# Multiple modules not communicating **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** ford\ **Created:** [October 23, 2024, 4:48pm UTC](https://community.cartalk.com/t/multiple-modules-not-communicating/197749 "2024-10-23T16:48:10Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![dianiskatomas\_191452](https://avatars.discourse-cdn.com/v4/letter/d/958977/32.png) [@dianiskatomas\_191452](https://community.cartalk.com/u/dianiskatomas_191452)\ **Post date:** [October 23, 2024, 4:48pm UTC](https://community.cartalk.com/t/multiple-modules-not-communicating/197749/1 "2024-10-23T16:48:10Z")
Hi I have trouble with diagnosing no comm between modules. The relays is clicking when I open or clôose door or when ignition is on. The network shows intermittent short (can low to can high and also to ground but only to ground pins on DLC not on physical metal.) When measured disconnected PCM the short was on PCM but also on BCM so when disconnected both of them the network was finally not shorted. I think something between these modules is shorted and making both of them go crazy. Both of them were replaced, checked the grounds… Any of you have some tips which I should do next? thanks ![topologynode_23-11-26-02](https://global.discourse-cdn.com/cartalk/original/3X/8/9/894fd9fd0ad0f0d3031e034e1b9c0bae728c2b80.png) ---
**Author:** ![Mustangman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mustangman/32/44130_2.png) [@Mustangman](https://community.cartalk.com/u/Mustangman)\ **Post date:** [October 23, 2024, 6:24pm UTC](https://community.cartalk.com/t/multiple-modules-not-communicating/197749/2 "2024-10-23T18:24:41Z")
I would say you have damaged comm wiring. Start searching the wiring looms until you find the short. Likely a rubbed through wire touching ground. ---
**Author:** ![eddo](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/eddo/32/2594_2.png) [@eddo](https://community.cartalk.com/u/eddo)\ **Post date:** [October 23, 2024, 6:37pm UTC](https://community.cartalk.com/t/multiple-modules-not-communicating/197749/3 "2024-10-23T18:37:09Z")
yep, start following wire looms and inspecting for rub points. it’s there somewhere. ---
**Author:** ![texases](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/texases/32/862_2.png) [@texases](https://community.cartalk.com/u/texases)\ **Post date:** [October 23, 2024, 6:37pm UTC](https://community.cartalk.com/t/multiple-modules-not-communicating/197749/4 "2024-10-23T18:37:40Z")
That, or squirrel/rat damage. ---
**Author:** ![asemaster](https://avatars.discourse-cdn.com/v4/letter/a/5f9b8f/32.png) [@asemaster](https://community.cartalk.com/u/asemaster)\ **Post date:** [October 23, 2024, 7:11pm UTC](https://community.cartalk.com/t/multiple-modules-not-communicating/197749/5 "2024-10-23T19:11:06Z")
What are the actual ohm readings when everything is connected, when just the PCM is disconnected, just the BCM disconnected, and both PCM and BCM connected? ---
**Author:** ![TwinTurbo](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@TwinTurbo](https://community.cartalk.com/u/TwinTurbo)\ **Post date:** [October 23, 2024, 7:16pm UTC](https://community.cartalk.com/t/multiple-modules-not-communicating/197749/6 "2024-10-23T19:16:05Z")
> [@dianiskatomas\_191452](#): > > When measured disconnected PCM the short was on PCM but also on BCM so when disconnected both of them the network was finally not shorted This would seem to indicate there is nothing wrong with the interconnect wiring. > [@dianiskatomas\_191452](#): > > Both of them were replaced, checked the grounds So still does not work with both modules replaced. Same symptoms? Do the measurements asemaster requested and post back the results. Any chance your vehicle was close to a lightning strike prior to this failure? ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [October 23, 2024, 9:31pm UTC](https://community.cartalk.com/t/multiple-modules-not-communicating/197749/7 "2024-10-23T21:31:58Z")
I think there’s only two wires in the Can bus. It seems like the best debug method would be to disconnect all the nodes and bus terminators then use a DVM in resistance mode to probe the two wires at node number 1 to make sure each of them gets to all the other nodes , and no short circuits between them. Disclaimer: I’ve never done this. Worse case, replace the entire can bus with a new one. ---
**Author:** ![davesmopar](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/davesmopar/32/41750_2.png) [@davesmopar](https://community.cartalk.com/u/davesmopar)\ **Post date:** [May 11, 2026, 1:00pm UTC](https://community.cartalk.com/t/multiple-modules-not-communicating/197749/8 "2026-05-11T13:00:16Z")
> [@ECM not communicating](https://community.cartalk.com/t/ecm-not-communicating/197864/8): > > RESOLVED: Finally after many many attempts I got it to work. The whole problem was 1 diesel injector internally shorted to ground. This injector was shorting also the ECM.