So in your testing, you believe the short on class 2 is from the ECM ?

All class 2 on the Starbus and the splice packs for the modules shown here
You need to save these and then enlarge to see them better as this forum limits photo sizes
Go back and review my posts as I showed what each wire is for the ECM,
Look at the splice packs below for Starbus/Class b
ALL Class B wires are purple

 

When you tested for the ECM where the other modules plugged back into the Starbus ?

When you read pin 2 of DLC at 8 volts, was the voltage from ECM steady or was the reading jumping up and down ?

Look at that video again when they talk about voltage staying high of a module

 

• When you tested for the ECM where the other modules plugged back into the Starbus ?
• 
  
• When you read pin 2 of DLC at 8 volts, was the voltage from ECM steady or was the reading jumping up and down ?
• 
  
• Look at that video again when they talk about voltage staying high of a module
• 
  
• By the way, the ignition was in the ON position.
• Yes, I plugged each module back in after I tested it and before I tested the next module!
• The voltage at 8 volts was steady.
• Will check out the high reading in the video.

 

So that would mean the ECM outputs about 8 volts constant, so it does not shut UP
the prevention the other modules cannot talk via class 2 on Starbus

As you recall from that video modules talk, then voltage goes to like 0, another module than can talk but if ECM is always high and hung up

Watch video from like 5 to 10 minutes into the run

 

So that would mean the ECM outputs about 8 volts constant, so it does not shut UP
Yes I remember now, Thank for that

 

As I posted back in #81 post the Class 2 is in C2 of ECM, pins 15 and 16 if the drawing you showed weeks ago is the right one
But the pinout you show above says 15–16 pins not used, so need to know what the exact PCM for your car is

So need to define what engine you have and if the ECM has 2 or 3 wiring connectors ?

As this image shows if engine is an LH2 than there is 3 connectors and class 2 is on pins 15&16
where if engine is a LY7, ECM has 2 wiring connectors and pin 48 is class 2
Again, all Class 2 wires should be purple in color

 

As I posted back in #81 post the Class 2 is in C2 of ECM, pins 15 and 16 if the drawing you showed weeks ago is the right one

• The correct pin configuration is in post 96. It was posted by 1997_eldorado. Sorry about that.
• I have a 2004 Cadillac SRX V8 4.6
• This is what my ECM looks like this
• I think you may have the wrong wiring diagram
• 
  

 

With 3 wiring connectors on ECM than the 2 class B purple wires are pins 15&16 of C1
Not C2.
I see no test you did where all modules are connected to the Starbus
but C1 of ECM disconnected while KE/EO

Or only C1 plugged in, and all others are not ?

If doing that, what is the read voltage on pin 2 of DLC ?

 

And it shows pins 15 & 16 are the class 2 purple wires

 

And it shows pins 15 & 16 are the class 2 purple wires

Correct 15 and 16 are Class 2 purple on C1

• I tried to isolate the location of the 8.25 High Hung
• With everything still plugged in the Pin #2 is still reading Modulating between 0.8 and 1.9 Hung Low
• Unplug Connector C2 only, the reading goes to 8.24 Steady Hung High
• With Just C1 Disconnected and all others connected readings modulate = 0.8 to 1.6
• With C1 Connected and All others (C2-C3-ECBM-TCM) disconnected readings = 7.9 volts steady
• Unplug C1 and C2 only the reading goes from 0.6 to 1.5 modulating Hung Low again
• Unplug Unplug C2 and C3 only, the reading is 8.24 Hung High
• Unplug C2 and the ECBM only, the reading is 8.25 Hung High
• Unplug C2 and TCM only the reading 8.12
• Plug everything back in and the reading modulates between 0.8 and 1.9.

Let me know if we can decide anything from this.

 

No idea why you keep pulling C2 and C3 for PCM when you know only C1 has the 2 class 2 Starbus wires
only making it confusing by pulling them

You were to look for the reason of P1301 ?
Which is a HIGH short (7 volts)

If your meter is good enough, and you're not seeing that 7 volts ramping up/down as the modules are sending out the SOH frames as I explained in another post, than that has to be found out as to why ?
I stated looking at that one video as it states most case a high short can be a module is bad and is non-stop
sending out on Starbus and always show 7 volts high

You need to leave ECM connected and as I mentioned pull the Starbus test splice pack then jumper each controller in one by one to find which one drives a steady 7 volts read on pin 2 of DLC

You can pull radio fuses, but that does not prevent if the class 2 wires for it cause the short

How about leaving connected the PCM, BCM and TCM (tranny) and see if any difference for engine start

I still am concerned on your stating from the start of all this how the ign key jams in the switch and those wires
from switch go, that would affect class 2

Of the 5 PDFs with wiring, only 1 shows calls 2 from ECM but none of the other 4 show the Starbus and all class 2 wires from modules

 

• No idea why you keep pulling C2 and C3 for PCM when you know only C1 has the 2 class 2 Starbus wires. Just to be clear: So you are saying the Class 2 wires are the Starbus wires.
• only making it confusing by pulling them
• Im just trying to do what you told me to do after watching the video. This is all new to me, so it has a learning curve
• You were to look for the reason of P1301 ? P1301 = Open or short poor electrical connection
• Which is a HIGH short (7 volts) We know it is a short because it is not pulsating, its holding steady
• 
  
• If your meter is good enough, and you're not seeing that 7 volts ramping up/down as the modules are sending out the SOH frames as I explained in another post, than that has to be found out as to why ? Correct and Understood
• I stated looking at that one video as it states most case a high short can be a module is bad and is non-stop
• sending out on Starbus and always show 7 volts high. Correct and Understood
• 
  
• You need to leave ECM connected and as I mentioned pull the Starbus test splice pack then jumper each controller in one by one to find which one drives a steady 7 volts read on pin 2 of DLC
• Just to be clear: Starbus wires are the wires that carry class 2 voltage
• Example of A Starbus test splice pack Would be like C1 connector plug, is that correct?
• 
  
• If I understand you correctly, you want me to pull C1 and Test each pin for 7 volts (Hung High voltage). If I find that I may have found the source of the problem.
• You can pull radio fuses, but that does not prevent if the class 2 wires for it cause the short Correct and Understood
• 
  
• How about leaving connected the PCM, BCM and TCM (tranny) and see if any difference for engine start. JUST to be Clear: I believe you told me the PCM is the same as a ECM. and the BCM (Body Control Module controls the interior and exterior functions of the car) and the TCM is the Transmission control module.
• 
  
• I still am concerned on your stating from the start of all this how the ign key jams in the switch and those wires
• from switch go, that would affect class 2. Since I cleaned up the connections (Bolts / nuts) to the ECM, the key no longer gets stuck in the ignition, it seems to work fine. So the key getting stuck had something to do with the ECM.
• 
  
• Of the 5 PDFs with wiring, only 1 shows calls 2 from ECM but none of the other 4 show the Starbus and all class 2 wires from modules. Yes, you told me to get the adjacent diagrams to see where they went from the ECM, so I made pdfs of all of them.

THANK you so much for the help. I'll get started on this tomorrow.

 

find that comb/spicepack....in the car and the wiring diagram

 

find that comb/spicepack....in the car and the wiring diagram

I had seen that video before but at the time I was working on something else. Unfortunately I don't have an oscillascope.

• Right now the battery is down a bit on my car so I'm charging it back up
• I pulled C1 and checked pins 15 16 and 37. They were modulating up and down so there is no clear number. Let me try again when I get the battery back up

 

That video is useful and should help the OP in using the Starbus class 2 test connector
Shows again how today really need a good OBD-II scanner and tools like an oscilloscope
help with the electronics in vehicles

They make hand help scopes that are multichannel and even test components like resisters,
caps, diodes, transistors, even will show what type they are

I have some and very useful when working on vehicles in a pinch when needed

 

That video is useful and should help the OP in using the Starbus class 2 test connector.

• I tried to start the car and the battery is low so it would not start. It was at about 12.3 volts, and it is on a charger. When I tried to start it, the Check Engine light began Blinking. I turned the ignition off and then back on again and the Check Engine light was off.
• So I used the video to take these readings. In the video he says each wire in the DLC is the single communication wire for each module in the car. If that's true, I only have 4 modules in the car.
• I know I have ECM, EBCM, TCM, BCM. Engine Control Module, Electronic Brake Control Module, Transmission Control Module, Body Control Module
• I also noticed we don't have any Hung High Readings anymore.
• 
  
• So my first question is, if the video is correct, how do I match theses pins up to those modules.

 

with the battery up and down will likely produce some codes.
do you clear the codes?

 

• When I put the Code reader on it I could see that it had recorded every event where I unplugged a connector, Like the ECBM and the TC, so I Deleted all the events/codes. Then I ran the code scanner again. Thats how I got the new codes.
  I still have the charger on it. I can scan it again tomorrow.

 

The star has the following 4 splice packs:
SP201 located in the center of the instrument panel, near the radio.
SP200 located in the left side of the instrument panel, near the steering column , taped to the instrument panel harness.
SP303 located in the right rear of the passenger compartment, taped to the body harness, approximately 24 cm (9.5 in) from the fuse block - right rear.
SP300 located in the left side middle of the passenger compartment, taped to the body harness, near the carpet seam.

 

info i've found....hope it helps

Class 2 Serial Data
The data link connector (DLC) allows a scan tool to communicate with the class 2 serial data line. This serial data line is the means by which the microprocessor-controlled modules in the vehicle communicate with each other. Once the scan tool is connected to the class 2 serial data line through the DLC, the scan tool can be used to monitor each module for diagnostic purposes and to check for diagnostic trouble codes (DTCs). Class 2 serial data is transmitted on a single wire at an average of 10.4 kbps. This value is an average, class 2 uses a variable pulse width modulation to carry data and depending on the message it may operate faster or slower. The bus will float at a nominal 7.0 volts during normal operation. Each module can pull this lower during the transmission. The bus is not at battery positive voltage or ground potential during normal operation. When the ignition switch is in RUN, each module communicating on the class 2 serial data line sends a state of health (SOH) message every 2 seconds to ensure that the module is operating properly. When a module stops communicating on the class 2 serial data line, for example if the module loses power or ground, the SOH message it normally sends on the data line every 2 seconds disappears. Other modules on the class 2 serial data line, which expect to receive that SOH message, detect its absence; those modules in turn set an internal DTC associated with the loss of SOH of the non-communicating module. The DTC is unique to the module which is not communicating, for example, when the inflatable restraint sensing and diagnostic module (SDM) SOH message disappears, several modules set DTC U1088. Note that a loss of serial data DTC does not normally represent a failure of the module that set it.

Class 2 Serial Data Circuit Left Hand Drive (LHD)
The class 2 serial data circuit on this vehicle consists of a hybrid ring and star configuration. Each module on the ring has 2 class 2 serial data circuits connected to it. If there is 1 open on the ring serial data communication will still take place. If there is more than 1 open on the ring, the modules not connected to the class 2 serial data circuit will not communicate. If there is 1 open on the star, the module not connected to the class 2 serial data circuit will not communicate. The following modules and splice packs are connected to the class 2 serial data circuit in a ring fashion:

• SP201
• The instrument panel cluster (IPC)
• SP200
• The electronic brake control module (EBCM)
• The electronic control module (ECM)
• The HVAC control module
• The radio
• The dash integration module (DIM)
• SP303
• The inflatable restraint sensing and diagnostic module (SDM)
• SP300

The star has the following 4 splice packs:

• SP201 located in the center of the instrument panel, near the radio.
• SP200 located in the left side of the instrument panel, near the steering column , taped to the instrument panel harness.
• SP303 located in the right rear of the passenger compartment, taped to the body harness, approximately 24 cm (9.5 in) from the fuse block - right rear.
• SP300 located in the left side middle of the passenger compartment, taped to the body harness, near the carpet seam.


The following devices are connected to the class 2 serial data circuit in star fashion via splice packs:

• SP201 located in the center of the instrument panel, near the radio.
• SP200 located in the left side of the instrument panel, near the steering column , taped to the instrument panel harness.
• SP303 located in the right rear of the passenger compartment, taped to the body harness, approximately 24 cm (9.5 in) from the fuse block - right rear.
• SP300 located in the left side middle of the passenger compartment, taped to the body harness, near the carpet seam.

The following devices are connected to the class 2 serial data circuit in star fashion via splice packs:

• SP201 - The DLC
• SP303
- The right rear door module (RRDM)
- The radio antenna module
- The TV antenna module
- The vehicle communication interface module (VCIM)
- The rear integration module (RIM)
- The front passenger door module (FPDM)

• SP300
- The audio amplifier
- The left rear door module (LRDM)
- The driver door switch assembly (DDSA)
- The driver door module (DDM)
- The memory seat module (MSM) w/A45

• SP200 - The theft deterrent control module

Power, Ground, GMLAN, and Key Word 2000 Serial Data

 

The following devices are connected to the class 2 serial data circuit in star fashion via splice packs:
SP201 - The DLC

SP303 - The right rear door module (RRDM)
- The radio antenna module
- The TV antenna module
- The vehicle communication interface module (VCIM)
- The rear integration module (RIM)
- The front passenger door module (FPDM)

SP300 - The audio amplifier
- The left rear door module (LRDM)
- The driver door switch assembly (DDSA)
- The driver door module (DDM)
- The memory seat module (MSM) w/A45

SP200 - The theft deterrent control module


this is the info i've found

Thanks for that, let me check it out

 

had to edit that due to some messed up cut and pasting.........maybe too much glue

 

i'd suggest putting things back together except any areas where the splice packs are located so that things don't get lost or forgotten.
you can test the class2 communications at the splicepack to see if it modulates between 0v and 7v.
my brain has gone on vacation this evening so i'll dig up some more info tomorrow
an oscilloscope would be beneficial but i think it can be handled with a volt meter

 

i'd suggest putting things back together except any areas where the splice packs are located so that things don't get lost or forgotten.

• Oh so I have to open the splice pack and test point for Highs and Lows or Modulation. Glad you pointed that out.

 

yes you'll need to open the splicepack and test

 

.
Have a couple of questions. I pulled the Theft Deterrent Control module off the Ignition switch and proceeded to test the pins. I don't have a copy/ picture of the plug to work with, so I made this picture.
1) Does anyone have pictures of the pin layouts for the various Modules 1997_eldorado provided?
2) I'm really suspicious of the zero readings I got from these two pins. They could be the source of my problem, but I don't know how to interpret them. They initially Read about 25 millivolts, but as you hold the probe on the pin, they slowly fall to zero. Very strange.
3) Well, it just occurred to me they could be grounds. In that case it would be correct reading from a ground to a ground should be Zero..

 

Theft Deterrent System Connector End Views

Pin​	Wire Color​	Circuit No.​	Function​
A​	OG​	1440​	Battery Positive Voltage​
B​	BK/WH​	351​	Ground​
C​	--​	--​	Not Used​
D​	PU​	1807​	Class 2 Serial Data​
E​	YE​	343​	Accessory Voltage​
F​	--​	--​	Not Used​

what i can find

 

Theft Deterrent System Connector End Views

How do you find them so quickly

 

i have some old software that covers that model so i can look it up on there......just had to dig it out after that last mess with the posted images
getting pics and tables from the software can take some work....but i will do what i can to help out

i'm currently trying to work out my issue of the key not coming out of the ignition.....hoping it's just a shifter linkage but the snow (and these old bones) keep me from being on the ground under the car right now

 

• I have the endcap off the driver side dashboard. There are two connectors in here, the yellow one that is said to be the steering wheel module?? Weird place to have it. But Im gona pass on it now because I can't get to the right rear fuse box right now.
• The second connecter (White) looks a lot like the C1, C2 C3 connectors on the ECM. It has a lift handle that is supposed to release the connector. It lifts fairly easy but does not release the connector. Any ideas how to get it out? Im being careful not to damage it.. See the second picture.
  By the way, I was having trouble with the key sticking in the lock and when I cleaned up the bolts on the ECM the problem went away. Even so the key is easy to remove with a screw driver in the little hole under the steering column. Instructions say you have to remove the cover to expose the hole, but I had trouble getting the cover off, until I forced a screwdriver into it and it just fell out.

 

i have some old software that covers that model so i can look it up on there......just had to dig it out after that last mess with the posted images
.

• I pulled this door switch assembly, and it has a module of connections attached, but I cant find it in my repair manual. I need the pin identification.
• This what the connector looks like
• 
  
• 
  
  

 

hoping someone with more knowledge than i can chime in....... but i believe that yellow connectors are part of the airbag system. im talking about the yellow connector with the orange lock below the area you are pointing to. don't mess with them unless necessary and you take the proper precautions

the part you are pointing to in that pic that looks like the comb and you have to remove the comb separate from the cover on some of them.

took some contorting but i got the body under there to get the plug out and release the key.....another 4" of snow today.....spring can't get here soon enough.
now i just have to diagnose why it is getting stuck.

 

hoping someone with more knowledge than i can chime in....... but i believe that yellow connectors are part of the airbag system. im talking about the yellow connector with the orange lock below the area you are pointing to. don't mess with

• You are correct about the yellow connector, I am not going to try to check it out since I cant get to the SIP fuse right now
• I wanted to ask you if you could give me a picture of the DVD for your software. I want to try to buy it online. Yours has much more information than mine

 

Door Switch Module - Driver

Pin​	Wire Color​	Circuit No.​	Function​
1​	--​	--​	Not Used​
2​	PU​	616​	Memory 2 Switch Signal​
3​	WH​	615​	Memory 1 Switch Signal​
4​	--​	--​	Not Used​
5​	YE​	1491​	Backlight Lamps Control​
6​	OG/BK​	781​	Driver Door Lock Switch Unlock Signal​
7​	OG/BK​	780​	Driver Door Lock Switch Lock Signal​
8​	BK/WH​	351​	Ground​
9​	RD/WH​	640​	Battery Positive Voltage/Inadvertent Power Relay Enable​
10​	PU​	1807​	Class 2 Serial Data​

 

View attachment 634445
Door Switch Module - Driver

• Thats the same plug my manual shows but it is wrong, its supposed to have two rows of pins with 12 pins on each side, everything about is correct excepts it has two rows

Pin​	Wire Color​	Circuit No.​	Function​
1​	--​	--​	Not Used​
2​	PU​	616​	Memory 2 Switch Signal​
3​	WH​	615​	Memory 1 Switch Signal​
4​	--​	--​	Not Used​
5​	YE​	1491​	Backlight Lamps Control​
6​	OG/BK​	781​	Driver Door Lock Switch Unlock Signal​
7​	OG/BK​	780​	Driver Door Lock Switch Lock Signal​
8​	BK/WH​	351​	Ground​
9​	RD/WH​	640​	Battery Positive Voltage/Inadvertent Power Relay Enable​
10​	PU​	1807​	Class 2 Serial Data​

 

try this?

this is 2008....sorry for confusion

corrected
This is 2004

Pin​	Wire Color​	Circuit No.​	Function​
1​	RD/WH​	540​	Battery Positive Voltage​
2​	BN​	4​	Accessory Voltage​
3​	PK​	3​	Ignition 1 Voltage​
4​	YE​	5​	Crank Voltage​
5​	OG​	300​	Ignition 3 Voltage​
6​	RD/WH​	1940​	Battery Positive Voltage​

 

try this? View attachment 634486 this is 2008....sorry for confusion

Pin​	Wire Color​	Circuit No.​	Function​
1​	RD/WH​	540​	Battery Positive Voltage​
2​	BN​	4​	Accessory Voltage​
3​	PK​	3​	Ignition 1 Voltage​
4​	YE​	5​	Crank Voltage​
5​	OG​	300​	Ignition 3 Voltage​
6​	RD/WH​	1940​	Battery Positive Voltage​

• This looks like the correct pins, but I need a picture.

 

 

• Looks good.
• These are my readings for the Ignition Switch:
• Personally, I think these readings are all good and appear to be normal. So, I think we can rule out a problem with the ignition switch. Anyone else have an opinion.

 

try using a pin and back prob the connection where the wires enter.
if you pierce or shave of the insulation make sure to seal that area real well.....don't need any potential shorts
i'm not sure how 2 thru 5 should look but i would think that they will change when connected to the switch which should apply voltage to those when in the appropriate position.

 

try using a pin and back prob the connection where the wires enter.

• I managed to peal back just enough wire to make a test on the Crank wire. When I turn th key to start it has 12.85 volts. So that answers a big question for me.
• Found this little guy and I'm not sure what to do with it, but its the only thing I didn't check on the ignition switch.
• Any ideas?
• 
  

 

possibly.......


Ignition Lock Cylinder Control Actuator

Pin​	Wire Color​	Circuit No.​	Function​
A​	PU​	5025​	Ignition Key/Shifter Interlock Switch Supply Voltage​
B​	RD/WH​	540​	Battery Positive Voltage​

 

(1)​	Inflatable Restraint Steering Wheel Module Coil​
(2)​	C208​
(3)​	Inflatable Restraint Steering Wheel Module Connector C1​
(4)​	Inflatable Restraint Steering Wheel Module Connector C2​
(5)​	Turn Signal/Multifunction Switch​
(6)​	Turn Signal/Multifunction Switch Connector C4​
(7)​	Turn Signal/Multifunction Switch Connector C3​
(8)​	Turn Signal/Multifunction Switch Connector C2​
(9)​	Turn Signal/Multifunction Switch Connector C1​
(10)​	Steering Wheel Position Sensor​
(11)​	C203​
(12)​	Fuse Block - Steering Column​
(13)​	C202​
(14)​	Theft Deterrent Control Module Connector​
(15)​	Ignition Lock Cylinder Control Actuator Connector​
(16)​	Ignition Switch Connector​
(17)​	Ignition Key Alarm Switch (Part of steering column harness)​
(18)​	Windshield Wiper/Washer Switch Connector​
(19)​	Windshield Wiper/Washer Switch​
(20)​	Theft Deterrent Control Module​
(21)​	Ignition Switch (Hidden) and Ignition Lock Cylinder Case​
(22)​	Ignition Lock Cylinder Control Actuator​

 

based on the wire colors i'd say that is the Ignition Lock Cylinder Control Actuator that i posted above. post 195
the first pic with the green and yellow or orange wire looks like a switch ? post 194

 

• Thinking a little bit ahead, I don't think there is anything wrong with the ignition switch. So I wanted to investigate the gas gauge is not registering 1/4 tank. It's the one gauge that has failed to register a correct reading since the problems started.
• Do you have any idea where to start on the gas gauge?