P0640 code definition
When your vehicle’s PCM stores a P0640 code, it means that abnormal input voltage
has been identified as coming from the intake air heater’s control circuit.
What the P0640 code means
This means that a voltage that exceeds the level stipulated by the manufacturer has
occurred. Usually, your Check Engine Light will come on, although sometimes the code
has to be recorded three times before this happens.
What causes the P0640 code?
Most often, the P0640 code is recorded when the intake air heater relay is faulty. There
can be other causes as well, though, including:
Faulty intake heater blower
Bad or disconnected temperature sensor
Burned out heater element
PCM failure (this is very rare)
What are the symptoms of the P0640 code?
Most of the time, there are no symptoms at all other than the Check Engine Light coming
on. You may, however, notice some loss in fuel efficiency, since the intake air heater
system works to warm the air entering the engine. If the air getting to the engine isn’t
warm enough, then you may notice a bit of a dip in your fuel economy.
Sometimes, the problem is not the intake air heater relay. Your Check Engine Light
could come on just because you have a dirty air filter.
How does a mechanic diagnose the P0640 code?
First off, your mechanic will use an OBD-II scanner and an ohmmeter to identify any
conditions that may result in a code being recorded. Next, your mechanic will:
Visually inspect all the wiring and connectors
Re-test your vehicle’s system to make sure that the replacements did the job and that everything is in proper working order
Connect the scanner again to make sure that the codes are no longer active
Test drive the car to see if the codes re-appear
Crank the engine and check the scanner again to make sure that the heater turns on
Ensure that the blower is working
Compare the findings with the vehicle manufacturer’s specifications
Common mistakes when diagnosing the P0640 code
Sometimes, mechanics fail to make sure that intake air temp sensors are properly
connected. This can cause a code to be improperly stored. Mechanics are also
sometimes too quick to blame the PCM itself for the problem, but the reality is that the
PCM hardly ever fails.
How serious is the P0640 code?
This is something that you can have repaired at you leisure. You may notice a slight
decrease in your engine performance, and you may also find that you are paying a little
more at the pump than you are accustomed to. However, this is not an issue that is
going to compromise your safety, or that of anyone who travels with you. It would be
a good idea to get the problem corrected, but if you have other things to do (as most of
us have), you can wait for a more convenient time.
What repairs can fix the P0640 code?
Sometimes all that is needed is to replace a dirty air filter. Other times, though, you may
need to have one or more of the intake air sensors replaced. Either way, this is not a
major maintenance or repair issue, and can be easily and economically dealt with by a
Additional comments for consideration regarding the P0640 code
Any voltage variation that is outside the manufacturer’s specifications can lead to a
P0570 code. It doesn’t necessarily mean that anything is terribly wrong, though.
Need help with a P0640 code?
YourMechanic can assist you with any problems that relate to fuel economy, or any
other problems that you may have with your vehicle. Our qualified mechanics are
always on standby, ready to go to your home or office to help you with whatever issues
you may be having. Call us at 1-800- 701-6230, or use our online form to arrange a
visit. Our mechanics are here for you.