Dodge Repair Questions? Ask a Mechanic for Answers ASAP
Hi there. Thank you for using our service.
PCI BUS is a single wire communication format that allowed electronic modules to share data. Things that can bring it down are ground or power issues with any of the modules on the BUS, or with any of the sensors that receive a 5 volt signal from the PCM.
As you probably know by now, this issue is not easy to diagnose without the aid of a DRBIII scan tool. Basically, you'd need to unplug every module and sensor one at a time unitl the culprit was found. However, since you mention a previous trans code, I would strongly advice you to do the following first:
If the NO BUS message is now gone, the issue lies with either a bad connection at the TCM, or a bad TCM itself.
Please let me know how it goes. Best Regards.
Happy New Year and thank you for the update.
Actually, 5.48 volts is quite high, it should be no more than 5.0 volts. Are you reading that voltage directly from the harness with a voltmeter, or seeing it displayed on a scan tool screen?
Also, any reason why you did not disconnect the TCM as I had suggested?
Lastly, you state "it cuts off". I need to know what cuts off: is it spark?, injector pulse?, fuel pressure?, power to the PCM? Power from the PCM to the ASD relay?
Your test at pin 85 of the ASD relay indicate the PCM is sending the correct ground signal. The problem could be somewhere else. For example, once the ASD is activated, it sends power to the O2 sensor heaters so if there is a problem with that circuit it can affect the signal the ASD sends back to the PCM.
I hope you understand that this kind of issue is best handled with the help of a DRBIII and a lab scope. Otherwise, all you can do is make sure you have a good PCM that's programmed to the vehicle, then, with the battery disconnected, unplug all the modules and sensors that receive and send a signal from and to the PCM and inspect all those connectors. Once everything is disconnected, reconnect the battery and check the odometer. If the NO BUS message is still there, replace the PCM. If it's gone, reconnect the sensors one by one until one of them makes the NO BUS message reappear. Replace that sensor and keep reconnecting until everything is reconnected back to normal and the NO BUS message is gone.
At this point, you can rate my service if you'd like. Best Regards.