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 P050D

Cold Start Rough Idle

Circuit/System Description

During a cold start, the engine control module (ECM) commands dual-pulse mode during Open Loop operation to improve cold start emissions. In dual-pulse mode, the injectors are energized twice during each injection event. As with misfire diagnosis, in dual-pulse mode the ECM monitors the crankshaft position sensor and the camshaft position sensors to calculate crankshaft rotation speed. In normal operation, optimum fuel delivery during dual-pulse mode produces a steady crankshaft rotation speed. If the variations exceed a calibrated value, the code will be set.

Conditions for Running the DTC

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DTCs P0010, P0011, P0013, P0014, P0090, P0091, P0092, P00C8, P00C9, P00CA, P0101-P0103, P0106-P0108, P0112, P0113, P0116-P0118, P0122, P0123, P0128, P0171, P0172, P0192, P0193, P0201- P0204, P0222, P0223, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0300, P0301-P0304, P0335, P0336, P0351-P0354, P0506, P0507, P0627-P0629, P0722, P0723, P1248, P1249, P124A, P124B, P2122, P2123, P2127, P2128, P2135, P2147, P2148, P2150, P2151, P2153, P2154, P2156, P2157 are not set.

•	The catalyst temperature is less than 500°C (932°F).

•	The engine coolant temperature is warmer than -10°C (14°F).

•	The barometric pressure is greater than 60 kPa.

•	The engine speed is between 250-1900 RPM.

•	The engine is running and a cold start has been detected.

•	DTC P050D runs once per cold start.

Conditions for Setting the DTC

This DTC will set if the ECM detects variations in crankshaft rotation speed caused by the lack of adequate fuel delivery during dual-pulse mode.

Action Taken When the DTC Sets

•	DTC P050D is a Type B DTC.

•	The ECM disables dual pulse mode and energizes the fuel injector as it would for a warm engine.

Conditions for Clearing the DTC

DTC P050D is a Type B DTC.

Diagnostic Aids

•	This DTC may be set with a misfire DTC, however the existence of this DTC is a higher priority and indicates the condition to diagnose is related to fuel and/or injectors, not the ignition/spark system.

•	A restricted fuel injector may cause this DTC to set.

•	High resistance in the injector circuits can activate a diagnostic trouble code related to a misfire without activating a diagnostic trouble code related to an injector. Test for high resistance in the injector circuits for the affected cylinders if you suspect a problem.

•	A drop in system voltage during cold start may set this 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 Testing

Note

Circuit/System Testing requires cold start. Do not start vehicle prior to connecting scan tool and preparing to evaluate the condition during engine crank.

1.	Start the engine and observe the Cylinder 1-4 Current Misfire Counters during first 500 engine cycles. The Cylinder 1-4 Current Misfire Counters should not be incrementing.

2.	If the misfire counters are incrementing on one or more cylinders, verify that the following conditions do not exist:

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Fuel pressure that is too low or too high-Refer to Fuel System Diagnosis.

•

Contaminated fuel-Refer to Alcohol/Contaminants-in-Fuel Diagnosis.

3.	If all conditions test normal, replace fuel injectors as indicated by high misfire counts.

Repair Instructions

Direct Fuel Injector Replacement

Repair Verification

Note

Repair Verification requires cold start.

1.	Ignition ON, engine OFF, clear the DTCs with a scan tool.

2.	Start the engine.

3.	Verify the DTC does not reset.