Will not start, No BUS error code

2002 DODGE DURANGO
156,000 MILES • 4.7L • V8 • TURBO • 4WD • AUTOMATIC
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GODSCHILD
  • MEMBER
  • 1 POST
I replaced my fuel pump and battery. truck wont start but will turn over. so it shows no BUS when I turn the key forward, but will not do anything. I went an got an ECM computer put it in hooked it back up. it still wont crank, still showing no BUS. please help me.
Dec 10, 2019 at 11:30 AM
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AL514
  • ✓ASE Certified Mechanic
  • 5,587 POSTS
  • ASE Certified Mechanic
Hello, so CAN BUS is the network that all the different modules talk to each other on. There is usually 2 can bus signals, each having 2 wires, a high and low signal. So one of the other modules is failing to communicate with the engine computer. The signal can only be monitored by an oscilloscope. It is blocks of square waves. Most likely it's the body control module due to the no start condition. But how you diagnose it is, while watching the faulty signal on an oscilloscope, you start unplugging modules until the signal returns to normal. Then you have located the faulty module.
https://www.2carpros.com/articles/how-a-car-computer-works-pcm-ecm-bcm
Dec 10, 2019 at 2:24 PM
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