6E2–35
RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS
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Inspect all wires in the engine compartment for proper
connections, burned or chafed spots, pinched wires,
contact with sharp edges or contact with hot exhaust
manifolds or pipes.
Basic Knowledge of Tools Required
NOTE: Lack of basic knowledge of this powertrain when
performing diagnostic procedures could result in an
incorrect diagnosis or damage to powertrain
components. Do not attempt to diagnose a powertrain
problem without this basic knowledge.
A basic understanding of hand tools is necessary to effec-
tively use this section of the Service Manual.
Serial Data Communications
Class 2 Serial Data Communications
Government regulations require that all vehicle
manufacturers establish a common communication
system. This vehicle utilizes the “Class 2” communication
system. Each bit of information can have one of two
lengths: long or short. This allows vehicle wiring to be
reduced by transmitting and receiving multiple signals
over a single wire. The messages carried on Class 2 data
streams are also prioritized. If two messages attempt to
establish communications on the data line at the same
time, only the message with higher priority will continue.
The device with the lower priority message must wait.
The most significant result of this regulation is that it
provides Scan tool manufacturers with the capability to
access data from any make or model vehicle that is sold.
The data displayed on other Scan tools will appear the
same, with some exceptions. Some Scan tools will only
be able to display certain vehicle parameters as values
that are a coded representation of the true or actual value.
On this vehicle the Scan tool displays the actual values for
vehicle parameters. It will not be necessary to perform
any conversions from coded values to actual values.
On-Board Diagnostic (OBD II)
On-Board Diagnostic Tests
A diagnostic test is a series of steps, the result of which is
a pass or fail reported to the diagnostic executive. When
a diagnostic test reports a pass result, the diagnostic
executive records the following data:
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The diagnostic test has been completed since the last
ignition cycle.
D
The diagnostic test has passed during the current
ignition cycle.
D
The fault identified by the diagnostic test is not
currently active.
When a diagnostic test reports a fail result, the diagnostic
executive records the following data:
D
The diagnostic test has been completed since the last
ignition cycle.
D
The fault identified by the diagnostic test is currently
active.
D
The fault has been active during this ignition cycle.
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The operating conditions at the time of the failure.
Remember, a fuel trim DTC may be triggered by a list of
vehicle faults. Make use of all information available (other
DTCs stored, rich or lean condition, etc.) when
diagnosing a fuel trim fault.
Comprehensive Component Monitor
Diagnostic Operation
Comprehensive component monitoring diagnostics are
required to monitor emissions-related input and output
powertrain components. The
CARB OBD II
Comprehensive Component Monitoring List Of
Components Intended To illuminate MIL is a list of
components, features or functions that could fall under
this requirement.
Input Components:
Input components are monitored for circuit continuity and
out-of-range values. This includes rationality checking.
Rationality checking refers to indicating a fault when the
signal from a sensor does not seem reasonable, i.e.
Throttle Position (TP) sensor that indicates high throttle
position at low engine loads or MAP voltage. Input
components may include, but are not limited to the
following sensors:
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Vehicle Speed Sensor (VSS)
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Crankshaft Position (CKP) sensor
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Throttle Position (TP) sensor
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Engine Coolant Temperature (ECT) sensor
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Manifold Absolute Pressure (MAP) sensor
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Mass Air Flow (MAF) sensor
In addition to the circuit continuity and rationality check,
the ECT sensor is monitored for its ability to achieve a
steady state temperature to enable closed loop fuel
control.
Output Components:
Output components are diagnosed for proper response to
control module commands. Components where
functional monitoring is not feasible will be monitored for
circuit continuity and out-of-range values if applicable.
Output components to be monitored include, but are not
limited to, the following circuits:
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Control module controlled EVAP Canister Purge
Valve
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Electronic Transmission controls
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A/C relays
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VSS output
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MIL control
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Cruise control inhibit
Refer to PCM and Sensors in General Descriptions.
Passive and Active Diagnostic Tests
A passive test is a diagnostic test which simply monitors a
vehicle system or component. Conversely, an active test,
actually takes some sort of action when performing
diagnostic functions, often in response to a failed passive
test. For example, the EGR diagnostic active test will
force the EGR valve open during closed throttle decel
and/or force the EGR valve closed during a steady state.
Either action should result in a change in manifold
pressure.