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2007 Cadillac CTS base 2.8 liter automatic - No start - R&R ECM but VIN Changed

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18 Feb 2019 20:18 #27155 by Marti
I have replaced the ECM but my two way communicating OBD scanner ( iLink 400 by Vident, with the GM package), says no communication to the ECU I think on the class 2 data line (slow network, which is a hybrid star type). In 2008 the CAN bus was required by the Environmental Protection Agency, EPA, on new cars so my 2007 CTS has both the slower data line (class 2 J18.... ) and the GM Lan high speed with two lines twisted that runs only between some of the modules, including the TCM and the ECU. I can read some of the data outputs from the ECM apparently through GLAN high speed system. The Vehicle Theft Deterrent VTD system is apparently keeping the key from starting the engine, I think because the VIN on the used ECM I used is currently wrong. It seems the VTD system will not allow a start If the VIN is not correct in the ECM.

I've got the Mitchell1 wiring diagrams for my CTS and I've checked continuity (only about 2 ohms resistance on the data line between the ECM and the two closest modules (EBCM and the HVAC module), having tested it with modules unplugged) on the Class 2 data lines (purple single line) and even used a test light which lights brightly when I unplug that line on both ends and short one end to ground so I could use the test light (test under some current flow). This line has "OL" resistance to ground so it seems good. There is a splice (S154) on the line from the ECU that forms a T allowing this single purple data line to split to the EBCM and the HVAC modules.

I checked powers and grounds on the ECM, which are good. I checked fuses and relays supplying power.

I put a hand held oscilloscope on the DLC, pin 2 for the class 2 data line and it looks normal (about 6.2 volts with square wave data packets moving normally).

Is there a way to input the new VIN on my replaced ECU? Do I need a Tech2 or something else? Can I send it somewhere to have the VIN changed on the ECU I bought from a junkyard? Where do you recommend?

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19 Feb 2019 07:09 - 19 Feb 2019 07:13 #27164 by juergen.scholl
You'll have to reprogram the ecm and the vehicle theft deterrent system by SPS in order to get the car working properly. NO work around, you'll need someone with online programming capabilities. Tech2 or J2534 and an active subscription to the GM/AC-delco website.

An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
Last edit: 19 Feb 2019 07:13 by juergen.scholl.
The following user(s) said Thank You: chief eaglebear, Marti

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09 Mar 2019 06:57 #27679 by Marti
I have been unable to resolve in about a month of trying, on my 2007 CTS base with 2.8 liter. The data system is set up in what they call a hybrid star type, having both the single line GM Class 2 data line to most of the modules, and the high speed GMLAN (twisted wires) for the ECM and TCM. The resistance is 60 ohms on that system. I lost some of the IPC's gage info (gas level and ECT) and began having more difficulty with the key not being recognized so I replaced the ECM with a junkyard ECM that I pulled myself (similar VIN and setup as my car). Now my gages are back but still I can't reprogram for key recognition although my scanner is a two way communication type and I have input VIN info before. My scanner can obtain some data from the ECM but when I look at the ECM's ID info I get an error "no communication". The advise I got from the repair forum was to take it to someone with a Tech2 and an active subscription in order to reflash and change the VIN. My problem is that with no communication to the ECM I'm likely to be charged a lot of money to troubleshoot the no communication issue before I can get the VIN changed on the junkyard ECM. I've looked at the Class 2 data line with a scope and it shows communication with square waves at about 6 volts peak. I've pulled the 3 splice packs on the Class 2 data line with no success on getting the ECM to show ID using my scanner. Is there no way of changing the VIN in the ECM somehow?

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15 Mar 2019 11:11 - 15 Mar 2019 11:14 #27846 by Doc n2mx
Hi
I don't known what scan tool you are using but try to tell it one year newer or even one year older.
You may need to use a different scan tool.

You might check your OBD2 plug may be a bad fuse
Good luck
Doc
Last edit: 15 Mar 2019 11:14 by Doc n2mx.

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18 Mar 2019 18:04 #27912 by Marti
I've got a Ilink 400 with the GM Package:
www.videnttech.com/product/item-79.html

It has two way communication and I have input VIN on modules before.

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18 Mar 2019 18:07 #27913 by Marti
Would a Tech2 be able to communicate where the Chinese brand shows no communication? Or would the Tech2 give other data that would help determine the cause of non-communication? My guess is that the ECM is bad because I see communication on the Class 2 data line coming from the ECM using a scope. What would you do next?

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