Skip the auto shop - Our mechanics make house calls

Q: I have codes and I need to know what I need to change.

asked by on

I have the codes P0300- Random/multiple cylinder misfire detected P0687- control module power relay control circuit/ high P0686- control module power relay control circuit/ low.

I have changed the spark plugs withing the past few weeks. I checked the coils (which are fine) and there is no weird misfire vibrations. Should I change the ecu or the icm? How would I know which if not both to replace? Is it a hard job? How urgent is it to fix? I'm a delivery guy for a Chinese resteraunt so idk if I can drive it for work safely.

My car has 140000 miles.
My car has an automatic transmission.

Hi there:

It’s very difficult to tell you precisely which parts you should replaced simply based on the error codes. A professional mechanic would not only download all trouble codes, but test drive the vehicle to match warning symptoms to the error codes triggered in order to recommend and make the right repairs. Before you invest in purchasing and replacing parts based on your error codes, you might want to have a professional mobile mechanic complete a check engine light inspection first; so they can pinpoint what issues you’re having and recommend the right repairs.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: I think I have a drain of power

When diagnosing electrical problems, always start with the simple solutions first. Begin checking the battery cables and terminals. Make sure they are not corroded, and are protected from the elements. Check the wires running to the distributor, and to the...

Q: Timing belt maintenance

The timing belt should be replaced at 100,000 miles. It takes a professional about 3 hours to replace the timing belt on your model. A novice will easily require double that time and maybe much more if you break a...

Q: How would I go about fixing my turbo that is smoking on my 2003 Saab 9-3

Hello. If you have oil leaking on the turbo then the leak needs to be located. Most of the time on this vehicle the issue is the turbo itself. When the turbo has an internal seal that fails you will...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...