P0687 OBD-II Trouble Code: ECM/PCM Power Relay Control Circuit High

Our certified mechanics come to you · Get a fair and transparent estimate upfront

Red-stars EXCELLENT RATING ON

Cost of diagnosing the P0687 code

P0687 is a diagnostic trouble code (DTC) for "ECM/PCM Power Relay Control Circuit High". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

Cars Estimate Credit towards follow-up repair Earliest Availability
Ford$20.00
Toyota$20.00
BMW$20.00
SCHEDULE P0687 DIAGNOSTIC Get a fair and transparent estimate upfront

P0687 code definition

A P0687 code is stored when the PCM (powertrain control module) detects an incorrect, abnormal, or erratic voltage reading from the relay control circuit that supplies it with its power.

What the P0687 code means

In most cases, when the PCM stores a P0687 code, it’s because it has detected overly high voltage from its power supply. When everything is working normally, the PCM receives a steady flow of power from the battery through a contact relay. If the voltage coming from the battery through this relay is too high, the PCM will store the P0687 code and illuminate the Check Engine light.

What causes the P0687 code?

Some of the most common causes for a P0687 code are:

  • An overcharging alternator
  • A defective ignition switch
  • A damaged or defective PCM power relay
  • A shorted or open circuit between the PCM and the PCM power relay

What are the symptoms of the P0687 code?

In most cases, the illuminated Check Engine light will be the only symptom for the P0687 code. In some instances, though, a no-start condition will occur, preventing the vehicle from starting in order to protect the PCM from damage.

How does a mechanic diagnose the P0687 code?

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. After each test and repair, they will clear the codes and retest the system.

Common mistakes when diagnosing the P0687 code

If you’re in too much of a rush to diagnose the problem, you may believe that the PCM needs to be replaced to allow the vehicle to start again. Doing this without fixing the actual underlying cause of the P0687 code will be expensive and unnecessary. With a thorough inspection and diagnosis, you may be able to save a lot of time, energy, and money.

How serious is the P0687 code?

If the P0687 code results in a no-start condition, then the problem will need to be resolved before the vehicle is drivable. Even if there isn’t a no-start condition and the vehicle can be started and driven, though, it’s important to note that too much voltage sent to the PCM can severely damage it. The longer you go without resolving the problem, the more likely you are to need an entirely new PCM to fix it.

What repairs can fix the P0687 code?

In many cases, the problem can be resolved by performing one of the following repairs:

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

Additional comments for consideration regarding the P0687 code

If the PCM receives too much voltage or its power supply is erratic, a number of other codes and symptoms can begin to appear. It’s important to note the order in which these codes were stored by the PCM, as this can tell you whether or not they’re related. Don’t just try to resolve the symptoms before thoroughly inspecting the problem, and remember that the PCM may not actually need to be replaced, even if it is malfunctioning and throwing several codes. Replacing a faulty PCM power relay could be the solution to the problem, and it could save you a great deal of money and frustration.

Need help with a P0687 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

P0687
trouble codes
Check Engine Light

No more waiting rooms! Our mechanics will come to you to diagnose and fix the P0687 code.

SCHEDULE P0687 DIAGNOSTIC
Get a $20 credit for the follow-up repair

Recent Check Engine Light is on Inspection reviews

Excellent Rating


YourMechanic Check Engine Light is on Inspection Service

Average Rating

4.8/5

Number of Reviews

5,504

Rating Summary
5,083
203
50
32
136
5,083
203
50
32
136

Luis

14 years of experience
90 reviews
Luis
14 years of experience
Mitsubishi Eclipse - Check Engine Light is on - Las Vegas, Nevada
Showed up a little late, but gps gets a little confusing in my neighborhood. He quick and informative. He told me everything I needed to do.

Tabitha

16 years of experience
209 reviews
Tabitha
16 years of experience
Toyota Tacoma - Check Engine Light is on - Spring Valley, California
She’s really talented, friendly and fast she did exceptional work on my Dodge Avenger and my Toyota Tacoma, the pricing is accurate, no up selling so very trustworthy. Highly recommended.

Chuy

13 years of experience
186 reviews
Chuy
13 years of experience
Chevrolet Equinox - Check Engine Light is on - Chicago, Illinois
Chuy came to service and look over a vehicle I purchased 12 days ago. He was extremely professional and told me off the top that I paid way to much money on a truck that is basically a lemon. He told me to take it back and get my money and the God I was able to do just that without issue. The truck has way to many issues going on and should not be sold to anyone for driving. The wait for my mechanic Chuy was well worth it and I will continue to use this company for my vehicles.

Andrian

31 years of experience
121 reviews
Andrian
31 years of experience
Honda Civic - Check Engine Light is on - Fort Lauderdale, Florida
Andrian was so nice and super knowledgeable. He got done in about half the time I was quoted. AMAZING JOB!


More related articles

Related questions

Engine coil keeps going bad

Hello there. This is more of an uncommon issue. A few different faults could cause the coil packs to fail. Most common would be not replacing all the coils at once, a wiring fault, or an ignition fault. Since you...

Would low engine oil cause the check engine light to come on in my 2002 Toyota Corolla

Hello. Typically low engine oil will not cause the check engine light to come on in your vehicle. Unless the oil level is low enough to cause a drop in engine oil pressure, the oil light will not even come...

Engine starts up on cold start, shakes/struggles, and then shuts off.

Hello. I'm not sure what is meant by saying the O2 sensor and catalytic converter problem codes were not the problem. Several component issues could cause the behavior you are seeing - from a dirty, clogged, or failing idle air...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1 (855) 347-2779 · hi@yourmechanic.com