Service Information

Cruze

DTC P050B

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 provide an overview of each diagnostic category.

DTC Descriptor

DTC P050B 00: Cold Start Ignition Timing Performance

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 catalyst must be warmed to efficiently reduce the emissions. The cold start strategy is to reduce the amount of time it takes to warm the catalyst. During a cold start, the engine idle speed is elevated to allow the catalyst to warm quickly.

Conditions for Running the DTC

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DTCsP0010 00, P0016 00, P0068 00, P0106 00, P0107 00, P0108 00, P0116 00, P0117 00, P0118 00, P0119 00, P0121 00, P0123 00, P0171 00, P0172 00, P0201 00, P0202 00, P0203 00, P0204 00, P0222 00, P0261 00, P0262 00, P0264 00, P0265 00, P0267 00, P0268 00, P0270 00, P0271 00, P0335 00, P0336 00, P0340 00, P0341 00, P0365 00, P0366 00, P0443 00, P0459 00, P0496 00, P2088 00, P2089 00, P2100 00, P2101 00, P2122 00, P2123 00, P2127 00, P2128 00, P2138 00 are not set.

•	The battery voltage is greater than 10 V.

•	The engine speed is at idle.

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

•	DTC P050B 00 runs continuously when the above conditions are met.

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

•	Heated Oxygen Sensor 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

Engine running, compare the Desired Idle Speed to the actual engine idle speed parameter. The actual engine idle speed should not deviate more than 175 RPM from the Desired Idle Speed.
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

Verify that no DTCs except P050B 00 are present.

⇒	If any DTC is present, refer to Diagnostic Trouble Code (DTC) List - Vehicle to diagnose that DTC prior to this diagnostic.

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

Inspect for the following conditions:

•	Vacuum leaks

•	A faulty positive crankcase ventilation system

Inspect the ignition coil spark plug boots for the following conditions:

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Damage

•	Carbon tracking

•	Oil contamination

•	Water intrusion

⇒	If you find any of the above conditions, repair as necessary.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Control Module References for ECM replacement, setup, and programming

•	Throttle Body Assembly Replacement

•	Ignition Coil Replacement

•	Spark Plug Replacement