P1404
FordIAT - B Circuit Malfunction
The engine computer has detected a fault in the designated Intake Air Temperature (IAT) B circuit. The IAT sensor reports intake-air temperature, which the computer may use when calculating fuel and engine-control adjustments. The code identifies a circuit condition; it does not prove the sensor itself has failed. The exact sensor arrangement and diagnostic procedure depend on the vehicle's model, year, and engine.
⚠️ Before You Begin (Safety First)
This fault is not usually an immediate reason to stop driving. Arrange diagnosis soon. If the engine stalls, runs severely poorly, or becomes unsafe to control, pull over safely and stop driving until it is checked.
Common Symptoms
- The check-engine light may be on, with no noticeable change in how the vehicle drives.
- If the faulty temperature signal affects engine control, starting, idle, or drivability may be affected.
- Fuel economy or emissions may change if the computer's temperature input leads to different control adjustments.
- There may be no symptoms beyond the stored code.
Common Causes
- A fault in the IAT B sensor or its internal circuit.
- A loose, damaged, or corroded connector or wiring in the IAT B circuit.
- An open, short, or other wiring fault affecting the circuit signal, power, or ground, as applicable to the vehicle.
- A fault in the computer input or related circuitry; this requires testing before it is considered.
Diagnostic Steps
- Check the exact model, year, and engine information so you can identify the correct IAT B component and circuit.
- With the vehicle safely parked and the engine off, visually inspect accessible wiring and connectors for damage, looseness, corrosion, or contamination.
- If you have a scan tool, observe the IAT readings and compare them with other temperature readings when conditions make a comparison meaningful; an implausible reading can help guide further diagnosis but does not identify the failed part by itself.
- Do not probe terminals or replace components without the vehicle-specific wiring information and test procedure. Have a qualified technician perform circuit testing if the visual checks do not reveal the issue.
When to Call a Professional
Use a scan tool to inspect IAT data and compare it with other temperature readings under suitable conditions. Confirm which sensor or circuit Ford designates as IAT B for the exact vehicle, then inspect the wiring diagram and test the circuit, connections, and sensor as applicable. Do not replace a part based on the code alone.
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Commonly Asked Questions
Does P1404 prove the IAT B sensor is bad?
No. It identifies a malfunction in the IAT B circuit. The sensor, wiring, connector, or related computer circuitry may be involved, so testing is needed before replacing parts.
What does the B designation mean?
It identifies a designated IAT circuit or sensor. Its exact meaning and location depend on the vehicle's model, year, and engine; it does not by itself identify a bank.
Can I keep driving with this code?
Often the vehicle remains drivable, but have the fault diagnosed. Stop safely if the engine stalls, runs severely poorly, or the vehicle becomes unsafe to control.
Can a scan-tool temperature reading identify the problem?
It can help show whether the reported temperature appears plausible, but it cannot alone distinguish a sensor fault from a wiring or computer-input fault.
Browse Available Code Guides
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