In this diagnosis I'm scanning the network with a Snap-on Verus Edge and using a Snap-on Vantage Pro two channel lab scope to view the can bus signals. I'm also using tge Vantage Pro in multimeter mode to measure resistance. At the DLC I'm using a breakout box I bought several years ago out of China. For schematics I have subscription access to Identifix. Thanks for asking.
Great video! I like your diagnostic strategy, I was just wondering (when you did the system scan) why I didn't see the RCDLR (Remote Control Door Lock Receiver) detected? Thanks! 👍
Hi Phillip, why wouldn't you retry the module after seeing all of that sand drop out of it when you removed it? I'm wondering if the ABS module simply had a faulty connection because of the dirt and grit. Otherwise, great video watching your thought process.
@@PhillipBailey Interesting.... question for you: I have a 2011 GMC Sierra 3500 HD. Battery is good, but it often won't crank over. When it doesn't crank over I can't hear the relay click over either. No DTC codes. Your thoughts?
@@northernlightsrenovations1710 you need to monitor the status of the park neutral switch on the scanner, as well as the crank request. Swap the starter relay if you haven't already. Jump 30 to 87 at the starter relay and it should crank. (Make triple sure it's in park) . If its a standard possibly clutch switch. Check for power at the starter S terminal when you're trying to start it. If the starter relay is not energizing I'd be focusing on its control circuit. Security issues should set a code unless your scanner isn't reporting it. HTH
@@PhillipBailey Thanks Phillip. Strangely, I get a 'Service Theft Deterrent System" message on the dash now, which happened about the same time. I'm starting to think it might be related.
I wish you were local to me. I'm having a to of issues with mine. 2010 silverado 1500 4x4 5.3. I hunt and diagnose and then change a part then get 7 more codes. 4 weeks I've been fighting this truck. On the verge of loosing my job. At my witts end.
Yes some diagnosis is frustrating. What is the symptoms you're experiencing and what codes are being generated in the various computers. What have you done so far?
Ok well it started as a no crank no start. Let it sit overnight and it started but shut off seconds later. Did that 4 times. Later that day it fired right up and used it all day. Then again, no crank no start. Original code was P1682. So I did the ignition switch and tumblers. Still nothing. Then the security light came on. Tried to reset but would not go off after 10 minutes. So I bought a used bcm. No change except security light went out. I noticed i had power every where except the fuel pump fuse. Purchased a new fuel pump. Original pump was leaking out of the electrical plugs and from the rusted top. I figured that was it, but no.. checked the fscm. It was getting juice. Bought a ecm and fuse box. No changes. Now getting like 7 codes. U0100, U0109, P0118, P0315, P0230, P0449, P0700. I'M at a loss. Ran out of money and about to lose my job and my mind. I hope you can help
@@dannyg7823 P1682 is a problem with one of the ignition feeds to the ECM. It is usually caused by a failing run/crank relay, PCM power relay or corroded connections in the fuse panel under the hood. Check the under hood relay center for corroded terminals on the relays and corroded fuses. P1682 sets when there is more than 3 volts difference between the 2 ignition voltage circuits to the ECM. The first ignition voltage is supplied by the powertrain relay through a fuse number 4 and the second is supplied by the run/crank relay through a fuse number 58. This can cause a no crank or start and die symptoms. I believe the fuel pump fuse is on the switched side of the fuel pump relay which only applies to LY9 and L96 options. I don't believe you have those as your truck has a fuel pump driver module in the rear and no actual fuel pump relay although the fuse box may have a place for one. Did you have the BCM programmed to the truck? If not you will have VIN mismatch codes in the ABS and Restraints system. I doubt your BCM is the problem. I'd focus on the fuse box and the P1682 code. The U codes will be generated due to a lack of communication with the ECM if there's a power problem to it. If you live in an area where salt is used on the roads the fuse panels are prone to failure. New from GM is not that bad and there are several versions depending on what options your truck was built with. Good luck and let me know what you find. You mentioned the fuel pump was rusted out so seems you are...
I actually replaced the fuse box yesterday. Mine was pretty bad. But didn't get the U codes until I changed it. I think I will start wiggling wires. Lol. I did find that G103 ground was soft in the front and the thinner ground had a break in it. Also was full of moisture or oil. I appreciate you taking the time. I'm stressed out over this truck.
Thank you for the video! I'm still learning CAN troubleshooting, and still trying to understand, The terminating resistor you measured was 34 ohms, I thought terminating resistors were about 120 ohms. I must be missing something. Could you help me understand? It would be very much appreciated!
Yes you are correct, terminating resistors are located at each end of the network. In this vehicle there is one inside the ECM and another in the harness in the rear as I showed in the video. On a properly working can system the two 120 ohm resistors should measure 60 because they are in parallel. One of the first tests you can do is measure this across the DLC pins 6 can high and pin 14 can low. You should actually disconnect the battery to be sure there is no voltage present or it will skew the resistance measurement. In this vehicle it measure 34 ohms indicating a shorted can bus. Since tge vehicle was actually running and because I've seen this before I assumed the problem to be in the rear half of the network from tge ABS to the rear resistor. At the ABS module you can measure both ends of the network and since they are now separated with the ABS disconnected they should both measure 120ohms as they did. Even if you don't have a lab scope the resistance test would have helped you narrow it down. As you see on tge scope the two signals are a mirror image biased at 2.5 volts with the can H pulled up 1 volt and the can L pulled down one volt. I'm actually amazed that this vehicle started with such a poor communication signal shows how fault tolerant the can system is. Here is another Duramax that had can issues among other things that would not crank unless the aftermarket tuner was connected to the DLC.. I'll post the link shortly...
great video, i have opposite issue, can Hi, Lo are over voltage,. getting 2.9v Hi and 2.6V Lo. also getting 120ohms but when I unplug rear Resister i only read 7.9ohms. also have U0100 code no Comm with ECM
Where are you measuring the resistance? If at pins 6 and 14 of the DLC a measurement of 120 indicates an open but disconnecting the terminating resistor should make it increase not decrease. There's a connector under the dash at the left junction block by your left foot that when unplugged will take the back of the truck off line. (Removes the onstar abs and fuelpump driver. Try unplugging that and see if you have com with the ecm afterwards. Seen ABS modules take down the network on these.
@@AtanasDimitrov954RR here's another video. It's basically the same system and talks about that connector x3 at the junction box. That's a 5 min into the video. ua-cam.com/video/_G4U1_tTFkM/v-deo.html
AWESOME/ great video about communication problems learning more from u Phillip thanks for the info and how to approach the problem. cheeeeers
Thanks for watching it's much appreciated.
Love these videos! What scanners, tools, or software are you using to diagnose?
In this diagnosis I'm scanning the network with a Snap-on Verus Edge and using a Snap-on Vantage Pro two channel lab scope to view the can bus signals. I'm also using tge Vantage Pro in multimeter mode to measure resistance. At the DLC I'm using a breakout box I bought several years ago out of China. For schematics I have subscription access to Identifix. Thanks for asking.
Great video Phil
Great video! I like your diagnostic strategy, I was just wondering (when you did the system scan) why I didn't see the RCDLR
(Remote Control Door Lock Receiver) detected?
Thanks! 👍
i'm not sure that this truck has the remote system.
@@PhillipBailey I was wondering that and no TPMS system then it didn't have that RPO option. Thanks!
Who else came over because of Ivan's video?
Thanks appreciate the visit.
@@PhillipBailey I'm all for learning from different masters 😉
@@Usmanthemecano yes thats for sure! Never stop learning...
Hi Phillip, why wouldn't you retry the module after seeing all of that sand drop out of it when you removed it? I'm wondering if the ABS module simply had a faulty connection because of the dirt and grit. Otherwise, great video watching your thought process.
No the dirt was not causing the issue. Internally shorted CAN Bus is pretty common on these. I've seen 5 or 6 now. HTH
@@PhillipBailey Interesting.... question for you: I have a 2011 GMC Sierra 3500 HD. Battery is good, but it often won't crank over. When it doesn't crank over I can't hear the relay click over either. No DTC codes. Your thoughts?
@@northernlightsrenovations1710 you need to monitor the status of the park neutral switch on the scanner, as well as the crank request. Swap the starter relay if you haven't already. Jump 30 to 87 at the starter relay and it should crank. (Make triple sure it's in park) . If its a standard possibly clutch switch. Check for power at the starter S terminal when you're trying to start it. If the starter relay is not energizing I'd be focusing on its control circuit. Security issues should set a code unless your scanner isn't reporting it. HTH
@@PhillipBailey Thanks Phillip. Strangely, I get a 'Service Theft Deterrent System" message on the dash now, which happened about the same time. I'm starting to think it might be related.
Yes the theft system can disable cranking. Need to do a network scan for codes.
I wish you were local to me. I'm having a to of issues with mine. 2010 silverado 1500 4x4 5.3. I hunt and diagnose and then change a part then get 7 more codes. 4 weeks I've been fighting this truck. On the verge of loosing my job. At my witts end.
Yes some diagnosis is frustrating. What is the symptoms you're experiencing and what codes are being generated in the various computers. What have you done so far?
Ok well it started as a no crank no start. Let it sit overnight and it started but shut off seconds later. Did that 4 times. Later that day it fired right up and used it all day. Then again, no crank no start. Original code was P1682. So I did the ignition switch and tumblers. Still nothing. Then the security light came on. Tried to reset but would not go off after 10 minutes. So I bought a used bcm. No change except security light went out. I noticed i had power every where except the fuel pump fuse. Purchased a new fuel pump. Original pump was leaking out of the electrical plugs and from the rusted top. I figured that was it, but no.. checked the fscm. It was getting juice. Bought a ecm and fuse box. No changes. Now getting like 7 codes. U0100, U0109, P0118, P0315, P0230, P0449, P0700. I'M at a loss. Ran out of money and about to lose my job and my mind. I hope you can help
@@dannyg7823 P1682 is a problem with one of the ignition feeds to the ECM. It is usually caused by a failing run/crank relay, PCM power relay or corroded connections in the fuse panel under the hood. Check the under hood relay center for corroded terminals on the relays and corroded fuses. P1682 sets when there is more than 3 volts difference between the 2 ignition voltage circuits to the ECM. The first ignition voltage is supplied by the powertrain relay through a fuse number 4 and the second is supplied by the run/crank relay through a fuse number 58. This can cause a no crank or start and die symptoms. I believe the fuel pump fuse is on the switched side of the fuel pump relay which only applies to LY9 and L96 options. I don't believe you have those as your truck has a fuel pump driver module in the rear and no actual fuel pump relay although the fuse box may have a place for one. Did you have the BCM programmed to the truck? If not you will have VIN mismatch codes in the ABS and Restraints system. I doubt your BCM is the problem. I'd focus on the fuse box and the P1682 code. The U codes will be generated due to a lack of communication with the ECM if there's a power problem to it. If you live in an area where salt is used on the roads the fuse panels are prone to failure. New from GM is not that bad and there are several versions depending on what options your truck was built with. Good luck and let me know what you find. You mentioned the fuel pump was rusted out so seems you are...
@@dannyg7823 here's a video I did on a Canyon with a P1682 code. It's similar to yours. ua-cam.com/video/_d8bdUmH_o8/v-deo.html
I actually replaced the fuse box yesterday. Mine was pretty bad. But didn't get the U codes until I changed it. I think I will start wiggling wires. Lol. I did find that G103 ground was soft in the front and the thinner ground had a break in it. Also was full of moisture or oil. I appreciate you taking the time. I'm stressed out over this truck.
Thank you for the video! I'm still learning CAN troubleshooting, and still trying to understand, The terminating resistor you measured was 34 ohms, I thought terminating resistors were about 120 ohms. I must be missing something. Could you help me understand? It would be very much appreciated!
Yes you are correct, terminating resistors are located at each end of the network. In this vehicle there is one inside the ECM and another in the harness in the rear as I showed in the video. On a properly working can system the two 120 ohm resistors should measure 60 because they are in parallel. One of the first tests you can do is measure this across the DLC pins 6 can high and pin 14 can low. You should actually disconnect the battery to be sure there is no voltage present or it will skew the resistance measurement. In this vehicle it measure 34 ohms indicating a shorted can bus. Since tge vehicle was actually running and because I've seen this before I assumed the problem to be in the rear half of the network from tge ABS to the rear resistor. At the ABS module you can measure both ends of the network and since they are now separated with the ABS disconnected they should both measure 120ohms as they did. Even if you don't have a lab scope the resistance test would have helped you narrow it down. As you see on tge scope the two signals are a mirror image biased at 2.5 volts with the can H pulled up 1 volt and the can L pulled down one volt. I'm actually amazed that this vehicle started with such a poor communication signal shows how fault tolerant the can system is. Here is another Duramax that had can issues among other things that would not crank unless the aftermarket tuner was connected to the DLC.. I'll post the link shortly...
Here is another one I did awhile ago that I never fixed but you will see the can testing ua-cam.com/video/_G4U1_tTFkM/v-deo.html
@@PhillipBailey Thank you, appreciate the help. Just trying to learn as much as I can!
@@PhillipBailey thank you again, appreciate it!
great video, i have opposite issue, can Hi, Lo are over voltage,. getting 2.9v Hi and 2.6V Lo. also getting 120ohms but when I unplug rear Resister i only read 7.9ohms. also have U0100 code no Comm with ECM
Where are you measuring the resistance? If at pins 6 and 14 of the DLC a measurement of 120 indicates an open but disconnecting the terminating resistor should make it increase not decrease. There's a connector under the dash at the left junction block by your left foot that when unplugged will take the back of the truck off line. (Removes the onstar abs and fuelpump driver. Try unplugging that and see if you have com with the ecm afterwards. Seen ABS modules take down the network on these.
@@PhillipBailey thanks for reply. i will try but which connector are you talking about. there is several. i do see the JB by left foot.
@@AtanasDimitrov954RR here's another video. It's basically the same system and talks about that connector x3 at the junction box. That's a 5 min into the video. ua-cam.com/video/_G4U1_tTFkM/v-deo.html
Whatever was this my trucks doing the exact same things right now