Dodge ram 1999 says no bus?

A "No BUS" message on a 1999 Dodge Ram's instrument cluster usually indicates a problem with the communication system between the various electronic control modules (ECMs) in the vehicle. This network, often called a Controller Area Network (CAN) bus, allows different parts of the truck (like the engine computer, transmission computer, ABS module, etc.) to talk to each other. A "No BUS" message means this communication is disrupted.

Here are the potential causes:

* Faulty PCM (Powertrain Control Module): This is the brain of the engine and transmission, and a malfunctioning PCM is a common culprit.

* Faulty BCM (Body Control Module): This controls many of the vehicle's electrical functions and is also crucial for the CAN bus.

* Faulty other ECMs: Problems with the ABS module, transmission control module, or other modules can also disrupt the network.

* Wiring Issues: Damaged, corroded, or loose wires within the CAN bus wiring harness are a significant possibility. This is often caused by rodents chewing wires or corrosion in connectors.

* Fuses and Relays: Check fuses and relays related to the communication system.

* Data Line Issues: Problems with the data lines themselves – the physical wires carrying the communication signals – can also cause a "No BUS" message.

* Ground Issues: Poor ground connections can disrupt the electrical system, including the CAN bus.

Troubleshooting Steps (Proceed with caution and consult a repair manual if you're not comfortable with car repairs):

1. Check fuses and relays: Consult your owner's manual to locate and check the fuses and relays associated with the PCM, BCM, and communication systems. Replace any blown fuses.

2. Visual Inspection: Inspect the wiring harness, particularly in areas prone to damage (under the hood, near the firewall, etc.), for any signs of damage, corrosion, or loose connections.

3. Battery Voltage: Ensure the battery is properly charged. Low voltage can disrupt the communication system.

4. OBD-II Scanner: Use an OBD-II scanner to retrieve any diagnostic trouble codes (DTCs). These codes can provide clues about the specific cause of the problem. A professional-grade scanner is often better than a basic code reader.

5. Professional Diagnosis: If you haven't identified the problem after these steps, it's best to take your truck to a qualified mechanic or Dodge specialist. They have the tools and expertise to diagnose and repair complex CAN bus issues. Trying to fix this without proper knowledge can lead to further damage.

The "No BUS" message is a serious issue because it can affect many critical systems. Don't drive the truck extensively with this message displayed, as it could lead to further damage or unsafe operating conditions.