P2608 moderate

Intake Air Heater B Circuit Range/Performance

The P2608 code means the vehicle's onboard diagnostic system has detected: Intake Air Heater B Circuit Range/Performance. This is a moderate severity code.

My Garage →

Keep driving?: Yes, but fix soon
DIY difficulty: moderate
Estimated cost: $200 - $600 (parts and labor)

Recommended Tool

ANCEL AD310 OBD-II Scanner

Best-selling code reader on Amazon. Reads and clears check engine codes on any 1996+ vehicle. Under $30.

Check Price on Amazon

Affiliate link -- we earn a commission at no extra cost to you.

Every Tech Needs This

AstroAI Digital Multimeter

Essential for diagnosing sensor codes, checking voltage, and testing circuits. Under $15 and pays for itself on the first job.

Check Price on Amazon

Affiliate link -- we earn a commission at no extra cost to you.

Common Symptoms

Hard cold starting
Uneven intake air heating
Extended crank time in cold weather
White exhaust smoke on startup

Probable Causes (Ranked by Likelihood)

Failing bank 2 intake air heater element Very High
Unequal voltage supply to heater banks High
Heater B relay performance degraded Moderate
ECM heater B timer miscalibration Low

Step-by-Step Diagnostic Procedure

Compare current draw between heater A and heater B circuits
Test heater B relay output voltage
Measure heater B element resistance
Check for voltage drops in heater B power supply

Frequently Asked Questions

Why are there two intake air heater circuits?

V-configuration diesel engines often have separate air heaters for each intake manifold bank to ensure even heating across all cylinders.

Can one bad heater bank affect starting?

Yes. If one bank is not heating properly, those cylinders will have difficulty achieving combustion temperature, causing rough starting and white smoke.

How do I compare heater A and heater B performance?

Measure current draw on each circuit with a clamp ammeter. Both circuits should draw similar amperage. A significant difference indicates a problem with one bank.