. There are other module on the bus: transmission, air bag module, trip computer, etc. to also check for similar issues, but the body computer plugs are the most likely culprits.
Roland
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QUESTION: Hi Roland-I sent a follow-up, I don't know if you got it, so I'll send it here. I checked the wires you mentioned, and I noticed both were cut & resoldered with shrink tubing at the ecm, the blue plug & at the body control module (the color of the wires are purple with a black sripe & white with a black stripe). Do you think somebody cut them to check continuity? Also would it be possible to bypass these wires with new ones, and if so, do they join together from the body control module, dashboard & ecm, or does one set draw power (routed through the fuse panel or another power source)? I would like to run new wires just to be sure they are good. Any additional comments/suggestions would be great. Thanks, Terry
AnswerHi Terry,
I saw your kind evaluation where you mentionned the follow-up but I never received that. As to the wires, they are routed around as a twisted pair (which I suspect is for electronic noise sensitivity reduction) to the ecm, tcm, body computer, air bag collision system, instrument cluster, trip computer, diagnostic readout box connector, etc., and they are essentially a shared network of data signals in which all the units send and receive as needed. I believe that the body computer is the site where a bias voltage is put on the wire (of +2.5 and -2.5 volts) and that location is probably the main node for all the data. I would not be inclined to change the wires if they are the original twisted pair and are routed inside an existing harness. You certainly can check the continuity with the battery disconnected, and maybe for safety the plugs disconnected from all the components that are wired into those data lines. I believe that if the wires are soldered properly there should be nothing wrong with their having been cut and reconnected. You could verify that the wires are in good shape by shaking them while you verify continuity.
Roland
