Error Code P050D is defined as Cold Start Rough Idle. This is a generic trouble code, meaning it applies to all vehicles equipped with OBD-II system, or vehicles made since 1996 up to present. It typically applies but not limited to Cadillac, Chevrolet, Chrysler, Dodge, and Jeep. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model to another.

When this code appears, it means the PCM (powertrain control module, also known as engine control module in other vehicle makes) has determined a rough engine idle during cold start. The ‘Cold Start’ is a term used engine drivability implemented only when the engine is at (or lower) than ambient temperature.

The PCM monitors the idle level of the engine. To do so, the intake airflow must be regulated during closed throttle conditions. The PCM regulates engine intake air at idle using an electronically controlled device called the IAC (idle air control). If an unregulated air enters the engine, then it may cause a rough engine idle at cold start, setting the Error Code P050D.

If the malfunction only happens during under cold start conditions that means the ECT (Engine Coolant Temperature) is malfunctioning. Engine drivability strategy is much different under cold start conditions. If the PCM gets an incorrect engine temperature signal at cold start-up, it may result in a rough idle due to insufficient fuel delivery or improper timing advance. An ECT sensor code may also be stored. As you have probably guessed, you will need to diagnose and repair any ECT sensor related codes before the P050D.

If during cold start conditions the PCM sees a rough idle that cannot be stabilized within the parameters set by the manufacturer, then the error code P050D will be set and Check Engine light will be illuminated. For some vehicles, multiple ignition cycles (with a failure) may be required for MIL illumination.

Common Symptoms

As with other error codes, this code activates the Check Engine light and registers the code to the vehicle’s memory system. Other common symptoms include:

  • Rich or lean exhaust
  • Cold start drivability issues
  • Hissing or sucking noise coming from the engine

In some cases, the vehicle may have other drivability related codes.

Possible Causes

  • Vacuum or air leaks
  • Insufficient fuel pressure or volume
  • Bad spark plugs, ignition coils, or plug boots
  • Shorted or open circuits or connectors
  • Defective ECT sensor

How to Check

If there are other lean exhaust codes or other IAC related codes present alongside with this code, then it’s important to diagnose and repair these codes first before addressing the P050D.

An engine misfire can also contribute to trough idle under cold start conditions. If there are other misfire codes present, then they must also be fixed first. Chances are a misfire that will fix the problem.

To accurately diagnose this code, you will need a vehicle information source, diagnostic scanner, and DVOM.

Vehicle information source will provide the diagnostic flow chart, connector face views, connector pin-out charts, wiring diagram, and component testing procedures and specifications that will help you diagnose the code accurately.

Get all the codes stored and record the freeze frame data by connecting the scanner to the vehicle diagnostic port. Take note of this information. Clear the codes and allow the engine to completely cool down before you test drive the vehicle.

If the code does NOT come back, and the PCM enters readiness mode, then the problem may be intermittent.

In some cases, the conditions which led to the code being stored may need to worsen before an accurate diagnosis can be made.

If the code is immediately reset, begin by focusing on factors which most dramatically impact cold start drivability.

To check for excessive air intake

If there is too much air getting into the intake, at a time when it demands a richer fuel mixture, a rough idle will occur.

  • Look for vacuum leaks or signs of cracked or collapsed vacuum hoses and lines. Listen for hissing or sucking noises. Also, make sure you listen to the throttle body, intake manifold gasket, brake booster and the PCV valve.
  • Also, there should be no cracks or holes in the air intake hose (from the air filter box to the throttle body).
  • The IAC valve plays an important role in cold start drivability. Thus, make sure that the valve and seat are clean and free of debris. Make sure that the throttle plate is clean and free of carbon coking.
  • Check EGR valve position; It should be closed at idle. If it is open, it creates a vacuum leak.

For low fuel pressure

  • Make sure there’s a good amount of fuel in the tank.
  • Search for obstruction if fuel pressure is low

For engine misfires

Engine misfire usually happens after the engine reaches normal operating temperature. In some cases, however, a misfire could only be detected during cold start conditions.

  • If this happens, check the spark plugs, spark plug boots, and ignition coils for signs of coolant, oil, or water contamination.
  • Check with the technical service bulleting (TSB). Often, manufacturers provide specific diagnosis and repairs for such problem.

How to Fix

Based on the diagnosis, common repairs for this code include:

  • Repair or replace vacuum leaks
  • Repair or replace bad spark plugs, ignition coils, or plug boots
  • Repair or replace shorted or open circuits or connectors
  • Make sure there’s good amount of fuel in the tank
  • Replace ECT sensor


Rough idle under cold start conditions could be a symptom of a more serious problem. Thus, it’s important to address it as soon as possible.