Using Diagnostic Trouble Code (DTC) Tables

Using Diagnostic Trouble Code (DTC) Tables
When diagnosing this powertrain, you will almost certainly need to use the diagnostic procedures in this or other powertrain sections. These diagnostic procedures are mostly in the form of tables. At the beginning of each DTC will be the diagnostic support information. The diagnostic support information will be a circuit diagram or illustration, and a brief description or explanation of the components, circuit, or system involved with the DTC being diagnosed in the table. Reading this diagnostic support information will help you understand the DTC and what the table is trying to accomplish. Following are explanations of the diagnostic support information provided with the tables for DTCs.

Circuit Diagram
The circuit diagram of the diagnostic support information will show the circuits and components involved in setting the DTC. This diagram may be used as a reference when circuit checks are required in the table. If more detailed circuit information is required, the Engine Controls electrical schematics may be referenced.

Circuit Description
The circuit description explains the sensor and circuits involved in setting the DTC. The circuit description may also give a brief description of when or how the DTC is set.

Conditions for Running the DTC
The Conditions for Running the DTC are the conditions that must be met before the PCM will test for a failure. These conditions are generally set up so that an input or system may be reliably checked and not give a false failure indication.

Conditions for Setting the DTC
The Conditions for Setting the DTC are the conditions that must be met for the DTC to set. A failure condition is checked for only after the running conditions (described previously) have been met. The diagnostic software in the PCM will test for certain faults and if a failure is present, the DTC will set.

Action Taken When The DTC Sets
The Action Taken When the DTC Sets are the steps the PCM takes after the DTC is set. These actions serve one of three purposes:
^ To inform the driver of the problem.
^ To preserve the driveability of the vehicle.
^ To prevent the failure from causing any damage to the vehicle.

Conditions For Clearing The MIL/DTC
These are the conditions that must be met for the MIL to be turned OFF and the DTC to clear.

Diagnostic Aids
Many tables have one result which reads Fault Not Present or Go to Diagnostic Aids. Fault Not Present means that the conditions (failures) that were present when the DTC set are no longer there. Sometimes, with the help of snapshot information (Freeze Frame or Failure Records) or information from the driver, the driveability concern may still be identified or narrowed down to a short list of possible intermittent or related system failures. The Diagnostic Aids information may tell to the technician what to look for and where to investigate, in order to diagnose an intermittent failure.

Test Description
The Test Descriptions are explanations of the reasons certain tests are being done and what the test being performed in that step is supposed to determine. This information is numbered and corresponds to the steps on the table. If you are performing a test and wonder why the test is being done or what the test is supposed to find, refer to the Test Description for additional information.

Diagnostic Table
Diagnostic tables are an organized and systematic approach to diagnosing a Diagnostic Trouble Code (DTC).
The table consists of five separate columns:
^ Step number
^ Action
^ Value(s)
^ Yes
^ No

The step number indicates which step is being performed. The action column contains all necessary information about how to perform a certain test. The last sentence in each action block will always be a question. The question can only be answered yes or no. The answer to the question will dictate which column you will go to next - yes or no. The value(s) column will contain any specifications that you are asked to test for. The yes or no answer to each test will lead you to the next step to be performed or a particular action to take. Most boxes will have a Go to Step X statement. If a yes or no block does not have a Go to Step X statement, the text inside that block will be the last instruction given in the table. The instruction will either be a solution (repair), a Fault Not Present, or a Go to Diagnostic Aids. Always begin with step 1 at the top of the table unless there is a notice or caution above it. Never skip steps or jump ahead in the table. Taking short cuts often leads to misdiagnosis. When a problem is found, make the necessary repairs and then verify the repair.