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 P050D: Cold Start Rough Idle

### Circuit Description

This diagnostic is performed when converter light off is enabled or when the converter light off is disabled due to idle instability. Converter light off refers to the transition of the converter from a cold start condition to the state when the converter has warmed up enough to begin catalytic conversion (Closed Loop). In order to help the converter heat up as quickly as possible and reduce emissions, the spark retard is modified under cold start conditions. This diagnostic monitors the enable and disable conditions of converter light off spark retard. The fail/pass determination is based on the monitoring for multiple key cycles and fueling cycles.

### Conditions for Running the DTC

• | DTCs P0106, P0107, and P0108 are not set.

• | The engine has been running between 5-150 seconds.

• | The engine coolant temperature (ECT) is between -5-45°C (23-113°F).

• | The fuel level is greater than 5 percent.

• | The barometric pressure (BARO) is greater than 72 kPa.

• | The calculated valve train temperature is less than 333°C (631°F).

• | The converter Light-off spark conditions are met.

• | The vehicle has been refueled at least once after the DTC set.

• | This DTC runs once per ignition cycle once the above conditions are met.

### Conditions for Setting the DTC

The ECM detects Converter Light-off spark retard is disabled due to idle instability.

### Action Taken When the DTC Sets

DTC P050D is a Type B DTC.

### Conditions for Clearing the MIL/DTC

DTC P050D 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

1. Engine running, observe the DTC information with a scan tool. DTC P050D should not set.
2. Inspect for the following conditions:

• | Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis.

• | Splits, kinks, or improper connections at the vacuum hoses

• | The fuel system is operating lean or rich. Refer to Fuel System Diagnosis.

• | The fuel injectors are operating lean or rich. Refer to Fuel Injector Solenoid Coil Test.

• | Missing, restricted, or leaking exhaust components--Refer to Symptoms - Engine Exhaust.

• | Vacuum leaks at the intake manifold, throttle body, and injector O-rings.

• | Leaking crankcase ventilation system.

• | The air intake duct for being collapsed or restricted possibly by a restricted air filter.

• | Leaking fuel pressure regulator--Inspect for evidence of fuel in the vacuum line. Refer to Fuel System Diagnosis.

3. If all conditions test normal, test the engine for a mechanical condition. Refer to Symptoms - Engine Mechanical.
4. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.