Open or broken wire in the intake air heater 'B' circuit, often due to corrosion or physical damage; Failed intake air heater element 'B' itself, typically an open internal filament; Poor electrical connection at the heater connector or the engine control module connector; Blown fuse or fusible link that supplies power to the intake air heater circuit; Faulty intake air heater relay or control module that fails to provide ground or power; High resistance in the ground circuit for the heater, causing the module to see unexpected voltage

DTC codes / P26xx · Computer and output circuits / P2608

P2608Intake Air Heater 'B' Circuit High

Q: What does code P2608 mean?

Intake Air Heater 'B' Circuit High. P2608 indicates that the engine control module has detected an abnormally high voltage on the intake air heater 'B' circuit, which typically points to an open circuit, a failed heater element, or a wiring fault rather than a short to ground. The computer expects a specific voltage drop across the heater when it commands the heater on, and a high reading means the circuit is not drawing the current it should.

P2608 indicates that the engine control module has detected an abnormally high voltage on the intake air heater 'B' circuit, which typically points to an open circuit, a failed heater element, or a wiring fault rather than a short to ground. The computer expects a specific voltage drop across the heater when it commands the heater on, and a high reading means the circuit is not drawing the current it should.

SystemPowertrain

Code typeGeneric (all makes)

SeverityLow

Fix difficultyIntermediate

AreaComputer and output circuits

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Hard starting or rough idle during cold ambient temperatures because the intake air is not being warmed
Extended cranking time before the engine fires when the outside temperature is low
White smoke or poor combustion quality immediately after a cold start
Possible reduction in fuel economy during warm-up if the heater is not functioning
In some vehicles, a message on the driver information center indicating a service engine soon reminder

Common causes, most likely first

Open or broken wire in the intake air heater 'B' circuit, often due to corrosion or physical damage
Failed intake air heater element 'B' itself, typically an open internal filament
Poor electrical connection at the heater connector or the engine control module connector
Blown fuse or fusible link that supplies power to the intake air heater circuit
Faulty intake air heater relay or control module that fails to provide ground or power
High resistance in the ground circuit for the heater, causing the module to see unexpected voltage

How to diagnose and fix it

Verify the code with a scan tool and check for any related powertrain codes before proceeding
Inspect the intake air heater 'B' connector and wiring for corrosion, looseness, or physical damage
Check the fuse and relay that supply power to the intake air heater circuit and replace if faulty
Measure resistance across the heater element 'B' with a multimeter and compare to the manufacturer's specification
Perform a voltage drop test on the power and ground sides of the heater circuit while commanding the heater on
If the circuit tests good, substitute a known-good heater element or relay to confirm the fault
Clear the code and road-test the vehicle to ensure the repair is complete and the code does not return

What a high voltage reading really means

A high voltage code on a heater circuit almost always indicates an open circuit rather than a short, because a short to ground would pull the voltage low and set a different code.
Many technicians replace the heater element first, but a corroded connector or chafed wire is just as common and far cheaper to fix.
The intake air heater is often confused with the glow plug system on diesel engines, but they are separate circuits and a fault in one does not always affect the other.
On some vehicles, the intake air heater only operates below a specific ambient temperature, so the code may not set during warm weather testing.
A weak battery or charging system can cause erratic voltage readings that mimic a heater circuit fault, so always verify system voltage first.

Can I keep driving with P2608?

You can generally continue driving with this code because the intake air heater is an emissions and cold-start aid, not a safety system. Avoid extended idling in cold weather and be aware that cold starts may be rougher until the fault is repaired.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.