For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
IAT Sensor Signal | P0112 | P0111, P0113 | P0113¹ | P0111¹
Low Reference | P0101, P0103 | P0111, P0113 | P0113² | P0101, P0111
¹ Sensor damage may occur if the circuit is shorted to B+. ² Internal ECM damage may occur if the circuit is shorted to B+.

### Typical Scan Tool Data

#### Intake Air Temperature Sensor

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Running Condition: The engine is running in closed loop. Parameter Normal Range: -40 to +135°C (-40 to +275°F), which varies with ambient temperature.
IAT Sensor Signal | 135°C (275°F) | -40°C (-40°F) | -40°C (-40°F)¹
Low Reference | -- | -40°C (-40°F) | -40°C (-40°F)¹
¹ Internal ECM or sensor damage may occur if the circuit is shorted to B+.

### Circuit Description

The intake air temperature (IAT) sensor is an integral part of the mass air flow (MAF) sensor. The IAT sensor is a variable resistor that measures the engine intake air temperature. The engine control module (ECM) supplies 5 volts to the IAT signal circuit and supplies a ground to the low reference circuit. The ECM monitors the IAT sensor performance in the normal operating range. If the ECM does not detects that the IAT sensor changes to the pre-set value at specified vehicle running conditions, this DTC will set.

The following table illustrates the difference between temperature, resistance, and voltage:

IAT | IAT Resistance | IAT Signal Voltage
--- | --- | ---
Cold | Large | High
Warm | Small | Low

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0111 Intake Air Temperature (IAT) Sensor Circuit Performance

### Conditions for Running the DTC

#### Idle Test

• | Before the ECM can report DTC P0111 failed, DTC P0101 must run and pass.

• | DTCs P0112, P0113, P0116, P0117, P0118, P0119, P0125, and P0128 are not set.

• | During an engine start, the engine coolant temperature is less than 60°C (140°F).

• | The vehicle speed is less than 10 km/h (6.3 mph).

• | Since the last turn OFF of the ignition, the engine control module (ECM) detects the engine coolant temperature dropping.

• | DTC P0111 runs continuously once the above conditions are met for more than 2 seconds.

#### Cruise Test

• | Before the ECM can report DTC P0111 failed, DTC P0101 must run and pass.

• | DTCs P0112, P0113, P0116, P0117, P0118, P0119, P0125, and P0128 are not set.

• | During an engine start, the engine coolant temperature is less than 60°C (140°F).

• | The vehicle speed is more than 40 km/h (25 mph).

• | The MAF is between 11-42 g/s.

• | Decel fuel cut-off (DFCO) is not active.

• | DTC P0111 runs continuously once the above conditions are met for more than 2 seconds.

### Conditions for Setting the DTC

• | The ECM detects that variation between the high intake air temperature and the low intake air temperature is more than 1.5°C (34.7°F).

• | The above condition is present for more than 4 seconds.

### Action Taken When the DTC Sets

• | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

• | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

### Conditions for Clearing the MIL/DTC

• | The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.

• | A current DTC, last test failed, clears when the diagnostic runs and passes.

• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• | Clear the MIL and the DTC with a scan tool.

### Diagnostic Aids

• | Use the J 35616-A/BT-8637 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.

• | The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to Front of Vehicle/Engine Compartment Component Views.

• | Use the Temperature vs Resistance table in order to test the IAT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor could result in a driveability condition. If the engine has sat overnight, the intake air temperature and the engine coolant temperature values should display within a few degrees. If the temperature is not within 3°C (5°F), refer to Temperature Versus Resistance - Intake Air Temperature Sensor.

• | For an intermittent condition, refer to Intermittent Conditions.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: (ECM Power, Ground, Serial Data, and MIL) Engine Controls Schematics Connector End View Reference: Component Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Is DTC P0112 or P0113 also set? | -- | Go to DTC P0112 or Go to DTC P0113 | Go to Step 3
3 |

1. Observe the Freeze Frame/Failure Records for this DTC.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 4

Go to Diagnostic Aids

4 |

1. Turn the ignition switch to OFF position, disconnect the mass air flow (MAF)/intake air temperature (IAT) sensor. Refer to Mass Airflow Sensor with Intake Air Temperature Sensor Replacement.
2. Turn the ignition switch to ON position, with the engine OFF.
3. Observe the IAT sensor parameter with a scan tool.

Is the temperature less than the specified value?

-40°C (-40°F)

Go to Step 6

Go to Step 5

5 |

1. Turn the ignition switch to OFF position, disconnect the engine control module (ECM).
2. Test the signal circuit of the IAT sensor for a short to ground. Refer to Circuit Testing and Wiring Repairs.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 11

6 |

1. Turn the ignition switch to OFF position.

Caution: Do NOT use a test lamp to test the continuity of the circuit. Damage to the control module may occur due to excessive current draw.

2. Remove the ECM/TCM fuse from the underhood electrical center.
3. Measure the resistance between the low reference circuit of the MAF/IAT sensor and the ECM housing with a DMM.

Is the resistance less than the specified value?

5 Ω

Go to Step 7

Go to Step 8

7 |

1. Turn the ignition switch to OFF position, install the ECM/TCM fuse into the underhood fuse block.
2. Turn the ignition switch to ON position, install a 3-amp fused jumper between the signal circuit of the IAT sensor and the low reference circuit of the IAT sensor.
3. Observe the IAT sensor parameter with a scan tool.

Is the temperature more than the specified value?

132°C (270°F)

Go to Step 10

Go to Step 9

8 | Test the low reference circuit of the MAF/IAT sensor for an open, a high resistance or a short to voltage. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 11
9 | Test the signal circuit of intake air temperature (IAT) sensor for an open, a high resistance, or a short to voltage. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 11
10 | Test for shorted terminals and for poor connections at the MAF/IAT sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 12
11 | Test for shorted terminals and for poor connections at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 13
12 | Replace the MAF/IAT sensor. Refer to Mass Airflow Sensor with Intake Air Temperature Sensor Replacement. Did you complete the replacement? | -- | Go to Step 14 | --
13 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 14 | --
14 |

1. Clear any DTCs with a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Does the DTC fail this ignition?

--

Go to Step 2

Go to Step 15

15 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle | System OK