Repair-It

Ordered a Tech 2 clone. Hopefully this project will progress.

Also, while waiting for tree people I finally noticed something about the STS: double pane laminated windows. Sew fawnsay.

Pasting from Cadillac forum for my convenience. I will add pics next.

Got my scan tool today. Amazed by the speed of the shipping. According to the DHL tracking, it was picked up on Tuesday and delivered Wednesday. Granted they are 13 hours ahead of us and I think times are local. Even still, picked up Monday afternoon from Hong Kong and delivered Wednesday by noon. That's awesome for free shipping. DHL said Hong Kong. Their packaged "invoice" said Shenzen (and a $55 value, lol). And the address on their website is in Chongqing which is waaaay deep into the mainland away from the coast. Maybe they just shipped it to some facility/port in Hong Kong where DHL actually came into the picture. Or they have a warehouse there. But I digress.

Anyway, let me cut to the chase here.

The scan tool booted up and worked great after I figured out how to connect everything. This thing is huge. Comically so. Also, this was some seriously advanced stuff for the 90s. A little clunky by today's standards and I guess that's where MDI shines. In the main menu this claims to cover 1991 through 2013 vehicles which is an incredibly wide range. I think Global A must have been on everything by 2014, so that date checks out.

The first thing I tried was to command the ALC exhaust and compressor. Of course, it didn't have those commands so I went back to this thread and was reminded I had to go to the 08 STS instead. Sure enough, that worked - I got the menu options.

However, when I commanded the compressor, I got a beep and an error. "Exhaust valve faulted." Same for when I commanded the exhaust solenoid. I scanned for DTCs and I had a C0660, symptom 1: exhaust solenoid short to battery. Each time I would reset the codes, it would immediately come back. Eventually I figured out that when it reset the codes, the ESCM reset somehow, and I'd hear the exhaust solenoid actually click once. I could also trigger this by plugging in the ESCM with key on engine off. When it boots up, it seems to immediately trigger the exhaust solenoid (one click) and then also set that code.

So I unplugged the ALC and did everything again. That seemed to work. It would hold a code reset. But then when I started commanding stuff, eventually it would set a C0660 symptom 6: short to ground.

I then followed the diagnostic chart (which I did not need the scan tool for) and it seems to suggest I need a new ESCM. Which is kind of what I thought before. I say seems because they want you to test with a test light and I only had a DVM. Where the test light is NOT supposed to light, I had well under 1V. At most 0.5V and typically more like 0.1 to 0.3V. I assume that is not enough to light a test light. If that is true, then the diagram logic definitely leads to new ESCM after checking connections.

And the fact is, the compressor and solenoid work perfectly, still, when I manually ground the pins on the ESCM harness after unplugging it. I don't see how any of my wiring or the ALC itself is faulty.

Anyway, so far I am very impressed with this tool and I don't regret buying especially since I split it with a buddy.

I guess I will get a used ESCM and go from there. Unless anyone has any ideas.

"Exhaust valve faulted" The code with symptom ID. I guess this doesn't command the MIL. Or even the "SERVICE SUSPENSION SYSTEM" warning. Unless I did something and when I drive tomorrow that will happen. This code came directly from the ESCM. My generic OBD-II reader would not read this. Though I didn't actually try... Brighter and blurrier version.

Merging.

kevm14 wrote:Lol

http://m.ebay.com/itm/05-06-CADILLAC-ST ... nav=SEARCH

Now that's cheap.

Relisted and price dropped to $30 with free shipping. Cheap enough to take a chance. Ordered.

Oh I did forget one thing. I performed the ALC ride height calibration. That didn't change any of my symptoms. Took probably 45 seconds or so.

Got my used ESC module today. Plugged it in. Same exact P/N, software # and calibration # as my original, verified with Tech 2. Good to note.

However, no change. I still get a C0660 symptom 1 (exhaust solenoid valve circuit short to battery). However, if I unplug the ALC harness, and reset, I did say before that I get no DTCs. But, it only takes another 10-15 seconds and it will again set a C0660 but with symptom 6 (exhaust solenoid valve circuit short to ground or open circuit). I believe this was happening before but I failed to mention it so explicitly. I made a request on the Cadillac forum for someone to unplug their ALC, and scan the ESC for codes, to see if a C0660 symptom 6 sets, or if nothing sets. I think that is actually a normal code for an unplugged ALC since the driver for the exhaust solenoid is built into the ESC, so it could directly monitor current, voltage, etc (unlike the compressor motor which goes through an external relay).

More testing (interrupted by one hell of a storm - with hail) revealed that while I am able to manually turn on the compressor and exhaust solenoid at the harness by grounding the pins, it would seem I am NOT able to do that if I ground both at the same time. I'm not sure what this means yet and I haven't done any conclusive testing as I was having trouble getting a jumper in both pins.

So this is not solved yet.

I did give myself a good scare though. Check this out.

In switching between the used one I got and the original (which I did not do more than once or twice), I triggered a massive freak out on the high speed LAN. All kinds of comms codes and stuff on all kinds of modules. A lot like that 2012 Lacrosse video. Car wouldn't even crank - even after I plugged the ESC back in, which NEVER happened when I was fooling around with my original ESC last week. I left it after it started pouring and went out later. Started and I was able to clear all the codes, which did not come back, except the C0660 symptom 1. Phew.

Anyway, I need to sort out if I really do think I have some kind of wiring problem. For starters, I think I should be able to run both the compressor motor and exhaust solenoid at the same time, since that is a normal/transient operation when the compressor first turns on. If I can get a good jumper in there, and confirm that I cannot run both at the same time, then I will start to look more closely into some kind of wiring issue I guess. Either that, or this used ESC has exactly the same problem as my original. I'm wondering if they are actually both working fine...

I have a big update.

I wired in a jumper and was able to actuate both the exhaust solenoid and compressor at the same time, by grounding both pins with ignition on. So I verified all that works.

Now get ready for the curve ball.

I really did some critical thinking about how the C0660 symptom 1 diagnostic would work. Eventually, I decided to try plugging in my old ALC. Of course, I had cut off the plug to protect the car side while I was driving around with no ALC for weeks. So I had to do some tricky soldering. But I soldered the wires back to the old plug and was able to stack the old compressor up on some blocks and plug it in to the car plug (which doesn't reach down very far).

Results?

First I cleared the codes. And, guess what, they didn't come back after clearing, unlike before where the C0660 symptom 1 would ALWAYS come back each time I cleared it (unless the compressor was unplugged then it would throw a symptom 6).

I started the car and sure enough, the compressor ran for the self-test cycle (which I have NEVER heard the new compressor do). And I was able to drive it via the Tech 2, on and off.

Naturally I am both relieved (that nothing is wrong with anything on the car wiring or the ESCM - and I guess I have a spare...), and pissed at the same time.

What I suspect is going on is, the Dorman exhaust solenoid is a different resistance than the GM one, and that causes it to fail the C0660 symptom 1.

I can easily measure my old solenoid but measuring the new will take some real effort because of where the ALC sits in the car. I will try. If I had to take a stab at it, I'd say the new solenoid impedance/resistance is too high. So the fix would be to add a small amount of extra resistance in series. Let me measure both and get back here.

HOWEVER - does anyone think the ESCM actually learns the impedance of the exhaust solenoid during some kind of setup procedure? This is one of the few modules that doesn't actually have a "setup" mode via the Tech 2 so other than flashing the calibration, I have no idea if any of that is worth pursuing.

Oh, one more thing - I COULD deal with Rockauto or Dorman but honestly I doubt the new ALC is really defective. Although, I will say that when triggering the exhaust solenoid manually, the rear of the car doesn't really drop much, even though the solenoid makes an unmistakable click when I manually actuate it. Looking at the shocks, the air bags don't have much travel/length at all so maybe that is normal for these. I could swap the exhaust solenoid but the old one is really nasty. The option does remain should I get desperate.

Pulled in garage to avoid the rain (which mostly stopped). Proof that the compressor runs via Tech 2. The old one of course. This was impossible with the new one. The "rig"

Hypothesis confirmed - almost.

Old ALC exhaust solenoid resistance: 27.85 ohms.

Probing the pins of the new ALC on the car was very difficult. At one point I got a reading of 4.xx ohms and I'm like...that can't be right. Read on.

I got out my DVM again and decided to check the current from the pin on the ESCM harness to ground. Off scale. Scale is 2A. Let's see...if it was really 4.xx ohms, the current would be roughly 12/4 = ~3A. Oh.

To sanity check that, I rigged up the old compressor again. If my math is right, should draw 12/27.85 = about 430mA. Survey says? 420mA.

So the Dorman exhaust solenoid is drawing roughly 7x as much current as the OEM one did. I don't know why it shows up as a C0660 symptom 1 (short to battery) but this is my working hypothesis and I think it must be correct.

The real question is where do I go from here? I'd really like to hear from a Dorman engineer at this point to see if this thing is working to their spec, and what their spec is supposed to be. I could add a ~20 ohm resistor in series, if that leaves enough current for the Dorman solenoid to function. I guess it would be cleaner to find out this solenoid is just defective/wrong and a simple exchange would make this all go away.

Maybe I'll start by reaching out to Rockauto.

This was kind of fun. A PHAD-style diagnosis. Though I shouldn't take too much credit until this is actually fixed.

It is worth mentioning, perhaps, that if I had no fancy tools at all, or even a DVM, I might have been lead to replace the ALC with a warranty unit. And if I do that, and it fixes it, then the fancy tools were just aids to figure out the problem without blindly swapping stuff. But it goes to show, you don't NEED these tools a lot of the time.

It's also worth mentioning that I think there is nothing at all wrong with the car itself...

My question to the Dorman Tech Line:

I installed a Dorman 949-032 replacement air leveling compressor in my 2005 Cadillac STS. It does not run via the car's control module (sets a code - one of the few checks it does is the exhaust solenoid circuit) but will run manually if I ground pins on the harness. After a very long troubleshooting process I have determined that the problem is the exhaust solenoid has extremely low resistance and is drawing way too much current. It is on the order of 4 ohms. My original was almost 28 ohms. I need to know if I need to exchange this or what your spec for this solenoid is supposed to be.

Received a response this morning:

Hi Kevin, good morning, our resistance is indeed the same as the OEM spec on this part, is the system setting any codes at all?

Nicholas Paris
Asst. Product Manager/Tech-Line
Dorman Products
215-712-5012-Desk
215-712-5512-Fax
Toll Free 1-800-868-5777 EXT-5012

And my reply back:

Nick,

Thanks for the quick response.

Yes, the system sets a code for a malfunction on that circuit. My troubleshooting suggests it is because the solenoid is drawing way too much current so circuit monitoring throws a code. The controlling module refuses to actuate the solenoid (and thus disables the entire system) because of this.

So you can confirm that the solenoid coil resistance is supposed to be ~28 ohms? If that is true, my unit is definitely defective as it is drawing on the order of 3 amps when it should be drawing less than half an amp.

Please advise.

Maybe I am getting somewhere?