Well, I don't have a STS (yet). But one of my friends bought it and asked me how to get in the self diagnostic mode. He used to own an Eldorado that the "good old way (press off and warmer)" worked with. Now he does not know how to. He can't write in English, so I am asking the question for him...

Would anyone here can let me know how to do it?

Thank you very much!

All cars and light trucks built and sold in the United States after January 1, 1996, were required to be OBD II equipped. Like other manufacturers, Cadillac now has an under-dash plug-in connection for a diagnostic tool that is semi-standardized for all makes. The interactive display previously available on Cadillacs was discontinued when the OBDII came along.

There is a considerable amount of information about the OBDII system on that web, if you are interested.

Thank you for your reply!

So, unless you have a scan tool, you simply cannot have an access to the computer to run the self disgnostics and other good stuff that I can do with my 95 DeVille, am I correct?

I found some web sites and this site:
http://myweb.accessus.net/~090/cadidiag.html,
seems to be most useful, but still it does not say anything on a 2005 STS. I was not sure why, but as you said, it may be because there is not a way to run diagnostics any more...

OBD codes would be the same across models
http://www.cadillacfaq.com/faq/answers/dtccode.html

If you don't own a scanner, any auto parts store will scan you for free, you just write down the codes and look them up.

[QUOTE=BenC]The interactive display previously available on Cadillacs was discontinued when the OBDII came along.
[QUOTE]

What?? My 2000 STS has an interactive display where I can read the OBD codes!

Thanks urbanski,

If you don't own a scanner, any auto parts store will scan you for free, you just write down the codes and look them up.

Well, I understand, but can those scan tools handle "input mode", "override mode", and other good stuff, just like my old last-century-technology car can?
Or even just simply to know TP angle, spark advance, ATF temperature, is it possible? No???

If not, it would be pretty ashame to get rid of those very nice functions from Cadillacs. Without specialized tools, no manual-shift, manual-lock-up, manual-injector-disable, and a lot more while you are sitting in the car??? Too bad...

beats me. i doubt the hand held scanners do anything but read codes. i mean you can buy a pocket one for 40 bux. check n clear.

to read all that spark advance, etc, i have EFILive tuning software but that's $700.

i doubt the hand held scanners do anything but read codes. i mean you can buy a pocket one for 40 bux. check n clear.

I am sure what those scan tools can do is only about basic OBD-II things, not Cadillacs' unique, ah, interactive menu things.

to read all that spark advance, etc, i have EFILive tuning software but that's $700.

This sucks. I can do those things in my 10+ years old car by pressing buttons just a few times, best of all, it is for free... When did this change happen? Sounds like caddydaddy's 2000 STS still came with these functions.

This sucks. I can do those things in my 10+ years old car by pressing buttons just a few times, best of all, it is for free... When did this change happen? Sounds like caddydaddy's 2000 STS still came with these functions.

As far as I know, all the Sevilles up through 2004 were the same as mine, where you can access the OBD right from the dash. I don't know about the 2005 STS', so I can't tell you about them. I know on my 2000 STS, I press the "info up" button and the "on/off" buttons to the right of the dash to access the OBD. The 2005-up STS may be similar.

Amazing how these threads wander off into sub-topics.

Amazing how these threads wander off into sub-topics.

Subtopics? We're still on the topic of figuring out if the 2005-up STS has dash accessable OBD! Since you're an new STS owner, help us out! :thumbsup:

2005 & later STS does not have access through the DIC to read codes. They changed the communication protocol, IIRC it's GM LAN, and you have to have a scan tool to read codes... It doesn't have anything to do with OBD I or OBD II...

Sounds like GM has recently changed their attitude toward the idea of accessing to built-in self diagnostics function in a Cadillac.

Again, it is too bad...

BMW is easy. Yet another reason I will buy no Cadillac after Seville 2004, Eldorado 2002, Deville 1999. Quality goes to hell then this electronic moo-job.

Redline is right.
All the new Cadis use a protocol called GMLAN, in the computer industry it's called a CAN. There are actually two kinds of GMLAN on the car, high speed and low speed. Although similar in operation, they do differ quite a bit in operation. They still have Class 2 buses for generic code readers but class 2 data (which started with OBD-II) on these cars will only get you powertrain DTCs and limited information. Even the factory scan tool needs a CANdi module to communicate with most systems on the newer cars.

DIC enabled diagnostics don't exist on any of the new platforms and it has nothing to do with OBD-II. It's simply a model change and elimination of a feature due to the more complicated new communication protocols.
You can't do it on XLR, the new STS, the new DTS or CTS. Escalade has never had this ability.
It's just something they phased out, no real reason was given, although I am sure they had some.

Here's an article I found on CAN. Good reading...if you're bored!

The Future of Diagnostics Is In The CAN

--------------------------------------------------------------------------------
By Larry Carley, Technical Editor

Since model year 2003, a growing number of domestic and import vehicles have been built with a new onboard communications protocol called CAN (Controller Area Network). CAN is essentially an engineering standard for how computers and modules talk to one another via the serial data bus in a vehicle’s wiring system. It’s a high-speed standard designed for powertrain control modules, antilock brakes and stability control systems.

The CAN protocol was created back in 1984 by Robert Bosch Corp. in anticipation of future advances in onboard electronics. The first production application was in 1992 on several Mercedes-Benz models, but CAN is now being used on more and more new vehicles. By 2008, all new vehicles sold in the U.S. will be required to have a CAN-compliant onboard diagnostic system. But you won’t have to wait until then to encounter CAN diagnostics because many of the early applications are already out of warranty and may be coming into your shop now.

Geek-Speak
If you’re not up to speed on the latest electronics and don’t know a data bus from a school bus, diagnosing CAN systems will be a challenge. Even so, you don’t have to be an engineer to perform basic diagnostics on CAN-equipped vehicles because the problem-solving is essentially the same as current OBD II vehicles. The only difference is that you need a CAN-compliant scan tool to read the vehicle serial data. Most current generation scan tools don’t have the right hardware or software to talk to CAN-equipped vehicles. Some scan tools have the right hardware, but must be upgraded with new software to handle the faster communication rates and to decipher the CAN messages.

Like many current vehicles, information in a CAN-equipped vehicle is shared over a serial data bus. The bus is the circuit that carries all the electronic chatter between modules (nodes). The bus may have one wire or two. If it has two, the wires are usually twisted to cancel out electromagnetic interference. The speed at which the bus carries information will vary depending on the “class” rating of the bus as well as the protocol to which it conforms.

~ A data bus with a “Class A” speed rating is a relatively slow, low-speed circuit that typically carries less than 10 kilobits (10 Kbps) of information per second. A data bus that operates at Class A speeds is limited to simple command functions like operating power mirrors, power seats, power widows, power door locks, remote trunk releases and lights.

~ A data bus with a “Class B” rating, by comparison, may operate from 10 Kbps up to 125 Kbps, depending on the operating protocol (SAE J1850 or Europe’s ISO 9141-2). This is fast enough to carry more complex information and time-sensitive data. Systems that may share a data bus with a Class B rating include electronic instrumentation, electronic transmission controls, security systems and climate control.

~ Class C is currently the fastest data bus rating. Class C systems can operate at speeds up to 1 megabit per second, which is up to 100 times faster than a typical Class B data bus. Many of the vehicles that are currently using a Class C data bus are operating at speeds of around 500 Kbps, which is fast enough for powertrain control modules, air bag modules, and fast-acting antilock brake and stability control systems. Down the road are even faster systems, with “Class D” ratings of over 1 megabyte per second. And some applications such as onboard entertainment systems require even higher speed audio and video streaming.

One thing to keep in mind about the CAN standard is that CAN (as well as other protocols such as SAE J1939, GMLAN, OBD II, SAE J1587 and LIN) has more to do with the way information is formatted, transmitted and received than how fast it is sent. This means the automotive engineers who design the onboard electronics for CAN-compliant vehicles are free to choose any operating speed they want (up to 1 megabit per second) as well as the type of bus conductor (one wire, twisted paired wires or a fiber optic cable). On most cars today, a high-speed data bus is needed to handle the volume of information going back and forth between all the onboard electronics.

In 1995, GM introduced its own “Class 2” data bus to handle communication between modules. The system ran at a speed of 10,400 bits per second (10.4 Kbps), which was more than adequate for vehicles a decade ago. In 2004, GM moved to their next generation data bus system, which they called “GMLAN” (GM Local Area Network). Introduced on the Cadillac XLR and Saturn Ion, GMLAN added the capability to operate at two speeds on two separate buses: a low-speed (33.33 Kbps) bus and a high-speed (500 Kbps) bus.

The low-speed side of the GMLAN system operates on a single-wire bus to handle body-related control functions, while the high-speed bus uses two wires to carry data between the powertrain, transmission and antilock brake modules. A “gateway” node connects the high-speed bus and low-speed bus, and allows information to be shared back and forth. For example, the radio (which is connected to the low-speed bus) may adjust volume based on engine speed and vehicle speed (from the high-speed bus) to offset road noise.

Mercedes also uses several different bus speeds on its vehicles. Depending on the application, there may be a high-speed 500 Kbps CAN-C bus for the powertrain, transmission and ABS modules, and a slower speed 83 Kbps CAN-B bus for the body control functions. On some Mercedes cars, there may be as many as 30 modules on the CAN-B bus. Up to model year 2002, all communication between the CAN-C and CAN-B bus went through the electronic ignition switch (EIS) module. After 2002, a new “gateway” module handles the inter-bus communications as well as onboard diagnostics via a CAN-D bus.

How Data Is Sent and Received
If your eyes haven’t glazed over yet with all this geek-speak, here’s how data is handled on a CAN-compliant system. Every module (node) that is attached to the data bus network is capable of sending and receiving signals. Each module has its own unique address on the network. This allows the module to receive the inputs and data it needs to function, while ignoring information intended for other modules that share the network. When a module transmits information over the network, the information is coded so all the other modules recognize where it came from.

Data is sent as a series of digital bits consisting of zeros and ones. If you looked at the data on a scope, you would see a square wave pattern that changes between a high and low voltage reading. The low voltage reading usually corresponds to the zero while the high voltage reading corresponds to the one. The actual voltage readings will vary depending on the application and protocols the vehicle manufacturer is using, but most operate in the 5 to 7 volts range.

The CAN standard requires a “base frame” format for the data. What this means is that for each distinct message sent or received by a module on the network, there is a beginning bit (called the “start of frame” or “start of message” bit), followed by an “identifier” code (an 11-bit code that tells what kind of data the message contains), followed by a priority code (“remote transmission request”) that says how important the data is, followed by 0 to 8 bytes (1 byte equals 8 bits) of actual data, followed by some more bits that verify the information (cyclic redundancy check), followed by some “end of message” bits and an “end-of-frame” bit.

Still with me? There’s more! One of the tasks of any network system is to keep all the messages separated so they don’t collide and garble one another. Usually the body control module or instrument cluster module is assigned the task of managing the network traffic. When it sees a message coming over the bus, it looks at the first bit in the data stream. If the bit is a zero, the message is given priority over the others. This is called a “dominant” message. If the first bit is a one it is given a lower priority (a “recessive” message). Thus, the highest priority messages always get through to their intended destinations but the low-priority messages may be temporarily blocked until the traffic eases up.

Real-World Diagnostics
So what does all of this have to do with diagnosing vehicle faults? For one thing, you need a special CAN-adapter module to use a Tech 2 scan tool on a newer CAN-compliant GM vehicle. All the automakers are currently in the process of upgrading or replacing their current scan tools with newer CAN-compliant tools (some of which will be PC-based unlike today’s dedicated hand-held scan tools). As for aftermarket scan tools, some are CAN-compliant and others are not, so check with your scan tool supplier before you buy. CAN-compliant vehicles are just as vulnerable to electronic faults as older vehicles. Though CAN systems use fewer wires and fewer connectors (to save weight and cost), they also use more modules and more complicated modules. Problems can occur if module connectors become corroded or loose, if wires become grounded, shorted or break, or system voltage is below specifications. Some modules may even forget their settings or locations if the battery is disconnected or goes dead.

On some Chrysler minivans, for example, the automatic climate control system will quit working if battery power is lost. This happens because the electric stepper motors that control the position of the blend doors forget their locations. The system has to be put into a “relearn” mode to re-establish all the motor locations and settings.

One of the features of CAN and other network systems is that modules can send and receive “OK” signals to let the main control module know if they are working or not. In theory, this makes diagnostics easier. On the other hand, it also means that one misbehaving module may generate enough noise to disrupt the entire network causing a complete shutdown of the vehicle!

When a serial bus communication problem occurs, it will usually set a “U” diagnostic trouble code and turn on the Malfunction Indicator Lamp. Depending on the fault, the vehicle may or may not start, or it may only operate in a “limp-in” mode with limited capabilities. Loss of communication between the engine controller and transmission controller (code U1026 on a GM, for example) may put the transmission into a limp-in mode where it will only operate in one or two gears.

Loss of communication codes may indicate a wiring problem on the bus, or a fault with a module. Isolating the fault may require unplugging modules one at a time until the fault is found. Just remember that all modules on a bus network need three things to function properly: power, ground and a serial data connection.

When diagnosing bus or module communication problems, you usually start by checking for voltage at the module, then the ground connection and finally the data line. If all three are good but the module isn’t working, the module needs to be replaced.

On GM applications, a code U100 or U1255 means a general loss of communication on the data bus. With a Tech 2 scan tool, you can go to Diagnostic Circuit Check, then Message Monitor to see a list of active modules and compare it to the list of modules that are supposed to be on when the key is on.

To minimize the parasitic current drain on the battery when the vehicle is off, a “sleep” signal is sent to the modules on the network. Some may remain on for a short period of time after the ignition is switched off (air bag module, for example), and some may never go to sleep (anti-theft module and keyless entry receiver, for example) but most are put into a sleep mode to save battery power. If the sleep signal is never sent, or a module fails to recognize the sleep signal, it may remain active and pull power from the battery. Depending on the current draw, this may run down the battery if the vehicle sits for a period of time.

A Growing List of CAN Applications:

2003 Ford Excursion
2003 Ford F-250 and F-350
2003 Ford Focus and Thunderbird
2003 General Motors Saturn ION
2003 Lincoln LS
2003 Mazda 6
2003 SAAB 9-3


2004 Buick Rendezvous
2004 Cadillac CTS, XLR and SRX
2004 Dodge Durango
2004 Ford Explorer
2004 Ford F-150, E-250 and E-350
2004 Ford Taurus
2004 Lexus LS430
2004 Mercury Mountaineer
2004 Mercury Sable
2004 Mazda 3 and RX-8
2004 Toyota Prius
2004 Volvo S40

2005 Audi A4 and A6
2005 Buick LaCrosse, Rendezvous and Rainier
2005 Cadillac STS
2005 Chevrolet Cobalt, Corvette and Malibu
2005 Chevrolet Equinox
2005 Chevrolet SSR
2005 Chevrolet Trailblazer EXT
2005 Chrysler 300C
2005 Dodge Dakota and Magnum
2005 Ford Crown Victoria, Five Hundred, Focus and Mustang
2005 Ford E-150
2005 Ford Escape and Expedition
2005 Ford Freestyle
2005 GMC Envoy ESV and XL
2005 Isuzu Ascender
2005 Jeep Grand Cherokee
2005 Lexus LS400 and GX470
2005 Lincoln Town Car
2005 Mercury Grand Marquis, Montigo and Sable
2005 Mercury Mariner
2005 Pontiac G6, Grand Prix and GTO
2005 Land Rover LR3
2005 Mazda MPV and Tribute
2005 Mercedes-Benz SLK350
2005 SAAB 9-7X
2005 Toyota Avalon
2005 Toyota 4Runner, Sequoia, Tacoma and Tundra
2005 Volvo S60, S80, V50, V70, XC90

OK, even ewill3rd does not know why it has become this way... I gave up.

And caddydaddy, thank you very much for your information. That is pretty intense, but very good information.

Cheapening. They didn't remove the feature, they just didn't design it into the new car.

My guess would be that the company that builds their HVAC controls and radios didn't want to be bothered with engineering a way to keep the feature in the cars. Since 2000 I have found code checking with the DIC to be unreliable. I can't tell you how many times I have checked codes to find none and then hooked up the tech 2 and found 2 or3. Also I have gotten one or two codes out of the DIC and then found 4 more with the scan tool.
There is no substitute for the scan tool IMHO.

It is truly a bummer, but it's the way of things.

Good article on CAN. Thanks for sharing it with us. Autoxray also has a less detailed article on CAN.
Sorry, but I believe the words are "very complex", not "cheap" in omitting significant built-in diagnostic abilities into the DIC. I would guess that a POST (Power-on-self-test) capability does exist, but not to a detailed level.
I suggest checking out a "LinearLogic Scanguage" ( www.scanguage.com).
I have an Actron ODBII that seems to read codes OK on my 1999 DeVille Concours and other vehicles, but I tried it on my 2005 SRX N* V8 without success. I checked with Actron and local auto suppliers, but found almost nothing (in early 2005) that would work or connect on the SRX. I found a few on the web that were said to be CAN capable @ $200-$400+++.
I then heard (on a local computer-geek radio program) which was discussing how modern autos are becoming more complex, using multiple processors/ computers interconnected, and how auto-diagnostics (like your personal computer diagnostics) are needed to identify and to locate problems, and that his group had developed this "scanguage" (auto-diagnostic-tool that can read these data from all of the computers, meet Intl-ISO & Calif-CARB for 2003-2008). I called 888-433-5664 (or 480-831-2845), spoke with "Ron, a techie type" in Mesa AZ, (he described its capabilities as more than a code reader: it combines the scan-tool-code-reader/ Digital-gauge-readout/ trip-computer) and ordered my scanguage. In July 2005, it cost $129.95 incl shipping, and arrived in a couple of days. I have tried it on quite a few different autos (1996 & newer). I find it great for all of my needs so far !!!