What is the P0687 fault number? What is the description of ECM/PCM Powerrelay Control Circuit High error code How do you fix the P0687 fault code What are the causes and symptoms for the P0687 fault code
What is the P0687 Fault code? What does it all mean?
When the engine control module or powertrain control modules (PCM), detects high voltage in the power relay control circuit, a code P0687 will be triggered.
The function of the power relays is to transmit the required electrical current to ECM/PCM and provide enough power for the system. The relay’s basic working principles are simple. The powertrain relay is usually set to the on position, and the battery voltage flows to the relay continuously. The ignition switch should be turned to the on position. “ON” position, the small coil within the relay is energized and the electromagnet causes two contacts to close. This completes the circuit by sending electrical current from the battery through a fused circuit to the ECM/PCM.
The ECM/PCM continuously checks the voltage current within the power relay circuit. The P0687 fault code will be set if it detects high voltage in the circuit.
Note: This code will only be applied to vehicles that use a relay power supply for the ECM/PCM. Some applications use an alternative to a power relay: a fused circuit. These vehicles do not have the P0687 fault code.
P0687 fault codes can be found on many vehicles, including, but not limited, to Isuzu and Saab models.
What is the P0687 Fault Code?
Here are some reasons why P0687 should be set.
- Problems with charging system
- – Power relay for defective ECM/PCM
- – Shorted, damaged, burned, disconnected, or corrosion wires and/or connectors including battery terminals
- Defective ignition switch
- – Battery problems
- – Defective ECM/PCM (rarely)
What are the symptoms for P0687 Malfunction Codes?
You may experience the following symptoms if your vehicle has the code P0687:
- – Illumination for the check engine light
- – If there is no starting condition, the engine may not turn on at all
- – Engine stalling right after starting
- – The ECM/PCM has the ability to enter fail-safe mode in order to limit engine power
- – You can adjust fault codes that relate to the charging system
Note: This code will allow the vehicle to run for most of its life, but the PCM can shut down the engine in some cases to protect the whole system.
How to Fix the P0687 Fault Code
Because this code is about electrical components, don’t rush to make a choice and try to replace the ECM/PCM immediately. This can be a costly repair and often the only option to resolve the problem. This fault code is often caused by shorted cables or problems with the charging system. These should be checked first.
The following repairs may be able to resolve the P0687 fault code:
- – Test the charging system and repair or replace the alternator.
- – Replacing an inoperable ignition switch
- Repair of short circuits caused by faulty wiring, terminals or connections to ECM/PCM relays
- ECM/PCM relay replacement
- – Check the battery and cables for damage and replace it if necessary
- – Examining the fuse box and replacing it if necessary.
- – ECM/PCM replacement, reprogramming (rarely).
How serious is the P0687 Fault code?
Even if your vehicle started with a P0687 fault code set, you must immediately fix the problem. Excessive electrical current can cause damage to components and even failure. This is a costly repair that may require you to buy a new ECM/PCM.
