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Discussion Starter #1
All - hoping someone has been through this because there's some moving pieces involved. P1698 code and non-functioning instrument cluster, including no odometer readout. Cluster issue was intermittent but is now fulltime. Code P1698, no CCD messages received from TCM. If I go to the scan section of my scanner it will show me P1695, no messages received from BCM...but that P1695 doesn't throw the light on. I have tried multiple clusters, and I see from the diagram that there are no separate wires for the cluster gauges, just power, grounds, and the CCD wires. So that means all the info for the gauges is coming thru the CCD bus. Unplugging the climate control module seems to keep the CEL out, but doesn't solve the rest of it.

Originally when we bought this thing the CEL was on, and I noticed that someone had put a non-matching climate control module in it; the plugs are color coded, and they didn't match, plus there is a key way tab to keep this from happening, but the previous owner had cut it out so that they could install a module with blue connector instead of the white one that the vehicle uses. Got a used white one and that worked for a while but the issue never fully resolved. Now, the latest fun is that I am trying to get OBD monitors to run so I can smog this, but something is off here too. Last week simulating driving with front wheels off ground, I was surprised when O2 heater and EVAP monitors both ran quickly and easily, but then I found that the cooling fans were not working. In my brilliance I disconnected the fan relay and jumpered it, not realizing that this would set a code for the relay. So had to clear codes which of course reset the monitors.

Okay, so I diagnosed the fan problem as a bad relay and got one at the junkyard, so fans work. But now when I go try to run monitors again the O2 heater runs quickly, which is good because that one is usually stubborn on these, but not only can I not get the EVAP to run again, I can't even get the easier ones like O2 sensor or EGR to run. I am totally flummoxed because I really don't want to run down this CCD bus problem until I make sure this passes smog, and no matter what I do I cannot get any more monitors to run. I've done more of these accelerated monitor driving cycles than I care to admit but this one is somehow different.

On that CCD thing, I cannot find any shorts or opens in the wiring, I have disconnected one module at a time and nothing makes the cluster work. My feeling was that it's probably the BCM but I don't believe you can simply grab one from a yard and expect it to work right, because it stores VIN and odometer info. Then again, I'm not totally sure it's a bad BCM. I wonder if it could be a bad ECU, which might be contributing to the monitor problem. I do not have an oscilliscope which I think you need on these bus systems. At this point I'm considering just grabbing a used BCM and seeing if it at least lets the cluster work, even if it has to come back out again so that I can send out the original one for repair. I don't do dealerships so that's out. If anybody knows direction I could take I would appreciate it. I have the stripped-down Voyager with manual windows and no ABS but it runs like a Swiss watch. Thanks,

MT
 

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The first thing I'd check is the CCD bus terminations. Check resistance with a multimeter, there should be 60 ohms between pin 3(CCD +) and pin 11 (CCD -) on the OBD2 port. There is a 120ohm termination resistor at both ends of the CCD bus.
 

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Discussion Starter #3
Thank you. I'll do that today and advise. Yeah, with CCD the terminating resistors are in the ECU and instr. cluster,

MT
 

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Okay, there is 60 ohms at 3 & 11 on the DLC, and when I disconnect the instr cluster, I get 120. IPC has a termination resistor so I think that all checks out ok. Leaning toward bad BCM but totally open to any direction. Thanks,

MT
 

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Discussion Starter #5
Tying this off, scored a used BCM at the yard today, same P/N as mine, and now all gauges work. Even have a tach now...I suspect the CEL will stay out. Will advise if not, but otherwise thanks,

MT
 

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Congrats on diagnosing and fixing it! Thanks for posting the fix.
 
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