Once you have chosen an engine, it is time to select a computer and wiring harness to control the engine. While many industry names have been used to describe the computer that controls the engine, Ford refers to its system as the Powertrain Control Module or PCM. Wiring the system is the most difficult part of any swap, and with all the changes Ford has made over the years and the upgrades to computers, it is a source of apprehension to most builders. Unlike other makes where the basic scheme doesn’t change much, the Ford system has changed considerably over the years and has had at least four base configurations as of this writing.
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You can choose between an aftermarket or the factory system that originally came with your engine. Both types have benefits and drawbacks. Follow the recommendations in this chapter to select the best computer and wiring system for your engine. The newer the engine, the more difficult it is to use a factory system. If you have a Coyote engine, therefore, you should strongly consider an aftermarket or Ford Control Pack system, which will allow you to tune your engine according to your application. If you use a factory Ford computer and harness, make sure you acquire or have all the necessary parts, including sensors, boxes that bolt to the firewall, etc. You know that the car runs with all the components plugged in; you can determine later if a component isn’t needed.
Determine what, if any, other components from the donor vehicle you would like to use (e.g., transmissions, ABS, electric windows). Some of these systems are best controlled using a factory computer. If you want to use only the engine, an aftermarket computer may be your best option. Make sure that the system you choose is legal. Some of these systems cannot be used in pollution-controlled vehicles.
Factory Systems Overview
The factory system allows you to use and control components such as automatic transmissions, ABS units, and fuel systems without extra controllers. Retaining the original computer and harness for your engine type is simpler and easier than using an aftermarket computer because you can use the factory plugs and the original wiring and sensors. In addition, you don’t have to verify the sensors that are installed on the engine, as some aftermarket systems require a change to generic sensors.
Ford has used at least four different computer systems to control the modular engines. These computers are all mass airflow design, so they must use an airflow meter to measure the amount of air going into the engine. Ford made constant improvements to the engines and controls throughout the years, and along with the base computer, the control systems also changed.
The location of components can be a disadvantage and often an obstacle with the factory system. For example, the PCM mounting on the donor vehicle may be in a place that doesn’t work on your swap, and changing the placement may be difficult. And the same goes for the wiring; you may have to extend, trim, or tuck away wiring that doesn’t quite fit. Ford also has used some creative routing for some of the wires, requiring you to get all the wiring harnesses from your donor car.
Ford is generally very good at keeping wire colors consistent, but is notorious for changing the location of signals in a connector and changing the sex of the connector, even within model years. Ford made it increasingly difficult to mix and match the wiring harnesses because of various options on the vehicle. Ford may have multiple harnesses within a year and model that cannot be interchanged.
If you are going to use a Ford harness and computer in your swap, make sure you get all the wiring and electronic parts from the donor car. Buying every sensor or component from Ford can be very expensive.
The following are brief synopses of the Ford computer systems:
The EEC-IV computer was installed on the earliest modular engines in full-size Ford cars. Ford used this computer system throughout the 1980s and EEC-V replaced it in 1994. All of these systems were the mass airflow type and used coil packs (modular engines do not use a distributor). The EEC-IV computer module is easily identified by its three rows of pins on the main plug. These systems were unusual in layout because they had some extra relay boxes, and this makes the conversion a bit cumbersome compared to later wiring harnesses.
Ford implemented the EEC-V computer to comply with the mandated On Board Diagnostic II (OBDII) industry standard. Several versions of the EEC-V system were developed and installed on Ford vehicles. During the EEC-V era, Ford transitioned away from coil pack ignition to a coil-on-plug (COP) system. Ford also introduced a returnless fuel system for which the PCM regulated fuel pressure. As a result, the old mechanical fuel pressure regulator and fuel tank return line were eliminated. About 1999, the Passive Anti-Theft System (PATS) was improved, and installing aftermarket components such as instrumentation became difficult. The EEC-V computer can be identified by the four rows of control pins in its main connector.
As more gadgets continued to consume computer resources, the computer needed to evolve. The jump to EEC-VI and improvements such as drive-by-wire technology and Variable Cam Timing (VCT) came in 2005.
EEC-VII (2014– )
The EEC-VII system uses a computer housing similar to the EEC-VI’s, but it uses the three connectors on the end or top. As regulations and features are added to new vehicles, its computers will be replaced with greater frequency. In 2015 the control box shape changed slightly, going back to a two-connector design.
Ford Wiring and Connectors
Using Ford factory wiring harnesses is an option for most engines and projects. However, the newer the engine and vehicle, the more difficult it is to use the factory components. When using factory computers and wiring, pay close attention to the connectors. Ford frequently changed them, even within model years. For example, a 2003 Mustang Cobra uses a male plug on the engine harness, and on the 2003 Mustang GT it is a female. Ford also changes the wire locations in the connectors. A Crown Victoria engine and a Mustang engine may have the same connector, but Ford changes the pinouts of the wires in the connector. Ford is very good at keeping the wiring colors consistent, but it doesn’t really want you interchanging harnesses.
Here are some of the bigger hurdles to consider if using a Ford wiring harness and computer.
The Passive Anti-Theft System (PATS) has evolved over the years and the newest system is now the biggest hurdle to overcome in an engine swap. Starting in 1996, the Ford Securilock system was integrated into Ford cars and trucks, and in 1999, Ford upgraded to the PATS II system. The PATS II looked at the serial numbers of certain components such as the gauge cluster and wouldn’t start if they had been changed. However, a simple software jump in the PCM programming could defeat these systems.
About the time the VI-VCT engines came out, Ford improved the PATS system to the point that aftermarket performance tuners found it difficult to bypass the system. Programmers were first told that PATS was hard-wired into the computer, but this turned out to be not true or they were able to get around it. The problem has been resolved, and now programming the new computers is no problem. But it may prove more challenging as Ford continues to improve its security systems.
In 2005 Ford introduced the throttle-by-wire system that actuated the throttle plate using an electric motor rather than a traditional cable. The gas pedal is an electronic device that sends signals to the throttle motor via wiring. This means provisions need to be made in your swap to accommodate the throttle-by-wire gas pedal.
Returnless Fuel System
In the late 1990s Ford introduced the returnless fuel system that eliminated the mechanical fuel pressure regulator and fuel return line used since the 1980s. The PCM controls the voltage applied to the pump and reads the pressure via a pressure transducer mounted on the fuel rail.
Unless you will be using the stock pump and controller in your existing tank, you need to reprogram the computer to tell the fuel pump circuit to maximize output all the time and run an old-style regulator and return line to the tank.
Variable Camshaft Timing (VCT and TI-VCT)
Ford introduced variable camshaft timing starting in 2005. VCT allows the computer to advance or retard the camshaft timing via a control solenoid. Many aftermarket computers cannot control the variable timing, and the camshafts have to be locked down. VCT and the improved PATS system make using the factory wiring more difficult in most cases.
Ford PCM Communication
As I outlined in the introduction, one of the advantages to a modular engine swap is the ability to get information from the computer for both maintenance and performance tuning. This information is useful not only for drag racers with laptops; familiarity with the capabilities of your engine’s computer system and ways to optimize your engine swap will help you meet the goals for your project.
Even the earliest EEC-IV computers could communicate running information and errors incurred. They did this through a series of binary pulses that generated engine error codes with the Key On Engine Off (KOEO) test. The computer could also run checks on the sensors in Key On Engine Running (KOER) mode. An old swing-arm voltmeter could be used to read the pulses put out by the computer.
With the introduction of the EEC-V system in 1994 came the OBDII (On-Board Diagnostic II) set of standardized error codes, which are still in use as of this writing. Along with the standard industry error codes, each manufacturer has some proprietary codes that are available to cover specific features of its vehicles. The latest systems cannot only give you the basic error codes, but can log information on the engine and systems when an error occurs, provide real-time running information on the performance of the engine, and be programmed over the Internet for engine and drivetrain improvements for both performance and efficiency.
All communications with the computer are done through the DLC (Data Link Connector), which is a standardized plug that is usually mounted under the driver’s side of the dashboard. This plug connects to the Ford communications network and to the PCM.
Reading Error Codes
There are three levels of communication with the PCM, and these three levels require three different tools. The first is a basic low-cost code reader, the second is scan tools and data loggers, and the third is programmers. The basic code reader can read error codes stored in the computer. Error codes are primarily used for emissions issues, and when your PCM senses a problem, it stores a DTC (Diagnostic Trouble Code) and turns on the check engine light on the dash. The DTC follows the industry standard OBDII numbering system. Low-cost code readers, available at most auto parts stores, read these codes, and can erase them, as well. With the exception of being able to erase codes, this is pretty much one-way communication, but it is still beneficial.
Scan Tools and Data Loggers
The next step up is the ability to read the data stored in the computer and the ability to perform specific tests on certain items controlled by the PCM. For this, you need a scan tool, which costs more than the error code readers, depending on what level of features your scan tool possesses. This is more of a two-way communication with your computer, and the computer can respond to your inquiries and perform tests for you. Over the years, improvements in the PCM and the software running the PCM have increased the level of communication and the amount of data acquisition. With this level of communication, you are going to hear your tuner or mechanic talk about specific terms. Here are just a few that you need to be aware of:
Parameter Identification (PID)
This allows a scanner to access the analog and digital sensors that are controlled by the PCM. OBDII rules dictate a standard set of PIDs that all scan tools can read; Ford has some proprietary ones that may or may not be readable by non-Ford scan tools. This function can test whether a sensor or switch is turning on or off, can measure the percentage of sensor in use, or the voltage reading of the sensor.
Output Test Mode (OTM)
With this mode, you or your technician using a scanner can turn on and off specific items in the car. An example would be a two-stage fan relay module. Through the scanner you can turn on the low and high fan outputs on the Ford system before you fire up your engine and know you will have the cooling fans on first start.
With more and more information being stored by the computer systems, one thing that comes in handy is the freeze frame data. When your computer sets an error code, it records exactly what was happening when the error occurred. The newer the computer and the greater the number of sensors, the more information there is available. Freeze-frame data records the engine performance, as well as speed, emissions, what gear you were in, everything. (A friend test drove a newer Mustang GT and while he was cruising at 95 mph and backup system threw a minor code.
The computer recorded all the data of the vehicle at the time of the error, including his “test drive” speed. He had some explaining to do.)
Gone are the days of the old oscilloscope, and now every mechanic has a scan tool to talk to the computer. The computer can tell you more about what is happening with the engine than any external device. New diagnostic equipment scans live and stored data, graphs operating conditions, and even recommends a plan to correct the problem.
The third level of communication allows you to reprogram your computer system, and this is what you need to get around systems such as PATS. Most aftermarket programmers have data logging and error code reading capabilities built in, so they are all-in-one solutions.
Some earlier EEC-V computers have a port where you can plug in an external computer chip and override the original program. These chips, depending on their complexity, can store multiple tunes for different uses (e.g., driving to the dragstrip and changing the tune for your passes; changing the tune on your truck when you are pulling for max torque).
Some system’s computers can be reprogrammed via the Internet through built in Wi-Fi or through a laptop. Tuning an engine is a science, and most companies who sell the programmers work with trained tuners to maximize the performance and efficiency of the engine. Some sell pre-programmed tunes based on experience, but specific tunes are generally left to the experts. You can certainly purchase a programmer and work with tuning your vehicle, but there is a learning curve to becoming adept with tuners. If you plan to develop your ride for racing or top performance, a programmer may be right for you.
Unless you are a wizard with fuel curves and shift points, you will be working closely with a tuner, and they will probably use the tuner they are most comfortable using (see Chapter 10). A programmer manufacturer can give you a list of tuners in your area, or you can work with one over the Internet.
Programming Factory Computers
With the factory PCM, any time you change something on the engine, you need to reprogram the PCM to accommodate the change. You need to program around the PATS system, something most aftermarket companies say they can do (but check with your tuner). Anything that can affect what the computer thinks it is seeing needs to be addressed. You need to notify the tuner of any changes to items such as the intake, injectors, oxygen sensors, or any hardware that affects the performance of the car.
If you bypass items such as the EVAP or EGR for off-road use, or you are converting a mechanical fuel pressure regulator, you need to let the PCM know what you are changing. Some tuner dealers don’t like to deal with swaps because the owners generally don’t tell the tuner everything they have done, or the swap builder makes a mistake with the wiring and blames the failure on the programmer. Find a good tuner dealer and work closely to get your conversion right.
Factory Wiring Notes
If you plan on using the factory computer and wiring, here are the requirements: It is best to have a complete donor car; it gets very expensive running back to your dealer every time you are missing a sensor. Ford tends to route wires through multiple harnesses, so you need them all, and depending on the year, you’ll need items such as fuel pumps and controllers, perhaps even components you won’t be using. If you can’t get the entire donor car, try to get as much as you can: computer, all the wiring harnesses, throttle pedal (if using throttle-by-wire), fuel pumps, and controllers.
You will be shortening, lengthening, and removing circuits from your harnesses in almost every case. Make sure you have a good, professional multimeter, quality crimp tools for general connections, and the proper pin insertion/removal tool for your job.
You need to buy a wiring diagram! Whether you prefer a physical book,
CD, or direct online schematics, it is up to you. Wiring diagrams for Ford can be purchased online at helminc. com. Other services are available for online wiring and diagnostics.
Purchase the tools you need to successfully lengthen and shorten wires, or remove and install pins. Typical installations do not use all the wiring from a factory harness, and to save space and weight you will be pulling some wires out of the harness. You may also have to move pins within connectors if you have mismatched harnesses, or if you are trying to combine harness connectors.
Factory Computers with Aftermarket Wiring Harnesses
It is possible to run your factory computer using an aftermarket wiring harness. Through the years, numerous companies have attempted to build harnesses, and I have tried many of them, with varying degrees of success. Some harness manufacturers require you to send in your old harness so they can reuse some of the original Ford connectors, which may be obsolete and not readily available (some that are available are not good quality). Others can get the connectors, and some use a central junction point that permits remote mounting, but it is big and bulky. Some other harness suppliers require you to convert to GM-style generic sensors, which may make it difficult in the future to remember what is installed in the car.
You need to have some experience in wiring and making proper connections, and these aftermarket harnesses only control the engine and, if equipped, the transmission, and may not be capable of running any other components from your donor car.
Ford Performance Power Parts Control Pack
For the later throttle-by-wire engines, Ford has developed a control pack that uses a stock-style Ford computer and a plug-and-play wiring harness that controls just the engine. For the later VCT engines, the Ford Control Pack will also control the variable cam timing. The early 2005– 2006 engines require a modification to the wiring harness to work with the control pack.
Using the control pack requires you to convert your system back to a mechanical fuel regulator and return system. It also requires the use of the 2011–2013 Mustang GT airbox and inlet hose, which can be cumbersome when installing in a non-Mustang application. Your tuner may be able to help you program around this.
Aftermarket Computer Systems
You have several aftermarket systems to choose from, but the choice boils down to three different types: Mass Air Flow, Speed Density, and Alpha-N. Which you choose depends on the type of driving you plan for your project. Here is a brief overview of the different types of computers and how they work. With the introduction of the Ford Control Pack, it has taken over as the best and easiest-to-use computer control system. Holley and FAST both sell speed density systems that will work with the modular engine and have specific Coyote harness converters to run these engines.
All Ford modular engines came with Mass Airflow (MAF) computer systems for control. A mass airflow system features a meter mounted ahead of the throttle plate that measures the amount of air going into the engine. The computer calculates the amount of fuel to be delivered to the engine based on air volume, air temperature, manifold pressure, and exhaust gas mix. Most MAF systems use sequential fuel injection, which means the fuel injectors are only firing once per cycle, making them more efficient than some speed density systems that fire every revolution (also called waste spark).
Mass air systems are typically less tolerant of big tuning changes than speed density systems due to the sizing of the mass air meter. A big change in fuel injection or camshafts may mean that a larger MAF meter is required, and the system can’t be tuned without changing several items at once.
Some aftermarket companies use speed density systems to make big horsepower because they are easier to tune and do not have some of the restrictions of mass air. The speed density system calculations are based on engine speed, manifold pressure, exhaust output, and a Manifold Absolute Pressure (MAP) sensor to measure the pressure in the intake manifold and then calculate the fuel required. It doesn’t measure the volume of air coming into the engine; it uses a big internal table of fuel curves and uses these calculations to determine the amount of fuel to deliver to the engine. Ford used speed density on engines from 1986 to mid-1989, when they converted to mass air systems. Some manufacturers still use speed density. Most aftermarket systems still use speed density to run the engine because it allows for flexibility in tuning without having to change major components.
Alpha N computer controls are a simple form of fuel injection. Fuel is delivered based on throttle plate position and engine RPM, and the computer reads the manifold vacuum and controls fuel accordingly. While this is a simple system used in some race cars, it is not recommended for most street and street/strip applications, as it doesn’t take into consideration any exhaust gas information or emission information. Because of this, it can sometimes be very inefficient on fuel mileage.
Spotlight Build: 1967 Pro/Street Cobra Mustang Coupe
The 2003–2004 Cobra Terminator engines continue to be a popular swap engine because they are easy to modify and produce a lot of power. In addition, they don’t have some of the issues with throttle by wire and VCT. Programming the computer is very easy and the wiring from the donor Cobra can be used.
This build-in-progress is a 1967 Mustang coupe and it is receiving the full pro/street build out with a complete running driveline from a 2003 Ford Mustang Cobra donor car. Like with the Mustang in Black (see Chapter 2), this owner wanted to take full advantage of all the capabilities of the newer Cobra such as ABS, modern cruise control, and returnless fuel injection.
To start the conversion, Rod and Custom Motorsports performed extensive fabrication work and installed a Mustang II front suspension. The shock towers were removed to make room for the wide DOHC heads. The engine and transmission were set back about 4 inches to help with the clearance of the stock Eaton-style supercharger snout, as this build will use a stock 1967 turn-signal hood. This required a set of custom fabricated mounts to place the engine back far enough. The crossmember was notched slightly to clear the curve of the factory oil pan. This also allowed the T-56 shifter to protrude into the original shifter hole without any modifications. The factory air-intake tubing was used and mounted to the old battery area. The only other fitment issue was the IAC solenoid, which was mounted on top of the supercharger intake. It was contacting the factory underframe, so it was turned 180 degrees and rewired and no longer touches the hood. A custom-made transmission crossmember was fabricated to hold the transmission to the firewall extensions.
The rear suspension is also out of a 2003 Cobra, but it’s slightly modified to work with the mini tubs provided by Autoworks International. The IRS cradle was narrowed to make room for the 11-inch-wide rear wheels. A set of custom-made subframe connectors was also installed. The rear IRS is already equipped with the ABS wheels, and the front spindles are retrofitted. To get the pro/street look the factory fender flares have been widened 11⁄2 inches in the back and 1 inch in the front.
The fuel system was custom designed to use the components from the 2003 Cobra. New stock 1967 fuel tanks are being fabricated out of stainless steel, and this was the choice for modifications for the 2003 dual fuel pump. The fuel ring from a donor tank was grafted to the top of the tank and a custom baffle was installed for the in-tank pump. The stock fuel pump controller was mounted down in the driver-side quarter panel. The battery was also relocated to the trunk.
The hydroboost from the Cobra was mounted to the original 1967 brake pedal, and a hydraulic clutch conversion from Modern Driveline works with a McLeod throwout bearing. A Lokar throttle cable is used along with an accelerator pedal from a 1970 Mustang to run the throttle body. Up front, the Cobra radiator and cooling fan fit nicely between the frame rails and the intercooler is mounted between the radiator support and the hood latch bracket. The original Bosch intercooler pump is mounted on the underside of the original battery tray. A remote oil filter mount and oil-to-air cooler are also used. Electronic speed control is tucked under the driver-side splash shield.
The exhaust features a custom 21⁄2-inch pipe system with off-road X pipe running from the stock Cobra manifolds. Electronics are also borrowed from the Cobra donor car and the stock EEC-V computer is re-flashed. The air conditioning is adapted to the original 1967 A/C box. A custom set of Speedhut gauges including a GPS speedometer is used.
With 390 hp, the 2003–2004 Terminator engines continue to be a popular option when making a modular engine conversion. They have horsepower, can make more horsepower very easily, are not as complicated as a newer throttle-by-wire engine, and look fantastic under the hood.
Written by Dave Stribling and Posted with Permission of CarTechBooks
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