Overview
The Diagnostic Methods article provides information on routine diagnostic tasks.
When following powertrain diagnostics on OBD II vehicles, the system may be checked by an off-board tester referred to as a scan tool. This article contains information for performing diagnostics with a scan tool. A scan tool has certain generic capabilities that are standard across the automotive industry in the United States. All functions are selected from a menu. Refer to the instruction manual provided by the tool manufacturer.
Description
The Parameter Identification (PID) mode allows access to powertrain control module (PCM) information. This includes analog and digital signal inputs and outputs along with calculated values and system status. There are two types of PID lists available and both are used throughout this service information. The first is the Generic (J1979) OBDII PID list. This is a standard set of PIDs for all manufacturers all scan tools must be able to access. The second is a Ford specific (J2190) list which can be accessed by an adequate scan tool. When accessing any of these PIDs, the values will be continuously updated. The Generic or Ford PID list provides definitions and values in appropriate units. For more information, refer to the Society of Automotive Engineers (SAE) J2205 document.
All OBD II scan tools display the On-Board System Readiness (OSR) Test. The OSR will display 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 run continuously and will always display "YES" status. Clearing the continuous diagnostic trouble codes (DTCs) and resetting the emission monitors information in the powertrain control module (PCM) or resetting the keep alive memory (KAM) causes the non-continuous monitors to change to a "NO" status.
Freeze Frame Data allows access to emission-related values from specific generic PIDs. These values are stored when an emission-related DTC is stored in Continuous Memory. This provides a snapshot of the conditions that were present when the DTC was stored. Once one set of freeze frame data is stored, this data will remain in memory even if another emission-related DTC is stored, with the exception of Misfire or Fuel System DTCs. Once freeze frame data for Misfire or Fuel System DTC is stored, it will overwrite any previous data, and freeze frame will not be further overwritten. When a DTC associated with the freeze frame is erased or clearing the continuous diagnostic trouble codes (DTCs) and resetting the emission monitors information in the powertrain control module (PCM) is performed, new freeze frame data can be stored again. In the event of multiple emission-related DTCs in memory, always note the DTC for the freeze frame data.
| Acronym | Description | Measurement Units |
|---|---|---|
| ECT | Engine Coolant | DEGREES |
| FUELSYS1 | Open/Closed Loop1 | OL/CL/OL DRIVE/OL FAULT/CL FAULT |
| FUELSYS2 | Open/Closed Loop2 | OL/CL/OL DRIVE/OL FAULT/CL FAULT |
| LONGFT1 | Long Term Fuel Bank1 | PERCENT |
| LONGFT2 | Long Term Fuel Bank2 | PERCENT |
| LOAD | Calculated Load Value | PERCENT |
| RPM | Engine RPM | R/MIN |
| SHRTFT1 | Short Term Fuel Bank1 | PERCENT |
| SHRTFT2 | Short Term Fuel Bank2 | PERCENT |
| VSS | Vehicle Speed | MPH-KMH |
FREEZE FRAME DATA
Some unique parameters (PIDs) are stored in the Keep Alive Memory of the PCM to help in diagnosing the root cause of misfires. These PIDs are collectively called misfire freeze-frame (MFF) data. These parameters are separate from the generic freeze-frame data that is stored for every MIL code. They are used for misfire diagnosis only. The MFF data is more useful for misfire diagnosis than the normal diagnosis only. It is captured at the time of the highest misfire rate and not when the DTC is stored at the end of a 1000 or 200 revolution block. (Generic freeze-frame data for misfire can be stored minutes after the misfire actually occurred.)
Note. MFF PIDs are supported on all vehicles but may not be available on all scan tools because enhanced PID access may vary by scan tool manufacturer.
| PID Name | Description | PID # | Measurement Units |
|---|---|---|---|
| MFF RPM | Engine RPM at the time of misfire | 16D3 | RPM |
| MFF LOAD | Engine load at the time of misfire | 16D4 | PERCENT |
| MFF VS | Vehicle speed at the time of misfire | 16D5 | MPH/KPH |
| MFF IAT | Intake air temperature at the time of misfire | 16D6 | DEGREES |
| MFF SOAK | Engine-off soak time at the time of misfire | 16D7 | MINUTES |
| MFF RNTM | Engine running time at the time of misfire | 16D8 | SECONDS" |
| MFF EGR | EGR DPFE sensor at the time of misfire | 16D9 | VOLTAGE |
| MFF TP | Throttle Position at time of misfire | 16DA | VOLTAGE |
| MFF T CNT | Number of driving cycles at the time of misfire (at least one 1,000 rev block) | 16DC | # TRIPS |
| MFF PNP MP LRN | 1= in drive during the time of misfire 1= Misfire wheel profile learned in KAM | 16DD b1 16DD b0 | MODE NONE |
MISFIRE FREEZE-FRAME PIDs
The Output Test Mode (OTM) aids in servicing output actuators associated with the PCM. This mode allows the technician to energize and de-energize most of the system output actuators on command. When entering OTM, the outputs can be turned off and on without activating the fan control. The low and high speed fan control(s) may be turned on separately without energizing the other outputs. This function is supported by each vehicle strategy and may not be available on all scan tools.
As a safety precaution, Output Test Mode will default to the off state after 10 minutes and fuel pump off after approximately 7-10 seconds. OTM will also turn off after the vehicle is started or after cycling the key off then on.
| WARNING | SAFETY MUST BE OBSERVED WHEN USING OUTPUT TEST MODE: WHEN ALL OUTPUTS ARE ON, THE ELECTRIC FUEL PUMP IS BRIEFLY ENERGIZED, SO MAKE SURE FUEL SYSTEM IS INTACT AND IS NOT BEING SERVICED AT THIS TIME. WHEN LOW SPEED OR HIGH SPEED FAN CONTROL(S) ARE TURNED ON, MAKE SURE FAN BLADES ARE CLEAR OF ANY OBSTRUCTION. |
Note. Clear the continuous diagnostic trouble codes (DTCs) and reset the emission monitors information in the powertrain control module (PCM) was previously called PCM reset.
All 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/reset all emission-related diagnostic information. While carrying out this operation a DTC P1000 will be stored in the PCM until all the OBD system monitors or components have been tested to satisfy a drive cycle without any other faults occurring. For more information about a drive cycle, refer to «DRIVE CYCLES» in this article.
The following events occur when the continuous DTCs and emission monitors information is cleared from the PCM
- Clears the number of DTCs.
- Clears the DTCs.
- Clears the freeze frame data.
- Clears the diagnostic monitoring test results.
- Resets the status of the OBD system monitors.
- Sets DTC P1000.
Resetting the KAM returns the PCM memory to its default setting. Adaptive learning contents such as idle speed, refueling event, and fuel trim are included. To clear the continuous DTCs in the PCM and have it reset the emissions monitors information, is also 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)» in this article. Both can be useful in post repair retest.
After the KAM has been reset, the vehicle may exhibit certain driveability concerns. It is necessary to 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.
If an error message is received or the scan tool does not support this function, disconnecting the battery ground cable for a minimum of 5 minutes may be used as an alternative procedure.
Flash Electrically Erasable Programmable Read Only Memory (EEPROM) is contained in an Integrated Circuit (IC) internal to the PCM. The EEPROM contains the vehicle strategy including calibration information specific to the vehicle and is capable of being reprogrammed or reflashed repeatedly.
As part of the calibration there is an area referred to as the Vehicle Identification (VID) block. The VID block must be programmed when replacing the PCM as described under Programming the VID Block for a Replacement PCM.
Failure to perform this procedure may generate fault codes: P1635, P1639, VID Block not programmed or is corrupt. The VID block in an existing PCM can also be tailored to accommodate various hardware/parameter changes made to the vehicle since production. Failure to perform this procedure properly may generate fault code: P1635, Tire/Axle Ratio out of Acceptable Range is one of the main causes for code: P1639. 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 VIN number, octane adjust, fuel octane, fuel type, vehicle speed limit, tire size, axle ratio, the presence of speed control and four wheel drive electronic shift on the fly versus manual shift on the fly. Only items applicable to vehicle hardware and supported by the VID block will be displayed on the scan tool.
When changing items in the VID block, the strategy will place range limits on certain items such as tire and axle ratio. The VID block is also limited to the number of times to be reconfigured. When this limit is reached, the scan tool will display a message indicating the need to flash the PCM again to reset the VID block.
Each of the procedures described below use the Worldwide Diagnostic System (WDS). Reprogramming can be performed by a local Ford dealer for any non Ford facility. There are other Enhanced Scan Tools that may have reprogramming capabilities available. Refer to the manufacturers users manual for details.
Description of OBD II Drive Cycle
The following procedure is designed to execute and complete the OBDII monitors and to clear the Ford P1000, I/M readiness code. 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 "OBDII Monitor Exercised" column. When the ambient air temperature is outside 4.4 to 37.8°C (40 to 100 °F), or the altitude is above 2438 meters (8000 feet), the EVAP monitor will not run. If the P1000 code must be cleared in these conditions, the PCM must detect them once (twice on some applications) before the EVAP monitor can be "bypassed" and the P1000 cleared. The EVAP "bypassing" procedure is described in the following drive cycle.
The OBDII Drive Cycle will be performed using a scan tool. Consult the instruction manual for each described function.
Note. A detailed description for clearing the DTCs is found in this article. Refer to «CLEAR THE CONTINUOUS DIAGNOSTIC TROUBLE CODES (DTCS) AND RESET THE EMISSION MONITORS INFORMATION IN THE POWERTRAIN CONTROL MODULE (PCM)».
Basic circuit checks help to minimize pinpoint test steps by providing a procedure to diagnose harness faults associated with the Electronic Engine Control (EC) System. The following techniques provide helpful reminders for diagnosing open circuits (continuity), shorts to ground and shorts to power.
Note. The suspect circuit must be isolated before testing. When disconnecting any harness connector, always inspect for damaged or pushed out pins, corrosion and loose wires. Repair as necessary. The digital multimeter must be set to the correct scale. The techniques do not apply in all situations, therefore, it is necessary to follow each pinpoint test step accurately and completely. General resistance and voltage values are specified below. Always use the pinpoint test values if they differ. Always turn the key to the OFF position unless directed otherwise by the pinpoint test.
Each of the following procedures will require the powertrain control module (PCM) and component to be disconnected to isolate the harness.