Target Idle
Target idle is determined by the following inputs:
• Gear position
• ECT Sensor
• Battery voltage
• Ambient/Battery Temperature Sensor
• VSS
• TPS
• MAP Sensor
DATA LINK CONNECTOR—PCM OUTPUT
DESCRIPTION
The data link connector is located inside the vehi-
cle, below instrument panel next to the center col-
umn (Fig. 15).
OPERATION
The data link connector (diagnostic connector)
links the DRB scan tool with the Powertrain Control
Module (PCM). Refer to On-Board Diagnostics in the
General Diagnosis section of this group.
MALFUNCTION INDICATOR (CHECK ENGINE)
LAMP—PCM OUTPUT
DESCRIPTION
Refer to the Instrument Panel Systems for more
information.
OPERATION
The PCM supplies the malfunction indicator (check
engine) lamp on/off signal to the instrument panel
through the PCI Bus. The PCI Bus is a communica-
tions port. Various modules use the PCI Bus to
exchange information.
The Check Engine lamp comes on each time the
ignition key is turned ON and stays on for 3 seconds
as a bulb test.
The Malfunction Indicator Lamp (MIL) stays on
continuously, when the PCM has entered a Limp-In
mode or identified a failed emission component. Dur-
ing Limp-in Mode, the PCM attempts to keep the
system operational. The MIL signals the need for
immediate service. In limp-in mode, the PCM com-
pensates for the failure of certain components that
send incorrect signals. The PCM substitutes for the
incorrect signals with inputs from other sensors.
If the PCM detects active engine misfire severe
enough to cause catalyst damage, it flashes the MIL.
At the same time the PCM also sets a Diagnostic
Trouble Code (DTC).
For signals that can trigger the MIL (Check
Engine Lamp) refer to the On-Board Diagnos-
tics section.
RADIATOR FAN RELAYS—PCM OUTPUT
DESCRIPTION
The low speed and high speed fan relays are
located in the Power Distribution Center (PDC) near
the battery. A decal on the inside of the PDC covers
shows the locations of each relay and fuse contained
in the PDC. It is an ISO relay.
OPERATION
The cooling system uses two fans. Both fans oper-
ate at two different speeds, low and high. Depending
on engine coolant temperature and A/C system high
side pressure, the both fans operate at either low or
high. The PCM controls radiator speed by grounding
the coil side of either the low speed fan relay or the
high speed fan relay. The ignition switch supplies
voltage to the coil sides of the relay. When the PCM
grounds the coil side of the relay, the contacts close
and the battery supplies power to the fans.
TACHOMETER—PCM OUTPUT
DESCRIPTION
Refer to the Instrument panel System for more
information.
OPERATION
The tachometer receives its information across the
PCI Bus from the Body Control Module (BCM). Infor-
mation on engine RPM is transmitted from the Pow-
ertrain Control Module (PCM) across the PCI Bus to
the BCM. The BCM calculates the position of the
tachometer pointer based on the input from the PCM
and adjusts the position of the gauge pointer to the
Fig. 15 Data Link Connector
LH FUEL SYSTEM 14 - 35
DESCRIPTION AND OPERATION (Continued)
To Next Page
Loading...
