Cranking Enrichment Mode - Is that meant for racing with my neighbors car?...

The Enrichment Mode is a part of the ECM's programming that is activated during start up or while cranking. Deep knowledge of this operational mode is a must in today's auto repair. Get it here....



This section deals with the inner process of the ECM’s software operation. A generic approach has been taken in explaining each of the operational modes, regardless of manufacturer. This is done in an effort to prepare the technician for implementation of the diagnostic techniques offered throughout this book. By the simply “thinking like the vehicle’s ECM”, the technician can follow various clues in order to reach a diagnostic conclusion. The technician should always ask the primordial question, “what does the ECM needs to see in order to do what it’s doing ? ”

Modern engine control systems are digital systems. By digital ECM we means that it uses a series of mathematical calculations, using 1’s or 0’s (On or Off switches), to perform its job of controlling the engine. A typical ECM employs a microprocessor (main computer chip) and the needed operational circuitry, such as injector driver transistors and related electronic components. In essence, a modern ECM is a dedicated computer, with specific programming (software) that allows it to operate. Early ECMs were slow 8 bit systems, which contrasts with today’s 32 bit or even faster systems. The bits are the amount of ON/OFF switches that the ECM can process at a time. A Pentium-4, for example, is a 32 bit system. This tremendous amount of processing power is making possible the further integration of every possible automotive electronic system. By means of modern vehicle networks, any vehicle system from entertainment to electronic power steering is being integrated to one another. However, by far the biggest catalyst for the heavy use of electronics in modern vehicles has been the increasingly stringent exhaust emissions and fuel economy regulations. Such level of efficiency and environmental cleanliness would not be possible without the modern digital ECM.

Virtually all computers are divided into two separate parts, the hardware and software. The hardware is the actual module, with all its electronic parts, including transistor drivers, memory chips and related circuitry. The software is the actual programming residing in the hardware or inside the ECM’s memory chips. The ECM’s memory is further subdivided into the ROM (read only memory) and RAM or KAM (random access memory or keep alive memory). The ROM memory chips, also called keep alive memory, are permanent storage chips used to store the programming for the different operational modes, as well as the look-up tables for all the sensors and actuators. The RAM memory chips are used to store any manufacturing or aging variations (adaptive memory) of each fuel control component, whether it is an injector that is 10 % clogged, a slower O2 sensor or a new crank sensor that has just been installed. This adaptive feature gives the ECM the ability to adapt as operating and environmental conditions change.

A modern module use multiple modes to achieve a desired output. A multi-mode ECM operates in one of many possible modes of operation. At the same time, the ECM always refers to the look-up tables to determine injector pulse and ignition patterns at any given condition. An example would be a cold engine that has just been started, in which case, the ECM would refer to the coolant temperature sensor and adjust injector pulse accordingly until it has reached the proper warm-up temperature level. In this example, the ECM’s programming is constantly referencing the look-up tables stored in ROM memory to determine the injector pulse throughout the entire coolant sensor range. Furthermore, any smaller variations in the operation of each sensor/actuator due to manufacturing differences, aging, etc are stored in RAM or adaptive memory, which the ECM also references continuously. The RAM/KAM memory is volatile, which means that it gets erased in the event of any power disruptions, hence the term KAM (keep alive memory). The digital multi-mode capability allows engine controllers to hold the engine as close to the stoichiometric ratio for as long as possible. So it can be argued, that the biggest thrust for the wide use of electronics in today’s automobiles are government emissions regulations. It would be virtually impossible to manufacture clean and fuel efficient automobiles without a massive array of electronic components.

There are seven main modes of operation built into the software of any vehicle ECM found today, as well as several other system specific sub-modes. The use of an operational mode is dictated by the particular conditions under which the engine has to work. Each of these conditions is significantly different to warrant a different control software or mode for it. The ECM must determine the operational mode from the existing sensor data. The seven main fuel control modes are – cranking enrichment, engine warm-up, open-loop, closed-loop, acceleration enrichment, deceleration enleanment and idle speed control. Several other modes of operation exist and apply to specific systems or conditions. These are – clear flood, limp-in-mode, variable valve timing, selective fuel injector cut-off and synchronous and asynchronous fuel injection. These modes are explained in the following pages.

Cranking enrichment mode – The ECM provides the extra fuel needed to start the engine. This is done by increasing the injector pulse width to as much as 40 mS and using injector group firing, as opposed to sequential. This mode is activated whenever the ignition key is switched on. As soon as the engine starts and its speed goes above a certain RPM value, the ECM switches to the next logical mode, whatever that may be. On certain vehicles, a start/crank input from the starter relay or solenoid is provided to the ECM. This signal may reach the ECM through either a fuse or a direct wire connection. A failure in this circuit may cause severe performance problems, such as excessive fuel delivery – if this signal is shorted to power. Or it may also cause long cranking time – if this signal does not reach the ECM (the ECM does not know it has to go into cranking mode). During cranking mode, the ECM constantly compares the ECT sensor value with a look-up table stored in ROM memory to determine the correct injector pulse width. Normal cranking mode A/F ratio is between 1.5:1 to 12.0:1 depending on engine coolant temperature. The main reason for this mode is that at colder temperatures the fuel tends to form into large droplets, which do not burn as efficiently. For this reason, manufacturers are constantly looking for ways to reduce the cranking and warm-up mode times as much as possible, since they are the greatest cause of automotive air pollution in modern engines. As a side note, the low voltage sub-mode also plays a role while at cranking enrichment mode. The low voltage submode program code instructs the ECM to further increase injector pulse to compensate for the lower fuel pressure, brought about by the lower available fuel pump voltage from the starter motor cranking the engine. Regardless of whatever mode is active, a low supply voltage will increase injector pulse.


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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

 OBD-2 Codes

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 Code Setting Criteria

Dodge CSC                 Ford CSC                    GM CSC                     Honda/Acura CSC        Hyundai CSC               Isuzu CSC                   Kia CSC                      Mazda CSC                 Mitsubishi CSC            Nissan/Infinity CSC      Subaru CSC                Toyota/Lexus CSC

SRS Airbag DTC

GM SRS Airbag Code   GM Truck SRS Code    Ford SRS Airbag Code  Ford Truck SRS Code   Dodge SRS Code        Dodge Truck SRS Code Acura/Honda SRS Code Isuzu SRS Codes         Mazda SRS Codes        Subaru SRS Codes Infinity/Nissan SRS       Kia SRS Codes     Hyundai SRS Codes     Mitsubishi SRS Codes Lexus/Toyota SRS

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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