General Description - Pcm And Sensors; 58X Reference Pcm Input; A/C Request Signal; Crankshaft Position (Ckp) Sensor - Isuzu 1999 RODEO Workshop Manual

GENERAL DESCRIPTION — PCM
AND SENSORS

58X Reference PCM Input

The powertrain control module (PCM) uses this signal
from the crankshaft position (CKP) sensor to calculate
engine RPM and crankshaft position at all speeds. The
PCM also uses the pulses on this circuit to initiate injector
pulses. If the PCM receives no pulses on this circuit, DTC
P0337 will set. If the PCM receives a number of pulses
other than the expected amount, DTC P0336 will set. The
engine will not start and run without using the 58X
reference signal.

A/C Request Signal

This signal tells the PCM when the A/C mode is selected
at the A/C control switch. The PCM uses this signal to
adjust the idle speed before turning ON the A/C clutch.
The A/C compressor will be inoperative if this signal is not
available to the PCM.
For A/C wiring diagrams and diagnosis for the A/C
electrical system, refer to A/C Clutch Circuit Diagnosis.

Crankshaft Position (CKP) Sensor

The crankshaft position (CKP) sensor provides a signal
used by the powertrain control module (PCM) to calculate
the ignition sequence. The CKP sensor initiates the 58X
reference pulses which the PCM uses to calculate RPM
and crankshaft position. For additional information,
refer to Electronic Ignition System.
Camshaft Position (CMP) Sensor And
Signal
The camshaft position (CMP) sensor sends a signal to
the PCM. The PCM uses this signal as a "sync pulse" to
trigger the injectors in the proper sequence. The PCM
uses the CMP signal to indicate the position of the #1
RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
0013
piston during its power stroke. The CMP allows the PCM
to calculate true sequential fuel injection (SFI) mode of
operation. If the PCM detects an incorrect CMP signal
while the engine is running, DTC P0341 will set.
If the CMP signal is lost while the engine is running, the
fuel injection system will shift to a calculated sequential
fuel injection mode based on the last fuel injection pulse,
and the engine will continue to run. It will run in the
calculated sequential mode with a 1–in–4 chance of the
injector sequence being correct.
For further information, refer to
DTC P0341
DTC P0342.

Engine Coolant Temperature (ECT) Sensor

The engine coolant temperature (ECT) sensor is a
thermistor (a resistor which changes value based on
temperature) mounted in the engine coolant stream. Low
coolant temperature produces a high resistance of about
100,000 W at –40°C (–40°F). High temperature causes a
low resistance of about 70 W at 130°C (266°F).
The PCM supplies a 5–volt signal to the ECT sensor
through resistors internal to the PCM and then measures
the voltage after the internal resistor. This signal voltage
will be high when the engine is cold and low when the
engine is hot. By measuring the voltage, the PCM
calculates the engine coolant temperature. Engine
coolant temperature affects most of the systems that the
PCM controls.
The Tech 2 displays engine coolant temperature in
degrees. After engine start–up, the temperature should
rise steadily to about 85°C (185°F). It then stabilizes
when the thermostat opens. If the engine has not been
run for several hours (overnight), the engine coolant
temperature and intake air temperature displays should
be close to each other. A hard fault in the engine coolant
sensor circuit will set DTC P0117 or DTC P0118. An
intermittent fault will set a DTC P1114 or P1115.
6E1–425
014RX007