Therefore, repairing a P0700 code requires a systematic approach to diagnose the underlying issue:
1. Check the Obvious:
* Battery and Connections: A weak battery or corroded battery terminals can disrupt electrical signals. Clean the terminals thoroughly and check the battery voltage.
* Fuses and Relays: Inspect fuses and relays related to the transmission and PCM. Replace any blown fuses. Consult your owner's manual for the correct fuse and relay locations.
* Wiring Harness: Visually inspect the wiring harness connecting the TCM and PCM for any damage (breaks, chafing, corrosion). Pay close attention to areas that experience movement or vibration.
2. Advanced Diagnostics:
Because P0700 is a communication error, you'll need more advanced tools and knowledge or professional help at this point:
* OBD-II Scanner: A basic scanner will only display the P0700 code. You need a more advanced scanner capable of reading data streams from both the TCM and PCM. This allows you to see if communication is happening and monitor various transmission parameters while the engine runs. Look for live data capabilities.
* Specific Diagnostic Trouble Codes (DTCs): The advanced scanner might reveal more specific codes related to the transmission *after* you've cleared the P0700. These codes will help isolate the root cause. For example, a sensor failure might be causing the communication issue, not a broken wire.
* Voltage and Ground Checks: Use a multimeter to check the voltage and ground connections to both the TCM and PCM. Low voltage or poor grounds will prevent proper communication.
* TCM/PCM Replacement (Last Resort): If all else fails, the problem might lie within the TCM or PCM itself. Replacing these modules is expensive and should only be considered after thorough troubleshooting.
Important Considerations:
* Professional Help: Unless you have experience working with automotive electrical systems and diagnostic tools, it's strongly recommended you take your PT Cruiser to a qualified mechanic or transmission specialist. Improper diagnosis or repair can lead to further damage.
* Transmission Fluid: While unrelated to the P0700 itself, ensure your transmission fluid is at the correct level and is clean. Low fluid or contaminated fluid can cause other transmission issues that could indirectly lead to communication problems.
In short, the P0700 code is a symptom, not the disease. Finding the underlying problem requires a systematic approach using diagnostic tools to identify the cause of the communication failure between the TCM and PCM.
