Emissions Control: Overview Dodge Charger VI

DESCRIPTION

There are several components that will affect vehicle emissions if they malfunction. If one of these components malfunctions the Malfunction Indicator Lamp (Check Engine) will illuminate.

Some of the component monitors are checking for proper operation of the part. Electrically operated components now have input (rationality) and output (functionality) checks as well as continuity tests (opens/shorts). Previously, a component like the Throttle Position sensor (TPS) was checked by the PCM for an open or shorted circuit. If one of these conditions occurred, a DTC was set. Now there is a check to ensure that the component is working. This is done by watching for a TPS indication of a greater or lesser throttle opening than MAP and engine RPM indicate. In the case of the TPS, if engine vacuum is high and engine RPM is 1600 or greater and the TPS indicates a large throttle opening, a DTC will be set. The same applies to low vacuum and 1600 RPM.

Any component that has an associated limp in will set a fault after 1 trip with the malfunction present.

Refer to the Diagnostic Trouble Codes Description Charts in this information and the appropriate Powertrain Diagnostic Procedure information for diagnostic procedures.

The following is a list of the monitored components

1. Catalyst Monitor
2. Comprehensive Components
3. EGR (if equipped)
4. Fuel Control (rich/lean)
5. O2S sensor Monitor
6. O2S sensor Heater Monitor
7. Purge
8. Misfire
9. Evaporative System Integrity Monitor (ESIM)

OPERATION

The switch inputs to the Powertrain Control Module (PCM) have two recognized states; HIGH and LOW. For this reason, the PCM cannot recognize the difference between a selected switch position versus an open circuit, a short circuit, or a defective switch. If the State Display screen shows the change from HIGH to LOW or LOW to HIGH, assume the entire switch circuit to the PCM functions properly. From the state display screen, access either State Display Inputs and Outputs or State Display Sensors.

Scheme 1

The Powertrain Control Module (PCM) monitors many different circuits in the fuel injection, ignition, emission and engine systems. If the PCM senses a problem with a monitored circuit often enough to indicate an actual problem, it stores a Diagnostic Trouble Code (DTC) in the PCM's memory. If the code applies to a non-emissions related component or system, and the problem is repaired or ceases to exist, the PCM cancels the code after 40 warmup cycles. Diagnostic trouble codes that affect vehicle emissions illuminate the Malfunction Indicator Lamp (MIL). Refer to MIL ILLUMINATION in this information.

Certain criteria must be met before the PCM stores a DTC in memory. The criteria may be a specific range of engine RPM, engine temperature, and/or input voltage to the PCM.

The PCM might not store a DTC for a monitored circuit even though a malfunction has occurred. This may happen because one of the DTC criteria for the circuit has not been met. For example , assume the diagnostic trouble code criteria requires the PCM to monitor the circuit only when the engine operates between 750 and 2000 RPM. Suppose the sensor's output circuit shorts to ground when engine operates above 2400 RPM (resulting in 0 volt input to the PCM). Because the condition happens at an engine speed above the maximum threshold (2000 RPM), the PCM will not store a DTC.

There are several operating conditions for which the PCM monitors and sets DTC's. Refer to MONITORED SYSTEMS MONITORED COMPONENT , and MONITORED COMPONENT in this information.

Note. Various diagnostic procedures may actually cause a diagnostic monitor to set a DTC. For instance, pulling a spark plug wire to perform a spark test may set the misfire code. When a repair is completed and verified, use the scan tool to erase all DTC's and extinguish the MIL.

Technicians can display stored DTC's. For obtaining the DTC information, use the Data Link Connector with the scan tool. (Scheme 1)

Scheme 2

The evaporative emissions system is designed to control the release of fuel vapors into the atmosphere. The fuel tank check valve (4) and control valve (5) are used to reduce emissions due to the venting of vapor expansion within the fuel tank. When fuel evaporates from the fuel tank, vapors pass through a vent hose to the evaporative charcoal canister (3) where they are temporarily held. When the engine is running, the vapors are drawn into the intake manifold (8). In addition, fuel vapors produced during vehicle refueling are allowed to pass through the vent hose to the evaporative charcoal canister (3) for temporary storage (prior to being drawn into the intake manifold). The fuel tank check valve (4) and control valve (5) are non-serviceable components of the fuel tank assembly. The system is equipped with self-diagnosing capability using an Evaporative System Integrity Monitor (2). Refer to SWITCH, EVAPORATIVE EMISSIONS SYSTEM MONITOR, OPERATION .

The fuel tank pressure sensor (7) provides the PCM with information on vapor pressure inside the fuel tank. Excessive fuel tank pressure could cause fuel vapors to vent out the fuel filler cap or damage system components while insufficient fuel tank pressure (vacuum) caused by lack of fresh air entering the tank (1) to take the place of consumed fuel could lead to collapsed tank, lines or loss of fuel pressure.

The inlet check valve (6) prevents fuel from splashing back on the customer during vehicle refueling. This valve is also a non-serviceable component of the fuel tank assembly.

Scheme 3

Scheme 4

Scheme 5

Scheme 6

1. Disconnect the negative battery cable.
2. Remove the fuel tank filler cap.
3. Raise and support the vehicle.
4. Remove the right rear tire.
5. Remove the right rear wheelhouse splash shield.
6. Disconnect the ESIM electrical connector (1).
7. Disconnect the fuel tank vapor line (2) quick-connect fitting from the EVAP canister and position aside.
8. Disconnect the vapor purge line (3) quick-connect fitting from the EVAP canister and position aside.
9. Remove the vapor canister retaining nut (1).
10. Lower the front of the vapor canister.
11. Slide the vapor canister forward off of rear mounting brackets.
12. Make sure you do not lose the rear mounting bracket rubber mounts.
13. Remove the vapor canister, ESIM, and fresh air filter from the vehicle as an assembly.

The following procedure has been established to assist technicians in the field with enabling and running OBD II Monitors. The order listed in the following procedure is intended to allow the technician to effectively complete each monitor and to set the CARB Readiness Status in the least time possible.

Note. Once the monitor run process has begun, do not turn off the ignition. By turning the ignition key off, monitor enabling conditions will be lost. EVAP Monitor runs after key off. By performing a Battery Disconnect, or Selecting Erase DTCs, the CARB Readiness and all additional OBD II information will be cleared.

The PCM is responsible for efficiently coordinating the operation of all the emissions-related components. The PCM is also responsible for determining if the diagnostic systems are operating properly. The software designed to carry out these responsibilities is call the "Task Manager".

The Task Manager determines when tests happen and when functions occur. Many of the diagnostic steps required by OBD II must be performed under specific operating conditions. The Task Manager software organizes and prioritizes the diagnostic procedures. The job of the Task Manager is to determine if conditions are appropriate for tests to be run, monitor the parameters for a trip for each test, and record the results of the test. Following are the responsibilities of the Task Manager software

1. Test Sequence
2. MIL Illumination
3. Diagnostic Trouble Codes (DTCs)
4. Trip Indicator
5. Freeze Frame Data Storage
6. Similar Conditions Window