I'm working on a 1999 Blazer trying to check for DTC's with an OBD-II scanner and message is that it cannot establish a link with the VCM. Is there a way to test the VCM directly? Are there any electrical connections between the Data Link terminal and the VCM that can be checked or does it go straight to the VCM? Left side of vehicle was under water (Relay/fuse block side), ECM was not. Vehicle starts for short period (2 seconds) and stalls. It may be a Passlock issue but I can't pull the DTC's. I have already installed a new ignition switch and have checked the fuel pump and relays. I have also tried the Passlock re-learn process with the start-stall, leave in run position for 10 minutes, key off for 5 seconds for 3 cycles ....... no luck.
Appreciate any help.

 

Check the CIG fuse. Replace it if it is blown. This also powers the DLC.

Have you monitored the fuel pump power source as well as fuel pressure during the stall?

 

All fuses check out okay and relays. There is power at the DLC, it just doesn't establish a communication link with the VCM. The OBD-II is new and works on my other vehicles. I have been communicating with you about this vehicle under a fuel related thread. All of the fuel check information is in that thread. I did replace the ignition switch based on your recommendation. I was thinking it was a fuel problem, but I was told by a mechanic that it could be the Passlock issue and there would be a DTC stored. My new problem is that I can't get the tool to read the codes.

Is it possible that the water intrusion to the left hand side could have shorted out the VCM requiring a replacement? Is there any way to check the VCM other than with the scanner tool?

 

I suppose that anything is possible.

 

On the top row of the DLC, the pin #'s are 1-8, bottom row 9-16 2 is your data line, don't shove anything in there or kiss the computers goodbye (probably). 4 & 5 are grounds, 16 is 12v+ from the CIG fuse. Check those with a test light. From pin #2 is a purple wire, on the harness going into your body relay block (under the dash, to the right of the dashboard fuse block is a splice pack. The purple wire goes into it. That splice pack is where all the data lines from the modules in your truck link together, check that? Check your scanner first on another GM similar in year just in case..... To really test things out you need a scanner capable of communicating with more than the VCM to see if any of the computers can be interrogated.

 

Thanks for the info RonJon.

I checked the 12+ and (2) grounds which are okay. I added an attachment with a photo of what I believe you are calling the splice pack. It is a large multi wire connector with relays and a few fuses with a plastic cover. Is this correct?

I do have a few questions about the VCM wiring.
1). The wiring diagram shows that the data line wire at the VCM is dark green, but purple at the DLC. Where does this change color, at the splice pack?
2). Is it possible to temporarily wire another DLC at the VCM using the dark green wire and 12+ with the (2) negatives? This would tell me if it is a wiring/connector issue that is preventing the communication issue.
3). The wiring diagram shows wires labeled with either an A, B,C, or D prefix followed by numercial ID's. For example, the Data Line is D11 at the VCM. Do these letters correlate to the RED, BLUE, WHITE, and BLACK therminal packs on the VCM?
4). If not, how can I find the dark green D11 wire?

I also installed a replacement IP cluster unit (the original one drowned) and I found that all the gages and lights work. The SECURITY lights stays on full time as suspected, which brings me back to the reason for trying to scan the VCM ........ to clear the Passlock DTC and try a re-learn process on it.

Thanks for any and all help.

 

I don't have the schematic in front of me but purple goes from the splice pack to the DLC, every other module has its own color. The picture you attached is the body relay cluster, it is not a splice pack. Trace back from that and the splice pack should be attached to that harness. Supposedly it's attached to the outside of that harness (that's what the illustration shows) Unless you have a super good scanner you're not going to be able to clear the passlock DTC anyhow... (most scanners just talk to the powertrain computer) The more in depth instructions say if you've made it to this point and haven't found a problem you'd disconnect all other modules except the VCM then probe that pin #2 with a test light. But can you establish communications with other modules? BCM, IPC, 4WD, Security, etc.? Did you try disconnecting the battery for a few minutes before trying the passlock clear procedure? That clears the current codes from the VCM anyhow. Did you try your scanner on another vehicle to confirm it's working? (hey, ya never know). (edit addon).. The VCM connects to the splice pack via a dark green wire pin 11/black connector on the VCM. BUT it also has a direct data connection between the VCM ( pin 14 blk connector) and the BCM (pin A1, connector C2), yellow wire. The BCM connects to the splice pack via a light green wire pin A12/C1 connector.

 

Thanks again RonJon, you have provided me with wealth of very useful information. I don't think you know the history of this vehicle, so here it is. This 1999 Blazer belongs to my son, which he drove into a water filled ditch. The water was up to the top of the engine on the driver's side, but not on the passenger side. Water was trapped in the interior and filled the front when the tow truck lifted it rear end first from the ditch. The water sloshed around and was up to the IP cluster. I had removed nearly every electrical component and dried them out. Nearly all work fine. I installed a used IP which works fine and a new ignition switch.
From the last post, I believe that I found the splice pack (sorry for my ignorance). I found a small (2"x2" white) connector unit that only has wires leading in from one side and has a "comb" like metal connector that is inserted in the other end.
Regarding the tool, I am using a brand new Innova OBDII scan tool that communicates only with the VCM and can clear DTC's along with providing the "Freeze Frame" data that occurred during the trouble code. I have tested it on a few other vehicles and it is working properly.
I have just discovered a problem that I will need to correct right away thanks to your last posting. I was totally unaware that the BCM was located at the bottom of the HVAC unit near the floor. This component was completely submerged in water and surely is damaged. This is one of the components that makes up the Passlock system and needs to be replaced. I have found a few on eBay for around $70, but the sellers state that it may have to be flash programmed to the VIN. I will check tomorrow at the dealer to see if this is the case.
Are there any other electronics that are located in the interior that need to be checked?
I will let you know in a few days about the progress. Please feel free to provide any ideas as to what I may need to do. I do appreciate you help.

 

If you replace the BCM it will be to need to be reprogrammed to your truck. VIN number and all options on the truck and it's a dealer job. I kept mentioning the BCM because it's where the DTC regarding passlock is stored. One thing you could try is disconnecting it, turning the truck on (don't try to start it) and see if your scanner works. If it does at least you'll know it's the BCM grounding out your computer network. If you're still not having luck I suppose the next step would be to remove your center console and under it near the front is another module attached to the floor of the truck, the Security Module. Same thing, try disconnecting that and test. If you had water intrusion in the BCM it's right on the same level. <laughing> and you're not ignorant for not knowing what a splice pack was, my directions were general at best. You're the one lying on muddy rugs hunting thru the dash wiring trying to follow 'em. I do recall reading the story of the half flooded truck but I don't remember the subject at the time.

 

Thanks a million !!!! I will get to your recommended tests tomorrow and see where that takes me. I also believe that the transfer case control module located on the passenger front body hinge pillar is ruined too. Sooner or later I hope that my son will have a running vehicle. It's either that or part it out. It would really be a shame because it was in very good condition all the way around.

I'll post back tomorrow.

Hey RonJon .......... YOU ARE AWESOME !!!! I just ran the test with the BCM disconnected and it was able to establish communication with the VCM. There are no DTC's stored and no freeze frame data due to disconnecting that earlier. I will definitely get a different BCM and hopefully this will end the "SECURITY" issue. I looked real quick for the Security Module, but not sure where it is. Everything has been removed and the IP is hanging temporarily with (4) fasteners and I don't see it attached to the floor in the area that you described. What does it look like and might it be in a different location. This Blazer had a cassette player in the center console which was directly over the floor and adjacent to the BCM.

Thanks again. You have rekindled my hope!