Throttle Body Air Flow - The engine controller
cannot detect a clogged or restricted air cleaner inlet or
filter element.
Evaporative System - The engine controller will
not detect a restricted, plugged or loaded evaporative
purge canister.
Vacuum Assist - Leaks or restrictions in the
vacuum circuits of vacuum assisted engine control
system devices are not monitored by the engine con-
troller. However, these could result in a MAP sensor
fault being stored in the engine controller.
Engine Controller System Ground - The engine
controller cannot determine a poor system ground.
However, a fault code may be generated as a result of
this condition.
Engine Controller Connector Engagement - The
engine controller cannot determine spread or damaged
connector pins. However, a fault code may be generated
as a result of this condition.
HIGH AND LOW LIMITS
The engine controller compares input signal voltages
from each input device with established high and low
limits that are programmed into it for that device. If
the input voltage is not within specifications and other
fault code criteria are met, a fault code will be stored in
memory. Other fault code criteria might include engine
RPM limits or input voltages from other sensors or
switches that must be present before a fault condition
can be verified.
FAULT CODE DESCRIPTION
A fault code indicates that the engine controller has
recognized an abnormal condition in the system. Fault
codes can be obtained from the Check Engine lamp on
the Instrument Panel or from the Diagnostic Readout
Box II (DRBII). Fault codes indicate the results of a
failure but do not identify the failed component di-
rectly.
SYSTEM TESTS
Be sure to apply parking brake and/or block
wheels before performing idle check or adjust-
ment, or any engine running tests.
OBTAINING FAULT CODES
(1) Connect DRBII to the diagnostic connector lo-
cated in the engine compartment near the driver side
strut tower (Fig. 15).
(2) Start the engine if possible, cycle the transmis-
sion selector and the A/C switch if applicable. Shut off
the engine.
(3) Turn the ignition switch on, access Read Fault
Screen. Record all the fault messages shown on the
DRBII. Observe the check engine lamp on the instru-
ment panel. The lamp should light for 2 seconds then
go out (bulb check).
Fault code erasure; access erase fault code data
STATE DISPLAY TEST MODE
The switch inputs used by the engine controller have
only two recognized states, HIGH and LOW. For this
reason, the engine controller cannot recognize the
difference between a selected switch position versus an
open circuit, a short circuit, or a defective switch. If the
change is displayed, it can be assumed that the entire
switch circuit to the engine controller is functional.
From the state display screen access either State
Display Inputs and Outputs or State Display Sensors.
STATE DISPLAY INPUTS AND OUTPUTS
Connect the DRB II tester to the vehicle and access
the State Display screen. Then access Inputs and
Outputs. The following is a list of the engine control
system functions accessible through the Inputs and
Outputs screen:
Park/Neutral Switch
Speed Control Resume
Brake Switch
Speed Control On/Off
Speed Control Set
A/C Switch Sense
Z2 Voltage Sense
S/C Vent Solenoid
S/C Vacuum Solenoid
A/C Clutch Relay
EMR Lamp
Auto Shutdown Relay
Fuel Pump Relay
Radiator Fan Relay
Purge Solenoid
Check Engine Lamp
.
FUEL SYSTEM
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