P0687 - OBD Trouble Code

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Oftentimes, Engine Warning Light turns up almost immediately it senses the OBD code error. This directly impacts the engine performance as it struggles with power and acceleration as well as failed ignition system causing increased consumption of fuel by the engine along with engine stalling and not starting.

OBD-II Code Hard or no start in cold weather is defined as an ECM/PCM Power Relay Control Circuit High

Most OBD-II equipped vehicles use a contact relay to supply the PCM with battery voltage. A few manufacturers continue to use just a fused circuit but this design is becoming less common. Power relays are normally of a five-terminal design with a constant supply of battery voltage at the primary input terminal. When the ignition switch is placed in the ON position, the secondary input terminal is supplied with battery voltage (via a fused circuit). Terminal number five is a signal wire for the controller area network (CAN). The fourth terminal supplies an output voltage signal for the PCM. These are the three primary circuits related to the conditions of a P0687 code being stored.

What causes this problem with the ECM/PCM Power Relay Control Circuit High?

• The alternator may be overcharging
• Faulty PCM power relay
• A faulty ignition switches
• Shorted wiring or wiring connectors

1. Engine Control Module - Wrong OBD Error Code can also be stored due to faulty ECMs. It’s better to get the faulty ECM electricals replaced as soon as possible.
2. Powertrain Control Module - P0687 error code can also flash due to rare problems with the PCM. Replace faulty PCM related components immediately.
3. Diagnostic Tool - Choose a high grade and accurate diagnostic tools to detect and correct the OBD code error. Find all types of professional tools from us.
4. Ignition Switch - Any fault in the ignition switch will result in the faulty ignition system causing start-up issue and problems. Buy and replace new ignition switch now!
5. Car Battery & Cables - Buy quality car battery and cables and replace the damaged and corroded parts now!
6. ECU Fuse - Blown fuses must be replaced as it can solve OBD code P0687 error. Buy new ECU fuses from us!

It is vital to know the symptoms of an issue as only then you would be able to solve the problem. So that’s why we have listed out some major symptoms of OBD Code P0687 here:

Common Symptoms

• Engine is hard to start or doesn’t start at all
• Decreased engine power and acceleration
• Engine misfires
• Check Engine Light illumination

Want to correct the Trouble Code P0687? Read these points mentioned below:

• Repairing or replacing the alternator and/or its wiring and connectors
• Ignition switch replacement
• Replacing the PCM power relay
• Repairing or replacing any faulty wiring or connectors between the battery, the PCM power relay, and the PCM

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If you want to easily diagnose this fault code, then all you have to do is to follow the steps which are mentioned below:

• After identifying the P0687 code with an OBD-II scanner, the mechanic will begin by inspecting the wiring and connectors between the battery and the PCM.
• If there is evidence of damage, corrosion, a short, or an open circuit, they will repair the issue and then clear the code and attempt to start the vehicle again to check if the code is set once more.
• If the code still sets after this, they will inspect and test the alternator’s performance, the ignition switch, and all other components and wiring related to the PCM power relay.
• Clear all diagnostic trouble codes from the powertrain control module (PCM) and complete a test drive to see if the P0687 diagnostic trouble code comes back.
• If the P0687 trouble code comes back, it is possible that the powertrain control module will need to be replaced. It is rare that for the powertrain control module (PCM) to malfunction, but it is possible.

Common Mistakes When Diagnosing the P0687 Code

• Failure to check the PCM relay for proper operation
• Failure to inspect PCM connector for damage or corrosion
• Failure to inspect PCM wiring for frays, breaks or shorts
• Failure to check faulty ignition switch
• Failure to check on faulty car battery and related cables/connections