6E1-68 DRIVEABILITY AND EMISSIONS
ENGINE CONTROL MODULE
(ECM) DIAGNOSIS
To read and clear diagnostic trouble codes, use a
Scan Tool.
Important: Use of a Scan Tool is recommended to
clear diagnostic trouble codes from the ECM memory.
Diagnostic trouble codes can also be cleared by
turning the ignition OFF and disconnecting the battery
power from the ECM for 30 seconds. Turning off the
ignition and disconnecting the battery power from the
ECM will cause all diagnostic information in the ECM
memory to be cleared. Therefore, all the diagnostic
tests will have to be re-run.
Since the ECM can have a failure which may affect
only one circuit, following the diagnostic procedures in
this section will determine which circuit has a problem
and where it is.
If a diagnostic chart indicates that the ECM
connections or the ECM is the cause of a problem,
and the EPROM or ECM is replaced, but this does not
correct the problem, one of the following may be the
reason:
• There is a problem with the ECM terminal
connections. The terminals may have to be
removed from the connector in order to check them
properly.
• The problem is intermittent. This means that the
problem is not present at the time the system is
being checked. In this case, refer to the Symptoms
portion of the manual and make a careful physical
inspection of all components and wiring associated
with the affected system.
• There is a shorted solenoid, relay coil, or harness.
Solenoids and relays are turned ON and OFF by the
ECM using internal electronic switches called
drivers. A shorted solenoid, relay coil, or harness
will not damage the ECM but will cause the solenoid
or relay to be inoperative.
MULTIPLE ECM INFORMATION
SENSOR DTCs SET
Circuit Description
The engine control module (ECM) monitors various
sensors to determine the engine operating conditions.
The ECM controls fuel delivery, spark advance, and
emission control device operation based on the sensor
inputs.
The ECM provides a sensor ground to all of the
sensors. The ECM applies 5 volts through a pull-up
resistor, and determines the status of the following
sensors by monitoring the voltage present between
the 5-volt supply and the resistor:
• The throttle position (TP) sensor
• The manifold absolute pressure (MAP) sensor
The ECM provides the following sensors with a 5-volt
reference and a sensor ground signal:
• Intake Air Temp Sensor (IAT).
• Engine Coolant Temp Sensor (ECT).
• Manifold Absolute Pressure Sensor (MAP).
• Throttle Position Sensor (TPS).
The ECM monitors the separate feedback signals
from these sensors in order to determine their
operating status.
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