The P0688 code is a common issue for Chrysler vehicles. It indicates a problem with the engine control module (ECM) or powertrain control module (PCM) power relay control circuit. This article will delve into the P0688 Chrysler code, explaining its meaning, symptoms, causes, diagnostic procedures, common mistakes, severity, and possible repair solutions. Understanding this code can save you time and money on repairs.
What Does the P0688 Code Mean for Your Chrysler?
The P0688 diagnostic trouble code specifically points to an issue with the ECM/PCM power relay sense circuit. This circuit is responsible for supplying power to the ECM/PCM, the brain of your vehicle’s engine. When the ECM/PCM detects an abnormal voltage signal from this circuit, it triggers the P0688 code. This essentially means the computer that controls your engine isn’t receiving the correct power supply. This is crucial because without the proper power, the ECM/PCM can’t effectively manage your engine’s functions.
alt text: Close up of a car engine with visible wiring and components
Symptoms of a P0688 Code in a Chrysler
The symptoms of a P0688 code can vary, ranging from barely noticeable to severely impacting drivability. Here are some common indicators:
- Illuminated Check Engine Light: This is the most common symptom. The check engine light might be steady or flashing, depending on the severity of the issue.
- No Start Condition: In some cases, the engine might crank but fail to start due to the ECM/PCM not receiving power.
- Rough Running Engine: The engine might run rough or misfire due to improper fuel delivery or ignition timing caused by a malfunctioning ECM/PCM.
- Poor Fuel Economy: A faulty ECM/PCM can lead to inefficient fuel consumption.
- Other Driveability Issues: You might experience a loss of power, stalling, or other unusual driving behaviors. Sometimes, there may be no noticeable symptoms other than the stored code.
Causes of the P0688 Code in Chrysler Vehicles
Several underlying issues can trigger the P0688 code in a Chrysler. These include:
- Faulty ECM/PCM Power Relay: A defective relay is the most common culprit, preventing the proper flow of power to the ECM/PCM.
- Wiring Harness Issues: Damaged, corroded, or loose wiring in the relay control circuit can disrupt the power supply.
- Connector Problems: Loose or corroded connectors can interrupt the electrical connection to the relay or ECM/PCM.
- Low Battery Voltage: A weak or discharged battery might not provide sufficient voltage to engage the relay.
- Faulty ECM/PCM: While less common, a malfunctioning ECM/PCM itself can sometimes cause this code.
Diagnosing the P0688 Chrysler Code
Diagnosing the P0688 code requires a systematic approach:
- Retrieve the Code: Use an OBD-II scanner to confirm the presence of the P0688 code and any other stored codes.
- Inspect the Relay: Visually check the ECM/PCM power relay for signs of damage or burning.
- Test the Relay: Use a multimeter to test the relay’s functionality, ensuring it’s properly switching power.
- Check Wiring and Connectors: Inspect the wiring harness and connectors for damage, corrosion, or looseness.
- Check Battery Voltage: Ensure the battery is fully charged and providing the correct voltage.
- Test ECM/PCM Power and Ground: Verify that the ECM/PCM is receiving the correct power and ground signals.
Common Mistakes When Diagnosing the P0688
A common mistake is immediately replacing the ECM/PCM without thoroughly checking other components. Replacing the ECM/PCM is a complex and costly procedure that often requires reprogramming. Always start with simpler and more likely causes, such as the relay, wiring, and connectors.
How Serious is the P0688 Code?
The P0688 code can be a serious issue as it affects the core functionality of your engine’s control system. Ignoring this code can lead to further damage and potentially leave you stranded. Prompt diagnosis and repair are crucial to prevent more extensive problems.
Repairing the P0688 Code in Your Chrysler
Once the cause is identified, the appropriate repair can be performed:
- Replace the Relay: If the relay is faulty, replace it with a new one.
- Repair Wiring or Connectors: Repair or replace any damaged wiring or connectors in the relay control circuit.
- Address Battery Issues: Charge or replace the battery if necessary.
- Replace the ECM/PCM: In rare cases, the ECM/PCM might need replacement, which requires professional expertise and programming.
Conclusion
The P0688 Chrysler code signifies a potential problem with the power supply to your vehicle’s engine control module. Addressing this issue promptly is crucial to avoid further damage and ensure the safe and reliable operation of your vehicle. By understanding the code’s meaning, symptoms, causes, and diagnostic procedures, you can effectively troubleshoot the problem and get your Chrysler back on the road. Remember to consult with a qualified mechanic if you’re unsure about any diagnostic or repair steps.
