What it means
The control circuit of intake air heater C reports a circuit high condition. Cold-start preheating cannot be commanded as expected.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Intake air heater C helps warm incoming air for cold starting, and the control module monitors its command circuit and the heater’s electrical response. This code sets when the circuit reads higher than expected, which can happen if the control wire is shorted to battery power or the heater path is open.
Common causes
Most likely first.
- Control wire shorted to B+
- Open heater element
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light
- Hard starting in cold weather
- Rough running or white exhaust smoke after a cold start
How to diagnose it
- Use a scan tool to save freeze-frame data and check whether the fault appeared during a cold start, when heater C would be needed.
- With the engine off, inspect heater C’s wiring and connector for a short to a power feed, corrosion, loose pins, or heat damage.
- Check the heater C element and its wiring for continuity using the vehicle’s wiring diagram and the manufacturer’s specification.
- With the connector unplugged, check whether the control wire remains high; isolate the harness from the heater to distinguish a wiring short from an open heater.
- If the harness and element pass, test the heater C control circuit and module output using the manufacturer’s diagnostic procedure.
Common fixes
- Clean and secure corroded or loose heater C connector terminals.
- Repair a control wire shorted to battery power or an open in the heater C circuit.
- Replace the failed heater C element if it does not meet the manufacturer’s specification.
- Repair the heater control circuit or module only after confirming the wiring and element are sound.
Can I keep driving?
If the engine starts and runs normally, you can usually drive cautiously, but cold starts may become difficult and produce rough running or white smoke. Avoid relying on the vehicle in very cold conditions until the heater circuit is repaired.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.