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Home >> Mazda Truck >> 2009 >> B2300 L4-2.3L >> Repair and Diagnosis >> Powertrain Management >> Computers and Control Systems >> Description and Operation >> Electronic Engine Control (EEC) System >> Part 3

Part 3




Part 3 of 3

Continued From Part 2 Part 2

Communication Error

It is possible to receive a communication error from a IDS or equivalent tester when initiating a diagnostic test or accessing PIDs. The communication error can be caused by operator error, the vehicle wiring, connectors, the PCM or other control modules connected to the DLC wiring. The PCM will respond to a IDS or equivalent tester whenever the tool requests a test. These are not DTCs. Listed below are numeric codes and generic descriptions that a scan tool may display when trying to perform some PCM operations. It is possible to get other numeric codes not listed. For a complete list of communication response codes, see Society of Automotive Engineers (SAE) document J2190 enhanced E/E Diagnostic Test Modes. Some are normal responses to valid requests. The others are communication error responses. If the tool displays any of the communication error responses check scan tool connections, cable/adapters and entry of vehicle information.





Vehicle Check/Preparation
Visual Checks

- Inspect the air cleaner and inlet ducting.
- Check all engine vacuum hoses for damage, leaks, cracks, kinks and proper routing.
- Check EEC system wiring harness for proper connections, bent or broken pins, corrosion, loose wires and proper routing.
- Check the PCM, sensors and actuators for physical damage.
- Check the engine coolant for proper level and mixture.
- Check the transmission fluid level and quality.
- Make all necessary repairs before continuing with the Quick Test.Vehicle Preparation

- Perform ALL safety steps required to start and run vehicle tests. Apply parking brake, place shift lever firmly into PARK position (NEUTRAL on manual transmission) and block drive wheels.
- Turn off all electrical loads: radios, lamps, A/C, blower and fans.
- Start engine and bring up to normal operating temperature before running quick test.

Intermittent Diagnostic Techniques

Intermittent diagnostic techniques help find and isolate the root cause of intermittent faults associated with the EEC system. The information is organized to help find the fault and perform the repair. The process of finding and isolating an intermittent starts with re-creating a fault symptom, accumulating PCM data and comparing that data to typical values, then analyzing the results.Before proceeding, be sure that:

- Customary mechanical system tests and inspections do not reveal a concern. (Remember, mechanical component conditions can make a PCM system react abnormally.)
- Service Bulletins, if available, are reviewed.
- Quick test and associated pinpoint tests have been completed without finding a fault, and the symptom is still present.

Re-creating the Fault

Re-creating the fault is the first step in isolating the cause of the intermittent symptom. A thorough investigation should start with a review of the customer concern on the work order, if necessary talk to the service advisor or contact the customer to obtain more details about the concern. If freeze frame data is available, it may help in re-creating the conditions at the time of a MIL DTC. Listed below are some of the conditions for re-creating the fault:

CONDITIONS TO RE-CREATE 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. Pinout Values and Diagnostic ParametersThis 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).

Analyzing Data From Playback of Stored PIDs

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 TP, MAF and RPM that change abruptly when the vehicle is traveling at a constant speed are clues to a possible fault area.
Look for agreement in related signals. For example, if TP is changed during acceleration, a corresponding change should occur in IAC, RPM and SPARK ADV RD.
Make sure the signals act in proper 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.

Comparing PCM Data

After the PCM values have been acquired, it is necessary to determine the fault area. Typically, it will require the comparison of the actual values from the vehicle to the typical values. See Pinout Values and Diagnostic ParametersThe charts apply to different vehicle applications (i.e., model, engine, transmission, etc.).

Diagnostic Monitoring Test Results

The purpose of this test mode is to allow access to the results of OBD II monitor diagnostic test results. The test values that are stored at the time of the particular monitor completion are displayed when the particular test identification is requested. See the following table for test information.

DIAGNOSTIC MONITORING TEST RESULTS TABLE

Diagnostic Monitoring Test Results Table (Part 1):





Diagnostic Monitoring Test Results Table (Part 2):





a= hexadecimal
b= These test IDs are signed values. Scan tool may display them as unsigned.

The conversion is done as follows: If the value is > 32767 then complement (change 0's to 1's and 1's to 0's), add 1 and a negative sign.
Example:





On-Board System Readiness

Description

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 CONT status. Only a PCM reset or a keep alive RAM reset will cause the non-continuous monitors to reinitialize to NO status.

Freeze Frame Data

Description

Freeze frame data allows access to emission-related values from specific generic PIDs. These values are stored the instant an emission-related DTC is stored in continuous memory. This provides a snapshot of the conditions that were present when the DTC was stored. When 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 a PCM memory reset 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. See Freeze Frame Charts.

Output Test Mode

Description

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 the IDS or equivalent tester and may not be available on all generic scan tools.
As a safety precaution, output test mode will default to its normal state after 10 minutes, after the vehicle is started or after cycling the key off then on. See - On - Board Diagnostic Tests.

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.Failure
to follow these instructions may result in personal injury.

Powertrain Control Module (PCM) Reset

Description

All OBDII scan tools support the PCM reset.The PCM reset allows the scan tool to command the PCM to clear all emission-related diagnostic information. When resetting the PCM, a DTC P1000 will be stored in the PCM until all the OBD II system monitors or components have been tested to satisfy a drive cycle, without any other faults occurring. For more information about a drive cycle, See Drive Cycles.The following events occur when a PCM reset is performed:

- Clears the number of DTCs
- Clears the DTCs
- Clears the freeze frame data
- Clears diagnostic monitoring test results
- Resets status of the OBD II system monitors
- Sets DTC P1000

NOTE:When using the IDS or equivalent tester to perform a PCM reset, press the CLEAR button. This function is performed only after retrieval of continuous DTCs.

Resetting Keep Alive Random Access Memory (RAM)

Resetting keep alive RAM will return PCM memory to its default setting. Adaptive learning contents such as idle and fuel trim are included.
After keep alive RAM has been reset, the vehicle may exhibit certain driveability concerns. It will be necessary to drive the vehicle to allow the PCM to relearn values for optimum driveability and performance.A keep alive RAM reset is done as follows:

- During KOEO with the IDS or equivalent tester, use the reset keep alive memory function. This is found in the Active Command Modes menu on the IDS or equivalent tester.
- If a generic scan tool is used, this function may not be supported. See scan tool manufacturer's instruction manual.
- If an error message is received or the scan tool does not support this function, disconnecting the negative battery cable for a minimum of 5 minutes may be used as an alternative procedure.

Resetting Keep Alive Memory (KAM)

Resetting keep alive memory will return PCM memory to its default setting. Adaptive learning contents such as idle speed, refueling event, and fuel trim are included. A PCM reset is also part of a KAM reset. Both can be useful in post repair retest.
After keep alive memory has been reset, the vehicle may exhibit certain driveability concerns. It will be necessary to drive the vehicle to allow the PCM to relearn values for optimum driveability and performance.
This function may not be supported by all scan tools. See the IDS or equivalent tester manufacturer 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.

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