Overview
When following powertrain diagnostics on vehicles with on board diagnostic (OBD), the system may be checked by an off-board tester referred to as a scan tool. This article contains information for carrying out diagnostics with a scan tool. A scan tool has certain generic capabilities that are standard across the automotive industry in the United States and Canada. All functions are selected from a menu. Refer to the instruction manual provided by the tool manufacturer.
International Standards Organization (ISO) 14229 DTC Descriptions
The ISO 14229 DTC is a set of common requirements for diagnostic systems. The scan tool displays a failure type and a status type with the DTC. The types display additional information on the scan tool for the condition that set the DTC. For a list of failure type descriptions, refer to «POWERTRAIN CONTROL SOFTWARE», International Standards Organization (ISO) 14229 Diagnostic Trouble Code (DTC) Descriptions.
Description
All on board diagnostic (OBD) scan tools support the clearing of continuous DTCs and resetting of emission monitors information in the PCM.
The clearing of the continuous DTCs allows the scan tool to command the PCM to clear and reset all emission related diagnostic information.
The following events occur when the continuous DTCs and the emission monitors information is cleared from the PCM
- the number of DTCs is reset
- the DTCs are cleared (on vehicles with permanent DTCs, additional vehicle operation is required to complete and pass the appropriate monitors to complete the clearing of permanent DTCs)
- the freeze frame data is cleared
- the diagnostic monitoring test results are reset
- the status of the OBD system monitors is reset
Resetting the KAM returns the PCM memory to its default setting. Adaptive learning contents such as adaptive airflow, idle speed, refueling event, and fuel trim are included. Clearing the continuous diagnostic trouble codes (DTCs) and resetting the emission monitors information in the PCM, is part of a KAM reset. Refer to «CLEAR THE CONTINUOUS DIAGNOSTIC TROUBLE CODES (DTCS) AND RESET THE EMISSION MONITORS INFORMATION IN THE POWERTRAIN CONTROL MODULE (PCM)». Both can be useful in post-repair testing.
After the KAM has been reset, the vehicle may exhibit certain driveability concerns. It is necessary to allow the engine to idle at normal operating temperature with the A/C off for 2 minutes. Then drive the vehicle to allow the PCM to learn the values for optimum driveability and performance.
This function may not be supported by all scan tools. Refer to the scan tool manufacturer's instruction manual.
All on board diagnostic (OBD) scan tools display the OSR test. The OSR displays the supported monitors on the vehicle and the status of all monitors (complete or not complete) at that time. Fuel, misfire, and comprehensive component monitors (CCMs) run continuously and always display a YES status. Clearing the continuous diagnostic trouble codes (DTCs) and resetting the emission monitors information in the PCM, or resetting the keep alive memory (KAM) causes the non-continuous monitors to change to a NO status.
A detailed description of completing the OBD monitors is found in this information. Refer to «ON BOARD DIAGNOSTIC (OBD) DRIVE CYCLE».
| WARNING | SAFETY MUST BE OBSERVED WHEN USING OSC. FAILURE TO FOLLOW THESE INSTRUCTIONS MAY RESULT IN PERSONAL INJURY. |
The OSC aids in diagnosing output actuators associated with the PCM for the engine. This mode allows the technician to command the individual actuator state. For example, the output can be enabled or disabled, the duty cycle or the angle of the output can be increased or decreased. The OSC helps test the electrical, hydraulic or mechanical components of the vehicle. This function is supported by the vehicle strategy but may not be present on all vehicles or available on all scan tools.
Retrieve the continuous diagnostic trouble codes (DTCs) and carry out a key ON, engine OFF (KOEO) and key ON, engine running (KOER) on demand self-test before using any OSC. Any DTCs related to the transmission range (TR) sensor, output shaft speed (OSS) sensor or the vehicle speed sensor (VSS) must be fixed or the PCM will not allow the OSC to operate.
Each OSC function has a unique set of vehicle operating requirements the technician is required to meet before operating the OSC. If the vehicle requirements are not met while commanding the OSC value, an error message appears. When the error message is received, OSC is canceled.
To confirm the scan tool sent the OSC value and the PCM has accepted the OSC substitution, a corresponding parameter identification (PID) for each OSC parameter must be monitored.
The PID mode allows access to PCM information. This includes analog and digital signal inputs and outputs along with calculated values and the system status. There are two types of PID lists available and both are used throughout this information. The first is the generic (J1979) OBD PID list. This is a standard set of PIDs that all scan tools must be able to access. The second is a Ford specific (J2190) list which can be accessed by an appropriate scan tool. When accessing any of these PIDs, the values are continuously updated. The generic or Ford PID list provides definitions and values in appropriate units.
The flash EEPROM is contained in an integrated circuit internal to the PCM. The flash EEPROM contains the vehicle strategy including calibration information specific to the vehicle, and is capable of being programmed or flashed repeatedly.
As part of the calibration there is an area referred to as the vehicle identification (VID) block. The VID block is programmed when installing a new PCM as described under Programming the VID Block for a Replacement PCM. Failure to carry out this procedure may generate DTC P1635 or P1639. The VID block in an existing PCM can also be programmed to accommodate various hardware or parameter changes made to the vehicle since production. Failure to carry out this procedure correctly may generate DTC P1635, Tire or Axle Ratio out of Acceptable Range. An incorrect tire or axle ratio is one of the main causes for DTC P1635. This is described under Making Changes to the VID Block and also under Making Changes to the PCM Calibration. The VID block contains many items used by the strategy for a variety of functions. Some of these items include the vehicle identification number (VIN), octane adjust, fuel octane, fuel type, vehicle speed limit, tire size, axle ratio, the presence of speed control, and 4 wheel drive electronic shift on the fly (ESOF) versus manual shift on the fly (MSOF). Only items applicable to the vehicle hardware and supported by the VID block are displayed on the scan tool.
When changing items in the VID block, the strategy places range limits on certain items such as tire and axle ratio. The number of times the VID block may be reconfigured is limited. When this limit is reached, the scan tool displays a message indicating the need to flash the PCM again to reset the VID block.
For Fiesta, the instrument panel cluster (IPC) communicates the VIN to the PCM. When a new PCM is installed, the PCM obtains the VIN the first time the ignition is turned to the ON position. If there is a concern with the VIN not being received or being invalid, DTC P0630 is set.
On some vehicles, the VIN, tire size, axle ratio, and cruise control configuration are communicated to the PCM from the body control module (BCM). If a new PCM is installed, the new PCM obtains this data the first time the ignition is turned to the ON position. If the data is not received, DTCs U0140 and U0422 set and DTC P0630 may set. If the data is received but the values are invalid or not configured, DTC U0422 sets and DTC P0630 may set. If the data received is valid but the proper learning command has not been received from the diagnostic tool, DTC P160A sets. There are associated PIDs to indicate the status of each data item.
On vehicles equipped with permanent DTC reporting capabilities, neutral profile correction should be learned after a PCM replacement in order to activate the misfire monitor. This is accomplished using the Misfire Monitor Neutral Profile Learn function on the scan tool. Refer to the scan tool manufacturer's instruction manual for details.
Description of On Board Diagnostic (OBD) Drive Cycle
The following procedure is designed to execute and complete the OBD monitors. To complete a specific monitor for repair verification, follow steps 1 through 4 , then continue with the step described by the appropriate monitor found under the OBD Monitor Exercised column. For the evaporative emissions (EVAP) monitor to run, the ambient air temperature must be between 4.4 to 37.8°C (40 to 100°F), and the altitude below 2, 438 meters (8, 000 feet). If the OBD monitors must be completed in these conditions, the PCM must detect them once (twice on some applications) before the EVAP monitor can be bypassed and OBD monitors readied. The EVAP bypassing procedure is described in the following drive cycle.
Use a scan tool to carry out the OBD drive cycle. Refer to the scan tool manufacturer's instruction manual for each described function.
A detailed description for clearing the continuous diagnostic trouble codes (DTCs) is found in this information. Refer to «CLEAR THE CONTINUOUS DIAGNOSTIC TROUBLE CODES (DTCS) AND RESET THE EMISSION MONITORS INFORMATION IN THE POWERTRAIN CONTROL MODULE (PCM)».
See also:
• TYPICAL DIAGNOSTIC REFERENCE VALUES