DTC P0111 Intake Air Temperature (IAT) Sensor Performance. Chevrolet Metro 1998

For 1990-2009 cars
Engine Controls Components
Cell 21: Engine Data Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The intake air temperature (IAT) sensor is a thermistor. A thermistor is a resistor whose value varies with temperature. The IAT sensor's resistance is high when the air temperature is cold, and the IAT sensor's resistance is low when the air temperature is warm. The IAT sensor is wired in series with a fixed resistor in the powertrain control module (PCM). The PCM applies 5 volts to the IAT sensor. The PCM monitors the voltage across the IAT sensor and converts the voltage into a temperature reading. The PCM will receive a high voltage input when the air temperature is cold. The PCM will receive a low voltage input when the air temperature is warm.

### Condition for Running the DTC

• | Engine coolant temperature at engine start is less than 30°C (86°F).

• | Engine has been running from start conditions above for at least 10 minutes.

### Conditions for Setting the DTC

The IAT sensor signal indicates a smaller change than expected in the voltage input during the warm-up cycle.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL) after two consecutive ignition cycles in which the diagnostic runs with the fault active.

• | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.

### Conditions for Clearing the MIL/DTC

• | The MIL turns OFF after three consecutively passing trips without a fault present.

• | A History DTC clears after 40 consecutive warm-up cycles without a fault.

• | Use the scan tool Clear DTC Information function or disconnect the PCM battery feed in order to clear the DTC.

### Diagnostic Aids

Check for a faulty electrical connection to the PCM.

Use the Temperature vs Resistance table in order to check the IAT sensor at various temperature levels and evaluate the possibility of a shifted (incorrectly calibrated) sensor. A shifted sensor could result in a DTC P0111. Refer to Temperature vs Resistance .

An intermittent malfunction may be caused by a fault in the IAT sensor electrical circuit. Inspect the wiring harness and components for any of the following conditions:

• | Backed out terminals.

• | Improper mating of terminals.

• | Broken electrical connector locks.

• | Improperly formed or damaged terminals.

• | Faulty terminal to wire connections.

• | Physical damage to the wiring harness.

• | A broken wire inside the insulation.

• | Corrosion of electrical connections, splices, or terminals.

If a DTC P0111 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

### Test Description

The numbers below refer to the step numbers in the Diagnostic Table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. This step checks for a faulty IAT sensor.

3. This step checks the integrity of the IAT sensor input circuit (5 volt reference).

4. This step checks the integrity of the IAT sensor ground circuit.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check

2

1. Turn ON the ignition, leaving the engine OFF.
2. Install a scan tool.
3. Let the engine cool to ambient air temperature.
4. Compare the IAT sensor value with the ambient air temperature.

Is the IAT value within the specified value of the ambient air temperature?

0°C to 5°C (0°F to 9°F)

Go to Step 3

Go to Step 4

3

Important: Observe the IAT sensor scan tool display continuously while performing the tests below.

1. Disconnect the IAT sensor electrical connector.
2. Remove the IAT sensor from the air cleaner assembly.
3. Connect the IAT sensor electrical connector to the IAT sensor.
4. Wrap a cool damp shop towel around the IAT sensor in order to lower the temperature while monitoring the IAT sensor parameter on the scan tool.
5. Remove the cool shop towel and place a warm damp shop towel around the IAT sensor while monitoring the IAT sensor parameter on the scan tool.

Did the scan tool indicate a skip, jump, or fixed value in the IAT sensor display?

--

Go to Step 9

Go to Diagnostic Aids

4

1. Disconnect the IAT sensor electrical connector.
2. Jumper the IAT sensor electrical connector (harness side), with a fused jumper wire.

Does the scan tool indicate the specified value?

119°C (246°F)

Go to Step 9

Go to Step 5

5

1. Remove the fused jumper wire.
2. Disconnect the PCM electrical connector.
3. Measure the resistance of the IAT sensor input circuit (wire), from the sensor to the PCM, with a DMM.

Did the DMM indicate a resistance reading that was less than the specified value?

0.5 ohms

Go to Step 6

Go to Step 7

6 | Measure the resistance of the IAT sensor ground circuit (wire), from the sensor to the PCM, with a DMM. Did the DMM indicate a resistance reading that was less than the specified value? | 0.5 ohms | Go to Step 10 | Go to Step 8
7 | Repair the short to ground or high resistance in the IAT sensor input circuit (5 volt reference) between the PCM and the IAT sensor. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 11 | --
8 | Repair the open circuit or high resistance in the IAT sensor ground circuit between the PCM and the IAT sensor. Refer to Wiring Repairs in Wiring Is the action complete? | -- | Go to Step 11 | --
9 | Replace the IAT sensor. Refer to Intake Air Temperature Sensor Replacement . Is the action complete? | -- | Go to Step 11 | --
10 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 11 | --

11

1. Perform the scan tool Clear DTC Information function and road test the vehicle within the Freeze Frame conditions that set the DTC.
2. Review the scan tool data and check for DTCs. The repair is complete if no DTCs are stored.

Are any DTCs displayed on the scan tool?

--

Go to the Applicable DTC Table

System OK