P2199: Intake Air Temperature Sensor 1/2 Correlation
What to do
The car will usually drive, perhaps with slightly reduced performance on a turbocharged engine because the module protects itself against an intake temperature it thinks is too high. If this only ever appears on the first start of the day, that is expected — the comparison is only valid after the car has stood overnight, so a fault cleared in the afternoon will look fixed until the next morning. Ask for both sensors to be compared against the coolant and outside temperature readings after a long stand; whichever disagrees with the other three is the one to replace, and that check costs nothing.
What this code means
Two intake air temperature sensors disagree by more than the module will accept.
Why an engine has two, and where they sit. One is normally in the air intake ahead of everything, often built into the mass airflow sensor; the other is downstream, in the intake manifold or after the intercooler. As with the paired coolant sensors at P2182, the difference between them is the useful quantity: on a turbocharged engine it measures how much heat the intercooler is actually removing, which is information no single sensor can provide. Compression heats intake air substantially, and dense cool air is the entire point of an intercooler, so the module wants to know whether it is working.
The check runs at cold soak, and that detail explains the symptom pattern. A running engine legitimately produces different readings at the two points, so no comparison is possible then. What is reliable is a vehicle that has stood long enough for everything under the bonnet to settle to ambient — overnight, typically. At that moment every temperature sensor on the engine should read the same, and any that does not has drifted. So this code is set on the first start of the day and effectively never at any other time, which is why clearing it appears to fix it and why the fault seems to return by itself the following morning. That is not intermittent behaviour; it is the test only getting one chance a day.
It also means a drifted sensor is caught while the engine is cold, which is precisely when it does the most harm. Intake air temperature is an input to fuelling and to ignition timing, and on a turbocharged engine to boost limits — a sensor reading twenty degrees warm makes the module retard timing and reduce boost to protect against detonation that is not occurring, which costs real power for no reason.
The correlation code names a relationship rather than a part, as every correlation code does. Which of the two has drifted is settled by comparing both against the coolant temperature and the ambient sensor after a long stand — the odd one out is the faulty one, and that comparison requires no test equipment beyond the live data the workshop already has on screen.
Likely causes
Start here
Less common
- Corroded or loose connector · easy
- Damaged wiring harness · moderate
- Blocked or failing intercooler · moderate
Rare
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
Sign in or create an account to add what you found about P2199.