GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2008 🢒 Vibe - FWD 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC P050A

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 (IAC) System Performance

Circuit/System Description

The powertrain control module (PCM) uses input from several engine sensors in order to determine the correct engine speed at idle. With the desired idle speed calculated, the PCM determines the correct throttle opening and the corresponding throttle position (TP) needed to obtain the desired engine speed. The PCM sends the desired throttle position or target value to the TAC module. The TAC module achieves the desired throttle position by commanding the throttle control motor to position the throttle valve at the target value. If necessary, the PCM adjusts the target throttle position in order to achieve the desired engine idle speed.

The PCM also determines the typical volume of intake air used by a properly operating engine during the first moments of cold start operation. The PCM monitors the mass air flow (MAF) sensor readings during the first 13 seconds of cold engine operation and compares those to the calculated values. If the accumulated value of the MAF sensor output differs from the calculated value, the DTC can set.

Conditions for Running the DTC
    • DTCs P0011, P0012, P0031, P0032, P0100, P0101, P0102, P0103, P0115, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0130, P0133, P0134, P0171, P0172, P0220, P0222, P0223, P0300, P0301-P0304, P0335, P0340, P0341, P0351-P0354, P0385, P0500, P0850, P2102, P2103, P2111, P2112, P2118, P2119, P2120, P2121, P2122, P2123, P2125, P2127, P2128, P2135, P2138 are not set.
    • The battery voltage is greater than 8 volts.
    • The engine coolant temperature is greater than -10°C (14°F).
    • The engine is running at idle conditions.
    • Vehicle speed is less than 3 km/h (2 mph).
    • DTC P050A runs once an ignition cycle when the above conditions are met.

Conditions for Setting the DTC

The accumulated value of the MAF sensor output differs from the PCM calculated value greater than a predetermined value.

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.

Diagnostic Aids

Verify the accuracy of the MAF sensor. Test for good electrical circuits and connections.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Powertrain Control Module Connector End Views
    •  Engine Controls 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. Observe the DTC information with a scan tool.
    2. ⇒If there are any throttle actuator control (TAC), throttle position (TP) sensor, or accelerator pedal position (APP) sensor DTCs set, refer to Diagnostic Trouble Code (DTC) List - Vehicle.
  2. 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.

Circuit/System Testing
  1. Observe the Long Term FT and Short Term FT values in the Freeze/Frame failure records. Add the two percentages together, the total should be between -20 percent and +20 percent.
    2. ⇒If the total FT value is greater than or less than the specified range test the operation of the camshaft position (CMP) actuator system. Refer to DTC P0011.
  2. Verify that one of the following conditions is not present:
    3. • Vacuum leaks
    • The throttle valve for the correct operation--A throttle valve that does not close correctly sets this DTC.
    • Restricted air intake system
    • The throttle body for damage and/or tampering
    • Incorrect or malfunctioning positive crankcase ventilation (PCV) system--refer to Crankcase Ventilation System Inspection/Diagnosis.
    • Excess deposits in the throttle body
    • Obstruction, damage, or contamination of the sensing element of the MAF sensor
         ⇒Repair the condition as necessary.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Throttle Body Assembly Replacement