What is the P0688 fault number? What is the ECM/PCM Power Relay Sense Circuit/Open error code? How do I fix the P0688 fault code What are the symptoms and causes for the P0688 fault code
What is the P0688? What is Fault Code What does it mean?
Common code P0688 refers to problems with output circuits, as well as internal computer malfunctions. A fault code of P0688 is triggered when a high or abnormally voltage signal is sent by the relay that powers powertrain control module (PCM), also called the engine control module(ECM).
The PCM power relay sends battery voltage safely to the ECM/PCM circuits. It is a contact relay activated by a cable connected to the ignition switch. This type of relay is usually five-wire in design.
Relay’s working structure is simple. The powertrain relay is normally set in the on position. The relay receives continuous voltage from the battery. When the ignition switch turns to the off position, the relay is activated. “ON” position, a small coil in the relay is energized. The electromagnet then causes the relay’s two contacts to close. This completes the circuit, and the electrical current is sent from the battery to a PCM via a fused circuit.
This code can only be used in vehicles that use relays for power and ground signals to ECM/PCM. Some applications use a fused system instead of a power-relay.
P0688 fault codes can be found on vehicles made by Mercedes Benz and Audi as well as Jeep, Dodge, Alfa Romeo (Seat), Chrysler, Volkswagen, and Chevrolet.
What is the P0688 Fault Code?
Below are some reasons to set fault code P0688:
- – ECM/PCM power relay defect
- – Shorted, damaged, burned, disconnected, or corrosion wires and/or connectors including battery terminals
- – Inadequate electrical connection between ECM/PCM and power relay
- – ECM/PCM fuse blown or fusible link
- – A dead or weak battery
- – Low voltage during cranking
- – Defective ECM/PCM (rarely)
What are the symptoms for P0688 Malfunction Codes?
You may experience the following symptoms if your vehicle has the code P0688:
- – Illumination at the check engine lights
- – The instrument panel does not have lights
- – If there is no starting condition, the engine may not turn on at all
- – Engine may not start but it starts
- – The engine may stop instantly after starting
- You may have to return the accessory.
- The engine can show a number of drivability problems.
- – To limit engine power, the ECM/PCM may enter fail-safe mode
How do I fix the P0688 fault code?
This code refers to electrical components. Do not rush to make a decision. This can be a costly repair and often the only option to resolve the problem. This fault code is typically caused by corroded or loose connections to the relay. They should be checked first.
The following repairs may be able to resolve the P0688 fault code:
- – Repair of damaged or loose battery cables
- – Fully charge your battery
- Replace the battery if it is dead
- – Replacing blownfuses
- – Repair or replacement damaged or worn electrical wiring, and the associated connectors
- – Replacing an ECM/PCM relay that is damaged or defective
- – Replacing the ECM/PCM that is not working
How serious is the P0688 Fault code?
Your vehicle may still stop if it starts with a P0688 fault code. The code can impact all security components. This code can cause your headlights to go out suddenly, or the lights on the instrument panels may disappear. The ABS and traction control systems may also be affected. This code should be rectified immediately to prevent any accidents or damage to other parts.
