A 2012 Toyota Corolla 1.8L came in with intake air temp and MAF codes, P0113 and P0102.
On this engine the IAT sensor and the mass airflow sensor are built into the same unit. The plug has five pins. Two go to the IAT, and the other three go to the MAF.
The pin-out and voltage check is for a 2012 Corolla 1.8L, but it is very similar on mid-2000s through around 2013 or 2014 Corolla, Matrix, Scion, and a lot of other Toyota 1.8L setups.
Where is the Toyota 1.8L MAF IAT Sensor Located?
The MAF/IAT is on the air intake box, where the airflow goes into the engine.
Unplug the connector before probing. These voltage checks are done with the sensor unplugged and the key in the on position.
Toyota 1.8L MAF IAT Sensor Pin-out
Click the diagram to open the full size so the pin numbers stay readable.
Looking at the plug, pin 1 is on the left. That first pin is a pink wire.
- Pin 1 (THA, pink) – IAT 5V / air temp signal
- Pin 2 (E2, brown/white) – IAT ground
- Pin 3 (+B, black, middle) – MAF 12V from the EFI fuse
- Pin 4 (E2G, black) – MAF ground
- Pin 5 (VG, violet) – MAF signal
If you just need the schematic, that is what was used while tracing this circuit.
How Do You Check IAT Sensor Pin Voltages?
Pin 1 should have about 4.5 to 5 volts coming from the computer, sensor unplugged, key on.
Pin 1 was probed, meter negative on battery negative, and it read 4.99 volts. That wire is good.
Check across pin 1 and pin 2 next. That same 4.5 to 5 volts should still be there. If it is, both IAT wires back to the computer are good.
If pin 1 to battery ground shows 5 volts, but pin 1 to pin 2 shows nothing, the IAT ground wire is the problem.
On this Corolla both IAT wires checked out.
How Do You Check MAF Sensor Pin Voltages?
The middle pin, pin 3, is power for the MAF. It comes from the EFI fuse and should be about 11 to 12 volts, key on, sensor unplugged.
That third wire was probed to battery negative and had 12 volts. That feed is good.
Next is the MAF ground on pin 4. Probe that pin and touch battery positive. If the ground is good there should be about 12 volts.
This one had nothing. That is what set the codes. The MAF ground was open.
What Was Wrong With This Toyota 1.8L MAF Circuit?
The IAT side had its 5 volts. The MAF had battery voltage from the EFI fuse. The MAF ground wire was dead.
That open E2G ground was repaired on this one. After the ground was restored, P0102 and P0113 were taken care of.
A bad ground on this 5-pin MAF/IAT pack can throw both the MAF code and the IAT code even though they are not the same circuit inside the sensor.
Have you had a Toyota 1.8L MAF/IAT throwing P0102 or P0113 from a bad ground? Let us know your thoughts below.