This is from the GM SI dealing with the BCM and the power modes. Beyond this, my pay grade goes to zero...Could you tell me what wires should be energized at the ignition switch given the key position?
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This is from the GM SI dealing with the BCM and the power modes. Beyond this, my pay grade goes to zero...Could you tell me what wires should be energized at the ignition switch given the key position?
I have replaced the switch already. The car’s state changes when I turn my key so I’m positive it is indexed right. Did you see my bit about the BCM?I ordered my GM ignition switch from NAPA and had it pretty quick. I still think you either have a defective switch from AZ or is not cammed right. My 2 videos at you tube explain this. This is such a long thread, you may have already replaced with another switch and I did not see it.
I do have the electronic cleaner, but I’ve already sprayed the pcm connectors so I’ll go ahead and do the fusebox connections. I also have a 5.3 so my pcm connectors are different. Which pins should I be checking for continuity, for example? Also what am I looking for with the APP and cam position sensor? My CPS also has a different connector since it’s a 5.3.Besides having these PCM Pin-Out Diagrams for Continuity Tracing between the PCM and the BCM, the link to the On Topic Thread may assist you with more information about Diagnosing BCM Issues:
BCM Bench Programming
Hi, so I recently got a VCX Nano (USB) model to do bench programming of Ecu, Bcm, and radios. I built a hardness with what I thought was the property connections. My question that when I try to program the bcm. I get a “naodrui” communication error. I setup everything properly and have...gmtnation.com
Also... Investigate completely removing (Cleaning and Replacing) the Under Seat Rear Fuse Block and BCM and check for any Debris, Detritus, Liquid Invasion and Broken Wiring at the Harness and Connectors, too:
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That doesn’t sound familiar, what is fuse 17 supposed to be? I do remember getting 12v out of the NSS and constant 12V on the starter relay. I’m definitely not going to get the pcm ground on that relay since the bcm is misbehaving. Do you have any thoughts on fuses 16, 22, and 28 not being energized in ACC?In all of this, I don't think that I have seen you check fuse 17 although maybe you mentioned it somewhere that the pcm was getting a start signal (12v).
Would that have power in RUN? or START?well fuse 17 is for the start signal to the pcm.
Yes, did you see both of my you tube videos about install and a correction of the install for the teeth being cammed/aligned wrong? It would still start and run but the no crank/no power was intermittent.I have replaced the switch already. The car’s state changes when I turn my key so I’m positive it is indexed right. Did you see my bit about the BCM?
My car’s dash light behaviors are repeatable if I connect/disconnect the data line for the BCM. I did see your videos but I’m not having the same issues as the ones in the videos. Admittedly, the shop I got this back from did say my switch was one tooth off but I haven’t touched it since. Perks of being in a rush.Yes, did you see both of my you tube videos about install and a correction of the install for the teeth being cammed/aligned wrong? It would still start and run but the no crank/no power was intermittent.
Thank you, I’ll give that a look. How does this translate to the 5.3 though? The connectors aren’t the same on the PCM. Will the pin names match?Try *Pin Tracing* the Class 2 Network Connections for Continuity in between the P10 PCM and the BCM using THIS Bench Top Programming Harness Diagram originally conceived and shared here at GMT nation ...by Bill Reid:
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Just to make sure I understand correctly, for the top half in the ACC position, F&E are shorted together, and B&A are shorted together? Furthermore, F&E are sorted at all times? Thanks for putting this together!This is what I made and use for reference of a GMT360 Ignition switch. I made this as I disassembled said switch and explored the inner workings along with identifying circuitry using the wiring diagrams.
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The top panel showed the results of ohmeter/continuity tests as the switch was rotated. Some contacts were seen to close before others with regards to the location of detents in the switch.
The red and blue panels show the wire colors at the switch, the terminal designations, and the key positions when said wire is powered. Example: Terminal "E" is the white wire and it is powered in ACC, RUN, and START. Looking above you see it is powered from terminal "F" and that is the red wire, OGN A, powered from fuse 34.
For a quickish rundown of stuff that is relevant to this problem, check out posts 69, 73, 82, 86, and 87. 86 and 87 are the most important ones in my opinion.This will be a somewhat rushed and limited response and may be not fully fleshed out but there is a point I wish to make here. Today I did an experiment. No big surprise there I do this all the time.
I took one of my spare clusters and connected it to one of my Bluetooth OBD2 adapters and recorded the message traffic as I proceeded. There are NO OTHER modules involved or connected, this is a stand alone cluster right now. I connected the appropriate ground and then the 12 volt always hot power. The cluster cycled as expected, no lights at all but the stepper motors did the expected drop to zero as a reset and there is about 5 seconds of message traffic. One way traffic of course as there are no other modules here.
Next I powered the "hot in RUN and START" line which is the only other power to the cluster. This causes a lot of traffic and lights. Not ALL the lights but a good many. There was a 'click' heard but no gauge zero resets. Some lights go out after a few seconds then later some other lights go out and then the check gauges light comes on. Oh, also the DLC comes on displaying the expected unknown driver message followed by odometer.
In the above state the cluster continues to send its awake status message every 2 seconds all other traffic stopped.
At this point I added a BCM to the test, properly supplying the ground(s) and all of the "hot at all times" BCM powers. There are a handful of them. Within milliseconds all of the remaining lighted items on the cluster went off leaving the cluster dark.
WHY??
Well I'll tell you why. In the data traffic when the cluster was all alone on the network it repeatedly asks what is the current network status (power mode) but there was no BCM to answer so the cluster stayed in what I assume is a default state of awake and operating. The cluster also was seen asking for a VIN number but again there was no-one to answer. But within milliseconds of powering up the BCM broadcast the current power mode. Since there were no ignition switch powers coming to the BCM (key off position) the BCM announced that status. The cluster received that power mode message and complied. It made NO DIFFERENCE that the cluster still had the "HOT in RUN and START" signal still applied as the BCM power mode message takes precedence.
Oscilloscopes are nice tools and can verify the presence of a signal but they cannot tell you what module is sending that signal, who is receiving the message, nor what the message is conveying. Sometimes it can help a great deal.
I need to study your info from today and see what I can see. One thing I noticed is an error in the stated power status for the key in the ACC position. And it may have been my own error there as it looks familiar to me. Fuses 16, 22, and 28 should be powered in RUN but NOT in ACC.
If the BCM is not seeing all the signals it uses to determine key state then it may be possible that the BCM is sending a power mode message that is shutting down modules.
Just to make sure I understand correctly, for the top half in the ACC position, F&E are shorted together, and B&A are shorted together?
Yes, in post 86 I posted a short test video showing how adding in the BCM screws everything up, and disconnecting it lets the IPC power on and show me more dash lights and the fuel gauge readout. I later progressively added all the other modules on the splice pack in one by one minus the BCM and everything was still behaving as expected. My HVAC panel even started working and my airbag systems were online. No radio though, only the chimes were active without the BCM. Here's a video of that: https://photos.app.goo.gl/9fGK9PNg5Jm9YPpp6That is correct.
In another sheet I tried to list the various circuits that are powered by each of the ignition switch wires. There were some issues with having variations like a 5.3 vs a 4.2 and other such ciruit differences.
Ithink you posted a video maybe of your BCM tests? I will have a look there next. That ribbon cable is mission critical as it carries most (maybe all?) of the ignition switch signals to the BCM.
I'll recheck fuses 16, 22, and 28 in RUN, I must have misread.
My oscilloscope has a logic analyzer and it can read UART, 1Wire, and CAN among others, but I'm not sure which would work best with Class 2
Are these key states determined by pins A18-A20 on the ribbon connector for the BCM:
UART is related to serial data. I will do some research to see if I can have my iPhone see the MX+ as a serial device. What would be your preferred Android app to do this? My aftermarket radio is an android radio which came with the Torque app preinstalled so I may be able to load your app and connect to my OBDLink MX+ through there if I can still use BT to get serial data.I may have erred when I posted that data as well.
The Class 2 message protocol in use here is SAE J1850 VPW. I don't actually know much about oscilloscopes so I cannot say if any can decode this J1850 data stream.
Your MX+ can do it but I have zero iPhone knowledge so cannot advise there. You would need 2 things to work there. First the iPhone needs to allow an app to connect to the MX+ as a serial device and secondly you would need a serial terminal app that will work with that MX+ and allow you to record a logfile.
The serial terminal does not need to be anything automotive specific or the like, all that is needed is a 'dumb' terminal that will record a text logfile. Timestamps are nice but not essential.
Yes, that is at least some of them. Also the Accesory Voltage at B15 comes from the ign switch. Also there are several "hot all the time" 12 volt signals that should be there. I cannot say with certainty that these latter supplies are strictly essential but I would want them there.
What would be your preferred Android app to do this?
What would be your preferred Android app to do this
Great, I'll give that a shot tomorrow. If the radio doesn't work, I'll go buy a cheap android tablet off Marketplace or Walmart and use that. Anything else I should test while I'm there? For example, if you knew what pins the BCM gets its power states from the key position I could backprobe them to see if I get the right voltages.As an addendum in case the terminal app works on your android radio...
You may need to adjust some app settings for things like end of line characters, buffer size and so on. But to get started pair the MX+, select the MX+ in "devices", the app will try to connect to the MX+, once connected you should see an "OK". Enter the following at the prompts pressing return/enter after each entry. (don't type the content in parenthesis)
ATTP2 (try protocol 2)
ATH1 (display message headers)
ATS1 (display a space between each byte)
ATAL (allow long messages)
ATMA (monitor all)
If everything works you will see all message traffic on the class 2 serial data bus. It will be scrolling fast. If it works we can proceed from there.
edit: the above instructions are for ELM based devices or clones. I read that the MX+ has additional slightly different command set but also read they are mostly backward compatible units so it may work just as shown above. Or weay need modifications if any of the above "AT commands" fail.
That leaves me asking: why does removing the ribbon cable have the same effect as removing TBC 1, even though those two aren't related
the ribbon DOES contain various signals such as the Class 2 wire
You are right. My bad. I think my best move at this point would be to dump the class 2 network traffic and see what's going on rather than chasing different powers. Would it be a good idea to get a dump with JUST the BCM connected and another with the rest of the network connected?My data shows the the Class II signal on Connector 1, pin B1, not the ribbon cable.
Would it be a good idea to get a dump with JUST the BCM connected and another with the rest of the network connected?
He also tried to run the starter relay, but a message popped up and said it was being prevented by the immobilizer
That's the thing though, connecting the BCM doesn't cause them to drop out until after I power cycle the key. On the other hand, disconnecting the BCM while the key is in run and the cluster and HVAC are dropped out causes them to come back on after a few seconds.Best to see all traffic.
Assuming we can get that working we could then record certain events, like what is happening when you connect the BCM and the cluster and HVAC drop out.
I think his scan tool has some limitations, since his $6k scan tool told him that he couldn't even communicate with the BCM when it is almost certainly talking in the Class 2 line. The 2006 wiring diagrams mentioned theft deterrent systems, so I'm guessing my 2005 does too as they are very similar vehicles electrically.This interests me. I am unfamiliar with the "theft deterrent module" as my 2002 apparently does not have such a module. It makes me wonder just what does it do and how does it do it.