Introduction

INTRODUCTION
The engine has an ECM to control major systems such as fuel control, ignition control, idle air control system, etc. The ECM accepts input signals from sensors and instantly drives actuators. It is essential that both kinds of signals are proper and stable. At the same time, it is important that there are no conventional problems such as vacuum leaks, fouled spark plugs, or other problems with the engine. It is much more difficult to diagnose a problem that occurs intermittently rather than continuously. Most intermittent problems are caused by poor electric connections or improper wiring. In this case, careful checking of suspected circuits may help prevent the replacement of good parts. A visual check only may not find the cause of the problems, so a road test with a circuit tester connected to a suspected circuit should be performed. Before undertaking actual checks, take just a few minutes to talk with a customer who approaches with a driveability complaint. The customer is a very good supplier of information on such problems, especially intermittent ones. Through interaction with the customer, find out what symptoms are present and under what conditions they occur. Start your diagnosis by looking for "conventional" problems first. This is one of the best ways to troubleshoot driveability problems on an electronically controlled engine vehicle.




WORKSHEET SAMPLE




DIAGNOSTIC WORKSHEET
There are many kinds of operating conditions that lead to malfunctions on engine components. A good grasp of such conditions can make trouble-shooting faster and more accurate. In general, feelings for a problem depend on each customer. It is important to fully understand the symptoms or under what conditions a customer complains. Make good use of a worksheet like below in order to utilize all the complaints for trouble-shooting.

DESCRIPTION FOR WORK FLOW
Step I. Identify the trouble using the "DIAGNOSTIC WORKSHEET".

Step II. Be sure to carry out the Basic inspection, or the results of inspections thereafter may be misinterpreted. Initial Inspection (Basic Inspection)

Step III. Check the self-diagnostic results stored in the ECM of the failed vehicle. Reading Diagnostic Trouble Codes

Step IV. Perform inspection often selecting from the following tests according to the trouble observed.
1. ON-BOARD DIAGNOSTIC SYSTEM: Follow the self-diagnostic procedure for each item described in "How to Read and Display Diagnostic Trouble Codes". Non-self-diagnostic procedures described for some items will also provide results which are equal to the self-diagnostic results.
2. SYMPTOM BASIS: This inspection is of a simplified method. When performing inspection of a part, the corresponding system must be checked thoroughly by selecting the appropriate check item from "Diagnosis by Symptom". Symptom Related Diagnostic Procedures
3. FUNCTION TEST BASIS (Sequence test): In this inspection, the CONSULT judges "OK" or "NG" on each system in place of a technician. When performing inspection of a part, the corresponding system must be checked thoroughly by selecting the appropriate check item from the "Trouble Code Charts". Testing and Inspection
4. Diagnostic Procedure
- This inspection program is prepared using the data obtained when disconnection of harness or connectors has occurred in the respective circuit.
- Inspection of the "Non-Trouble Code Charts" does not actually start with the execution of on-board diagnostic system. However, inspection is started by assuming that the on-board diagnostic system has already been performed.
- A system with on-board diagnostic system function may contain any circuit placed outside its range of diagnostic function. In that case, it is arranged that "Not on-board diagnostic system item" of the system will be performed when the self-diagnostic results is OK. Example: CAMSHAFT POSITION SENSOR

Step V.
1. FINAL CHECK item is not described in the "Non-Trouble Code Charts". However, this FINAL CHECK must be performed without fail to ensure that the trouble has been repaired. The FINAL CHECK is also important to ensure the correct reassembly of the parts disassembled during the repair.
2. If the same trouble phenomenon is observed again in the final check: Go back to STEP IV, and perform the inspection using a method which is different from the previous method.
3. If the cause of the trouble is still unknown even after conducting step 2 above, check the circuit of each system for a short by using the voltage available at the ECM. Refer to "Normal Scan Data Values" for test values. Pinout Values and Diagnostic Parameters