Open-Loop, Wow !!! Is it a loop in the space time continuum? No my dear Spock, it's not....

 

THEORY OF OPERATION

(for more information please refer to the Cranking Enrichment Mode blog)

• Open-loop mode – simply leans that the ECM is NOT looking at the O2 sensor for A/F feedback and is reached after the engine has warmed-up sufficiently. At this point in time, the ECM enters open-loop mode and sets the injector pulse at base duration. The base injection duration is the beginning of any fuel control strategy, regardless of vehicle manufacturer. In the next mode (closed-loop), the base injection pulse duration is further modified, by adaptive memory values stored in RAM/KAM and based on system sensor readings. Open-loop mode simply means that the O2 sensor is not determining the injection pulse-width and the A/F ratio is not stoichiometric. The ECM adjusts injector pulse-width from a look-up table according to RPM, MAF/MAP value, intake air temperature (to calculate density) and throttle position. A further sub-mode that is also considered by the ECM is EGR operation, since it will affect the intake vacuum and/or air density. As soon as the O2 sensor starts cycling (crossing the 450 mV mark), the ECM switches to closed-loop and the A/F ratio is maintained at stoichiometric ratio. In closed-loop, the ECM uses the O2 sensor as a feedback to maintain the A/F mixture at stoichiometry. The open-loop mode is also a good indication of an ECM stuck in LIMP-in-MODE (sub-mode). A warmed-up engine stuck in open-loop points to a faulty condition outside the ECM’s control that is affecting the A/F ratio. While in limp-in-mode, the fuel trims PIDs can not be used to aid in diagnostics. A lean/rich condition (plugged injectors or leaky intake gasket), therefore, would not be apparent by FUEL TRIM PID analysis. A condition such as a faulty transmission solenoid (causing it not to shift) may take the fuel system into limp-in-mode masking any other A/F related problems.

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Sensors                 O2-Sensor                  APP-Sensor                CAM-Sensor               CRK-Sensor               ECT-Sensor               IAT-Sensor                 Knock-Sensor              MAF-Sensor                MAP-Sensor                TPS-Sensor                 VSS-Sensor                FRP-Sensor                AFR-Sensor              

Actuators               Fuel-Injectors            Ignition-Coil           Leak-Detection Pump  GM-Series Alternator   Idle-Control Valve      EGR-System            EVAP-System      

Repair Strategies Current-Ramping      Lack of Power           Fuel-Flow Volume     Ignition Waveform       Ignition Testing          A/F Ratio Diagnosis    Minimum Air Rate      No Fuel-Pressure       No Injector Pulse      No-Start/No-Spark     General No-Start      

ECM/PCM Modes Cranking Enrichment   Warm-up Cycle         Open-Loop            Closed-Loop            Accel. Enrichment Deceleration Leaning   Idle Control             Low-Voltage Correction Clear Flood Mode     Selective Inj. Cut-Off   Limp-In Mode           Exhaust Variable Valve

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 Code Setting Criteria

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SRS Airbag DTC

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How to Get SRS Codes

Retrieving Dodge SRS   Retrieving Ford SRS     Retrieving GM SRS      Retrieving Honda SRS   Hyundai/Kia/Mitsu SRS Isuzu/Mazda/Subaru     Retrieving Toyota SRS  Nissan/Infinity SRS

SRS-Airbag Repair Guide

Deleting SRS Codes   Dodge SRS Location       Dodge SRS Operation     Ford SRS Location          Ford SRS Operation        GM SRS Location            GM SRS Operation           Honda SRS Location       Honda SRS Operation     Isuzu/Mazda/Suba Loc.   Isuzu/Mazda/Suba Ope Kia/Hyun/Mitsu Location Kia/Hyun/Mitsu Oper.       Nissan/Infinity Location   Nissan/Infinity Operation Toyota/Lexus Location    Toyota/Lexus Operation 

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