P0640

Intake Air Heater Control Circuit

Q: Is it safe to drive with P0640?

In mild weather, generally yes. In cold weather the engine may be hard to start and run rough while warming up. Fix it before winter conditions.

Q: Can I just clear P0640?

It will return until the relay, fuse, wiring, or heater element is repaired. Clearing it won't restore cold-start heating.

Intake air heater Generic OBD-II High

What it means

P0640 means the ECM detected a fault in the intake air heater control circuit. This heater warms incoming air to aid cold starts, so a fault mainly shows up as hard starting and rough warm-up in cold weather. It is usually a relay, fuse, wiring, or heater-element problem.

High

Can I keep driving? Usually driveable in mild weather, but expect hard cold starts and rough warm-up until the intake air heater circuit is fixed.

Real-world scan data

Seen in

scans in the past year

Found in

<0.1%

of scans

<0.1%

of scans that found faults

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on
Hard starting in cold weather
Rough idle or stalling during warm-up
Reduced performance and economy on cold starts

Common causes

Most likely first

Faulty intake air heater relayLikely
Blown fuse in the intake air heater circuitCommon
Wiring or connector fault in the heater control circuitCommon
Faulty intake air heater control moduleLess often
Defective intake air heater elementLess often

How to diagnose & fix

Work through it in order

Read freeze-frame data and check the intake air heater fuse and relay first.
Inspect the heater control wiring and connectors for damage, looseness, or corrosion.
Test the intake air heater relay and replace it if it fails.
Measure the heater element's resistance and replace it if open or out of spec.
Test/replace the heater control module if the circuit checks out, then clear and re-test.

FAQ

Quick answers

Is it safe to drive with P0640?+

In mild weather, generally yes. In cold weather the engine may be hard to start and run rough while warming up. Fix it before winter conditions.

Can I just clear P0640?+

It will return until the relay, fuse, wiring, or heater element is repaired. Clearing it won't restore cold-start heating.

Read & clear P0640 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX