ignition coil, and oxygen sensor heating element. If
the PCM does not receive the camshaft position sen-
sor and crankshaft position sensor signals within
approximately one second, it de-energizes the ASD
relay and fuel pump relay.
The PCM energizes all injectors until it determines
crankshaft position from the camshaft position sen-
sor and crankshaft position sensor signals. The PCM
determines crankshaft position within 1 engine revo-
lution.
After determining crankshaft position, the PCM
begins energizing the injectors in sequence. The PCM
adjusts injector pulse width and controls injector syn-
chronization by turning the individual ground paths
to the injectors On and Off.
When the engine idles within664 RPM of its tar-
get RPM, the PCM compares current MAP sensor
value with the atmospheric pressure value received
during the Ignition Switch On (zero RPM) mode. If
the PCM does not detect a minimum difference
between the two values, it sets a MAP diagnostic
trouble code into memory.
Once the ASD and fuel pump relays have been
energized, the PCM:
²Determines injector pulse width based on engine
coolant temperature, MAP and the number of engine
revolutions since cranking was initiated.
²Monitors the engine coolant temperature sensor,
camshaft position sensor, crankshaft position sensor,
MAP sensor, and throttle position sensor to deter-
mine correct ignition timing.
ENGINE WARM-UP MODE
This is a OPEN LOOP mode. The following inputs
are received by the PCM:
²Engine coolant temperature
²Manifold absolute pressure
²Engine speed (crankshaft position sensor)
²Throttle position
²A/C switch
²Battery voltage
The PCM adjusts injector pulse width and controls
injector synchronization by turning the individual
ground paths to the injectors On and Off.
The PCM adjusts ignition timing and engine idle
speed. Engine idle speed is adjusted through the idle
air control motor.
CRUISE OR IDLE MODE
This is a CLOSED LOOP mode. The PCM recog-
nizes an abrupt increase in throttle position or MAP
pressure as a demand for increased engine output
and vehicle acceleration. The PCM increases injector
pulse width in response to increased fuel demand.
When the engine is at operating temperature this
is a CLOSED LOOP mode. During cruising speed the
following inputs are received by the PCM:²Engine coolant temperature
²Manifold absolute pressure
²Engine speed (crankshaft position sensor)
²Throttle position
²Exhaust gas oxygen content
²A/C control positions
²Battery voltage
The PCM adjusts injector pulse width and controls
injector synchronization by turning the individual
ground paths to the injectors On and Off.
The PCM adjusts engine idle speed and ignition
timing. The PCM adjusts the air/fuel ratio according
to the oxygen content in the exhaust gas.
ACCELERATION MODE
This is a CLOSED LOOP mode. The PCM recog-
nizes an abrupt increase in throttle position or MAP
pressure as a demand for increased engine output
and vehicle acceleration. The PCM increases injector
pulse width in response to increased fuel demand.
DECELERATION MODE
This is a CLOSED LOOP mode. During decelera-
tion the following inputs are received by the PCM:
²Engine coolant temperature
²Manifold absolute pressure
²Engine speed
²Throttle position
²Exhaust gas oxygen content
²A/C control positions
²Battery voltage
The PCM may receive a closed throttle input from
the Throttle Position Sensor (TPS) when it senses an
abrupt decrease in manifold pressure. This indicates
a hard deceleration. The PCM may reduce injector
pulse width or the number of injectors firing per
engine revolution. This helps maintain better control
of the air/fuel mixture (as sensed through the O2S
sensor).
WIDE OPEN THROTTLE (WOT) MODE
This is an OPEN LOOP mode. During WOT oper-
ation, the following inputs are received by the PCM:
²Engine coolant temperature
²Manifold absolute pressure
²Engine speed
²Throttle position
When the PCM senses WOT condition through the
Throttle Position Sensor (TPS) it will:
²De-energize the air conditioning relay. This dis-
ables the air conditioning system.
The exhaust gas oxygen content input is not
accepted by the PCM during WOT operation. The
PCM will adjust injector pulse width to supply a pre-
determined amount of additional fuel.
NSFUEL SYSTEM 14 - 31
GENERAL INFORMATION (Continued)
Generic Scan
Tool CodeDRB III Scan Tool Display
P0725 Engine Speed Sensor Dynamic Plausibility
Engine Speed Sensor Over Speed Recognition
Engine Speed Sensor Static Plausibilty
P1105 Atmospheric Pressure Sensor SRC High Exceeded
Atmospheric Pressure Sensor SRC Low Exceeded
P1201 Needle Movement Sensor SRC High Exceeded
Needle Movement Sensor SRC Low Exceeded
P1220 Fuel Quantity Actuator Neg. Gov. Deviation Cold
Fuel Quantity Actuator Neg. Gov. Deviation Warm
Fuel Quantity Actuator Pos. Gov. Deviation Cold
Fuel Quantity Actuator Pos. Gov. Deviation Warm
P1225 Control Sleeve Sensor Signal High Exceeded
Control Sleeve Sensor Start End Pos. Not Attained
Control Sleeve Sensor Stop End Pos. Not Attained
P1230 Timing Governing Negative Governor Deviation
Timing Governing Positive Governor Deviation
P1515 Accelerator Pedal Sensor Signal High Exceeded
Accelerator Pedal Sensor Signal Low Exceeded
Accelerator Pedal Sensor Signal PWG Plaus With Low Idle Switch
Accelerator Pedal Sensor Signal PWG Plaus With Potentiometer
P1600 Battery Voltage SRC High Exceeded
P1605 Terminal #15 Plausibility After Startup
P1610 Regulator Lower Regulator Limit
Regulator Upper Regulator Limit
P1615 Microcontroller Gate-Array Monitoring
Microcontroller Gate-Array Watchdog
Microcontroller Prepare Fuel Quantity Stop
Microcontroller Recovery Was Occurred
Microcontrller Redundant Overrun Monitoring
P1630 Timing Solenoid Valve Controller Open Circuit
Timing Solenoid Valve Controller Short Circuit
P1635 Glow Relay Controller Open Circuit
Glow Relay Controller Short Circuit
P1650 Diagnostic Lamp Open Circuit
Diagnostic Lamp Short Circuit
P1655 A/C Control Short Circuit
A/C Control Open Circuit
P1660 Redundant Emer. Stop Plausibility In After-Run
Redundant Emer Stop Powerstage Defective
P1665 Cruise Status Indicator Lamp Short Circuit
P1680 EEPROM Plausibility Checksum Error for Adj.
EEPROM Plausibility Checksum Error in CC212
EEPROM Plausibility Communication With EEPROM
EEPROM Plausibility Func. Switch Wrong or Missing
NS/GSEMISSION CONTROL SYSTEM 25 - 3
DESCRIPTION AND OPERATION (Continued)
