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.

### DTC Descriptors

DTC B0158 02: Outside Air Temperature Sensor Circuit Short to Ground
DTC B0158 05: Outside Air Temperature Sensor Circuit Short to Battery or Open

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Ambient Air Temperature Sensor Signal | B0158 02 | B0158 05 | B0158 05 | --
Low Reference | -- | B0158 05 | B0158 05 | --

### Circuit/System Description

The instrument cluster monitors the ambient air temperature sensor with a low reference circuit and 5-volt signal circuit. The instrument cluster monitors the voltage drop across the sensor, which is proportional to temperature. When the ambient air temperatures are cold, the resistance of the sensor is high and the voltage signals are high. When the ambient air temperatures are hot, the resistance of the sensors is low and the voltage signals are low. The instrument cluster converts the voltage value to a temperature value of Celsius or Fahrenheit that will be displayed by the driver information center.

### Conditions for Running the DTC

The system voltage is between 9 V and 16 V

### Conditions for Setting the DTC

#### B0158 02

The instrument cluster detects the sensor signal circuit is more than 88°C (190°F).

#### B0158 05

The instrument cluster detects the sensor signal circuit is less than -40°C (-40°F).

### Action Taken When the DTC Sets

The instrument cluster uses a default air temperature value for further calculations. The driver information center displays -°C ( -°F).

### Conditions for Clearing the DTC

The DTC will become history if the instrument cluster no longer detects a malfunction.

### Reference Information

#### Schematic Reference

Instrument Cluster Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Driver Information Center (DIC) Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

Ignition ON, observe the scan tool Ambient Air Temperature parameter. The reading should be between -40°C (-40°F) and 88°C (190°F) and change with air temperature changes.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the B9 Ambient Air Temperature.
2. Ignition OFF, test for less than 5 Ω between the low reference circuit terminal 2 and ground.

⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the P16 Instrument Cluster.

3. Ignition ON, test for 4.8-5.2 V between the signal circuit terminal 1 and ground.

⇒ | If greater than the specified range, test the signal circuit terminal 1 for a short to voltage. If the circuit tests normal, replace the P16 Instrument Cluster.

⇒ | If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the P16 Instrument Cluster.

4. If all circuits test normal, test or replace the B9 Ambient Air Temperature.

### Component Testing

#### Static Test

1. Test the B9 Ambient Air Temperature by varying the sensor temperature while monitoring the sensor resistance.
2. Compare the readings with the Ambient Air Temperature Sensor Resistance and verify that the resistance is within the range of the specification.

⇒ | If not within the specified range, replace the B9 Ambient Air Temperature.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Ambient Air Temperature Gage Sensor Replacement

• | Control Module References for instrument cluster replacement, setup, and programming