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1989 Cutlass International Serial Data Line contents/ origin


5stevo4
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Good clean battery connections. I believe the climate control display is an issue with the old solder connections inside the module (fixed DIC this way) and possibly the caps as RobertlSaar stated. But not sure why compressor doesn't run after car is started. Comes on after a few minutes. Possibly a little low on R12. As far as the gauges go, my manual says if you have corrupted DIC gauge info, check your serial data line. I have confirmed continuity from ECM to DIC, ALDL and no short to ground. Have not checked to see if it goes to gauge cluster. I suspect it does since I lost cluster tach at same time as DIC gauges showed corrupted readings. Already changed ECM. Could data problem start before ECM? Ignition module? crank sensor? car still runs and drives. 

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Don't know Cutlass but 89 Riviera had a jumper in the ALDL cap (says "do not remove") that completed the data loop. Without it any break in the data line would block intermodal communications. 

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I've established continuity on the orange wire SERIAL DATA LINE common to ALDL and DIC. By "cap" do you mean capacitor or was there actually a cap to cover the ALDL plug? I haven't noticed any at the ALDL plug and I don't see a jumper on the plug. BTW, I have an OBD 1 diagnostic scanner and I have never been able to read anything on this car. Says connect cable to ALDL. I've heard not all scanners will scan every car. Any one ever use scanner successfully?

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Thanks for your input rockfangd. Car runs and drives. The Climate Control works the same now as before I resoldered connections in the unit. Im not sure but I don't see why it would be integrated in the datalink. I believe the only sensing it does is internal and external air temps via thermostats. The DIC gauges and UB3 tach both went down at the same time and that was before I resoldered either the Climate Control or DIC. I do believe there is something affecting the datalink. I have established continuity of orange datalink (serial data line), confirmed no short to ground, good circuit ground and power supply. How else do you troubleshoot the datalink? I don't have an oscilloscope.

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Ok I suggest unplugging the plugs at the DIS and see if the cluster starts to work properly. 

I honestly never really had any issue with OBD1 datalink.

I  am going to have to do some research here 

Just take out the philips screws that secure the cover to the sport pod  (back side) just be careful as they tend to break easily

Edited by rockfangd
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Don't know Cutlass but 89 Riviera had a jumper in the ALDL cap (says "do not remove") that completed the data loop. Without it any break in the data line would block intermodal communications. 

 

Wasn't that the car with the touch screen? Or an I thinking the Reatta?

 

I've established continuity on the orange wire SERIAL DATA LINE common to ALDL and DIC. By "cap" do you mean capacitor or was there actually a cap to cover the ALDL plug? I haven't noticed any at the ALDL plug and I don't see a jumper on the plug. BTW, I have an OBD 1 diagnostic scanner and I have never been able to read anything on this car. Says connect cable to ALDL. I've heard not all scanners will scan every car. Any one ever use scanner successfully?

 

I'm assuming the ALDL cap. The older cars came with a cap on the computer port. I'm not sure what year they stopped it at, but my 93 Z34 has a cap and 94 Cutlass doesn't have the cap. Wasn't there since I bought it. I've kept the cap off the Z34 and it never caused any strange issues... 

 

What kind of scanner do you have? Some scanners need special add ons to the tool in order to function. 

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unless there is a resistor or jumper in the cap that contacts at least 2 of the pins I would say it is not necessary. I will mention I have never owned a vehicle that had a cap over the ALDL but have worked on many fords that had them. OBD1 and OBD2. They are useless in any other way than keeping dust out

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Just want to say, I really appreciate the conversation here. Didn't know there was such a following for these cars. I have already unplugged the DIC and checked if the UB3 tach would work, still did not work. I have an Actron OBDI and II. Even when its plugged in it doesn't read. Acts like its not plugged in. Scanner works on my other vehicles. I read codes by using jumper in ALDL and counting "service engine soon" light flashes. No touch screen. Does Serial Data Line only carry DIC gauge info (battery volts, coolant temp, tachometer) and UB3 gauge cluster tachometer? Thanks!

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serial line carries all info through the car except for possibly the ECC(that sometimes has it's own circuit, I don't know if they did in 89 for the CS). ECM, ABS, DIC are all on the same line.

 

sounds like the ALDL transceiver inside the ECM may be done. do you have an ALDL cable that you can hook up to a laptop? would help to see what the ECM is actually pushing out.

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Checked fuses first thing. Wouldn't hurt to double check though. I do have a computer cable with my scanner. Never used it. Scanner has never been able to read, even when tach and DIC were working right. Not communicating. I will look into that. I am convinced that there is something wrong with Serial Data Line. I have changed the  ECM with no luck. I do not have ABS but I think the cruise control also uses the Serial Data Line. I'm going to see if that is still working. Maybe one of the systems using Data Line is loading it down. Like unplugging DIS to see if gauge cluster tach comes back, I'll try to unplug the other systems one at a time and check cluster tach. Then unplug gauge cluster to see if DIC gauges come back. Thanks for the ideas!

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  • 2 weeks later...

Have not had chance to check other Serial Data Line systems but did talk with Actron about my scanner. Found out that the pinout for the early ALDL connectors are not necessarily the same as later years. They were not all uniform in the early days of computer control. It looks like my ALDL pins of +12V, ground and Serial Data Line (M) are different than the scanner connector. I'll be hooking up jumpers to see if I can read anything with the scanner.

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  • 3 weeks later...

Serial Data Line. Was driving and had open stretch of road so I punched it and low and behold, the cruise control started working. Then I noticed the gauge cluster tach was working. Checking other things, the Climate Control was not flashing "F" anymore (had 09 Serial Data Line error code), DIC volts, coolant temp and tach guages were now working. Punching it must have reconnected what had opened in the Serial Data Line somewhere. Hope it stays. Next job is to replace Climate Control unit since it will not turn on right away. Stay tuned and thanks for all your help!

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Find where the climate control is grounded, and clean the connection. I resoldered mine, and wouldn't come on every time. Had the console out for a month while driving the car, and unplugging then replugging the power cable would turn the climate control on. I have yet to find the grounding point to clean it. I believe that's the root cause. 

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Thanks for responding! I tried resoldering a couple of times with no luck. Unit doesn't come on when car is started but wait a few minutes and it comes on and works fine with full control. I have the original factory shop manual and it has ground diagrams. I'll try and locate that. Let you know. Keeping an eye on the junk yards for any replacements. I think 89'-91' Cutlass or Ninety Eight might be the same. Thanks

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If you know what needs grounded why not just establish a new ground? The factory one is obviously not the most suitable to begin with since they failed.

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