Here's a breakdown of troubleshooting steps, from least to most invasive:
1. Check the Obvious:
* Battery and Connections: A weak battery or corroded battery terminals can cause communication issues. Clean the terminals thoroughly and ensure a solid connection. Consider testing the battery's voltage and cranking amperage.
* Ground Connections: Poor ground connections can also disrupt communication. Locate the main ground points for the PCM and TCM (consult a repair manual for specific locations) and clean them.
* Wiring Harness Inspection: Visually inspect the wiring harnesses connecting the PCM and TCM. Look for any damage, chafing, or broken wires, particularly around areas that flex frequently.
2. Advanced Diagnostics:
* Professional Scan Tool: A code reader that can access more detailed data than a basic OBD-II scanner is crucial. It should be able to read live data from both the PCM and TCM, allowing you to see if any sensors are malfunctioning or sending erratic signals. This is the single most important step. A professional mechanic will have this.
* Data Logging: If you have access to a professional-level scan tool with data logging capabilities, this can help pinpoint intermittent issues. Driving while logging data might reveal patterns related to the communication problem.
* PCM/TCM Voltage and Ground Checks: A multimeter can be used to measure the voltage and ground at the PCM and TCM connectors. This checks for proper power supply and grounding. (Again, a repair manual is essential to know where to test.)
3. Potential Causes and Fixes (require professional help or significant mechanical knowledge):
* Faulty PCM or TCM: If all wiring and connections are good, a faulty PCM or TCM is a likely culprit. These modules are expensive to replace and require professional programming after installation.
* Faulty Wiring: If a damaged wire is identified, repair or replace it. This requires some electrical skills and the right connectors.
* Loose or Corroded Connectors: Carefully inspect all connectors to the PCM and TCM. A loose connection or corrosion can interrupt communication. If necessary, clean the connectors with an electrical contact cleaner.
* Intermittent Short Circuit: This is difficult to diagnose but can cause intermittent communication problems. A professional mechanic will need to use advanced diagnostic techniques to pinpoint this.
Important Considerations:
* Repair Manual: A factory service manual for your 1999 Dodge Caravan is invaluable for this type of repair. It shows wiring diagrams, connector locations, and component testing procedures.
* Professional Mechanic: If you're not comfortable working with automotive electrical systems, it's best to take your Caravan to a qualified mechanic. Diagnosing and repairing this code requires specialized tools and knowledge. Incorrectly diagnosing or repairing this could lead to further damage or even safety hazards.
Attempting to fix this yourself without proper diagnostic tools and knowledge could lead to wasted time and money, or worse. While the steps above offer guidance, professional help is strongly recommended for this type of problem.
