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Computer weird-ness...

4K views 67 replies 8 participants last post by  Dave2302 
#1 ·
All, I'm continuing to work on restoring my 2001 S500 and I'm running into issues where I'm chasing my tail on reported computer issues. e.g. one day the diagnostics I run say that the tail light is malfunctioning, but the next day or after a battery disconnect, the error is gone. It seems that virtually every computer system reports at least one error, which after a battery disconnect goes away. The car runs and drives fine, no issues at all...

I do work in the computer/micro-controller design industry and it's similar to a bad ground or very noisy reset messing up random circuits/systems.

Normally, I'd start with one system at a time and keep fixing them until the issues are gone, but I'm chasing a very elusive snipe here...

Has anyone else experienced these types of system/computer gremlins? Is there a more problematic system/computer/whatever to start looking?

Thanks in advance.
 
#2 ·
I would look at the battery and alternator performance. A weak alternator (especially if with a diode failure) would generate all sorts of pulses on the charge line, and if the battery is weak, it will cause spurious computer problems.

Have battery and alternator checked at a workshop with proper equipment to test the regulator and diodes (scope). It is usually free and if all is fine at least it is checked out.
 
#3 ·
Hi mrboca,

The battery is brand new and I took the alternator and had it tested before dropping the engine back in, all good. Thanks, but not it.

I'm expecting to find some water damage or corrosion somewhere, but this car was well cared for before the car sat for a while. I'm thinking it's a SAM or something else mystical causing the issues.

Thanks!
 
#4 ·
If you have a scanner (or a friend with one :)) find out what the error codes are. sometimes the hub for the body control sends al sorts of error messages due to corrupt or lost messages and the scanner thinks those modules are at fault. You need to identify what works and what does not, and based on that you will find the common denominator of the problem.
 
#5 ·
More info... It may be a complete coincidence but just discovered that my blower motor doesn't work on my climate control. I've read that leaves and dirt clog the drain holes and long story short, the water backs up, gets wicked by the carpet and winds up messing up the rear SAM. I'll start looking there...

If I find corrosion or whatever, I'll include pictures here.

Thank you to all.
 
#7 ·
You need to check the can_bus connector /coupler (x30/4) under the carpet at the passenger side. If that area is wet you need to remove the carpeting and check the connectors there. It is just in front of the right front bolted anchor for the passenger seat.
 
#11 ·
Hi all,

I wanted to give a quick update on my "weirdness" issue, well, not mine, the car's...

First, the blower motor was seized so I ordered a eBay replacement as well as the controller. I unclogged the drain hole and made sure that there's won't be any more water standing around in the vent area. I'll install the motor and controller in the morning. Done!

Now, the car's computer weirdness continues... The most common symptom is when I start the car, I get between 2 and 7 failures/malfunctions. There's no rhyme or reason to the errors, and the next time I start the car I'll get three or four. Errors such as tail lights not working, when I walk around the car all is fine. Thinking this is a CAN bus issue, as suggested by mrboca, bad SAM, evil spirits or poor grounding.

I do have a scanner but since the messages and errors are intermittent I'm pretty sure that I'm not going to have success with that. I did pull up the carpet on the passenger side in front of the seat and only found a boden cable for the seat, no CAN connector. Most of the sporadic errors are due to tail light or turn signal errors, so thinking something might be up with the SAM under the rear seat. I'm not really sure where to go with this since the area around the SAM seems clean and dry and no sign of standing water, either now or prior.

Anyone have any thoughts on how to debug this? Worst case, I'll use my handy contact cleaner on all of the connectors on the SAM and hope that slays this beast.
 
#13 ·
Hi,

I tried the stripping fuseboxes and cleaning, and also dousing the SAM and connectors with Electro Cleaner, but IMHO once a SAM gives problems then it is better just changed, mine didn't work after contact cleaner :wink

I understand that you have various issues that are intermittant, but you gotta start somewhere.......

Get a s/h SAM from EBay, and try that, I paid buttons for various Modules off EBay, and all are working fine :grin

If you lived nearer me I could lend you a rear to try.

HTH,

Cheers Dave
 
#15 ·
That's the problem really, I don't think it's been wet, at least I don't see any signs of water stains so far, but I haven't removed it. I do know that the idiot PO left the trunk open in one or more rain storms... not surprising since he also ran the engine without water... I'll go ahead and see if I can pick one up. Assuming that the rear SAM is the best place to start swapping things out.

Thanks to all!

P
 
#16 ·
One additional bit of possibly unrelated info... My trunk hydraulic opener doesn't work. The unit was empty when I got it, so I added tranny fluid but the motor doesn't energize. The fuse is good, so assuming it's the motor or the SAM. Coincidence?
 
#17 ·
Hi,

Ah, well, I can impart some of my learning from this Forum there too :laugh

Recently fixed that on a mates car.......

Rear SAM has nothing to do with that, it is controlled by the PSE.

First off, pull the plug off the motor and apply Battery + and - to see if the pump runs and the trunk goes up and down, swap polarity to reverse trunk movement.
If that's good, put plug back on motor and take the plug off at the PSE end and power it from that end, you are now testing the 2 relays. If all that checks out OK you'll need SDS next.......

Now read the PSE and see if, in the codings, it has the option for Power Trunk Closer, if not wrong PSE.

If it does have the option it may just need normalising, SDS will walk you through that procedure.

If some idiot has put the wrong PSE on the car you will need the later part number, or you'll never get it to work.

HTH,

Cheers Dave
 
#19 ·
Your blower motor was seized and the drain blocked, the PO had left it in the rain with the trunk open, there has been water in. The front SAM you will need to open it up to see, but I'll bet it has been wet, has for the rear if the water has been through the blower it has been in the floor of the car and will have made it's way to the rear SAM, again you will need to open it to see the damage. It could also be just the the rear connection have started to corrode slightly and will need a very good clean at all the connection points from the bulbs to the plugs, remove the bulb and the holders and check.

All so take note of the errors when you clear them and see what are the most common errors.
 
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#20 ·
#21 ·
Pinkster,

All good points and I agree with you, there's been water in there... I already started cleaning the tail lights and found a split tail light gasket and corrosion, and also found that someone had jammed a two filament bulb and connector into a one filament socket. Did a lot of cleaning and bench tested all the lights, all good now. I put everything back together and got no errors one time and then got the same old tail light errors the next time. I'll tear the interior and trunk apart this weekend and give everything a good cleaning as well as checking continuity. I'll also check out the trunk lift assist as well and see why that's not working. I'll post pics of what issues I find. My new blower motor and controller arrived yesterday so now I'll have A/C and heat, hopefully.

Thank you all
 
#25 ·
Ok, so based on the reasonable amount of rust on the two nuts on the positive terminals I'm going to assume, yes, there's definitely been water/moisture/h2o in the car at some point in the past. I did feel under the carpet and didn't find anything wet per se, but please know that I live west of Tampa and we haven't had much rain in over a month and temperatures in the high 70s and low 80s, and I unclogged the drain hole about a week ago and missed the last rain. Assuming the interior will remain dry from now on. (I'll also keep an eye on the drain hole every month or so. I did fashion a nice little de-clogging tool out the the metal edge of a legal sized file folder, the thing you put files in, usually green, from an old file cabinet.)

I'm happy to report that I just replaced the blower and fan controller and yippee, I have A/C and heat! Another bite taken out of my elephant!

Now, onto the CAN issue or SAM issue(s). Everyone's wonderful input has steered me to the rear SAM as the possible cause of my intermittent malfunction messages. I'll go ahead and remove the SAM and give all of the terminals a good cleaning and hope for the best. Worst case, I've got my eye on a replacement SAM for $100. I've also got the console removed, for a swap out, and plan to remove the driver's seat and replace that as well this weekend. Is there anything I should be looking at other than the SAM, possibly under the carpet wiring etc.? I don't mind pulling the passenger seat too... Now would be a good time since there won't be much of the existing interior that will remain in the car while I do the seat and console swaps.

Thanks again for everyone's sage advice!
 

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