DTC P0111 Intake Air Temperature (IAT) Sensor Performance. Cadillac Concours 1996

For 1990-2009 cars
Engine Controls Components
IAT/ ECT/ TP/ MAP and BBV Sensors
OBD II Symbol Description Notice
ESD Notice
ESD Notice

### Circuit Description

The Intake Air Temperature sensor is a thermistor, or variable resistor, that varies resistance based on temperature. Low temperature will result in a high signal voltage. This diagnostic test monitors Intake Air Temperature (IAT) sensor voltage. If the PCM detects a large change in sensor signal voltage in a 0.25 second period, DTC P0111 will set.

### Conditions for Setting the DTC

#### Test Condition

2 seconds have passed since key ON.

#### Failure Condition

Intake Air Temperature (IAT) sensor voltage has changed 0.3 volts in .25 second.

### Action Taken When the DTC Sets

• | The Malfunction Indicator Lamp (MIL) will not illuminate.

• | No message will be displayed.

### Conditions for Clearing the DTC

• | A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test.

• | A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.

• | Use a scan tool to clear DTCs.

• | Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation.

### Diagnostic Aids

Artificially changing the temperature of the IAT can be done by careful warming with a heat gun or by cooling the IAT (refrigerator, etc.) then allowing it to warm.

If fault is not present perform Powertrain Ground Check and also review Failure Rec. to determine conditions under which and how long ago the DTC set.

### Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. Checking DTC P0111 snapshot value to determine if an intermittent high resistance caused the DTC to set.

2. An intermittent high resistance can be caused by an open in the IAT Sensor ground cricuit or the IAT Sensor Signal circuit.

3. An intermittent low resistance can be caused by a short to ground on the IAT Sensor Signal circuit.

4. Checking the IAT sensor's ability to read a full range of temperatures.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to A Powertrain On Board Diagnostic (OBD) System Check
2 | Are DTCs P0112 or P0113 set? | -- | Go to DTCs that are set | Go to Step 3

3

1. Turn the key ON.
2. Connect a scan tool.
3. Select Failure Rec. and note the IAT sensor display.

Is snapshot IAT sensor reading less than the value specified?

-34°C (-29°F)

Go to Step 4

Go to Step 5

4

1. An intermittent high resistance reading occurred on the IAT sensor circuit.
2. Look for a possible open in the IAT Sensor ground circuit or the IAT Sensor Signal circuit.
3. Repair open condition if found.

Was an open condition repaired?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

Go to Step 7

5 | Is snapshot IAT sensor reading more then the value specified? | 144°C (291°F) | Go to Step 6 | Go to Step 7

6

1. An intermittent low resistance reading occurred on the IAT sensor circuit.
2. Look for a possible short to ground on the IAT Sensor Signal circuit.
3. Repair short if found.

Was a shorted to ground condition repaired?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

Go to Step 7

7

1. Artificially raise the temperature of the IAT sensor from cool to warm.
2. As the IAT sensor warms, watch the IAT sensor reading on the scan tool looking for a skip or jump in the value.

Was a skip or jump noted?

--

Go to Step 8

Fault not present. Refer to Diagnostic Aids

8 | Replace the IAT sensor. Refer to IAT Sensor Replacement . Is the replacement complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | --