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 Descriptor

DTC P050A: Cold Start Idle Air Control System Performance

### Circuit/System Description

The throttle actuator control (TAC) motor is controlled by the engine control module (ECM). The DC motor located in the throttle body drives the throttle blade. In order to decrease idle speed, along with spark and fuel delivery changes the ECM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the ECM commands the throttle plate open allowing more air to pass the throttle plate. The catalytic converter must be warmed to efficiently reduce the emissions. The cold start strategy is to reduce the amount of time it takes to warm the catalytic converter. During a cold start, the engine idle speed is elevated to allow the catalyst to warm quickly.

### Conditions for Running the DTC

• | DTCs P0096, P0097, P0098, P0099, P0117, P0118, P0121, P0122, P0123, P0125, P0300, P0336, P0446, P0455, P0496, P2101, P2176 are not set.

• | The startup engine coolant temperature (ECT) is between -10 and +40°C (+14 and +104°F).

• | The barometric pressure (BARO) is more than 65 kPa.

• | The engine is running.

• | DTC P050A runs continuously when the above conditions are met.

### Conditions for Setting the DTC

• | The actual idle speed is 100 RPM lower than the desired idle speed or 200 RPM greater than the desired idle speed during a cold start.

• | The above condition is present for 7 seconds.

### Action Taken When the DTC Sets

DTC P050A is a Type B DTC.

### Conditions for Clearing the DTC

DTC P050A is a Type B DTC.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

• | Engine Controls Connector End Views

• | Engine Control Module Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Scan Tool Data List

### Circuit/System Verification

• | Using a scan tool compare the desired engine idle speed to the actual engine idle speed.

• | Actual engine idle speed should be no greater than 100 RPM below desired.

• | Actual engine idle speed should be no greater than 200 RPM above desired.

### Circuit/System Testing

1. If there are any other DTCs set, diagnose those first.
2. Inspect for any condition that can reduce idle speed by increasing engine load.

• | Incorrect torque converter clutch (TCC) operation

• | Accessories that require additional torque to operate

• | Excessive deposits in the throttle body

• | Restricted exhaust

• | Mechanical conditions that limit engine speed

3. Inspect for the following conditions:

• | Vacuum leaks

• | A faulty positive crankcase ventilation (PCV) valve

### Repair Verification

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.