DReuther

The check engine light of my 1996 993 C4 has repeatedly been coming on based on trouble code P0112. Any tips on what might be causing this and/or any fixes?

I just got the OBD Fusion app and tracked the intake air temperature, but it has a constant value of 122F. Perhaps I have to wait until P0112 gets triggered again and see whether the intake air temperature is different at just that moment?

Cheers,
Dieter

pp000830

At least it is an inexpensive and very easy part to get to being attached with a rubber grommet to the airbox. I would spray clean its connector first and clear the code and see if it comes back.

DReuther

pp000830

There is a trick to make reinstalling the airbox easier if removing it can't be avoided. When reinstalling put the Mass air flow sensor in position first not bayonetted to the airbox. Slip the air flow sensor into the intake hose it is attached to with a socket tool on an extension prepositioned on the clamp band that holds the air flow sensor. Then fit the airbox partially in position over the sensor and rotate the sensor so it bayonets into the airbox. Line up the airbox mounting pegs and reattach the temperature sensor plug and the Air Flow sensor plug. Once the airbox/air flow sensor, as a unit, is in position tighten the clamp band on the airflow sensor with the prepositioned socket tool. Some remove the idle valve to gain better access to the clamp band. as it is hard to see up against the top of the engine.
Removing the airbox will involve loosening the clamp band above holding the air flow sensor.
Andy

IainM

can you measure it first? Put an ohmmeter across it and dunk in pan of hot water. Resistance should change in a repeatable way.

IainM

122F is implausible for air intake
Could be an open/short in wiring. Bad contact at connectors is #1 suspect here I'd say

DReuther

Well, the 122F is what the OBD Fusion app reports. I'll check the wires and try to measure the old and new temperature sensor with an ohmmeter when I replace it.

Here is the OBD Fusion graph:



I'll report back once I have replaced the temperature sensor.

Thanks for now,
Dieter

DReuther

I replaced the temperature sensor with a new one (Bosch 993-606-113-00-M14). The old one showed no response when measured with an ohmmeter, the new one gradually changed its impedance from 2100 Ohm at 73F to 700 Ohm at 120F. Once installed, temperatures ranged between 73.4F and 77F.

TurboIXXI

Did you have to reset the CEL and OBDII readiness or will the CEL go away on it's own after the IAT sensor was replaced?

DReuther

I had to reset the CEL.

IainM