Circuit Description
The Intake Air Temperature (IAT) sensor is a thermistor which measures the temperature of the air entering the engine. The PCM applies 5 volts through a pull up resistor to the IAT sensor. When the intake air is cold, the sensor resistance is high and the PCM will monitor a high signal voltage on the IAT signal circuit. If the intake air is warm, the sensor resistance is lower causing the PCM to monitor a lower voltage. DTC P1111 will set when the PCM detects an intermittently high signal voltage on the intake air temperature sensor signal circuit.
Conditions for Setting the DTC
| • | No VSS, ECT, or MAF DTCs present. |
| • | Vehicle speed is less than 35 mph. |
| • | IAT signal voltage indicates an intake air temperature intermittently less than -39°C (-38°F). |
| • | The above conditions are present for up to 3 minutes. |
Action Taken When the DTC Sets
The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.
Conditions for Clearing the MIL/DTC
| • | The DTC becomes history when the conditions for setting the DTC are no longer present. |
| • | The history DTC clears after 40 malfunction free warm-up cycles. |
| • | The PCM receives a clear code command from the scan tool. |
Diagnostic Aids
Check for the following conditions:
| • | Poor connection at PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. |
| • | Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the IAT display on the scan tool while moving connectors and wiring harnesses related to the IAT sensor. A change in the IAT display will indicate the location of the fault. |
Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain ON Board Diagnostic System Check performed? | -- | ||
2 | Select DTC info, Last Test Fail and note any other DTCs set. Is DTC P0113 also set? | -- | Go to DTC P0113 Intake Air Temperature (IAT) Sensor Circuit High Voltage | |
3 | Is DTC P1106, P1115, and/or P1121 also set? | -- | ||
4 |
Was a problem found? | -- | ||
5 | Check for a poor IAT signal circuit terminal connection at the IAT sensor. Refer to Wiring Repairs . Was a problem found? | -- | ||
6 |
Was a problem found? | -- | ||
7 |
Was a problem found? | -- | ||
8 |
Was a problem found? | -- | ||
9 |
Was a problem found? | -- | Go to Diagnostic Aids | |
10 |
Does scan tool indicate DTC P1111 failed? | -- | System OK |
