I have replaced the mass air sensor and the harness. If I reset the codes, it runs fine, but after I turn it off and on the code comes back, every time. It sometimes will stutter and not get proper acceleration. I can take my foot off the gas, hit it again and it’ll usually be fine.

Any suggestions?

 

Welcome to the forum

From your user name I assume you have a 2002 Ranger with a 2.3l DOHC Duratec engine, which is different than the Ranger 2.3l SOHC Lima engine used in earlier years

P0112 IAT sensor voltage low

IAT is intake air temp, also called ACT, air charge temp

IAT was on the upper intake on most engines
But on the 2.3l Duratec I think its was added to the MAF sensor housing
MAF sensors have 4 wires only, 2 for heater, 2 for sensor

If your MAF sensor has a 6 wire plug then the 2 outside wires were added for the IAT sensor added inside it
You changed the MAF/IAT sensor, did you also change the air filter?


You will need a Volt Meter and a sewing pin to pierce wires
Wires on MAF/IAT are numbered 1 to 6, 1 and 6 are the IAT wires
Set volt meter to DC Volts, ground the Black Probe, test meter on battery positive, should show 12.3-12.8volts

6 should be the input voltage, which is 5volts from the computer, this 5v is shared with most other sensors, a common wire, usually grey/red stripe
Key on engine off
pierce wire 6 with the pin and test its voltage, should be 4.8-5.0volts

Then test wire 1 with pin, if its 70deg outside then you should see about 3volts

You can remove air filter and use a hair dryer to heat up MAF/IAT to see if voltage changes, it should of course

P0112 is usually a wiring issue, so look at the wires on the MAF/IAT connector and the pins/contacts inside

Voltage readings by temp here: https://www.freeautomechanic.com/ima...ting-chart.gif

 

I have battery. But I got nothing in/out @ 1and 6 @ MAF/IAT, can I hardwire?

 

???


So you tested the two wires, with KEY ON and neither had volts?

So the Grey/red wire is bad, it should have 5volts with key on

But not to worry, you can get that 5volts from another sensor, about 10 sensors used that same 5volts on grey/red wire, so we know its working or you would have ALOT of codes

The CHT(cylinder head temp) sensor and the TPS(throttle position sensor) are probably the easiest to tap
But check them first
Key On, test either one's grey/red stripe wire it should have 5 volts, just to confirm testing method is correct

 

Can’t find 5v I’m having the same problem with not finding 5v at IAT or the computer on 91 or 39 Grey or Greywith red stripe. I proved several other sensors and can’t seem to find 5 volts their either. I am definitely not very experienced with electrical problems but was able to find the battery voltage. I REALLY hope I don’t need another computer since I can’t replace and program that myself. Mine is a 2002 2.3 automatic

 

It is a Pull Down(or pull up) circuit, so use a meter set to DC Volts(20v) and put meter's probes on the TWO wires on the connector, and see what voltage you get, + or - 5volt
If the +/- 5volts was gone ALL the sensors would set codes, not just 1 sensor

 

Ok. I was grounding to the negative battery terminal. Maybe that was my mistake.