Intake Air Heater Circuit Range/Performance
The P2604 code indicates that the powertrain control module (PCM) has detected a malfunction in the intake air heater circuit, specifically a range or performance issue. The intake air heater is used in diesel engines to warm the incoming air for improved cold starts and reduced emissions. This code sets when the PCM detects that the heater circuit resistance or current is outside the expected range, or the heater fails to reach the desired temperature within a specified time.
01. Most Common Causes
- Faulty intake air heater relay
- Open or shorted wiring in the heater circuit
- Failed intake air heater element
- Corroded or loose electrical connectors
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Hard starting in cold weather
- Rough idle or misfire during cold start
- Reduced fuel economy
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to confirm the code and check for related codes.
Step 2: Visually inspect the intake air heater and its wiring for damage, corrosion, or loose connections.
Step 3: Test the heater relay and circuit using a multimeter for proper voltage and resistance.
Step 4: If the relay and wiring are okay, test the heater element resistance and replace if out of spec.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally safe to drive, but you may experience hard starting in cold weather and reduced fuel economy. Prolonged driving with a faulty heater can cause additional strain on the engine and emissions system.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on whether the issue is a relay, wiring repair, or heater element replacement.