1999 dodge caravan 3.8, data link connector not communicating with pcm
Country: United StatesMake: DodgeModel: Caravan LEYear: 1999Engine: 3.8
I have checked all fuses, replaced pcm, recent repairs: fan relay, spark plugs,
Hello and welcome to JustAnswer!
Are you having problems with a scan tool not powering up or just a communication problem?
Are you able to communicate with other modules through the DLC, or is no communication possible with any module?
Do you have a digital voltmeter to do some electrical testing or are you looking to know possible causes?
I have digital volt meter, went for inspection sticker they told me it failed to communicate. Tried three OBII scanner powers up but fails to link
Are you having any other electrical problems at all?
Just bought van on monday have not experienced any other problems except rear hatch auto door lock is not working. On startup I do get check engine light& abs light
so I think all other electrical is working. Except fan relay whick I replaced and is now working fine. If it matters AC does not work and blower motor only works on high
Ground the black lead of your voltmeter and set the meter to 20v DC. Check the voltage on the pink wire.
Turn the key on and check the voltage on the white/black and violet/brown wires.
I have 2 pink wires one on top and one on bottom voltage is as follows
top pink 0v
green 4.55 v
bottom pink 12.26v
if it matters rear trunk hatch has been replaced with a 1998 dodge caravan hatch
What is the resistance to ground on the black/white wire?
Do you see any terminals that are damaged or pushed out?
all terminals seam fine, how do I test resistance on black/wht wire?
Set the meter to read resistance and probe the terminal. Set the meter to the 200 ohm scale.
not sure I set meter right, set to 200 key on 1.3 key off 0.4
That sounds ok.
Do you have a big chain parts store close like an Autozone, etc? They will normally read fault codes for free with a code reader. I'd like to see if they can communicate with the van. You don't have a problem with the fused battery voltage, ground, or bus wires to the DLC. If the terminals aren't damaged or pushed out then there's no reason it wouldn't communicate.
I have my own scanner, but yes I have an autozone close by
Do you have a scan tool or code reader? Have you tried it to see if it communicates?
I believe it is a scan tool Actron CP9135, I just connected it, it keeps saying link error.
Can I connect a jumper wire from DCL to PCM to see if there may be a break somewhere? If so which wire's on dcl and corresponding wire pin on pcm
The Actron CP9135 is a code reader so we wouldn't be able to use it to see if we could communicate with other modules like a scan tool would. Your bus voltages are fine but the PCM may not be communicating on the bus. It would be very helpful if we had a scan tool and could see if other modules will communicate or not.
The PCM is to the left of the battery and power distribution center area. What we would need to do next is backprobe on the bus wires by inserting paperclips into the back side of the connector until they contact the terminal, and then touch your meter lead to that and read the voltages with the key on. The bus wires are in pins 59 and 60 of connector 2 at the PCM.
are there numbers imprinted on connector? Do u know what color wire I am looking for on pcm
The bus wires are white/black and violet/brown wires, the same as we tested at the DLC. The terminal numbers should be printed on the inside of the connectors but you won't be able to get the connectors off with the PCM in place.
I donot have a problem disconnecting bus connectors and getting access to wires can I do this voltage test with bus connector removed from pcm or do I have to back probe them?
There isn't a bus connector. The bus wires are in connector 2 of the PCM along with about 50 other wires. You need to insert a straightened paperclip into the back side of the terminals on the wires that I described and read the voltages with the key on.
ok I will do that, it is going to take some time. How do I get back to you?
It is my understanding that pink#65 is the transmit wire,lt grn#75 is the recieving wire,vio/brn#59 is ocd+, wht/blk #60 is ocd-. Am I looking for the same voltage at pcm that I had at dcl? If they are not the same or if they read 0v can I try a jumper wire from dcl to pcm?
The pink and light green SCI wires are used by a factory scan tool. A code reader should be communicating over the CCD bus, which is what we are testing. Pins 59 and 60 are the bus wires that we are checking now. If the circuits are ok then they will show the same voltage at any point, just like any circuit.
Ok I will check them, how do I get back to you when Iam done?
Come back and reply to this same question just as you have been already and I'll get notification that you did.
ok get back to you when Iam done thanks
I checked them, #59 vio/brn 2.5v, #60 wht/blk 2.45v,#65 pink 0v, #75 grn 4.5v
I attached my code reader checked again the only one that changed was #65 pink it now read 4.6v... Any Ideas?
It doesn't sound like there is anything wrong here at all. Everything has checked out. Are you absolutely sure that the terminals at the DLC are in good condition? You may just have a connection issue there and that seems very likely. If it's not in the connector then it sounds like the PCM isn't communicating, but if that was the case then there should be warning lights on.
I am not getting any warning lights, except oil light comes on at an idle once in awhile. I think terminals are fine but I will clean them and apply some dialictic if that is recommended. I already replaced the pcm could it be a bad one? Don't want to spend another $350 on a pcm just guessing.
I don't want to throw a PCM at it either, which is why I didn't jump to replacing it. I really think you just have a connection issue if no other warning lights are on. If the PCM wasn't communicating then other modules would have set communication codes. This is another way that a scan tool would come in handy, checking to see if communication was possible with other modules and seeing if they had PCM communication codes.
Ok I will go to Autozone and see if they will connect a scan tool not a code reader to the car and see what they find. What sort of test do we check with the scan tool to see if pcm is communicating?
Just see if there is communication with the PCM and other any other modules, if they have an actual scan tool available. The free checks they do are usually done with a simple code reader.
Ok I will see what I can do and get back to you. Thanks again
Are you available?
I dont know if you remember me from yesterday but, I was NOT able to get ahlod of a scan tool but this is what I have tried.. My Dad has a 1998 caravan I checked my code reader on his van it worked fine, I put my pcm in his van it worked fine, I put his pcm in my van and still could not get a link... I then put my pcm back in my van using the volt meter and my code reader connected I back probed my DCL this what I found
pink wire #65 0v with key off 4.5v with key on when I asked my code reader to link up the voltage flucuated all over between 1.8 v - 4.5v while the code reader was trying to link.
also the blk/lt green wire has 0v with key on key off and van running
Do you have any suggestions?
Don't swap modules between vans. That could end up doing $1,500 worth of PCM/BCM damage to both vans.
Your next step was to check the bus voltages at the PCM connector. What did you find for that?
I had the same voltage for all wires#65,#75,#59,#60 except I did not check #65 with code reader attached I wasn't sure if it was safe. But if I get voltage at dcl on pink wire only when code reader is attached isn't the trasmit wire from the pcm? The best I can figure out is the blk/lt grn wire does not go to the pcm it goes up to something in center of dash. Am I mistaken?
What is the voltage on the white/black wire at the PCM with the key on?What is the voltage on the violet/brown wire at the PCM with the key on?
#60 wht/blk 2.45v
#59 vio/brn 2.5v
#65 pink 4.6v
#75 green 4.5v
at pcm with key on
Next measure the resistance of these two circuits.Put one meter lead at the light green wire at pin 75 of the PCM, the other meter lead at the light green wire in pin 8 of the DLC.Put one meter lead at the pink wire in pin 65 of the PCM and the other lead at the pink wire in pin 7 of the DLC.
Sorry volt meter set to 200 ohms for these test?
Yes, we want the 200 ohm scale again for this one.
Sorry key off wire harness left connected to pcm back probe with paper clip and battery left connected for these test?
ok be back in a few mins with results
The PCM unplugged and battery disconnected would be best but it really shouldn't matter.
pcm unplugged battery disconnected volt meter set to 200ohms
#65 - #7 0.4 ohms pink
#75 - #8 0.4 ohms lt green
Those numbers are good too.
All of the wiring between the PCM and DLC is ok and the DLC has it's powers and grounds. You have to either have a connection problem at the DLC or the PCM isn't communicating.
I have tried three different pcm's and two communicated fine in my dads van using my code reader, so would you assume the problem is in the dcl? Or could there be a problem in the connection of the wire harness to pcm?
You've just verified there is no wiring problem between the DLC and the PCM. It would be a good idea to make sure the terminals in the PCM and connector are ok if you haven't already. If they're ok then you know everything from the DLC to the PCM is ok and there has to be a problem of some sort at the DLC.
ASE Master and Advanced Certified, Chrysler/Dodge/Jeep Master Certified, Trans and Hybrid Specialist
Just wanted to let you know I figured out what the problem was with dcl not communicating with pcm.
#65 pink trasmit wire which had 4.5v should have 12v
I cut wire at pcm and dcl ran another wire and everything worked fine.
Thought I would let you know in case you have the problem again.
Thanks for trying, I appreciate all your help