Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means the car's computer isn't getting the power it needs because a switch isn't working right.
The P0688 code is triggered when the Engine Control Module (ECM) or Powertrain Control Module (PCM) detects a problem with the power relay sense circuit. This circuit is responsible for ensuring the ECM/PCM receives the necessary power to operate.
The ECM/PCM power relay provides power to the vehicle's computer system. If the relay sense circuit is open or malfunctioning, the ECM/PCM may not receive the correct voltage, leading to this diagnostic trouble code. The ECM/PCM monitors the relay's operation and sets the P0688 code when it detects an open circuit or a fault in the relay's sense circuit.
• Engine may not start
• Check Engine Light illuminated
• Intermittent engine operation
• Reduced engine performance
• Faulty ECM/PCM power relay
• Open or shorted wiring in the relay circuit
• Corroded or damaged connectors
• Faulty ECM/PCM
ECM: Engine Control Module
PCM: Powertrain Control Module
Relay: An electrical switch that opens and closes under the control of another electrical circuit
• Check for additional codes and address them first.
• Inspect the ECM/PCM power relay for proper operation.
• Examine wiring and connectors for damage or corrosion.
• Test the ECM/PCM for faults.
• Replace the ECM/PCM power relay if faulty.
• Repair or replace damaged wiring or connectors.
• Replace the ECM/PCM if necessary.
• OBD-II scanner
• Multimeter
• Relay tester
$100 - $500
Moderate
• Dodge Ram
• Jeep Grand Cherokee
• Chrysler 300
• Regularly inspect electrical connections.
• Keep the battery and charging system in good condition.
• Perform routine vehicle maintenance.
Electrical Circuit Issue
• Ensure the battery is fully charged.
• Avoid ignoring the Check Engine Light.
• Consult a professional mechanic if unsure.
Check with your vehicle manufacturer for warranty coverage on electrical components.
This code has been associated with electrical issues in vehicles with complex computer systems, often related to relay or wiring problems.
High – This issue can prevent the vehicle from starting or cause it to stall unexpectedly.
Driving with this code may lead to unexpected vehicle shutdowns, which can be dangerous. Address the issue promptly.
• Vehicle at operating temperature
• Battery fully charged
The ECM/PCM power relay is typically located in the vehicle's fuse box or relay panel under the hood.
Q: Can I drive my car with a P0688 code?
A: It's not recommended, as the vehicle may stall or fail to start.
Q: How can I reset the P0688 code?
A: After repairs, use an OBD-II scanner to clear the code, but ensure the issue is resolved first.
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