Part 3
ENGINE CONTROL (EC) SYSTEM
Exhaust Manifold Runners
The exhaust manifold runners collect exhaust gases from engine cylinders. The number of exhaust manifolds and exhaust manifold runners depends on the engine configuration and number of cylinders.
Exhaust Pipes
Exhaust pipes are usually treated during manufacturing with an anti-corrosive coating agent to increase the life of the product. The pipes serve as guides for the flow of exhaust gases from the engine exhaust manifold through the catalytic converter and the muffler
Heated Oxygen Sensor (HO2S)
The HO2Ss provide the PCM with voltage and frequency information related to the oxygen content of the exhaust gas.
Muffler
Mufflers are usually treated during manufacturing with an anti-corrosive coating agent to increase the life of the product. The muffler reduces the level of noise produced by the engine, and also reduces the noise produced by exhaust gases as they travel from the catalytic converter to the atmosphere.
Accelerator Pedal Position (APP) Sensor
Depending on the application either a 2-track or 3-track APP sensor is used.
Electronic Throttle Control (ETC) System Strategy
The torque-based ETC strategy was developed to improve fuel economy and to accommodate variable camshaft timing (VCT). This is possible by not coupling the throttle angle to the driver pedal position. Uncoupling the throttle angle (produce engine torque) from the pedal position (driver demand) allows the powertrain control strategy to optimize fuel control and transmission shift schedules while delivering the requested wheel torque.
The ETC monitor system is distributed across 2 processors within the PCM: the main powertrain control processor unit (CPU) and a separate monitoring processor. The primary monitoring function is carried out by the independent plausibility check (IPC) software, which resides on the main processor. It is responsible for determining the driver-demanded torque and comparing it to an estimate of the actual torque delivered. If the generated torque exceeds driver demand by a specified amount, appropriate corrective action is taken.ETC System With A 3-Track APP Sensor Failure Mode And Effects Management
a ETC illuminates or displays a message on the message center immediately; MIL illuminates after 2 driving cycles ETC System With A 2-Track APP Sensor Failure Mode And Effects Management
Electronic Throttle Monitor Operation
a Monitor execution is continuous. Monitor false detection duration is less than 1 second to register a concern.
APP and TP Sensor Inputs
Accelerator Pedal Position (APP) Sensor Check
a Correlation and range/performance - sensor disagreement between processors internal to the PCM. Monitor execution is continuous. Monitor false detection duration is less than 1 second to register a concern. See - .Throttle Position (TP) Sensor Check
a Correlation and range/performance - sensor disagreement between processors internal to the PCM, TP inconsistent with requested throttle plate position. Monitor execution is continuous. Monitor false detection duration is less than 1 second to register a concern. See - .
Electronic Throttle Actuator Control (TAC) Output
a For all DTCs, in addition to the MIL, the powertrain malfunction indicator (wrench) is on for the concern that caused the FMEM action. Monitor execution is continuous. Monitor false detection duration is less than 5 seconds to register a concern.
Variable Camshaft Timing (VCT) System
Overview
The VCT system enables rotation of the camshaft(s) relative to the crankshaft rotation as a function of engine operating conditions. There are 4 types of VCT systems.
- Exhaust phase shifting (EPS) system - the exhaust cam is the active cam being retarded.
- Intake phase shifting (IPS) system - the intake cam is the active cam being advanced.
- Dual equal phase shifting (DEPS) system - both intake and exhaust cams are phase shifted and equally advanced or retarded.
- Dual independent phase shifting (DIPS) system - where both the intake and exhaust cams are shifted independently.
All systems have four operational modes: idle, part throttle, wide open throttle (WOT), and default mode. At idle and low engine speeds with closed throttle, the PCM determines the phase angle based on air flow, engine oil temperature and engine coolant temperature. At part and wide open throttle the PCM determines the phase angle based on engine RPM, load, and throttle position. VCT systems provide reduced emissions and enhanced engine power, fuel economy and idle quality. IPS systems also have the added benefit of improved torque. In addition, some VCT system applications can eliminate the need for an external exhaust gas recirculation (EGR) system. The elimination of the EGR system is accomplished by controlling the overlap time between the intake valve opening and exhaust valve closing. Currently, both the IPS and DEPS systems are used.
The VCT system consists of an electric hydraulic positioning control solenoid, a camshaft position (CMP) sensor, and a trigger wheel. The CMP trigger wheel has a number of equally spaced teeth equal to the number (n) of cylinders on a bank plus one extra tooth (n+1). Four cylinder engines use a CMP 4+1 tooth trigger wheel. V6 engines use a CMP 3+1 tooth trigger wheel. The extra tooth placed between the equally spaced teeth represents the CMP signal for that bank. A crankshaft position (CKP) sensor provides the PCM with crankshaft positioning information in 10 degree increments.
VCT System
1. The PCM receives input signals from the intake air temperature (IAT), engine coolant temperature (ECT), engine oil temperature (EOT), CMP, throttle position (TP), mass air flow (MAF), and CKP sensors to determine the operating conditions of the engine. At idle and low engine speeds with closed throttle, the PCM controls the camshaft position based on ECT, EOT, IAT, and MAF. During part and wide open throttle, the camshaft position is determined by engine RPM, load and throttle position. The VCT system does not operate until the engine is at normal operating temperature.
2. The VCT system is enabled by the PCM when the correct conditions are met.
3. The CKP signal is used as a reference for CMP positioning.
4. The VCT solenoid valve is an integral part of the VCT system. The solenoid valve controls the flow of engine oil in the VCT actuator assembly. As the PCM controls the duty cycle of the solenoid valve, oil pressure/flow advances or retards the cam timing. Duty cycles near 0% or 100% represent rapid movement of the camshaft. Retaining a fixed camshaft position is accomplished by dithering (oscillating) the solenoid valve duty cycle.The PCM calculates and determines the desired camshaft position. It continually updates the VCT solenoid duty cycle until the desired position is achieved. A difference between the desired and actual camshaft position represents a position error in the PCM VCT control loop. The PCM disables the VCT and places the camshaft in a default position if a concern is detected. A related DTC is also set when the concern is detected.
5. When the VCT solenoid is energized, engine oil is allowed to flow to the VCT actuator assembly which advances or retards the camshaft timing. One half of the VCT actuator is coupled to the camshaft and the other half is connected to the timing chain. Oil chambers between the 2 halves couple the camshaft to the timing chain. When the flow of oil is shifted from one side of the chamber to the other, the differential change in oil pressure forces the camshaft to rotate in either an advance or retard position depending on the oil flow.
Diagnostic Tools
Below is an equipment list:
REQUIRED EQUIPMENT:
- Vehicle Communication Module (VCM) and Integrated Diagnostic System (IDS) software with appropriate hardware, or equivalent scan tool with functionality described under Scan Tool Setup and Functionality.
- Smoke Machine, Fuel Evaporative Emission System Tester.
RECOMMENDED EQUIPMENT:
- Vacuum/Pressure Tester. Range 0-101.3 kPa (0-30 in-Hg.) Resolution 3.4 kPa (1 in-Hg.)
- Vacuum Tester. Range 0-101.3 kPa (0-30 in-Hg.)
- Digital Volt Ohm Meter. Input impedance 10 Megaohm minimum.
- Spark Tester
- Non-powered test lamp.
OPTIONAL EQUIPMENT:
- Fuel (Gasoline) pressure test kit. (Use tool manufacturer's instructions.)
Scan Tool Setup and Functionality
- Connect the scan tool to the data link connector (DLC) for communication with the vehicle.
- The DLC is located in the driver side compartment under the steering column. It is attached to the instrument panel and accessible from the driver seat.
- The DLC is rectangular in design and capable of accommodating up to 16 terminals. The connector has keying features to allow easy connection.
- The required scan tool functions are described below:
- monitor, record, and playback of parameter identification (PIDs)
- freeze frame PID data
- diagnostic test modes; self-test, DTCs
- output test mode
- resetting keep alive memory (KAM)
- diagnostic monitoring test results (mode 6) for on board diagnostic (OBD) on board monitors
- on-board system readiness (OBD monitor completion status)
Some of these functions are described. Refer to the scan tool manufacturer's instruction manual for specific information on scan tool setup and operation.
Diagnostic Methods
Overview
The Diagnostic Method Section provides information on routine diagnostic tasks.
When following powertrain diagnostics on vehicles with on board diagnostics (OBD), the system may be checked by an off-board tester referred to as a scan tool. This section 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.
Vehicle Check/Preparation
Visual Checks
- Inspect the air cleaner and inlet duct.
- Check all engine vacuum hoses for damage, leaks, cracks, kinks and correct routing.
- Check the electronic engine control (EEC) system wiring harness for correct connections, bent or broken pins, corrosion, loose wires, and correct routing.
- Check the PCM, sensors, and actuators for physical damage.
- Check the engine coolant for correct level and mixture.
- Check the transmission fluid level and quality.
- Make all necessary repairs before continuing with the Quick Test.
Vehicle Preparation
- Carry out all safety steps required to start and run vehicle tests. Apply the parking brake, place the gear selector lever firmly into the PARK position on automatic transmission vehicles or NEUTRAL on manual transmission vehicles, and block the drive wheels.
- Turn off ALL electrical loads: radios, lamps, A/C, blower and fans.
- Start the engine (if the engine runs) and bring it up to the normal operating temperature before running the Quick Test.
Quick Test Description
Quick Test
The quick test is divided into 3 specialized tests:
- Key On Engine Off (KOEO) On-Demand Self-Test
- Key On Engine Running (KOER) On-Demand Self-Test
- Continuous Memory Self-Test
The quick test checks the integrity and function of the electronic engine control (EEC) system and outputs the test results when requested by the scan tool. The quick test also provides a quick check of the powertrain control system, and is usually carried out at the start of each diagnostic procedure with all accessories off. The quick test is also carried out at the end of most pinpoint tests for verification of the repair and to make sure no other concerns are incurred while repairing a previous concern. A system pass is displayed when no DTCs are output and a scan tool communication error does not exist. System pass means that hardware monitored by the PCM is functioning within the normal operating limits. Only a system pass, a DTC, or an incomplete on board diagnostic (OBD) drive cycle (P1000) is displayed.
For applications that use a stand-alone transmission control module (TCM) the PCM does not output TCM DTCs. For TCM self-test and diagnostics, see Diagnostics.
Key On Engine Off (KOEO) On-Demand Self-Test
The KOEO on-demand self-test is a functional test of the PCM carried out on-demand with the key on and the engine off. This test carries out checks on certain sensor and actuator circuits. A concern must be present at the time of testing for the KOEO self-test to detect the concern. When a concern is detected, a DTC is output on the data link at the end of the test as requested by the scan tool.
Key On Engine Running (KOER) On-Demand Self-Test
The KOER on-demand self-test is a functional test of the PCM carried out on-demand with the key on, the engine running and the vehicle stopped. A check of certain inputs and outputs is made during operating conditions and at a normal operating temperature. The brake pedal position, transmission control, and the power steering tests are part of the KOER on-demand self-test and must be carried out during this operation if applicable. These are described below. A concern must be present at the time of testing for the KOER on-demand self-test to detect the concern. When a concern is detected, a DTC is output on the data link at the end of the test as requested by the scan tool.
Brake Pedal Position (BPP) Test
The BPP test checks the ability of the EEC system to detect a change of state in the BPP switch. The brake pedal is briefly applied and released on all vehicles equipped with a BPP input. This is done during a KOER on-demand self-test.
Continuous Memory Self-Test
The continuous memory self-test is a functional test of the PCM carried out under any condition (engine running or off) with the key on. Unlike the KOEO and KOER self-tests, which can only be activated on-demand, the continuous self-test is always active. A concern does not need to be present when accessing continuous memory self-test DTCs, making the test valuable when diagnosing intermittent concerns. The vehicle may need to be driven or the on board diagnostic (OBD) drive cycle completed to allow the PCM to detect a concern. See On Board Diagnostic (OBD) Drive Cycle for more information. When a concern is stored in memory, a DTC is output on the data link when requested by the scan tool.
There are 2 types of continuous DTCs. The first type is an emission-related code which illuminates the malfunction indicator lamp (MIL) in the instrument cluster. The second is a non-emission related, non-MIL code which does not illuminate the cluster indicator.
For emission-related MIL DTCs, the PCM stores the DTC in continuous memory when a concern is detected for the first time. At this point the DTC does not illuminate the MIL and is considered a pending code. The purpose of pending codes is to assist in repair verification by reporting a pending DTC after one drive cycle. If the same concern is detected after the next drive cycle, the emission-related MIL code illuminates the MIL and sets both a confirmed MIL DTC and a permanent DTC. The MIL remains illuminated even if the concern is intermittent. A permanent DTC is stored until three consecutive passing drive cycles have been completed after a repair and the MIL turns off, or after a request to clear DTCs has been made using the scan tool and the next monitoring cycle has completed and passed for that DTC.
Confirmed emission-related MIL DTCs and any non-emission related, non-MIL DTCs are erased approximately 40 vehicle warm-up cycles after the concern was last detected, or if the DTCs are cleared by the scan tool.
Pending emission-related MIL DTCs that never detect a concern on a second consecutive drive cycle (and never light the MIL) are not retained in memory for any number of vehicle warm-up cycles; they are immediately cleared when the next monitoring cycle has completed and passed for that DTC, or until a request to clear DTCs has been made by the scan tool.
Any scan tool that meets OBD requirements can access the continuous memory to retrieve emission-related MIL DTCs. However, not all scan tools access pending and non-emission related, non-MIL DTCs in the same way.
During most diagnostic procedures in this information, it is required that all DTCs be retrieved and cleared. Permanent DTCs cannot be directly cleared by the scan tool. When a scan tool clears DTCs, pending and confirmed DTCs are immediately cleared. Permanent DTCs will not clear until the next monitoring cycle has completed and passed for that DTC. See Powertrain Control Software, Permanent DTC. See Engine OBD II Monitors. Consult the instruction manual from the tool manufacturer for specific instructions.
Clear the Continuous DTCs and Reset the Emission Monitors Information in the PCM
Description
All on board diagnostics (OBD II) 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 DTC P1000 is stored in the PCM until all the OBD system monitors or components have been tested to satisfy a drive cycle without any other concerns occurring.
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 II system monitors is reset
- DTC P1000 is set
NOTE:This function is carried out only after retrieval of continuous DTCs.
Resetting The Keep Alive Memory (KAM)
Description
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. Clear the continuous DTCs in the PCM and reset the emission monitors information, is part of a KAM reset.
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 air conditioning (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.
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.
A KAM Reset is done as follows:
During key on, engine off with the scan tool, use the reset keep alive memory function. This is found in the active command modes menu on the Integrated Diagnostic System (IDS) scan tool.
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.
On-Board System Readiness (OSR)
Description
All on board diagnostic (OBD) scan tools display the on-board system readiness (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 run continuously and always display YES status. Clearing the continuous 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.
Output State Control (OSC)
Description
WARNING:Safety must be observed when using Output State Control (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 is used to help 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 codes 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 sensor (OSS) or the vehicle speed sensor (VSS) must be fixed or the PCM does not allow the OSC to operate.
The OSC has 2 options for operation, the Bench Mode and the Drive Mode. The Bench Mode is functional only when the vehicle gear selector is in the PARK or NEUTRAL position. The Bench Mode may be used when the engine is on (running) or off (not running).
Each OSC function has a unique set of vehicle operating requirements that 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 that 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.
One Touch Integrated Start System
Some vehicles are equipped with one touch integrated start system. It may be necessary to disable the one touch integrated start system to carry out diagnostic procedures that require extended cranking. Connect the scan tool, access the PCM and select the one touch integrated start system control PID to disable the system.
Output Test Mode (OTM)
Description
The 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, OTM will default to its normal state after 10 minutes, 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.Failure to follow these instructions may result in personal injury.
The OTM aids in diagnosing 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 controls 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, OTM defaults to the off state after 10 minutes, and the fuel pump off state after approximately 7-10 seconds. OTM also turns off after the vehicle is started or after cycling the key off then on.