Jeep Cherokee (XJ): Trip definition. Component monitors. Non-monitored circuits
OPERATION 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-Contiuous OBDII Monitor, such as: fails twice in a row and turns ON the MIL, re-running
that monitor which previously failed, on the
next start-up and passing the monitor is considered
to be a Good Trip.
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 takes 3 Good Trips to
turn the MIL 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 160F and
has risen by at least 40F since the engine has been
started. OPERATION There are several components that will affect vehicle
emissions if they malfunction. If one of these components
malfunctions the Malfunction Indicator
Lamp (MIL) 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. 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 if
the TPS indicates a small throttle opening.
All open/short circuit checks or any component that
has an associated limp in will set a fault after 1 trip
with the malfunction present. Components without
an associated limp in will take two trips to illuminate
the MIL. Refer to the Diagnostic Trouble Codes Description
Charts in this section and the appropriate Powertrain
Diagnostic Procedure Manual for diagnostic
procedures. The PCM does not monitor the following circuits,
systems and conditions that could have malfunctions
causing driveability problems. The PCM might not
store diagnostic trouble codes for these conditions.
However, problems with these systems may cause the
PCM to store diagnostic trouble codes for other systems
or components. For example, a fuel pressure
problem will not register a fault directly, but could
cause a rich/lean condition or misfire. This could
cause the PCM to store an oxygen sensor or misfire
diagnostic trouble code OPERATION FUEL PRESSURE The fuel pressure regulator controls fuel system
pressure. The PCM cannot detect a clogged fuel
pump inlet filter, clogged in-line fuel filter, or a
pinched fuel supply or return line. However, these
could result in a rich or lean condition causing the
PCM to store an oxygen sensor or fuel system diagnostic
trouble code. SECONDARY IGNITION CIRCUIT The PCM cannot detect an inoperative ignition coil,
fouled or worn spark plugs, ignition cross firing, or
open spark plug cables. CYLINDER COMPRESSION The PCM cannot detect uneven, low, or high engine
cylinder compression. EXHAUST SYSTEM The PCM cannot detect a plugged, restricted or
leaking exhaust system, although it may set a fuel
system fault. FUEL INJECTOR MECHANICAL MALFUNCTIONS The PCM cannot determine if a fuel injector is
clogged, the needle is sticking or if the wrong injector
is installed. However, these could result in a rich or
lean condition causing the PCM to store a diagnostic
trouble code for either misfire, an oxygen sensor, or
the fuel system. EXCESSIVE OIL CONSUMPTION Although the PCM monitors engine exhaust oxygen
content when the system is in closed loop, it cannot
determine excessive oil consumption. THROTTLE BODY AIR FLOW The PCM cannot detect a clogged or restricted air
cleaner inlet or filter element. VACUUM ASSIST The PCM cannot detect leaks or restrictions in the
vacuum circuits of vacuum assisted engine control
system devices. However, these could cause the PCM
to store a MAP sensor diagnostic trouble code and
cause a high idle condition. PCM SYSTEM GROUND The PCM cannot determine a poor system ground.
However, one or more diagnostic trouble codes may
be generated as a result of this condition. The module
should be mounted to the body at all times, also
during diagnostic. PCM CONNECTOR ENGAGEMENT The PCM may not be able to determine spread or
damaged connector pins. However, it might store
diagnostic trouble codes as a result of spread connector
pins.Trip definition
Component monitors
Non-monitored circuits
High and low limits. Load value
Other materials:
Description and operation
Trip computer
A mini trip computer is available on this model to
provide several electronic functions and features. The
trip computer contains a central processing unit and
interfaces with other modules in the vehicle on the
Chrysler Collision Detection (CCD) data bus network.
The CCD data bu ...