- Preliminary Inspection

Basic knowledge Of Tools Required

Notice: Lack of basic knowledge of this powertrain when performing diagnostic procedures could result in incorrect diagnostic performance or damage to powertrain components. Do not attempt to diagnose a powertrain problem without this basic knowledge. A basic understanding of hand tools is necessary in order to effectively use this information.

Visual and Physical Underhood Inspection
Perform a careful visual and physical underhood inspection when performing any diagnostic procedure or diagnosing the cause of an emission test failure. This can often lead to repairing a problem without further steps. Use the following guidelines when performing a visual and physical inspection:

^ Inspect all vacuum hoses for the following conditions:

- Correct routing
- Pinches
- Cuts
- Disconnects

^ Inspect hoses that are difficult to see beneath the air cleaner, A/C compressor, generator, etc.
^ Inspect all wires in the engine compartment for the following items:

- Proper connections
- Burned or chafed spots
- Pinched wires
- Contact with sharp edges
- Contact with hot exhaust manifolds.

This visual and physical inspection is very important. Preform the inspection carefully and thoroughly.

Aftermarket (Add-On) Electrical And Vacuum Equipment
Aftermarket (Add-On) Electrical and Vacuum Equipment is defined as any equipment installed on a vehicle after leaving the factory that connects to the vehicle's electrical or vacuum systems. No allowances have been made in the vehicle design for this type of equipment.

Notice: Do not add on any Add-On vacuum operated equipment to this vehicle.

Notice: Connect the Add-On electrical operated equipment to the vehicle's electrical system at the battery (power and ground).

Add-On electrical equipment, even when installed to these strict guidelines, may still cause the Powertrain system to malfunction. This may also include equipment not connected to the vehicle's electrical system such as portable telephones and radios. Therefore, the first step in diagnosing any Powertrain problem is to eliminate all Aftermarket electrical equipment from the vehicle. After this is done, if the problem still exists, diagnose the problem in the normal manner.

Maintenance Schedule
Refer to the Maintenance Schedule for the maintenance that the owner or technician should perform in order to retain emission control performance.

Use of Circuit Testing Tools
Do not use a test lamp in order to diagnose the Powertrain electrical systems unless specifically instructed by the diagnostic procedures. Use the Connector Test Adapter Kit, J 35616 whenever diagnostic procedures call for probing any connectors.

Control Module Service Precautions
The control module is designed to withstand normal current draws associated with vehicle operations. Avoid overloading any circuit. When testing for opens or shorts, do not ground any of the control module circuits unless instructed. When testing for opens or shorts, do not apply voltage to any of the control module circuits unless instructed. Only test these circuits with a digital voltmeter J 39200, while the control module connectors remain connected to the control module.

Verifying Vehicle Repair
Verification of the vehicle repair will be more comprehensive for vehicles with OBD II system diagnostics. Following a repair, the technician should perform the following steps:

1. Review the fail records and the freeze frame data for the DTC which was diagnosed. Record the fail records or freeze frame data. The freeze frame data will only store for an A or B type diagnostic and only if the MIL has illuminated.
2. Clear the DTCs.
3. Operate the vehicle within the conditions noted in the fail records or the freeze frame data.
4. Monitor the DTC status information for the specific DTC which has been diagnosed until the diagnostic test associated with that DTC runs.

Following these steps are very important in verifying repairs on the OBD II systems. Failure to follow these steps could result in unnecessary repair.