P2608
Intake Air Heater B Circuit High
Intake air heater
Generic OBD-II
Low
What it means
P2608 means the engine computer sees high voltage (usually an open circuit) in the "B" intake-air-heater circuit. The intake air heater warms incoming air to help cold starts and cut cold-start emissions, mostly on diesels. Once the engine is warm it runs normally; you may just notice harder cold starts and the check-engine light.
Low
Can I keep driving? Safe to drive — you may notice harder cold starts or brief rough warm-up in cold weather, but the engine runs normally once warm.
Common symptoms
What you'll notice
- Check-engine light on
- Harder starting in cold weather
- Brief rough running or white smoke just after a cold start (mainly diesels)
- No noticeable change in warm conditions
Common causes
Most likely first
- Faulty intake air heater element or relayLikely
- Open or high-resistance wiring in the heater 'B' circuitCommon
- Corroded or loose heater connectorCommon
- Blown fuse feeding the intake air heaterLess often
- Faulty PCM heater driver (rare)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame; confirm the B-circuit heater code and note any companion heater codes.
- Inspect the heater relay, fuse, and connector for corrosion or looseness.
- Measure the heater element resistance and supply voltage against spec.
- Check wiring between the PCM/relay and heater for opens or high resistance.
- Replace the heater element or relay if out of spec; clear and retest after a cold soak.
FAQ
Quick answers
Is it safe to drive with P2608?+
Yes. The intake air heater only assists cold starts, so the engine runs normally once warm. In cold climates you may just notice slightly harder starting until it's repaired.
Can I just clear P2608?+
You can, but the logic mainly runs at cold start, so it will return on the next cold start unless the heater circuit is repaired.
Related codes
Often seen with P2608
Read & clear P2608 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX