What does it mean?
The engine control module tracks intake air temperature with more than one probe on engines that carry several induction paths, and sensor 3 on bank 2 is one of those additional thermistors, normally placed downstream in the charge air path of that cylinder bank. Its resistance falls as the air warms, so the module reads the voltage on a reference circuit and converts it into a temperature value used for air density, fuelling, spark and boost correction.
This code is not about a permanently high or low reading: it is stored when the signal jumps, drops out or changes faster than air temperature physically can. The module needs the unstable pattern to repeat within the monitoring window before it accepts the fault and turns on the MIL (check engine lamp). Because the input feeds several calculations, an unsteady value shows up as brief fuelling and driveability glitches rather than a constant complaint.
Symptoms
- MIL (check engine lamp) that comes on and later clears by itself
- Brief hesitation or a stumble that appears without warning and disappears
- Boost or spark advance pulled for a moment on turbocharged engines, felt as a flat spot under load
- Intake air temperature on a scan tool jumping to unrealistic values then returning to normal
- Slightly uneven idle or an inconsistent cold start
- Fuel consumption that varies more than usual over the same route
Likely causes
- Loose, spread or corroded terminals in the sensor connector on bank 2
- Chafed or brittle harness insulation letting the signal wire touch ground or a neighbouring circuit as the engine rocks
- Water, oil or coolant residue inside the connector creating a changing resistance path
- Hairline crack in the thermistor element that opens as it heats or vibrates
- High resistance sensor ground, often at a shared ground splice
- Harness routed against a hot charge pipe or turbocharger heat shield on that bank
- Rarely, a damaged input pin or driver inside the control module
How to fix it
- Read the freeze frame and note the temperature, load and engine speed at the moment the fault registered
- Compare all intake air temperature readings after an overnight soak; before the engine warms they should agree within a few degrees
- Watch the bank 2 sensor 3 value live while wiggling the connector and harness with the engine running, and look for the drop-out
- Back-probe the signal and reference terminals with a meter or a scope, then measure voltage drop on the ground side
- Clean the connector, repair spread terminals and re-pin any contact that no longer grips
- Repair chafed insulation and re-route or shield harness sections that touch hot or moving parts
- Replace the sensor only after the harness and connector test clean and the fault clearly follows the sensor