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 P000A, P0010, P0016, P0068, P0071, P0072, P0073, P0101, P0102, P0103, P0116, P0117, P0118, P0119, P0121, P0123, P0171, P0172, P0201, P0202, P0203, P0204, P0222, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0335, P0336, P0340, P0341, P0365, P0366, P0443, P0459, P0496, P0501, P061A, P1101, P2088, P2089, P2100, P2101, P2122, P2123, P2127, P2128, P2138, P2227, P2228, P2229, P2301, P2304, P2307, P2310 are not set.

• | The battery voltage is more than 10 volts.

• | The engine speed is at idle.

• | The vehicle speed equals 0 kph (0 mph).

• | The engine coolant temperature (ECT) is more than -9.75°C (+14.45°F).

• | The mass air flow (MAF) is within the calibrated range.

• | The pulse width modulated (PWM) signal for the canister purge solenoid is less than 90 percent.

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

### Conditions for Setting the DTC

• | The actual idle speed is 175 RPM lower than the desired idle speed or 175 RPM greater than the desired idle speed during a cold start.

• | The above condition is present for 3 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

Component 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

Control Module References for scan tool information

### 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 175 RPM below desired.

• | Actual engine idle speed should be no greater than 175 RPM above desired.

• | 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 data.

### 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) system

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.