What does it mean?
The P0110 occurs when the PCM reads a signal in the IAT circuit which is outside expected voltages. This is similar to P0111 except that the P0110 is a less specific error code. P0111 is set when the sensor itself is most likely at fault whereas P0110 is a general circuit problem. Understanding the IAT electrical circuit is important to correctly diagnosing a P0110 code.
IAT/ECT Circuit Operation and Troubleshooting Tips – See the IAT in depth article (P0112) for more background on the IAT sensor. Note: “Circuit Malfunction” indicates that there is a malfunction in the control circuit, as opposed to a fault in a sensor or other component. With “Circuit Malfunction” codes, replacement of sensors and components in the affected circuit will almost never resolve the problem, since as the code suggests, the trouble is in the circuit.
This distinction between “circuit” and “sensor/component” is a great help to anyone trying to diagnose a circuit malfunction code, since it narrows the list of possible causes down considerably.
The causes of “Circuit Malfunction” codes are much the same as those for “Open Circuits” i.e., broken wiring, poor connections across electrical connectors or previously repaired wiring, loss of ground that prevents current flow, blown fuses, defective relays, faulty switches, or any of a host of other issues and problems that prevents a flow of current through wiring. Issues like high/low/intermittent voltages can set a “Circuit Malfunction” code on some applications.
Moreover, “Circuit Malfunction” codes could also indicate a problem with negative current control / flow, as well as issues with failed or failing PCM’s (Powertrain Control Modules), although control module failure is a rare event.