2500 4x2 Pickup V8-318 5.2L Magnum (1994)
Powertrain Control Module: Description and Operation
Modes of Operation
Acceleration
This is a OPEN LOOP mode.
- The Powertrain Control Module (PCM) recognizes an abrupt increase in throttle position or MAP pressure, as a demand for increased engine
output to accelerate vehicle.
- The PCM increases injector pulse width, in response to increased fuel demand.
Cruise
THIS IS A CLOSED LOOP MODE.
With engine at operating temperature, the Powertrain Control Module (PCM) receives inputs from:
-
Air Conditioning Control Position (if equipped)
-
Battery voltage
-
Camshaft position (CMP) sensor
-
Engine coolant temperature (ECT) sensor
-
Manifold absolute pressure (MAP) sensor
-
Intake air temperature (IAT) sensor
-
Crankshaft position (CKP) sensor
-
Throttle position sensor (TPS)
-
Heated oxygen sensor (HO2S)
Based on these inputs the PCM will:
-
Apply voltage to the injectors. The PCM then controls injection sequence and pulse width by switching individual injector ground paths on and
off.
-
Monitor oxygen sensor and fine tune air/fuel ratio by varying injector pulse width.
-
Adjust engine idle speed through the IAC motor.
-
Adjust ignition timing.
-
Operate A/C Compressor Clutch relay (if equipped and selected).
Deceleration
This is an OPEN LOOP mode.
During deceleration the the Powertrain Control Module (PCM) receives inputs from:
- Air Conditioning Control Position
- Battery voltage
- Camshaft position (CMP) sensor
- Engine coolant temperature (ECT) sensor
- Manifold Absolute Pressure (MAP) sensor
- Intake air temperature (IAT) sensor
- Crankshaft position (CKP) sensor
- Throttle Position Sensor (TPS)
Based on these inputs the PCM will:
- Adjust engine idle speed through the IAC motor.
- Adjust ignition timing.
- Operate A/C Compressor Clutch relay (if selected).
- Ignore oxygen sensor input. The PCM will enter fuel cut-off strategy (under hard deceleration).
- Determine proper injector pulse width and continue injection (under normal deceleration).
