1998 Chrysler Concorde Auto Temp Control

No go.

Well, I put both BCMs in today and both resulted in a start/stall condition which is a security system feature of the BCM. Apparently when it finds itself in a car it doesn't recognize, it acts as though the car has been broken into and "zeroes out" the pulse width of the injector signal. This allows the engine to crank, start and run momentarily, then die.

I tried to get the ATC to do the self test, but I think the engine is supposed to be running for that. I need to research that again and maybe try it tomorrow if it's not raining.

Odd thing is that after I put the old BCM back in the car and ran an errand, it seems as though the auto temp function might be working. At least it didn't fail back into the manual mode and didn't go bonkers with the temperature and fan speed. I'll leave it in auto until I try a new BCM again.

When I installed the new BCMs, I could see the mileage display for the original car. I thought about why I have the BCMs out of these cars, and the only thing I can think of is that they were both totaled. Sad to think of the cars sitting in a junk yard all wiped out and that someone may have been seriously hurt or worse.

One of the issues that was a problem I thought was a bad BCM indicator was the trunk lid release not working. It seems like such a simple circuit and the wiring continuity and power all seem ok. I'm beginning to wonder if instead of the BCM being bad that I may have a bad junction block.

I really don't want to keep chasing gremlins. But, I'm now really on a mission. One way or another, I'm going to pin down what's going on with this beast.

Sorry this has turned into such a drama or epic story.

BG

Thanks for the support!

One thing that is really frustrating is how the maintenance manual constantly refers to the scan tool. I've heard that there is another manual, based on the manufacturer's info. Have you seen or used it? I can't recall who the manual publisher is. From what I've seen so far, I could use any and all other technical resources I can lay my hands on.

I'm thinking I'll just keep my eye on the ATC issue for now and see if I can't solve the trunk lid release button issue. That is such a simple circuit, that there has to be some way to resolve that one. Maybe in the process, I'll see or find something else that relates to the other issues. In the meantime, I'm going to hang onto the other BCMs, just in case. I've got something like 30 days before I have to return them for credit.

We were suppposed to see some rain today, but hopefully, it'll hold off and I can play with it some.

What I'd give my eye teeth for would be a scan tool. I may just call around and see if there isn't a shop or a dealer that has one and a gent who sounds like he knows how to use it. Sometimes, it's better to surrender the ego and ask someone else to fix it. This time, though, whoever I talk with is going to have to convince me they know how to troubleshoot electrical/electronic problems.

In the meantime, I'll keep pickin' away at it.

Have a nice Sunday, Sir!

BG

The "good old days".

I can totally relate to the 67 Camaro.

One of my favorite pictures from my younger days is one of me sitting on the fender of my 64 Impala with my feet INSIDE the engine compartment, resting on the frame while I was doing something under the hood with the engine. It was a great car that I had a lot of fun with.

Thanks for the schematic. I printed the same one last night just before throwing in the towel for the day and buttoning everything up. I've compared this schematic to the main one for the BCM circuits and just now realized that I was mistaken about the BCM schematic as it relates to the trunk release circuit. If you look for the C-4 pin 8 designation on the BCM circuit schematic you won't see it. It was really causing me some concern last night because the C-4 connector from the trunk release schematic isn't the C-4 on the BCM itself, like I misread the trunk release schematic to mean. I now see it should have been the C-4 of the junction block. This means that my problem with the trunk may be a junction block issue. DRAT! That also means the other issues may be junction block and not BCM.

I have an errand to run and will try to sort this out later. I think I need to do more digging in the manual and pull out more system-specific schematics. This is where I'm tempted to buy Chrysler manuals and schematic books. Paper docs are easier to navigate around.

Oh, by the way. The ATC went back to its old ways this morning. Figures.

Life is never dull.

BG

Just curious if you got the PM?

Hmmmmm.

Well this is interesting.

On the way to work this am, I got the temp inside where I wanted it then decided to try the Auto mode again. It went into the auto mode ok, adjusted the distribution to cool off the inside a little bit (had the temp at 85 to start with), then brought the temp down to the 78 that was currently set. I subsequently lowered the temp to 75 and it maintained it all the way to work with the fan never showing any tendency to go into a crazy fast mode.

I didn't do any maintenance on the car yesterday like removing and reinstalling the BCM or anything else. The only thing different is that the lights and windshield wipers were on because of rain.

I'll keep an eye on it and let you know how it's behaving. This week will probably not allow any investigations due to rain that's forecast until Friday and then being busy with Christmas related activities through most of the weekend.

I still plan to track down the exact reason the trunk release isn't working. As simple as that circuit is, I'll turn in my aviation electrician's union card if I can't fix that simple issue.

Quick question. Do you know if Chrysler has any higher level documentation on the operation of the BCM or the other systems other than what's available in the Mitchell manual? It would really help if I could get into the "brain" of the system a little more deeply than the Mitchell system allows.

Hope all's well in your neck of the woods and that you're looking forward to some relaxation during the Christmas and New Year's holidays.

Take care, Sir.

BG

Update.

First, clarification about the 75 and 85 degrees. That wasn't outside temp, that was what I was hoping the system might be able to provide inside. :-) Outside was a balmy 55. (Eat your heart out!) From the sound of it, you might be living in the Dakotas or up in those latitudes. Too cold for a SoCal boy!

I was thinking along the same lines you were. And, I'm thinking I might have to start keeping a logbook of what's going on at the time, lights, wipers, A/C, etc.

Today, it reverted back to its old ways with the temp and fan speed erratic and unpredictable. Had to go back to manual operation.

Your suggestion about the ground wire is a good one. And, looking at the BCM and A/C schematics, I see there are several types of grounds that these systems use: BCM-chassis grounds (BCM 20-pin connector, pins 1 and 20) and BCM sensor grounds (BCM C-1 pin 8 and BCM C-3 pin 10). When I can dedicate some time with the ohmmeter, I'll chases each of these and then see if I can't solder in temporary jumpers to ground for the chassis ground connections. For the sensor grounds, they really aren't a "ground" in the sense that they are "common" with the chassis grounds. They are technically signal returns for those circuits. Putting that to chassis ground could adversely affect the systems' operation or damage the BCM. What is interesting about the sensor ground issue is that the A/C system is acting as though the temps are going all over the place and it's chasing them with temp and fan speed variations. This could also be due to an intermittent ground for the system which your suggested jumper might reveal.

One thing that also is happening with the A/C system is that the temp display occasionally goes blank. It may come back in a few minutes or it may not for a longer time. I don't see that as a PCI bus communication failure because I can still control the A/C system manually which would be impossible if the PCI bus were open or shorted to ground.

As far as using a jumper for the hot side, I can pull the fuses individually for the BCM (fuse #s 14 and 19) to see what the system reaction is. I'm guessing that fuse # 19 is essential for system operation and will kill everything if it goes away. That would tell me that a jumper wouldn't be necessary. On the other hand, if pulling fuse doesn't give an immediate, obvious reaction, then using the jumper would be the next step. I'll also go through the same process for the ignition switch controlled fuse, # 14. That one, I suspect is just a "signal" input to tell the system that the system can operate because the ignition is in either run or start.

I really need to find out if there is a schematic for the Junction Block. There's a lot going on inside and going through that beast. Without a schematic, I'm assuming that the only info I need to know is what the other schematics tell me. I'm not built that way. I want to be able to wring out the continuity of all the circuits in it to eliminate it as a suspect.

What I'd really like to have is a full up test bench where I can run a complete systems simulation and verify the correct operation of all components. I've actually considered creating a breakout harness and installing it between the BCM and the Junction Block so I can monitor voltages while it's in operation. It really wouldn't be too hard; there are only 20 pins involved.

Didn't look for a mfr name on the BCMs. I'll do that when I get home tonight.

Last thought, then I'll sign off for now. Do you know if Chrysler has a technical services office we can tap into that might be able to supply me with more in-depth info regarding the operation of the BCM and things like the schematics for the Junction Block? You can see that I'm really on a mission now.

Have you seen any of my Personal Messages?

Back to work. Talk later, Sir. Stay warm.

BG

Heeyyyyyyy!

I think you might be holdin' out on me!

The repair manual I purchased from eAutorepair (Mitchell 1) doesn't have any M-1 fuses in it. And the diagram you included isn't in my manual. The Mitchell manual does the same thing by telling you to disconnect the battery negative terminal remote terminal. The Mitchell system doesn't indicate that the ATC will automatically enter the recalibration mode. They tell you to use the ATC "In-vehicle calibration and DTC check". Wondering what kind of super-manual you moderators are "Bogarting" for yourselves.

Sorry this has taken on a life of its own and is messing up your life. I haven't reached the point of it keeping me awake at night, but I do admit to thinking about this a lot most of the rest of the day.

I'm going to pass on the Chrysler help web site. I looked and it's similar to the 2carpros operation, except that you post a question and then a tech will tell you that he'll answer your question for some amount of dollars. Speaking of which, I just kicked a few more $$ into the kitty.

I'll stop by the dealership and see if the service writer is still talking to me and ask if I can find out what kind of manuals they're using. More than likely, they're an electronic system of some kind.

Too pooped to mess with this anymore tonight.

Buenos noches, amigo.

BG

Well, I know where to find the "secret" M-1 fuse now.

In pokin' around the net today (really busy at work as you can tell.) I found one of the other sites that offers help via a similar process that 2carpros uses and found a parallel discussion where the car owner basically said he had looked all over the car for an M-1 fuse and couldn't find it. Well it turns out that the name "M-1 fuse" actually refers to one of the fuses on the Junction Block rated at 10 amps. You know you got it when the radio display goes blank. I'm guessing this is the "always hot" fuse indicated on the BCM schematic. Less hassle this way as compared to removing the battery negative terminal. "Every day is a learning experience."

I'm very tempted to purchase the Chrysler body diagnostic manual (81-699-97229). I can get it for about $22 plus shipping from an online source. It would be great if the libraries had a technical manuals section where you could just go in, browse, make notes, copy pages, etc, then go home and play with the car. In looking around, I also ran across some Motor Manuals of the same vintage of the Beast. I used to use Motor Manuals all the time "back in the day". The other option is to cave in and order the Chrysler service manual on CD at $90. The problem is, I already know they're going to say, "Now, hook up your scan tool and write down the codes."

Here's an idea! We set up a scan tool in your house, interface it with your PC, and you and I can make megabucks from people who'd buy our OBD interface connector that they could hook into a USB cable to their PC and we could then run the scan tool over the net. WHAT AN IDEA. Now, run down to JC Whitney and buy one and we'll be in fat city in no time!

I'll have the mfr info, if there is any, for the BCMs as soon as I pull into the garage tonight. Probably Nippon Denso.

Have a good night, Sir. Don't eat too much popcorn!

BG

On again" today. The ATC was working normally today. Outside temps in the 40s and the inside was a stable temp based on what I set. Go figure.

A little more than minor. I was the bologna in a 3 car sandwich. The insurance company totaled the car, but I had taken such good care of it, they gave me some extra $$$ for its condition. I kicked in another $1800 and had it repaired. We have a really great body shop and you can't tell that the car has ever had a fender bender. Lift the hood and you don't even see overspray or buffing compound. They are first class.

As I recall the problems started at some point after the wreck. The car has also had the dash removed to have the air conditioner evaporator replaced. There's been more than the normal amount of disassembly and reassembly done on the Beast.

The image you included in your posting didn't really help that much because its size is reduced significantly and the resolution is way down. I've tried copying the image and viewing it outside of the posting, but the resolution prevents you from even reading the labels in the image. Thanks for the thought, though. If we were working from the same manuals, you could just tell me the image you're looking at. In some of the earlier postings, I recognized the images as being from the Mitchell manual I'm using. Those helped me to be sure I was in the right area.

I'm more than willing to buy whatever manual(s) will help me get through this. It's not like I'm going to fix a burned out fuse then sell the car. Not with all I've got invested in it.

Don't you wish we could just slap together a scan tool that's PC based and go into business for ourselves? Wouldn't that be a hoot?

I'm with you on the popcorn. When the wife and I go to the movie, that's dinner for me. I have a routine where I have to dump out half the popcorn then blend in butter and salt as I add it back to the box. Mmmmmmm.

BCM mfr is not indicated on them outside or inside. I'm guessing they're built for Chrysler by some outfit south of the border and sent to the factory for installation.

Probably won't be able to do anything else with it until the weekend. The rain and evening activities are getting in the way.

If I get a chance, I'll pull Mr. M-1, otherwise known as fuse 19, and see what happens.

More later, Sir.

BG

On again. Off again.

I had two different periods where the ATC was working as advertised. One was for the entire trip to work (23 miles) and the other was for a majority of the trip home. At about the half-way point, it went off the deep end and I went manual mode. On an errand, it worked fine. Coming home from the errand it immediately went bonkers. There's no particular operations that stand out where it was working right vs. Not. In one case it was daytime; in the other it was dark.

You may be right on the pinched or chaffed wire. As intermittent as the problem is, the front end damage it's experienced, and the removal of the dash, that's how it's acting.

As far as the S204 concept, I can check that out, next time I'm under the dash. I've been thinking the same thing about monitoring the voltage in various circuits. Regarding the loss of voltage to the trunk release circuit, I've already ruled that out. I have voltage on the pink wire at the switch and through the switch back to the junction block. What I haven't done yet is remove the junction block and check continuity through it for the various circuits. I'm pretty sure that at an earlier point I've confirmed the voltage was available through the switch and back to C-1 pin 1, which goes directly into the BCM. If the power is operating correctly from the fuse through the switch and back into the BCM and it doesn't release the trunk that says BCM to me. Especially if I can open the trunk with the key fob. This entire circuit will get closely scrutinized this weekend.

I was able to copy your response out during my reply and pasted it into a Word document. In Word, I'm able to expand the images and see what it is you're talking about. Can you please tell me what manual system you're using?

Well, again, it's late and I'm running out of steam.

Thanks for hanging in, Bob. When we get this puppy figured out and the mystery is solved, I'll buy you your favorite box of popcorn. :-)

Take care, Sir.

BG

Just about had it with the Manual system.

I looked at the trunk release issue again this afternoon and still have questions.

The power from fuse 19 (M-1 is visible below the fuse on its raised mount!) Is available from the fuse itself, through the junction block and connector C4 pin 8 to the trunk release switch and then to the BCM connector C1 pin 1. I checked continuity of the circuit as well as looking at the availability of power throughout the circuit. On the surface it would seem to definitely be the BCM since I have a signal in from the switch but no response from the BCM. Only problem is this is a logic circuit not just a simple switched circuit. The system will only unlock the trunk if it senses that the transmission is in Park. That is not shown on the manual's schematic. This information comes from the Owner's Manual.

I'm ready to ditch the Mitchell manuals and fork over the bucks for Chrysler maintenance manuals or another system that tells me the entire story. If I went entirely on what is in the Mitchell system, I'd be replacing the BCM for this problem. I have until Jan 5 to make a final decision on this and either keep and use a BCM I received or return them for credit. If I finally reach my limits and decide to just live with the non-auto ATC, I can rig a diode to pass the power around the BCM and direct to the circuit going to the trunk release solenoid. I'd much rather locate the real problem and fix it, but there may come a time where I decide it's not worth the headache, especially if I can't get a manual that will tell me all that I need to know about the system. :-(

Thoughts?

BG