破解DTC背后的代码（下）_谷朝峰与您聊车_新浪博客

Enabling Criteria Arsenal

启用标准

谷朝峰   译

To obtain the highest probability of a successful DTC subroutine test, enabling criteria will be used, which is a way of controlling the outcome of the test by controlling the variables. Just as in a laboratory, to obtain consistent results, the test must hold the variables to a minimum and use a set procedure.

若要获得成功的 DTC 子例程测试的可能性{zg}，启用标准将使用，这是一种通过控制变量来控制测试结果的方式。正如在实验室里，为获得一致的结果，测试必须控制变量到{zd1}范围同时使用一套设定的程序。

The enabling criteria accomplish this by allowing the DTC subroutine to run only under certain conditions. Once all the conditions have been met, the DTC subroutine is allowed to run. One example of this would be a small leak detected an evap system when running a test for DTC P0442. The enabling criteria might read as: Fuel tank level greater than 15% and less than 85% equals “true,” ambient temperature greater than 30°F and less than 95°F equals “true,” BARO greater than 70kPa equals “true.”

启用条件通过允许 DTC 子例程运行仅在某些特定的条件下有效。一旦符合所有条件DTC 子例程将被允许运行。 这一示例会体现在监测 evap 系统时。如果一个小泄漏检测到。 DTC P0442 将运行，启用条件可能理解为：燃料箱液面大于 15%，低于 85%等于"TRUE"状态，这大于 30 ° F 和小于 95 ° F 的环境温度等于"true，"状态，压力值大于 70kPa 等于"true"。

Since the test is dealing with pressure in the fuel containment system, all criteria that can affect the pressure changes within the system must be controlled. If the fuel tank is full, the nonliquid area within the tank is very small and may show a pressure change that’s not an actual leak and thus set a false DTC. If the fuel tank is empty, the nonliquid area is very large and may not show the pressure change of an actual leak. In this case, a DTC will not set that should be set.

既然该测试是关于燃料控制系统中处理压力，可能会影响系统内的压力变化的所有条件必须得到都控制。当燃油箱满时，油箱内非液态区域变得很小，可能所感应的压力变化不是一个实际的泄漏，因此会设置一个虚假的 DTC。当油箱为空时，油箱内的非液态区域变得非常大，也许所显示压力变化并不是一个实际的泄漏。在这种情况下一个 DTC 将设置。 

If the ambient temperature is lower than 30°F, the gaseous phase above the fuel could be contracting and show a pressure change that’s not an actual leak, thus setting a false DTC. If the ambient temperature is higher than 95°F, the gaseous phase above the fuel could be expanding and may cover up an actual leak. In this case a DTC will not set that should be set.

 如果环境温度低于 30 ° F，在燃料上方的气相可能缩小，所显示压力变动不是实际的泄漏，因此设置一个虚假的 DTC。如果环境温度高于 95 ° F，温度燃料上方的气相可能会扩大，掩盖了实际的泄漏的可能。在此情况下，也将不能设置一个 DTC 。

If the BARO is below 70kPa (high elevation), the pressure between the inside of the fuel containment system and the atmosphere will not be enough to change the sensed pressure inside the tank if a leak is present and may not set a DTC that should have been set. As you can see, the enabling criteria are a way to control the results of the DTC subroutine so the best possible conditions are present during the testing sequence.

如果压力低于 70kPa(高海拔) ，在泄漏因素存在的前提下，燃油箱燃料控制系统和大气之间的压力将不足以改变在油箱内部的传感器压力，为此不可能设置一个 DTC 应用设置的内容。正如你所看到的，对于控制 DTC 子例程的结果，加强标准化验是一种方法，如此，在测试过程的方式中{zh0}的可能条件都存在。

 It’s important to look at the enabling criteria at the beginning of the trouble tree for the DTC. This will show which sensors are being used to allow the DTC subroutine to run. If a sensor reading is inaccurate, it can allow the test to run at the wrong time, or may not run the test at all. In the P0442 example above, the fuel level, intake air temperature and manifold absolute pressure sensors are used. If the fuel level sensor malfunctioned and showed three-quarters of a tank when the fuel tank was actually full, it would allow the DTC subroutine to run and would set a false P0442.

在 DTC 故障树的开头仔细分析启用标准是非常重要的。这将显示哪些传感器用于允许 DTC 子例程运行。如果传感器感应传感数值不准确，它可能在错误的时间内使DTC测试运行，或者也许根本不可能运行测试。 在上面所给出 P0442 示例中，燃油箱液面位置，进气空气温度和歧管{jd1}压力传感器将被应用。如果燃油液位传感器运行不正常，在油箱满箱情况下，表现出四分之三的燃油液面，燃料箱将允许 DTC 子例程运行并会设置一个虚假的 P0442。 

When a DTC is set, you must check a wiring diagram to see which wires are present at the controller. To set a DTC, the CPU must be able to check the outcome of the DTC subroutine. To accomplish this, a circuit must be wired to the control unit that the programmer can use to check the outcome of the test. This can be done with a direct test or an indirect test.

当一个 DTC 设置时，您必须检查相关线路，去查看哪些线路出现在控制器所涉及的范围内。若要设置一个 DTC，CPU 必须能够检查 DTC 子例程的结果。要做到这一点，实现此目的，相关电路必须连接到控制单元，基于此程序员才可以用来检查测试的结果。这项工作适用于直接测试或间接测试。 

In a direct test, the circuit to be tested can be monitored by an electronic device such as an analog-to-digital (A/D) converter. The A/D converter changes an analog voltage to a digital code comprised of 0s and 1s. The CPU can be programmed to understand the sequence of 0s and 1s on a parallel bus, or the sequence can be read by a serial converter that can process this data and send it on a serial line to the CPU.

在一个直接的测试中，被测试电路可以由一种电子设备（例如模拟到数字 (A/D) 转换器）进行监视。 A/D 转换器将一个模拟电压变为由 0 和 1 组成的数字代码。 CPU 可以进行编程，以了解 0 和 1 在并行的总线上的顺序，或顺序为串形的转换器所读取，转换器可以处理此数据并将数据在串行线路发送给cpu 。

The CPU can then use this information to determine whether the voltage in the circuit had the anticipated and correct change. One example of a direct test is a transmission solenoid that was commanded to be activated (Fig. 4, page 34). Once the program set points for a shift have been met, the CPU instructions turn on the transistor driver for the solenoid. The program instructions then check to see whether the voltage state of the solenoid control circuit had changed to the expected value. If the voltage value did not change within the program set points for a stated time period, a DTC is stored and the appropriate instruction set is carried out. In order for a direct test to occur, the circuit board must be designed with the physical layer of the A/D converter to monitor the circuit. This adds an extra expense to the controller that may not be needed in all circuits.

CPU 然后可以使用此信息确定在电路中的电压是否符合预期和正确的更改。直接测试的一个示例是一个所要执行命令的变速箱电磁阀被jh（图 4 页）。 一旦换档的程序设定点执行， CPU指令将控制打开晶体管电磁阀驱动程序。程序指令检查是否电磁阀控制电路的电压状态已更改为所需的值。如果电压值未在程序设定标准内，在规定的时间段内，一个 DTC 存储，并调用适当的指令进行应急处理。为了能够直接测试，电路板中必须设计有监视电路，同时还要物理层的 A/D 转换器。这为控制器增加了一个额外的费用，并不是所有电路都需要这种额外的校验。

 In an example of an indirect transmission solenoid activation test (Fig. 5), the CPU commands the transistor driver on, then the CPU checks the input speed sensor and compares it to the output speed sensor. If the solenoid activation was completed, then the ratio between the input and output speed sensors changes to a known factor. If this factor does not change within the correct set points, a DTC is stored and the appropriate instruction set is carried out. With the indirect test design, the physical layer to check the input and output speed sensors is already on the circuit board, so additional controller expense is unnecessary. With this type of circuit design, it’s important to understand that a scan tool will display only the commanded state; it cannot show whether that state actually occurred.

在一个间接变速箱电磁阀jh测试 （图 5）的例子中， CPU命令晶体管驱动程序打开，然后 CPU 检查输入的速度传感器信息，并和输出速度传感器进行比较。如果电磁阀jh已完成，输入和输出速度传感器之间的比率将为一个已知的系数。如果这个系数不在正确的设置标准内，一个 DTC会被存储，适当的指令集将会作为补正措施执行。在间接测试设计，用于检查输入和输出速度传感器的物理层已设计在电路板上，因此附加控制器的开支是不必要。对于这样的电路设计，扫描工具将只显示命令执行的状态，它不能显示状态动态真实的发生。了解这一点是比较重要的。

Another example of a direct or indirect circuit test is a P0135 oxygen sensor heater circuit fault. If the oxygen sensor heater circuit is wired directly to the control unit, an A/D converter with a basic shunt circuit is used to directly check the current of the circuit (Fig. 6). This test circuit allows a voltage drop to occur that the A/D converter can read and that’s directly proportional to the current flow. Now the programmer can write an instruction set that converts this voltage from the A/D converter to an amperage reading. If this voltage is not within the program set point, a DTC is stored. In the case of an indirect reading for the oxygen sensor heater circuit, there’s no heater circuit wire connected to the control unit (Fig. 7). The heater circuit power wire is supplied directly from the ignition circuit or a relay and the heater circuit ground is connected directly to the ground plane.

直接或间接的电路测试的另一个例子是 P0135 氧传感器加热电路故障。如果氧传感器加热电路直接连接到控制器，具有一个基本的并联电路的 A/D 转换器可用于直接检查当前的电路 (图 6)。 此测试电路允许发生的一个电压降， A/D 转换器由此可以读取的当前电流成正比的数值。 现在，程序员可以编写一个将此电压从 A/D 转换器转换为一个安培数读取的指令集。如果此电压不在程序设定点内，将存储一个 DTC。对于氧传感器加热电路间接读数的情况下，并没有加热器电路导线连接到控制单元 (图 7)。加热器电路接地线直接连接到地面，加热器电路电源线也直接从点火电路或继电器盒处提供。 

When you check a wiring diagram and see that the wiring for the associated DTC is not directly connected to the control unit, you must look for the wire that could convey the information to the CPU directly. For the programmer to write instructions for the DTC subroutine, a circuit must be connected to the control unit that can be used to obtain the information for the DTC. With the P0135, the CPU has a circuit inside the control unit that applies a bias voltage to the oxygen sensor signal wire. When the zirconium dioxide oxygen sensor sensing bulb is cold, the resistance is greater than 100 megohms, and when this sensing bulb is heated to 700°F, the resistance drops to less than 100 ohms.

当您检查线路图，可看出与 DTC关联 的布线未直接连接到控制单元，但您必须寻找能直接传达至 CPU 信息的线路。 对程序员来讲，编写的 DTC 子程序指令是需要相关电路必须连接到可用于获取 DTC 的信息的控制单元。 对于 P0135故障码， CPU 有一个适用于氧传感器信号线的偏置电压的控制单元内的电路。当温度低时，二氧化锆氧传感器感应头的电阻大于 100 的 兆欧，而当传感球被加热到 700 ° F，电阻值将降到小于 100 欧姆。 

This sensing bulb resistance change can be used to check the operation of the heater circuit by applying a regulated voltage to a very large resistor inside the control unit that’s connected in series to the sensing circuit. This creates a voltage divider circuit. The resistor inside the control unit is fixed and the sensing bulb has a variable resistance that changes when heated. If the heater circuit is working, it heats the sensing blub, thus changing the resistance of the bulb. As the resistance of the sensing bulb drops, so does the voltage between the resistor and the sensing bulb. By checking the voltage change between the fixed resistor and the sensing blub over a set time period, the programmer writes an instruction set that can run the DTC subroutine. This allows a check of oxygen sensor heater circuit without a direct connection to the CPU.

这种传感头的电阻值变化可用于检查加热器电路的操作，方式为：提供一个稳定的电源压给电控单元内部的一个非常大的电阻，而且大电阻要与传感器电路连接。这就意味着创建了一个分压电路。控制单元内的电阻是固定的，而随着氧传感器的加热，传感球的电阻则是变化的。如果加热电路工作，它加热温度传感头，从而改变传感头的阻值。随着传感头电阻值的下降，在电阻与传感球之间的电压也下降。通过检查固定的电阻器和传感球之间的电压变化，在设置的时间段，在程序员编写一个可以运行 DTC 子例程的指令集。 这允许可以对没有直接连接到 CPU 的氧传感器加热电路进行检查。 

It’s important to understand the digital logic behind the operation of computer-controlled vehicle systems, so they can be quickly and accurately repaired.

了解计算机控制汽车的系统运作背后的数字逻辑是非常重要的，它能帮助可以快速而准确地修复故障车。