Intake Air Heater "B" Circuit/Open
The intake air heater B circuit has an open electrical connection, preventing the heater element from warming incoming air during cold engine starts. This primarily affects cold-weather starting and can cause rough idle and extended cranking times until the engine warms naturally.
What You Might Notice
- Engine difficult to start in cold conditions
- Longer than normal cranking time
- Rough idle at cold temperatures
- Check Engine Light illuminated
- Engine stalling when cold
Most Common Causes
- 1
Faulty heater element relay
The relay controlling the intake air heater B circuit has failed or is not engaging properly, breaking the electrical path to the heater element.
- 2
Corroded or damaged connector
Connectors in the heater circuit have corroded, loosened, or sustained physical damage, preventing proper electrical contact and current flow.
- 3
Defective heater element
The intake air heater element itself has failed internally or burned out, creating an open circuit that the PCM cannot energize.
- 4
Damaged or faulty wiring
Wiring in the intake heater B circuit has corroded, broken, or disconnected from terminals, interrupting the electrical signal path.
How to Diagnose It
- 1
Check Faulty heater element relay — The relay controlling the intake air heater B circuit has failed or is not engaging properly, breaking the electrical path to the heater element.
- 2
Check Corroded or damaged connector — Connectors in the heater circuit have corroded, loosened, or sustained physical damage, preventing proper electrical contact and current flow.
- 3
Check Defective heater element — The intake air heater element itself has failed internally or burned out, creating an open circuit that the PCM cannot energize.
- 4
Check Damaged or faulty wiring — Wiring in the intake heater B circuit has corroded, broken, or disconnected from terminals, interrupting the electrical signal path.
How to Fix It
- 1
Inspect and repair intake air heater connectors
Check all connectors in the intake air heater B circuit for corrosion, damage, or loose connections. Clean corroded contacts with electrical cleaner and reseat connectors firmly, or replace damaged connectors as needed.
- 2
Test and replace heater element relay
Use a multimeter to test the intake air heater relay for continuity and proper engagement. Replace the relay if it fails testing or does not click when energized.
- 3
Inspect and repair wiring harness
Trace the entire intake air heater B circuit wiring from the relay to the heater element. Look for breaks, corrosion, or disconnected terminals. Repair or replace damaged wiring sections.
- 4
Replace intake air heater element
If the heater element tests as open circuit with a multimeter, it has failed internally and must be replaced. Remove the old element and install a new one according to manufacturer specifications.
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