QuestionQUESTION: My speedometer,and odometer are inop, the check engine light is on and the vehicle is not shifting properly. fuse? relay? sensor? please help
ANSWER: Hi Troy,
I have two suggestions:
Check fuses # 14, 19, and 5 in the fuse box behind the left end-cap of the dash. These fuses power the body control module which supports the digital data communication system that is required for properly operating the instrument cluster and the transmission. Look at them carefully for a crack in the internal wire or test them for continuity with an ohmmeter.
The other thing would be to get a code readout for fault codes that should be stored in the memories of the engine and transmission controllers as the result of the check engine light alert. An Autozone parts store or similar nationwide chain will ofter do that for free. You could also try the ignition key:"on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the odometer window of the cluster to see if the mileage changes to show any 4-digit numbers preceded by a P. Let me know these fault code number no matter which way they are obtained and we'll go from there to find the cause if it isn't one of those fuses.
Roland
PS Please 'rate' my answer. Thanks
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QUESTION: the code is P1684, all three fuses good to go with no break in continuity,
Troy
ANSWER: Hi Troy,
That 1684 means that the battery power to the pcm was disconnected sometime in the past 50-100 key on-off cycles. Have you actually disconnected the battery that recently? If not, then I wonder if fuse 16 or 28 might be flaky? So check those similarly. If you have disconnected the battery, then that would explain the 1684 for sure.
Aside from those ideas, I can't in the absence of a more substantive code give you any specific ideas as to what to look for. The one obvious item is the 'output speed sensor' on the transmission which provides the signal for the speedo/odo and also is involved with shifting of the transmission. That sensor would normally cause a P0720 when it fails, so you can either keep checking for that code or take a chance that it might be starting to fail but not so badly as to 'set' a code. It is under $100 for the part, and is a simple unscrew/screw to replace.
See if any of these bear fruit.
Roland
PS Please 'rate' my answer. Thanks
---------- FOLLOW-UP ----------
QUESTION: Hey Roland, fuse 16 is good, I cannot locate fuse 28 ( it only goes to 25? is it in another location? also I tried the codes again and in adition to 1648, I also got a 1698, any other ideas
Troy
AnswerMy error, disregard the fuse 28 suggestion.
OK, the 1698 says there is a failure in there not been digital communication from the transmission controller to the powertrain controller. Aside for the possibility of faulty wiring, diagnosis of whether the issue is due to the tcm or the pcm requires a diagnostic readout box with some sophistication.
So let me give you the wires that carry the digital data and you could pull the plugs and verify continuity while shaking the harnesses. If you can't find a loose connection, I think an electronics shop/dealer will have to sort it out.
The output or transmission line from the tcm is on pin 7 at the tcm and you should find that to be connected to pin 65 at the pcm and as well to pin 7 at the data link connector under the dash by the steering column. There is also a connection from pin 43 of the tcm to pin 7 of the white plug of the body control module under the dash. Finally there is a connection from pin 46 of the tcm to pin 14 of the data link connector. So see if those seem to be patent, while also shaking the harnesses.
The symptoms you have would of course be explained by the code 1698.
Roland
PS Thanks for the very kind rating.
PPS Check the following pins at the tcm plugs when the ignition is in the 'run' position to verify that the transmission control module is getting 12V so as to be able to operate: pin 11 and pin 56
I suspect that if either were missing due to fuse/wiring that would also shut down the tcm digital communication output.
Also, first check fuse Q in the power box under the hood. That one puts 12v on pin 56. I just noticed that a minivan owner, about a month ago, who also had a code 1698 found that fuse to be the cause of his problem!
