2006 DODGE RAM SRT-10 catalytic converter

The primary components within the assembly are: A three port solenoid thatactivates both of the functions listed
above; a pump which contains a switch, two check valves and a spring/diaphragm, a canister vent valve (CVV) seal
which contains a spring loaded vent seal valve.
Immediately after a cold start, between predetermined temperature thresholds limits, the three port solenoid is briefly
energized. This initializes the pump by drawing air into the pump cavity and also closes the vent seal. During non
test conditions the vent seal is held open by the pump diaphragm assembly which pushes it open at the full travel
position. The vent seal will remain closed while the pump is cycling due to the reed switch triggering of the three
port solenoid that prevents the diaphragm assembly from reaching full travel. After the brief initialization period, the
solenoid is de-energized allowing atmospheric pressure to enter the pumpcavity, thus permitting the spring to drive
the diaphragm which forces air out of the pump cavity and into the vent system. When the solenoid is energized
and de energized, the cycle is repeated creating flow in typical diaphragmpump fashion. The pump is controlled in
2 modes:
Pump Mode: The pump is cycled at a fixed rate to achieve a rapid pressure build in order to shorten the overall test
length.
Test Mode: The solenoid is energized with a fixed duration pulse. Subsequent fixed pulses occur when the dia-
phragm reaches the Switch closure point.
The spring in the pump is set so that the system will achieve an equalized pressure of about 7.5” H20. The cycle
rate of pump strokes is quite rapid as the system begins to pump up to this pressure. As the pressure increases, the
cycle rate starts to drop off. If there is no leak in the system, the pump would eventually stop pumping at the equal-
ized pressure. If there is a leak, it will continue to pump at a rate representative of the flow characteristic of the size
of the leak. From this information we can determine if the leak is larger than the required detection limit (currently
set at .040” orifice by CARB). If a leak is revealed during the leak test portion of the test, the test is terminated at
the end of the test mode and no further system checks will be performed.
After passing the leak detection phase of the test, system pressure is maintained by turning on the LDP’s solenoid
until the purge system is activated. Purge activation in effect creates a leak. The cycle rate is again interrogated and
when it increases due to the flow through the purge system, the leak check portion of the diagnostic is complete.
The canister vent valve will unseal the system after completion of the testsequence as the pump diaphragm assem-
bly moves to the full travel position.
Evaporative system functionality will be verified by using the stricter evap purge flow monitor. At an appropriate
warm idle the LDP will be energized to seal the canister vent. The purge flowwill be clocked up from some small
value in an attempt to see a shift in the02 control system. If fuel vapor, indicated by a shift in the 02 control, is
present the test is passed. If not, it is assumed that the purge system is notfunctioning in some respect. The LDP
is again turned off and the test is ended.
MISFIRE MONITOR
Excessive engine misfire results in increased catalyst temperature and causes an increase in HC emissions. Severe
misfires could cause catalyst damage. To prevent catalytic convertor damage, the PCM monitors engine misfire.
The Powertrain Control Module (PCM) monitors for misfire during most engine operating conditions (positive torque)
by looking at changes in the crankshaft speed. If a misfire occurs the speedof the crankshaft will vary more than
normal.
FUEL SYSTEM MONITOR
To comply with clean air regulations, vehicles are equipped with catalytic converters. These converters reduce the
emission of hydrocarbons, oxides of nitrogen and carbon monoxide. The catalyst works best when the Air Fuel (A/F)
ratio is at or near the optimum of 14.7 to 1.
The PCM is programmed to maintain the optimum air/fuel ratio of 14.7 to 1. This is done by making short term
corrections in the fuel injector pulse width based on the O2S sensor output. The programmed memory acts as a self
calibration tool that the engine controller uses to compensate for variations in engine specifications, sensor toler-
ances and engine fatigue over the life span of the engine. By monitoring theactual fuel-air ratio with the O2S sen-
sor (short term) and multiplying that with the program long-term (adaptive) memory and comparing that to the limit,
it can be determined whether it will pass an emissions test. If a malfunction occurs such that the PCM cannot main-
tain the optimum A/F ratio, then the MIL will be illuminated.

CATALYST MONITOR
To comply with clean air regulations, vehicles are equipped with catalytic converters. These converters reduce the
emission of hydrocarbons, oxides of nitrogen and carbon monoxide.
Normal vehicle miles or engine misfire can cause a catalyst to decay. This can increase vehicle emissions and
deteriorate engine performance, driveability and fuel economy.
The catalyst monitor uses dual oxygen sensors (O2S’s) to monitor the efficiency of the converter. The dual O2S’s
sensor strategy is based on the fact that as a catalyst deteriorates, its oxygen storage capacity and its efficiency are
both reduced. By monitoring the oxygen storage capacity of a catalyst, itsefficiency can be indirectly calculated. The
upstream O2S is used to detect the amount of oxygen in the exhaust gas beforethe gas enters the catalytic con-
verter. The PCM calculates the A/F mixture from the output of the O2S. A low voltage indicates high oxygen content
(lean mixture). A high voltage indicates a low content of oxygen (rich mixture).
When the upstream O2S detects a lean condition, there is an abundance of oxygen in the exhaust gas. A function-
ing converter would store this oxygen so it can use it for the oxidation of HCand CO. As the converter absorbs the
oxygen, there will be a lack of oxygen downstream of the converter. The output of the downstream O2S will indicate
limited activity in this condition.
As the converter loses the ability to store oxygen, the condition can be detected from the behavior of the down-
stream O2S. When the efficiency drops, no chemical reaction takes place. This means the concentration of oxygen
will be the same downstream as upstream. The output voltage of the downstream O2S copies the voltage of the
upstream sensor. The only difference is a time lag (seen by the PCM) betweenthe switching of the O2S’s.
To monitor the system, the number of lean-to-rich switches of upstream anddownstream O2S’s is counted. The
ratio of downstream switches to upstream switches is used to determine whether the catalyst is operating properly.
An effective catalyst will have fewer downstream switches than it has upstream switches i.e., a ratio closer to zero.
For a totally ineffective catalyst, this ratio will be one-to-one, indicating that no oxidation occurs in the device.
The system must be monitored so that when catalyst efficiency deteriorates and exhaust emissions increase to over
the legal limit, the MIL will be illuminated.
TRIP DEFINITION
The term “Trip” has different meanings depending on what the circumstances are. If the MIL (Malfunction Indicator
Lamp) is OFF, a Trip is defined as when the Oxygen Sensor Monitor and the Catalyst Monitor have been completed
in the same drive cycle.
When any Emission DTC is set, the MIL on the dash is turned ON. When the MIL is ON, it takes 3 good trips to turn
the MIL OFF. In this case, it depends on what type of DTC is set to know what a “Trip” is.
For the Fuel Monitor or Mis-Fire Monitor (continuous monitor), the vehicle must be operated in the “Similar Condition
Window” for a specified amount of time to be considered a Good Trip.
If a Non-Continuous OBDII Monitor fails twice in a row and turns ON the MIL, re-running that monitor which previ-
ously failed, on the next start-up and passing the monitor, is considered tobeaGoodTrip.Thesewillincludethe
following:
Oxygen Sensor
Catalyst Monitor
Purge Flow Monitor
Leak Detection Pump Monitor (if equipped)
EGR Monitor (if equipped)
Oxygen Sensor Heater Monitor
If any other Emission DTC is set (not an OBDII Monitor), a Good Trip is considered to be when the Oxygen Sensor
Monitor and Catalyst Monitor have been completed; or 2 Minutes of engine run time if the Oxygen Sensor Monitor
or Catalyst Monitor have been stopped from running.
It can take up to 2 Failures in a row to turn on the MIL. After the MIL is ON, it takes3GoodTripstoturntheMIL
OFF. After the MIL is OFF, the PCM will self-erase the DTC after 40 Warm-up cycles. A Warm-up cycle is counted
when the ECT (Engine Coolant Temperature Sensor) has crossed 160°F (71.1C) and has risen by at least 40°F
(4.4°C) since the engine has been started.