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AP
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Accelerator Pedal Position Sensor
Load/demand input; PCM uses this to determine mass fuel
desired, adjusts fuel delivery through IPR duty cycle and fuel
pulse width and injection timing; 5 volts in, 0.5-0.7 volts at
idle, 4.5 volts at WOT.
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BARO
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Barometric Pressure Sensor
Strategy input; PCM uses this to adjust fuel quantity and
injection timing for optimum running and minimum smoke, also
glow plug on time to aid starting at higher altitudes; 5 volts
in, @ 4.6 volts/14.7 psi at sea level, decreasing as altitude
increases.
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CMP
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Camshaft Posistion Sensor
Strategy and load input; PCM uses this to monitor engine speed
to determine engine state and load, and cylinder position in
order to control timing and fuel delivery; Hall Effect sensor
which generates a digital voltage signal; high: 12 volts, low:
1.5 volts.
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DTC
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Diagnostic Trouble Code
System malfunction or fault codes stored in the PCM to aid in
diagnosis.
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EBP
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Exhaust Backpressure Sensor
Feedback input; PCM uses this to monitor and control EPR
operation; 5.0 volts in, 0.8-1.0 volts/14.7 psi KOEO or at
idle, increases with engine RPM/load, decreases as altitude
increases.
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EOT
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Engine Oil Temperature Sensor
Strategy input; PCM uses this for determining glow plug on
time, EPR actuation, idle speed, fuel delivery and injection
timing and adjusts as temperature increases; 5.0 volts in,
4.37 volts@32°F, 1.37 volts @ 176°F, .96 volts @ 205°F.
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EPR
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Exhaust Backpressure Regulator, also EBP Regulator
Output. For quicker engine warm-up at cold temperatures.
If the IAT is below 37°F (50°F on some models) and the EOT is
below 140°F (168° on some models) the PCM sends a duty cycle
signal to a solenoid which controls oil flow from the turbo
pedestal. This causes a servo to close a valve at the
turbo exhaust outlet. The PCM monitors the EBP input to
determine if the EPR needs to be disabled to provide power for
increased load, then reapplies the EPR as load demand
decreases until EOT or IAT rises.
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GPC
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Glow Plug Control
Output. The PCM energizes the glow plug relay for 10 to 120
seconds depending on EOT and BARO.
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GPL
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Glow Plug Light
Output. The PCM controls the "Wait to Start" light
independently from the GPC output. 1 to 10 seconds
depending on EOT and BARO.
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GPM
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Glow Plug Monitor
Feedback input. On 1997 and newer California emission
vehicles, the PCM monitors glow plug relay output voltage to
determine if any glow plugs are burned out or if the relay is
functioning.
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IAT
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Intake Air Temperature Sensor
Strategy input. The PCM uses this for EPR control.
5 volts in, 3.897 volts @ 32°F, 3.09 volts @ 68°F, 1.72 volts
@ 122°F.
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ICP
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Injection Control Pressure Sensor
Feedback input. The PCM monitors the high pressure oil
system to determine if it needs to be increased if load demand
increases. It also uses this to stabilize idle speed.
Volts in: 1.0 volt @ 580 psi, 3.22 volts @ 2520 psi.
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IDM
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Injector Driver Module
The PCM sends a Cylinder Identification and Fuel Demand
Control signal to the IDM. The IDM sends a 110 volt
signal to the injectors. It then grounds each injector
as fuel is required for that cylinder. Fuel Pulse width
is increased to deliver more fuel. The IDM sends a
feedback signal to the PCM for fault detection.
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IPR
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Injection Pressure Regulator
Output. The PCM controls the high pressure oil system by
varying the duty cycle of the IPR. The IPR controls the
oil bypass circuit of the high pressure pump. 0% = full
return to sump (open valve), 100% = full flow to injectors
(closed valve). The PCM monitors the system with the ICP
input. The PCM can control fuel delivery to the
injectors by increasing the IPR duty cycle which increases
fuel pressure through the injector nozzles.
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IVS
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Idle Validation Switch
Strategy input. On-off switch that the PCM uses to
identify required operating mode; idle or power. 0 volts
at idle, 12 volts off idle.
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MAP
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Manifold Absolute Pressure Sensor
Strategy and feedback input. The PCM monitors manifold
pressure to control fuel delivery in order to minimize smoke.
It also optimizes injection timing for detected boost.
It also monitors boost to limit fuel delivery to control
maximum turbo boost. Frequency output: 111Hz = 14.7 psi,
130Hz = 20 psi, 167Hz = 30 psi.
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MIL
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Malfunction Indicator Lamp
"Check Engine" or "Service Engine" light that the PCM
illuminates when certain system faults are present.
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PCM
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Powertrain Control Module, also ECU or ECM for Electronic
Control Unit or Module
The computer which monitors sensor inputs and calculates the
necessary output signals to the engine control systems.
It also checks for readings outside of normal parameters and
records trouble codes for these faults.
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PID
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Parameter Identification, also Data Stream or Sensor Data
Sensor readings displayed to a scan tool that represent sensor
readings to and output signals from the PCM.
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