Diagnostic System Check - NV 1500

Diagnostic System Check- Manual Transmission








Circuit Description

Important: Do not perform this check if no driveability condition exists.

The Diagnostic System Check is an organized approach to identifying a condition created by an electronic engine control system malfunction. The Diagnostic System Check is the starting point for any driveability diagnosis. This directs the service technician to the next logical step in order to diagnose the condition. Understanding the table and using it correctly will reduce diagnostic time, and will prevent the replacement of good parts.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
1. In order to correctly diagnosis any driveability malfunctions, the scan tool must be able to power-up.
2. The diagnostic tables in this portion of the database are designed for use with a properly functioning scan tool. Serial data communication must be corrected before beginning any other diagnostic procedures. Class 2 serial data will not transmit if the system voltage is less than 9.0 volts or more than 16.0 volts.
5. By storing the Freeze Frame and Failure Records data on the scan tool, an electronic copy of the data is created when the malfunction occurred. This information is stored on the scan tool and can be referred to later. Type C DTCs do not store Freeze Frame data. If this option is not available, manually record the information for later reference.
6. If multiple DTCs are stored, diagnose in the following order:
1. System voltage DTCs
2. PCM Error DTCs
3. Component level DTCs, or DTCs that indicate a malfunctioning part
4. System level DTCs, or DTCs that indicate a system malfunction.
9. After the engine is at normal operating temperature, comparison of actual control system data with the typical values is a quick way to determine if any parameter is not within limits. Keep in mind that a base engine problem such as advanced cam timing may substantially alter sensor values.
Inspect the following sensors for proper operation:
^ The Engine Coolant Temperature (ECT) sensor-Look for an initial coolant temperature reading that is close to ambient, then observe the rise in temperature to the normal operating temperature while the engine is warming up.
^ The Throttle Position (TP) sensor-Look for proper sweep from 0 percent to 100 percent.
^ The Manifold Absolute Pressure (MAP) sensor-Look for quick changes during changes in various engine loads.
^ The Oxygen Sensor (O2S1) -Look for proper rich/lean and lean/rich sweeps in operation.
^ The Idle Air Control (IAC) valve-Look for proper idle control and proper transition while operating the high load components such as the Air-Conditioning (A/C) control.
Inspecting the sensors for proper operation during warm-up can be a crucial step in correctly diagnosing any driveability concern. Careful observation of these sensors during engine warm-up may reveal a slow responding sensor or a sensor that malfunctions only within a small portion of its range.