instrument panel cluster would be my guess. im not sure if there is another module responsible for that data.....possibly the body control module.
it is also possible that the fuel sending unit/fuel pump is the issue.

 

quick look it appears
sending unit to ecm then class 2 network comms between ECM and IPC

 

fuel gauge issue may be related to U1301 Class 2 Circuit Short to Battery Conditions

 

fuel gauge issue may be related to U1301 Class 2 Circuit Short to Battery Conditions

• Im not fluent reading these diagrams. I can follow the lines and understand the connections, but drawing conclusions is something else. I can see how thy all connect but that's where its ends. So if I were to comment about this, I would say this illustrates how the class 2 data interacts with other modules.
• Our problem is: which one of these is causing a problem with the class 2 communications network.
• Looks like its trial and error to find the problem.
• You are pointing out that the sending unit (for instance the gas tank) sends class 2 data to the ecm, which in turn then sends class 2 via the network to the IPC (Instrument Panel Cluster). Took me a few reads and re-reads to decipher your comment.

 

i wonder if the issue is being caused by a messed up ecm

 

I can go back and check but I thought my tests were good

 

yes you are getting voltage where it is supposed to be but the ecm may still be toast.
trying to recover from a computer crash so may be slo in response

 

• I managed to pull the instrument panel out, it was rather easy and I found the Connector, so I need a pin count so I can begin testing.
• This is what it looks like and it does have pins in both tracks. I think this should provide some workable data to diagnose what is really going on.
• 
  
  
  

 

Pin​	Wire Color​	Circuit No.​	Function​
1​	--​	--​	Not Used​
2​	BN​	818​	Vehicle Speed Signal​
3​	D-BU​	1537​	ABS Indicator Signal​
4​	--​	--​	Not Used​
5​	PK​	239​	Ignition 1 Voltage​
6​	--​	--​	Not Used​
7​	BK/WH​	351​	Ground​
8​	--​	--​	Not Used​
9​	PU​	1807​	Class 2 Serial Data​
10​	--​	--​	Not Used​
11​	L-BU​	1134​	Park Brake Switch Signal​
12-15​	--​	--​	Not Used​
16​	L-BU/WH​	1314​	Left Turn Signal Indicator Lamp Supply Voltage​
17​	BN/WH​	419​	MIL Control​
18​	--​	--​	Not Used​
19​	WH​	121​	Engine Speed Signal​
20​	--​	--​	Not Used​
21​	RD/WH​	1440​	Battery Positive Voltage​
22​	--​	--​	Not Used​
23​	BK/WH​	351​	Ground​
24​	--​	--​	Not Used​
25​	PU​	1807​	Class 2 Serial Data​
26​	--​	--​	Not Used​
27​	PU​	333​	Brake Fluid Level Sensor Signal​
28-30​	--​	--​	Not Used​
31​	D-GN​	5525​	Tap Up/Tap Down Trans Enable Switch​
32​	D-BU/WH​	1315​	Right Turn Signal Indicator Lamp Supply Voltage​

 

View attachment 634787

Thank you so much

 

notice no fuel signal in the ipc, that is because that info is transmitted thru the class 2
the class 2 bus is going to be where you will likely need to concentrate on.
disconnecting the various module and testing the bus for proper modulation of the signal.
if one of the modules in the system goes bad it can disrupt all communications on the system.
that's why removing the comb and testing has been recommended.
check the class2 lines on the ipc connector and see what they read

 

notice no fuel signal in the ipc, that is because that info is transmitted thru the class 2

• I checked the battery terminals at pin 5 and 21, they read the same as the battery. I did a continuity test at 7 and 23 (ground) and there is no continuity. Sounds like that is the problem. But how do I find the bad ground?
• Your diagram on post 201 doesn't show a ground point. Sounds like the ground comes from the ECM. The ECM has a single ground pin on an incoming pin on C2 terminal.
  Is the ECM not reporting a ground?

 

there are multiple ground points
it appears that the ipc ground point is at G200. not sure where it is located but it looks to be under the dash from what i've read.....left kick panel
wiring issues are not fun nor necessarily easy to diagnose.

has the starter relay been tested?

 

• Yeah the G200 is in the kick panel AND that's the ground I was using to test the pins on the connector.
• This is a list you gave me a while back of all of the grounds on the car. As you can see I've found most all of them
• The ones with a "?" mark are not found.
• If I had to guess which grounds the Instrument Panel was using I would guess #3 or #4. #4 is at the starter, #3 is the kick panel.
• Let me do some research and see if I can tell where the ground is going.
• One more note, I think I already checked the grounding at the Ignition switch, and it was okay, so that would eliminate a problem with the ground at #4. If the ignition switch is good, then the #4 ground is okay.
• NEW EDIT
• I went back and checked to see if the ignition switch was getting 12 volts. Do you remember when I had the ignition switch apart, I deliberately cut the covering off the lead 12-volt wire so I could test it with the key turned to START. I checked it again it has 12 volts. So that eliminates the possibility of the ignition not being grounded.

 

pin 7 from the ipc goes to G200 so if you have no ground there then the wire is damaged.

 

• How do you know pin #7 goes to G200, is it on a wiring diagram?
• I think my theory has a flaw. With the ignition switch turned to start I touched the power wire on the ignition switch to the ground (G200) and I said that is proof it is getting a ground. That's not necessarily true. I provided it with a ground when I used the Mulgtimeter to touch it to the ground, (G200) In order to test it correctly I would have to touch the power wire to its own ground wire to see if it is being grounded.
• Need to devise a way to test its own ground wire with the ignition turned to start
• I think I will need three hands to perform that stunt.

 

 

• Without a little help I'm not seeing how you determined the ground point is G200. I believe you are correct, but I don't see it from this diagram.
• I'm still trying to figure a way I can show the ignition is grounded or not grounded.
• I think we are close

 

the instrument panel cluster is connected thru pin 7 to ground bottom left in the diagram

 

the instrument panel cluster is connected thru pin 7 to ground bottom left in the diagram

• How many times I looked at that and didn't see it
• I'm distracted by other events right now
• Thanks for your patience

 

so if pin 7 on the ipc connector isn't showing continuity to ground there is an issue with the wiring.
although i don't think that is the no start issue

ground point G200 is likely connected to many other things in that area

 

so if pin 7 on the ipc connector isn't showing continuity to ground there is an issue with the wiring.

• Making progress, not solving any problems
• touched pins 7 and 5 and got battery voltage.
• Touched pins 7 and 21 and got Battery voltage.
• Touched pins 7 and 23 and got continuity.
• Whats next?
• NEW Edit
• Plan to test the Various pins for volatility, Ill get back to you

 

class 2 line read?

 

Okay

 

has the starter relay been tested

 

• NEW EDIT
• I can test the starter relay tomorrow. When I try to start the car I can hear it clicking, but thats where it ends.
• Sorry for the lack of response, but we have some cold weather here, difficult working conditions
• Will get back to you as soon as possible

 

i hear ya......been pretty cold here as well so my car sits neglected too

 

I have been following along these 12 pages and learning a lot about the electrical system in this car. It is very interesting and informative. .I still would have went low tech on the starting issue though.

 

What do you mean by the low tech side
NEW EDIT

• On post # 237 I reported
• 1) Pin 23 to Pin 25 with ignition in Off position Reading was 8.9 steady
• 2) Pin 7 to Pin 9 with ignition in Off position Reading was 8.8 steady
• So my obvious question is: does this qualify as a "Hung High" on a Class 2 serial Pin? The ignition was off but it still had what appears to be a "Hung High" situation.
• And this is what my G200 ground looks like it has only one wire attached.
• 
  
• 

 

I will note neither G200 or 201 looked unusual. No visible corrosion. My only clue was both were attached to a painted surface and I couldn't tell how well the grounds were attached to the grommet. Don't know if removing the paint or the solder was the fix but the vehicle runs great (no DTC's driving various trips) and the daughter is very happy!

 

• I will note neither G200 or 201 looked unusual. No visible corrosion. My only clue was both were attached to a painted
• You know I cleaned those up but Im willing to take your advice and sand them down to bare metal. Its worth a shot
• I was out testing today but it was inconclusive, still need to verify my results.

 

n7don_srx cadillac A12
My post got deleted for some reason, so I am reposting.

• on 3/23 I got back to work, sorry I was taking care of some important business.
• So I took new readings on the Class 2 serial pins, and this is what I got.
• 1) Pin 23 to Pin 25 with ignition in Off position Reading was 8.9 steady
• 2) Pin 7 to Pin 9 with ignition in Off position Reading was 8.8 steady
• 3) Pin 23 to Pin 25 with ignition in Run position Reading was Modulating 1.1 to 1.9
• 4) Pin 7 to Pin 9 with ignition in Run position Reading was Modulating 1.2 to 1.5
• 5) Pin 7 to Pin 23 Continuity Beeps but is Modulating 1.2 to 1.5
• As you suggested I removed Grounds G200 and G201 and ground the paint down to bare metal and re-installed them
• I'm planning to start to put some of this stuff back together so I can "test start" it and see what happens.
• Any new suggestions

 

n7don_srx cadillac A12
My post got deleted for some reason, so I am reposting.

• As you suggested I removed Grounds G200 and G201 and ground the paint down to bare metal and re-installed them
• I'm planning to start to put some of this stuff back together so I can "test start" it and see what happens.
• Any new suggestions

Might also consider running some solder on the wires that are flatten and attached to the grommet connector. I used a propane torch (not ideal) on low. My large soldering iron was 130 miles away!

 

N7don_srx

• I just noticed your G200 has more than one wire attached to the ground. Mine only has the black braided wire.
• 
  
  
  

 

1997_eldorado
Report
n7don_srx

NEW EDITED

• Im looking at the end cap on the left side of the dashboard. There is a rather large plug (Like C1 C2 C3 on teth ECM) in that has a lift clamp that holds the plug in place. I'm trying to trace the wires coming out of this plug to see if any of them go to the G200 grounding points
• Bottom line it looks like none of them go to G200. The G200 goes down to the floor and turns and runs back toward the rear of the car.

 

Maybe just the difference between an 2004 and 2007. Once it was clear my issues were solved I stopped looking! As mentioned don't know if G200 or G201 was the culprit

 

200 is likely the location based on modules connected
• SP200
• The electronic brake control module (EBCM)
• The electronic control module (ECM)
• The HVAC control module
• The radio
• The dash integration module (DIM)

but as stated prior any module on the class 2 bus can take the system down. so 201 may also be needed.
in the module diagram you can see how the modules interconnect

i think they should have been more clear when describing the splicepack that the actual number doesn't matter and may appear different with other models.

the further down the system the modules may still need to be accessed and diagnosed at the appropriate splicepack if you find that removing the connection at the 200 splice pack indicates the the problem is with modules further down.

 

200 is likely the location based on modules connected
• SP200
• The electronic brake control module (EBCM)
• The electronic control module (ECM)
• The HVAC control module
• The radio
• The dash integration module (DIM)

• NOTE that I have the Radio disconnected from the system because the disc player is malfunctioning. Its too expensive to fix so I just unplugged it. I'm wondering now it that would cause a problem with the class 2 reporting system. What do you think?

 

have you tried jumping the starter relay?

 

a module that is disconnected from the system will result in no communications with that module it wouldn't cause a U1301.

 

• I found the SP 200 or whatever it's supposed to be. I have everything below the steering column removed to get to it. But it is just as described: Located on the left side of the instrument panel near the steering column, taped to the instrument panel harness. It had a lift release handle very similar to the C1 C2 C3 on the ECM
• 
  
  
• And this is what the pins look like. I just need the pin numbers.
• 
  
  
  

 

Looks like someone was hacking/splicing wires for a reason ?
If so, better check closely for broke or weak splices

 

Looks like someone was hacking/splicing wires for a reason ?
If so, better check closely for broke or weak splices

View attachment 635492

• I think you are correct, the tape had a very soft sticky glue on it, not what you would expect. Evey time I tear something apart on this car, I find myself saying someone has been here before me. Aside from the sticky tape I didn't see anything irregular.
• Oh I didn't notice the possible splices, I will check that out. You know I literally have everything in the dash apart to get to that connector, What would someone be doing in there. I can actually see the firewall.