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The "Ins" and "Outs" of Control Modules
The goal of any engine management system (EMS) is to control combustion so emissions, fuel economy and performance are regulated at optimal levels. This is achieved by monitoring operating conditions on a moment-by-moment basis, typically via the powertrain control module (PCM). The EMS measures the amount of air entering the engine, applies the right quantity of gasoline and then calculates when to ignite the mixture in the cylinders to attain a vehicle's specific emission, fuel economy and performance objectives.

The EMS continually monitors input data to calculate operating conditions and control outputs to "close the gap" between what is currently occurring and what's desired. The PCM employs an "if this ... then that" strategy to achieve this. Input data from a variety of monitored aspects of the powertrain provide the "if this" part of the calculation and execution strategy. Common input data includes, but is not limited to:

• Throttle position – determined by the signals from the throttle position sensor, which relays driver demand on the powertrain. It"s also used to validate airflow and engine mechanical timing.
• Airflow – determined by signals from the mass airflow sensor to calculate the quantity of gasoline needed to support combustion.
• Engine speed/piston position – determined by signals from the crankshaft position sensor. The speed or velocity of the crankshaft tells the EMS whether the crankshaft is accelerating from adequate combustion or decelerating due to misfires. Crankshaft signals are required by the EMS to keep the fuel pump relay energized.
• Camshaft position – determined by signals from the camshaft position sensor, which are used to synchronize fuel injector timing to crankshaft position and control spark timing.
• Exhaust oxygen content – determined by signals from oxygen sensors. Oxygen content validates that proper combustion has occurred and is used to drive short-term fuel trim to control the catalyst's operating environment and meet performance objectives. OBD II compliant vehicles must operate in "self-regulating" closed loop fuel control within 4 minutes and 20 seconds of an engine start. Heated oxygen sensors reduce this time and can provide closed loop control within 30 seconds of a start-up, long before the powertrain is up to operating temperature.
• Intake air temperature – determined by signals from the intake air temperature sensor. Intake air temperature is an essential part of the spark timing calculations to maintain proper combustion temperatures for catalyst efficiency.
• Engine coolant – determined by signals from the engine coolant temperature sensor. During start-up and open loop and closed loop warm-up phases of EMS operation, fixed pulse width schedules are established based on coolant temperature.
• Vehicle speed – determined by signals from the vehicle speed sensor. Vehicle speed is used in the control of transmission shifts and to validate vehicle deceleration in conjunction with throttle angle.

The "then that" part of the computing sequence is provided by such output components as fuel injectors, ignition coils, emission control solenoids, transmission shift solenoids, plus fuel pump and air conditioning compressor relays. These parts are typically provided either battery or ignition switched power and are turned "on" and "off" by having the PCM controlling the ground path. They are switched on and off based on calculations that use data from input components. The EMS then uses input data to validate that the expected output control actually occurred.

Changing a vehicle"s operating strategy can be accomplished by reprogramming a PCM. In some instances, a replacement PCM requires vehicle specific programs to be installed before the PCM will function. Reprogramming, or a "reflash," updates the module"s vehicle-specific calibrations. It does not modify the base operating instructions that allow the PCM to function as a computer. Physical malfunctions in a PCM including memory, circuit boards and internal wiring cannot be repaired by reprogramming a module. In these instances, a replacement PCM would be required.

When servicing A/C systems, specifically during compressor repairs, it pays to look beyond the basics. Of course, solid installation and repair skills are essential for any technician that wants to do the job right the first time. But problems that can crop up when installing compressors aren't always obvious — and overlooking them can result in unwanted comebacks or warranty issues. Here are some tips to help ensure that every installation or repair is a successful one.

Inspect the system for contamination
When repairing any A/C failure, carefully inspect all components in the system for any signs of foreign material or contamination. These may include metal chips, contaminated lubricant or chemical residue found in any part of the system. Properly replacing the components, correctly flushing the system and installing an in-line filter will help to ensure the longevity of the repair.

Use the right lubricant oil
Failure to add the correct amount or type of lubricant oil will cause compressor failure, leaving the part unwarrantable. For vehicles with R-134a systems, use PAG oil RL488 (Delphi part no. RL10006) for H6, V5 and R4 compressors and PAG oil RL 897 (Delphi part no. RL10007) for CVC compressors. Use 525 mineral oil for vehicles with R-12 systems. Use of any other lubricant, such as ester oil, can lead to premature system failure, especially under extreme operating conditions.

For compressors with crankcase bolts, the oil must be installed through the crankcase bolt hole. All other compressors can have the oil removed from the discharge port and added through the suction port. Once the lubricant has been put into the compressor, is it important to turn the compressor shaft with the appropriate hand tool, such as the Delphi Compressor Turning Tool (CB10049), so the compressor is properly lubricated before it is installed on the vehicle. Failure to do this can also result in premature compressor failure. To further determine the correct amount, type and process for applying lubrication, consult the replacement checklist/instruction sheet located in the part's original box.

The importance of proper evacuation
It is important to remove all moisture inside the system when replacing a compressor. This is accomplished by evacuating the system until the correct vacuum level is reached. If all moisture is not removed when the system is recharged, the moisture will react with the oil and will become acidic and corrode the inside of the system components, creating the potential for premature failure and poor performance issues.

Non-warranty issues
Typical unwarrantable situations include complete compressor kits with no evidence of installation; parts that are damaged due to rough handling and/or incorrect installation (such as broken electrical connectors or holes in the compressor case); contamination of the compressor; and severe overheating of the compressor, indicated by burnt paint or blistered/melted labeling.

When servicing fuel pumps and fuel modules, it pays to look beyond the basics. Of course, solid installation and repair skills are essential for any technician who wants to do the job right the first time. But problems that can crop up when installing fuel pumps and fuel modules aren't always obvious — and overlooking them can result in unwanted comebacks.

Here are some tips to help ensure that every fuel pump and fuel module installation or repair is a successful one:

Inspect the electrical connector for signs of damage
For a variety of reasons, some vehicles may be prone to electrical connector failures. These failures often can be seen as overheated terminals and wiring, so it"s essential to replace the mating vehicle wiring when replacing the fuel module or pump on these vehicles. Otherwise, the new service part can fail prematurely. If a new wiring pigtail is included with the module or fuel pump kit, be sure to install it. The new pigtail may often look different than the original part, but the improved electrical connector can easily be installed by using the parts and following the detailed instructions included in the kit.

Examine the fuel tank and fuel module bucket for contamination
Fuel pump and module failures can often be attributed to contaminants found inside the fuel tank or fuel module. These contaminants can cause excessive wear of the fuel pump, plug strainer and filters. If contamination is found, the fuel tank should be drained and cleaned before installing the new part. Also look for rust inside the tank or bucket of the fuel module, which indicates water is in the fuel delivery system. Metal fuel lines and fuel rails should be examined for signs of internal rust or corrosion and replaced as needed. Contaminants can be drawn into a vehicle's fuel system if the evaporative emissions system is not operating properly. It"s essential to determine the cause or source of the contamination and correct it before installing the new part.

Install the float arm onto the level sensor of the fuel module
New fuel module service kits may come with the float arm assembly detached from the fuel level sensor. It"s important to install the float arm onto the level sensor prior to installing the fuel module into the tank. Failure to install the float arm will cause the fuel level sensor to operate incorrectly and create a customer complaint. Detailed instructions on how to properly install the float arm onto the level sensor are included in the fuel module service kit.

Replace the fuel filter and strainer when installing a new fuel pump or fuel module
Most fuel module kits include new strainers with the fuel module assembly. These strainers can be internal, external or both depending on the fuel module design. If a new strainer is not included with the fuel pump, one should be obtained and installed on the pump prior to installation into the vehicle. Be sure it"s correctly seated so contaminants can't pass around it. Replace the fuel filter on vehicles that have serviceable fuel filters. Many late-model fuel modules now incorporate the fuel filter into the fuel module, so the filter is replaced when the module is replaced.

Delphi offers a broad array of fuel pumps, fuel level sensors and other fuel system components for the aftermarket, all developed and engineered based on Delphi's decades of experience with original equipment (OE) applications. In particular, Delphi"s fuel pumps have a reputation for quiet, durable performance with little flow or pressure variation in hot fuel situations — features proven in competitive studies. For more information visit iam.delphi.com.