6E2–322
6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS
D
Diagnostics
– Malfunction Indicator Lamp
– Data Link Connector (DLC)
– Data Output
D
Transmission Control Module
D
Alternator Gain Control
PCM Service Precautions
The PCM is designed to withstand normal current draws
associated with vehicle operation. Avoid overloading any
circuit. When testing for opens and shorts, do not ground
or apply voltage to any of the PCM’s circuits unless
instructed to do so. These circuits should only be tested
using digital voltmeter (5–8840–0285–0). The PCM
should remain connected to the PCM or to a
recommended breakout box.
Throttle Position (TP) Sensor
The throttle position (TP) sensor is a potentiometer
connected to the throttle shaft on the throttle body. The
PCM monitors the voltage on the signal line and
calculates throttle position. As the throttle valve angle is
changed (accelerator pedal moved), the TP sensor signal
also changes. At a closed throttle position, the output of
the TP sensor is low. As the throttle valve opens, the
output increases so that at wide open throttle (WOT), the
output voltage should be above 4 volts.
The PCM calculates fuel delivery based on throttle valve
angle (driver demand). A broken or loose TP sensor may
cause intermittent bursts of fuel from an injector and
unstable idle because the PCM thinks the throttle is
moving. A hard failure in the TP sensor 5-volt reference
or signal circuits will set either a DTC P0122 or DTC
P0123. A hard failure with the TP sensor ground circuit
may set DTC P0123 and DTC P0112. Once a DTC is set,
the PCM will use an artificial default value based on
engine RPM and mass air flow for the throttle position,
and some vehicle performance will return. A high idle
may result when either DTC P0122 or DTC P0123 is set.
The PCM can also detect a shifted TP sensor. The PCM
monitors throttle position and compares the actual TP
sensor reading to a predicted TP value calculated from
engine speed. If the PCM detects an out-of-range
condition, DTC P0121 will be set.
0021
Transmission Fluid Temperature (TFT)
Sensor
The transmission fluid temperature sensor is a thermistor
which changes its resistance based on the temperature of
the transmission fluid. For a complete description of the
TFT sensor, refer to
4L30-E Automatic Transmission
Diagnosis
A failure in the TFT sensor or associated wiring will cause
DTC P0712 or DTC P0713 to set. In this case, engine
coolant temperature will be substituted for the TFT
sensor value and the transmission will operate normally.
Transmission Range Switch
IMPORTANT:
The vehicle should not be driven with the
transmission range switch disconnected; idle quality will
be affected.
The four inputs from the transmission range switch
indicate to the PCM which position is selected by the
transmission selector lever. This information is used for
ignition timing, EVAP canister purge, EGR and IAC valve
operation.
For more information on the transmission on the
transmission range switch, refer to
4L30-E Automatic
Transmission.
Vehicle Speed Sensor (VSS)
The PCM determines the speed of the vehicle by
converting a plusing voltage signal from the vehicle speed
sensor (VSS) into miles per hour. The PCM uses this
signal to operate the cruise control, speedometer, and the
TCC and shift solenoids in the transmission. For more
information on the TCC and shift solenoids, refer to
4L30-E Automatic Transmission.