Part 4

ENGINE CONTROL (EC) SYSTEM

Parameter Identification (PID)

Description

The parameter identification (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 2 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 Mazda-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 Mazda PID list provides definitions and values in appropriate units. For more information, refer to the Society of Automotive Engineers (SAE) document J2205.

The ETB has the following characteristics:

- The throttle actuator control (TAC) motor is a DC motor controlled by the PCM (requires 2 wires).
- There are 2 designs: parallel and in-line. The parallel design has the motor under the bore parallel to the plate shaft. The motor housing is integrated into the main housing. The in-line design has a separate motor housing.
- An internal spring is used in both designs to return the throttle plate to a default position. The default position is typically a throttle angle of 7 to 8 degrees from the hard stop angle.
- The closed throttle plate hard stop is used to prevent the throttle from binding in the bore (approximately 0.75 degree). This hard stop setting is not adjustable and is set to result in less airflow than the minimum engine airflow required at idle.
- The required idle airflow is provided by the plate angle in the throttle body assembly. This plate angle controls idle, idle quality, and eliminates the need for an IAC valve.
- There is one reference voltage and one signal return circuit between the PCM and the ETB. The reference voltage and the signal return circuits are shared with the reference voltage and signal return circuits used by the accelerator pedal position (APP) sensor. There are also 2 throttle position (TP) signal circuits for redundancy. The redundant TP signals are required for increased monitoring reasons. The first TP signal (TP1) has a negative slope (increasing angle, decreasing voltage) and the second signal (TP2) has a positive slope (increasing angle, increasing voltage). The TP2 signal reaches a limit of approximately 4.5 volts at approximately 45 degrees of throttle angle.

Generic OBD PID List

An X in the Freeze Frame column denotes both a mode 1 and mode 2 PID (real time and freeze frame).









- OL = Open loop, have not satisfied conditions for closed loop.
- Percent engine load adjusted for atmospheric pressure.

- CL = Closed loop using HO2S(s) as feedback for fuel control.
- OL DRIVE = Open loop due to driving conditions (heavy acceleration).
- OL FAULT = Open loop due to fault with all upstream HO2S sensors.
- CL FAULT = Closed loop fuel control, but fault with one upstream HO2S sensor on dual bank vehicles.

Mazda PID List

NOTE:This is not a complete list of Mazda PIDs available. This is a list of Mazda PIDs for engine control system troubleshooting.

















Freeze Frame Data

Description

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 remains in memory even if another emission-related DTC is stored, with the exception of misfire or fuel system DTCs. Once freeze frame data for a misfire or fuel system DTC is stored, it overwrites any previous data, and freeze frame data is no longer overwritten. When a DTC associated with the freeze frame data is erased or the DTCs are cleared, 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.





Some unique PIDs are stored in the keep alive memory (KAM) 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 could be more useful for misfire diagnosis than the generic freeze frame data. It is captured at the time of the highest misfire rate, and not when the DTC is stored at the end of a 1,000 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. Misfire Freeze-Frame PIDs





Flash Electrically Erasable Programmable Read Only Memory (EEPROM)

Description

The EEPROM is contained in an integrated circuit internal to the PCM. The 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 DTCs P1635 or P1639. The VID block in an existing PCM can also be tailored 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/Axle Ratio out of Acceptable Range. An incorrect tire/axle ratio is one of the main causes for DTC 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 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 is 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.
On selected 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 can be accomplished using the Misfire Monitor Neutral Profile Learn function on the scan tool.
Programming can be carried out by a local Mazda dealer or any non-Mazda facility. Refer to the scan tool manufacturer's instruction manual for details.

Neutral Profile Correction

In order for the misfire detection system to function correctly, any mechanical inaccuracies in the crankshaft position (CKP) sensor must be learned by the PCM. This information is stored in non-volatile memory (NVM) in the PCM. It is not cleared when the keep alive memory (KAM) is reset.
Neutral profile learning is accomplished using the scan tool any time a PCM is replaced. It should also be relearned any time the CKP sensor is replaced or major engine repairs have been completed.
To determine if the neutral profile learning has been completed, check the MPLRN PID using the scan tool. The PID should read YES if the neutral profile learning has been completed. If the PID reads NO, complete the neutral profile learning prior to diagnosing any misfire DTC.

Programming the VID Block for a Replacement PCM

The VID block on a replacement PCM is blank and requires programming. There are 2 procedures available. The first is an automatic data transfer from the old PCM to the new PCM, and the second is manual data entry into the new PCM.
Automatic data transfer is carried out if the old PCM is capable of communicating. This is done by using a scan tool to retrieve data from the old PCM before removing it from the vehicle. The stored data can be downloaded to the new PCM after it has been installed.
Carry out manual data entry if the old PCM is damaged or incapable of communicating. Remove and install a new PCM. Using a compatible scan tool, select and carry out the module/parameter programming, referring to the scan tool manufacturer's instruction manual. Make certain that all parameters are included. Failure to correctly program tire size in revolutions per mile, (rev/mile equals 63,360 divided by the tire circumference in inches), axle ratio, 4x4/4x2, and/or MSOF/ESOF may result in DTCs P1635 and P1639. You may be instructed to contact the As-Built Data Center for the information needed to manually update the VID block with the scan tool. Contact the center only if the old PCM cannot be used or the data is corrupt. For Mazda technicians, contact your National Hotline or the Professional Technician Society (PTS) website for As-Built data listed under the Service Publications Index. Non-Mazda technicians use the Motorcraft website, use the search function to find the Module Programming or As-Built Data.

Making Changes to the VID Block

A programmed PCM may require changes to be made to certain VID information to accommodate the vehicle hardware. Refer to Module Reprogramming on the scan tool.

Making Changes to the PCM Calibration

At certain times, the entire EEPROM needs to be completely reprogrammed. This is due to changes made to the strategy or calibration after production, or the need to reset the VID block because it has reached its limit. Refer to Module Reprogramming on the scan tool.

Diagnostic Monitoring Test Results - Mode 6

Mode 6 allows access to the results of on board diagnostic (OBD II) monitor diagnostic test results. The test values are stored at the time of the particular monitor completion. Refer to mode 6 on the scan tool for test information

Intermittent Diagnostic Techniques

Intermittent diagnostic techniques help find and isolate the root cause of intermittent concerns associated with the electronic engine control (EEC) system. The information is organized to help find the concern and carry out the repair. The process of finding and isolating an intermittent concern starts with recreating a fault symptom, accumulating PCM data, and comparing that data to typical values, then analyzing the results. Refer to the scan tool manufacturer's instruction manual for the functions described below.Before proceeding, be sure that:

- Customary mechanical system tests and inspections do not reveal a concern.
NOTE:Mechanical component conditions can make a PCM system react abnormally
- Service bulletins, if available, are reviewed.
- Quick Test and associated diagnostic subroutines have been completed without finding a concern, and the symptom is still present.

Re-creating the Fault

Recreating the concern is the first step in isolating the cause of the intermittent symptom. A thorough investigation should start with the customer information worksheet located in the back of this information. If freeze frame data is available, it may help in recreating the conditions at the time of a malfunction indicator lamp diagnostic trouble code (MIL DTC). Listed below are some of the conditions for recreating the concern:Conditions To Recreate Fault





Accumulating PCM Data

PCM data can be accumulated in a number of ways. This includes circuit measurements with a multimeter or IDS or equivalent tester PID data. Acquisition of PCM PID data using the IDS or equivalent tester is one of the easiest ways to gather information. Gather as much data as possible when the fault is occurring to prevent improper diagnosis. Data should be accumulated during different operating conditions and based on the customer description of the intermittent fault. Compare this data with the known good data values located in PID/DATA Monitor Reference.
This will require recording data in four conditions for comparison: 1) KOEO, 2) HOT IDLE, 3) 48 km/h (30 mph) and 4) 89 km/ h (55 mph).

Peripheral Inputs

Some signals may require certain peripherals or auxiliary tools for diagnosis. In some cases, these devices can be inserted into the measurement jacks of the scan tool or DMM. For example, connecting an electronic fuel pressure gauge to monitor and record the fuel pressure voltage reading and capturing the data would help find the fault.

Comparing PCM Data

This typically requires the comparison of the actual values from the vehicle to the typical values from the PID/DATA Monitor. The charts apply to different vehicle applications (engine and transmission).

Analyzing PCM Data

Look for abnormal events or values that are clearly incorrect. Inspect the signals for abrupt or unexpected changes. For example, during a steady cruise most of the sensor values should be relatively stable. Sensors such as throttle position (TP), mass air flow (MAF), and RPM that change abruptly when the vehicle is traveling at a constant speed are clues to a possible concern area.
Look for agreement in related signals. For example, if TP changes during acceleration, corresponding changes should occur in idle air control (IAC), RPM, and SPARK ADV PID.
Make sure the signals act in correct sequence. An increase in RPM after the TP is increased is expected. However, if RPM increases without a TP change, then a fault may exist.






Scroll through the PID data while analyzing the information. Look for sudden drops or spikes in the values. (Refer to the following TP1 example). Notice the major jump in the TP1 voltage while scrolling through the information. This example would require a smooth and progressive accelerator pedal travel during a key on and engine off mode.

Adaptive Fuel DTC Diagnostic Techniques

The Adaptive Fuel Diagnostic Trouble Codes (DTC) Diagnostic Techniques help isolate the root cause of the adaptive fuel concern. Before proceeding, attempt to verify if any driveability concerns are present. These diagnostic aids are meant as a supplement to the pinpoint test steps. For a description of fuel trim, see POWERTRAIN CONTROL SOFTWARE, FUEL TRIM. Obtain Freeze Frame Data: Freeze frame data is helpful in duplicating and diagnosing adaptive fuel concerns. The data (a snapshot of certain parameter identification (PID) values recorded at the time the DTC is stored in Continuous Memory) is helpful to determine how the vehicle was being driven when the concern occurred, and is especially useful on intermittent concerns. Freeze frame data, in many cases, helps to isolate possible areas of concern as well as rule out others. See FREEZE FRAME DATA for a more detailed description of this data.Using the LONGFT1 and LONGFT2 (Dual Bank Engines) PIDs: The LONGFT1/2 PIDs are useful for diagnosing fuel trim concerns. A negative PID value indicates that fuel is being reduced to compensate for a rich condition. A positive PID value indicates that fuel is being increased to compensate for a lean condition. It is important to know that there is a separate LONGFT value that is used for each RPM/load point of engine operation. When viewing the LONGFT1/2 PIDs, the values may change a great deal as the engine is operating at different RPM and load points. This is because the fuel system may have learned corrections for fuel delivery concerns that can change as a function of engine RPM and load. The LONGFT1/2 PIDs display the fuel trim currently being used at that RPM and load point. Observing the changes in LONGFT1/2 can help when diagnosing fuel system concerns. For example:

- A contaminated mass air flow (MAF) sensor results in matching LONGFT1/2 correction values that are negative at idle (reducing fuel), but positive (adding fuel) at higher RPM and loads.
- LONGFT1 values that differ greatly from LONGFT2 values rule out concerns that are common for both banks (for example, fuel pressure concerns, MAF sensor, etc. can be ruled out).
- Vacuum leaks result in large rich corrections (positive LONGFT1/2 value) at idle, but little or no correction at higher RPM and loads.
- A plugged fuel filter results in no correction at idle, but large rich corrections (positive LONGFT1/2 value) at high RPM and load.

Resetting Long Term Fuel Trims: Long term fuel trim corrections are reset by resetting the keep alive memory (KAM). See RESETTING THE KEEP ALIVE MEMORY (KAM). After making a fuel system repair, reset the KAM. For example, if dirty/plugged injectors cause the engine to run lean and generate rich long term corrections, installing new injectors and not resetting the KAM causes the engine to run very rich. The rich correction eventually leans out during closed loop operation, but the vehicle may have poor driveability and high carbon monoxide (CO) emissions while it is learning.
DTCs P0171/P0174 System Too Lean Diagnostic Aids:
NOTE:If the system is lean at certain conditions, then the LONGFT PID would be a positive value at those conditions, indicating that increased fuel is needed.
The ability to identify the type of lean condition causing the concern is crucial to a correct diagnosis.Air Measurement System: With this condition, the engine runs rich or lean of stoichiometry (14.7:1 air/fuel ratio) if the PCM is not able to compensate enough to correct for the condition. One possibility is that the mass of air entering the engine is actually greater than what the MAF sensor is indicating to the PCM. For example, with a contaminated MAF sensor, the engine runs lean at higher RPM because the PCM delivers fuel for less air than is actually entering the engine. Examples:

- The MAF sensor measurement is inaccurate due to a corroded connector, contaminated or dirty connector. A contaminated MAF sensor typically results in a rich system at low airflows (PCM reduces fuel) and a lean system at high airflows (PCM increases fuel).

Vacuum Leaks/Unmetered Air: With this condition, the engine runs lean of stoichiometry (14.7:1 air/fuel ratio) if the PCM is notable to compensate enough to correct for the condition. This condition is caused by unmetered air entering the engine, or due to a MAF sensor concern. In this situation, the volume of air entering the engine is actually greater than what the MAF sensor is indicating to the PCM. Vacuum leaks are normally most apparent when high manifold vacuum is present (for example, during idle or light throttle). If freeze frame data indicates that the concern occurred at idle, a check for vacuum leaks/unmetered air is the best starting point. Examples:

- Loose, leaking, or disconnected vacuum lines
- Intake manifold gaskets, or O-rings
- Throttle body gaskets
- Brake booster
- Air inlet tube
- Stuck/frozen/aftermarket positive crankcase valve (PCV)
- Unseated engine oil dipstick.

Insufficient Fueling: With this condition, the engine runs lean of stoichiometry (14.7:1 air/fuel ratio) if the PCM is not able to compensate enough to correct for the condition. This condition is caused by a fuel delivery system concern that restricts or limits the amount of fuel being delivered to the engine. This condition is normally apparent as the engine is under a heavy load and at high RPM, when a higher volume of fuel is required. If the freeze frame data indicates that the concern occurs under a heavy load and at higher RPM, a check of the fuel delivery system (checking fuel pressure with engine under a load) is the best starting point. Examples:

- Low fuel pressure (fuel pump, fuel filter, fuel leaks, restricted fuel supply lines)
- Fuel injector concerns

Exhaust System Leaks: In this type of condition, the engine runs rich of stoichiometry (14.7:1 air/fuel ratio) because the fuel control system is adding fuel to compensate for a perceived (not actual) lean condition. This condition is caused by the heated oxygen sensor (HO2S) sensing the oxygen (air) entering the exhaust system from an external source. The PCM react to this exhaust leak by increasing fuel delivery. This condition causes the exhaust gas mixture from the cylinder to be rich. Examples:

- Exhaust system leaks upstream or near the HO2S
- Cracked/leaking HO2S boss
- Inoperative secondary air injection system

DTCs P0172/P0175 System Too Rich Diagnostic Aids:
NOTE:If the system is rich at certain conditions, then the LONGFT PID would be a negative value at that airflow, indicating that decreased fuel is needed.
System rich concerns are caused by fuel system concerns, although the MAF sensor and base engine (for example, engine oil contaminated with fuel) should also be checked.Air Measurement System: With this condition, the engine runs rich or lean of stoichiometry (14.7:1 air/fuel ratio) if the PCM is not able to compensate enough to correct for the condition. One possibility is that the mass of air entering the engine is actually less than what the MAF sensor is indicating to the PCM. For example, with a contaminated MAF sensor, the engine runs rich at idle because the PCM delivers fuel for more air than is actually entering the engine. Examples:

- MAF sensor measurement inaccurate due to a corroded connector, contamination/dirt. A contaminated MAF sensor typically results in a rich system at low airflows (PCM reduces fuel) and a lean system at high airflows (PCM increases fuel).

Fuel System: With this condition, the engine runs rich of stoichiometry (14.7:1 air/fuel ratio), if the PCM is not able to compensate enough to correct for the condition. This situation causes a fuel delivery system that is delivering excessive fuel to the engine.
Examples:

- Fuel pressure regulator (mechanical returnless fuel systems) causes excessive fuel pressure (system rich at all airflows), fuel pressure is intermittent, going to pump deadhead pressure, then returning to normal after the engine is turned off and restarted.
- Fuel injector leaks (injector delivers extra fuel).
- EVAP canister purge valve leak (if the canister is full of vapors, introduces extra fuel).
- Fuel rail pressure (FRP) sensor (electronic returnless fuel systems) concern causes the sensor to indicate a lower pressure than actual. The PCM commands a higher duty cycle to the fuel pump driver module (FPDM), causing high fuel pressure (system rich at all airflows).

Air Inlet System: A restriction within any of the following components may be significant enough to affect the ability of the PCM adaptive fuel control.

- Air inlet tube
- Air cleaner element
- Air cleaner assembly
- Resonators
- Clean air tube

Base Engine: Engine oil contaminated with fuel can contribute to a rich-running engine.