Electrical Repairs to OBD II Vehicles

Subject:
Making Electrical Repairs to Vehicles with On-Board Diagnostics (OBD II) Systems

CATEGORY
Maintenance

SECTION PAGE
1 48

ISSUE CODE
10/95-0627 100

Application: 1996 900 and 9000 Models

All model year 1996 vehicles are equipped with the On-Board Diagnostics System, OBD II. OBD II monitors and stores various engine management information.

^ Vehicles with excessive emissions-related problems are quickly identified.

^ The length of time between the occurrence of an emissions-related problem and its repair is minimized. Any significant increase in emissions will turn on the MIL (CHECK ENGINE light) and set a code.

^ Assistance is provided in diagnosing and repairing emissions-related problems.

OBD II regulations identify specific systems that must be monitored for any problem that would allow emissions to increase to a level above 1.5 times the Federal standards which that vehicle was certified to meet when new. An OBD II system checks for:

^ Catalytic converter efficiency

^ Heated catalytic converter heating function (when applicable)

^ Engine misfire

^ Evaporative emission system effectiveness

^ Secondary air injection system function

^ Fuel trim system monitoring

^ Pre-catalyst oxygen sensor efficiency

^ Post-catalyst oxygen sensor efficiency

^ EGR System function (when applicable)

^ Comprehensive component monitoring





Great care must be taken when repairing vehicles to ensure that the integrity of the systems being monitored is maintained.

^ When repairing wiring harness it is extremely important that the repair be carried out properly. Otherwise, you run the risk of illuminating the malfunction indicator lamp (CHECK ENGINE) and generating a diagnostic trouble code (DTC).

^ Gold-plated cable terminals must be replaced with gold-plated cable terminals; tin-plated terminals must be replaced with tin-plated terminals.

^ Crimp connections must be correctly made. If they are not and a gap exists between the crimp and a single copper strand, the malfunction indicator lamp (CHECK ENGINE) will light. Special pliers will be made available shortly. A PSI bulletin will be issued to announce their availability.

^ Always insulate crimps and damaged insulation using adhesive shrink hose. Never use electrical tape.

^ When soldering wiring harnesses be sure the area of repair is secure and not hanging loose as this may cause a diagnostic trouble code (DTC) to be generated.

^ The cable attached to components such as the oxygen sensor, various position sensors, etc... must not be repaired. Rather, change the entire component.