Engine Controller Testing Application Note

General

This application note will give you some ideas on how the Thermotron Product Test System (PTS) can be applied to your Engine Controller testing needs. Modular design, flexibility, low cost and the ability to run multiple tests on multiple products are some of the reasons why the PTS is an excellent choice for this task. Refer to the applicable PTS data for detailed information on devices mentioned in this application note.

Typical Engine Controller Product

A typical automotive engine controller consists of a potted metallic module with a single connector. For a particular engine controller to operate properly, it must receive signals representing the condition of the engine in addition to any control signals. If possible, a special test program may be loaded into the unit under test, in which case stimulus and output would be different. An engine controller will typically output signals to control the ignition and fuel systems of the automobile as well as a wide variety of other analog and digital signals.

General Testing Strategy

Figure 1

Typically, engine controllers may be tested in several modes. One mode of testing would be to simulate actual operation in an automobile. Another mode of testing would first require the "download" of a special test program to the unit(s), with subsequent appropriate testing performed. Both modes of testing can be accomplished with a single PTS system. A general strategy appropriate for testing some types of engine controllers is illustrated in Figure 1.

Providing Engine Controller Power

One or more power supplies, under control of the PTS, can provide a programmable power source capability for the engine controllers to be tested. This capability includes the ability to stress the product with lower and higher than normal operating voltages. To control a power supply, a Power Supply Programming Module (PSM-2) function module is utilized. The PSM-2 is capable of controlling 2 independent power supplies with resistance programming.

Providing Engine Controller Stimulus

To provide stimulus to the product, several PTS function modules may be used. One or more Analog Output Modules (AOM-16) function modules can be utilized to produce analog signals that simulate variables such as fuel pressure, fuel level, throttle position, coolant temperature, and AC pressure. One or more Digital Waveform Generators (DWG-08) function modules may be used to simulate variables such as the crank, cam, brake switch, and AC select. Note that in complex configurations, a DWG-08 may be used to synchronize the operation of other function modules. A function module such as the Automotive Bus Module (ABM-05) module can be utilized to provide a serial communications link to the engine controller for the purpose of downloading test programs.

Sensing Engine Controller Outputs

The outputs of the engine controllers must be monitored for failure detection. A Frequency Input Module (FIM-16) function module could be utilized to detect periodic outputs from the product and indicate when the frequency deviates from the defined range. An Analog Input Module (AIM-32) function module can be used to monitor steady state analog outputs from the engine control module. To detect problems in either injector or ignition outputs, the Digital Waveform Analyzer (DWA-04) is an excellent choice. The DWA-04 is often used with a High Frequency Multiplexer (HFM-08) to monitor the current and/or voltage levels produced by these types of product outputs.

Load Boards

Load boards provide loads that a product would expect to see in normal or test modes of operation. For example, if a product expects to be driving an air pump relay in normal operation, the load board may contain an inductor that provides this type of load. Additionally, load boards offer a method of interfacing the PTS unit to the unit(s) under test. Minor modifications on a load board may be all that is required to modify a PTS for another model of an engine controller. Load boards are custom modules that contain items like inductors, multiplexing relays, voltage dividers and test points.

PTS Profiles

After the PTS equipment is set up, the PTS software must be configured. To configure the PTS software, profiles must me defined for the function modules that are used. No programming is required, but it is important to have a clearly defined idea as to the signal required for product stimulus, the product produced signals and the PTS to product configuration. For example, a profile may be created for the DWA-04 that specifies that a particular waveform (example: injector pulse) must obtain a particular amplitude during a particular time interval after triggering. If the waveform does not reach the defined amplitude, a failure is reported for that unit.

Possible ABS Controller Tester Physical Configuration

Figure 2

A 19 inch console is typically used for PTS equipment mounting. AC power is normally distributed with an outlet strip and excess heat is dissipated with a blower located at the top of the console. Casters on the bottom of the console will contribute to convenience. Figure 3 illustrates a possible PTS configuration.

Load boards are typically located toward the top of the console and the PTS base unit is located toward the bottom, near the power supply. The PTS PC is typically located at a height that allows for easy operator access.

Connections between the PTS console and the products can be accomplished via cables that connect to the back of the PTS cabinet. These cables can connect directly to the air bag controllers, or to replaceable adapters. Note that is often desirable to locate PTS and product connections inside the console (as opposed to the front of the console). This increases the cabling protection, limits cable lengths and reduces the chance of tampering.

Conclusions

As shown by the information presented in this application note, the PTS from Thermotron Industries provides an excellent method of testing engine controllers. This testing can be done in either production or laboratory environments. The advantages of the modular PTS testing method includes flexibility, low-cost and ease of implementation. Contact Thermotron to have your testing needs analyzed and solved.