OBD SYSTEMS
OBD II
"OBD" is an acronym for the On Board Diagnostic System.
California OBD II applies to all gasoline engine vehicles up to 14,000 lbs. Gross Vehicle Weight Rating (GVWR) starting in the 1996 MY and all diesel engine vehicles up to 14,000 lbs. GVWR starting in the 1997 MY.
Several states in the Northeastern United States have chosen to adopt the California emission regulations starting in the 1998 MY and are known as "Green States".
Green States receive California-certified vehicles for passenger cars and light trucks up to 6,000 lbs. GVWR. Starting in the 2004 MY, Federal vehicle over 8,500 lbs. will start phasing in OBD II.
Starting in 2004 MY, gasoline-fueled Medium Duty Passenger Vehicles (MDPVs) are required to have OBD II. Federal OBD II applies to all gasoline engine vehicles up to 8,500 lbs. GVWR starting in the 1996 MY and all diesel engine vehicles up to 8,500 lbs. GVWR starting in the 1997 MY.
OBD II system implementation and operation is described in the remainder of this document.
MALFUNCTION INDICATOR LAMP ILLUMINATION
"MIL" is an acronym for the Malfunction Indicator Lamp.
If the ECM recognizes a malfunction that leads to increased emissions values, it indicates them by lighting the MIL which is located in the instrument cluster.
The ECM switches on the MIL after the ignition is switched on. Shortly after the engine is started, The MIL goes out if the ECM does not detect a malfunction that increases the emissions values.
If the ECM recognizes a malfunction that leads to increased emissions during the operation of the engine, the ECM switches on the MIL and an entry is stored in the DTC memory of the ECM.
CAN DATA LINK
"CAN" is an acronym for Controller Area Network.
The ECM communicates with all databus capable control modules by a CAN Data Link.
The databus capable control modules (i.e. Engine Coolant temperature Sensor) are connected by two data bus wires which are twisted together (CAN_High and CAN_Low), and exchange information (messages) to the ECM. Missing information on the databus is then recognized and stored as a malfunction.
The ECM illuminates the MIL through the CAN data link and tells the MIL to turn on, turn off, or blink.
ELECTRONIC POWER CONTROL WARNING LAMP
"EPC" is an acronym that stands for the Electronic Power Control (E-gas).
The ECM monitors all EPC components after the ignition is switched on.
If a malfunction is recognized in the EPC system during the operation of the engine, the ECM switches on the EPC which is located in the instrument cluster and an entry is stored in the DTC memory of the ECM.
PRELIMINARY CHECK
Before performing any pin point test or component diagnosis, a preliminary check must be performed.
Connect the scan tool.
Switch the ignition on.
Using the scan tool, check for any stored or related DTC's. Refer to DIAGNOSTIC MODE 03 - READ DTC MEMORY .
If other DTC's are stored
Repair these DTC's first before performing the following procedure.
If no other DTC's are stored
Using the scan tool, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
Perform a road test to attempt to duplicate the customers complaint.
If the DTC returns
Perform the diagnostic procedure.
If the DTC does not return
The fault is intermittent or a sporadic condition may exist.
Check the suspected component, electrical harness and electrical harness connectors for damage, corrosion, loose or broken terminals.
If necessary, repair the faulty wiring connection.
Perform a road test to verify the repair.
If the DTC returns
Perform the diagnostic procedure.
If the DTC does not return
The fault may have been the result of a loose electrical connection.
Generate readiness code. Refer to READINESS CODE, SETTING .
End diagnosis.
READINESS CODE
The following table provides quick links to all specific locations in this service information.
| READINESS CODE, SETTING |
READINESS CODE, SETTING
Diagnostics are performed at regular intervals during normal vehicle operation. After repairing an emissions related system, a readiness code is generated by road testing the vehicle.
If a malfunction is recognized during the drive cycle, it will be stored in the DTC memory.
The OBD drive cycle operation will be monitored with a hand held diagnostic tool. Consult the manufacturer's instruction information for correct tool operation.
The readiness code is erased every time the DTC memory is erased or any time the battery is disconnected. If the DTC memory has been erased or the battery is disconnected, a new readiness code must be generated.
Only erase the DTC memory if a DTC has been stored.
General Recommendations
Most monitors will complete easier and quicker using a "steady-foot" and "smooth" acceleration during the drive cycle operation, cruise, and acceleration modes.
Operating Conditions
For the EVAP monitor test, the coolant temperature and the ambient air temperature must be between 10° C and 35° C with a difference between them no greater than 4° C. The ambient air temperature must not change more than 4° C during the drive cycle procedure (e.g. when driving out of a heated workshop in the winter).
Test requirements
- Erase the DTC memory «DIAGNOSTIC MODE 04 - ERASE DTC MEMORY»(ref-460545-S22784966642012032900000) .
- Coolant temperature must be between 80° C - 110° C.
- The Intake Air Temperature (IAT) must be between 10° C - 35° C.
- Battery voltage must be a minimum of 12.5 volts.
- Fuel tank level 1/4 - 3/4 full.
| WARNING | When performing the drive cycle operation, pay strict attention to driving conditions and please observe and obey all posted speed limits. Failure to follow these instructions may result in personal injury or possible death. |
Drive Cycle Procedure
Connect the scan tool.
Switch the ignition on and start the vehicle.
Idle the vehicle for 2-3 minutes. This executes the O2S Heater, Misfire, Secondary AIR, Fuel Trim, and Purge system monitors.
Drive the vehicle at 45-55 mph for a continuous 7 minute period, avoid stopping. This executes the EVAP, O2S, Fuel Trim, and Misfire monitors.
Accelerate the vehicle to an engine speed of 5000 RPM (with automatic transmission use the tip-tronic mode); lift off the throttle until the engine speed is around 1200 rpm. This executes the fuel cut off
Accelerate the vehicle smoothly to 60-65 mph, cruise constantly for 5 min, this executes the Catalyst; O2S, Misfire, Fuel Trim, and Purge System monitors.
Decelerate and idle the vehicle again for 3 minutes. This executes the Misfire, Secondary AIR, Fuel Trim, and Purge system monitors.
Check the status of the readiness code.
Note. Depending on the scan tool used. The readiness code status may be displayed as complete, passed or OK. 2
If any engine monitor fails the drive cycle test. Repeat the drive cycle test until all engine monitors have successfully run through and passed.
Note. When repeating the drive cycle operation for a failed EVAP monitor or thermostat-monitor, allow the engine to cool until the coolant temperature and the ambient air temperature are be between 10° C - 35° C with a difference between them no greater than 4° C is observed and repeat the drive cycle operation.
If the drive cycle operation fails again.
Check the DTC memory for stored DTC's DIAGNOSTIC MODE 03 - READ DTC MEMORY .
Repair the vehicle if necessary.
Repeat the drive cycle operation until all engine monitors have successfully run through and passed.
Remove the scan tool and switch the ignition off.
End of procedure.