Powertrain Control Hardware
POWERTRAIN CONTROL HARDWAREPowertrain Control Module (PCM) and Location
The PCM is the control center for the engine powertrain system. The PCM and the transmission control module (TCM) are stand-alone modules. The PCM and the TCM communicate through the high speed control area network (CAN). The PCM has a 2 pocket connector assembly with a total of 154 pins. The 96-pin connector is dedicated to engine related inputs and outputs. The 58-pin connector is dedicated to chassis related inputs, outputs, powers and grounds. The PCM receives input from sensors and other electronic components (switches and relays) and places this information into random access memory (RAM) or keep alive memory (KAM). Based on information programmed into its read-only memory (ROM), the PCM generates output signals to control various relays, solenoids, and actuators.
The PCM is located inside the cowl on the passenger side.
Glow Plug Control Module (GPCM)
NOTE: The wait-to-start indicator on-time is controlled by the PCM and is independent from the GPCM on-time.
The glow plug system consists of a solid state GPCM, glow plugs, and the associated wiring harnesses. The glow plug on-time is controlled by the PCM and is a function of engine coolant temperature, barometric pressure, and battery voltage. The PCM enables the GPCM to power the individual glow plugs, which it does by providing direct battery voltage. Glow plug on-time normally varies between 1 to 120 seconds. In addition to PCM control, the GPCM internally limits the glow plug operation to 180 seconds regardless of the PCM commanded on-time. The power to the glow plugs is provided through the GPCM solid-state drivers from the vehicle battery. Battery power is fed to the GPCM via two fuses in the power distribution box, then through the vehicle harness (12A581) and the engine harness (12B637), which connects to the GPCM. The GPCM monitors and detects individual glow plug functionality and the control and communication links to the PCM. Concerns detected by the GPCM are transmitted to the PCM using a serial communication signal on a diagnostic line.
Glow Plug Control Module (GPCM):
Keep Alive Memory (KAM)
The PCM stores information in the KAM (a memory integrated circuit chip) about vehicle operating conditions. and then uses this information to compensate for component variability. The KAM is a non-volatile memory.
Hardware Limited Operation Strategy (HLOS)
This system of special circuitry provides minimal engine operation should the PCM (mainly the central processing unit or EEPROM) stop functioning correctly. All modes of self-test are not functional at this time. Electronic hardware is in control of the system while in HLOS.
HLOS Allowable 9utput Functions:
- fixed fuel pulse width synchronized with the crankshaft position (CKP) signal
- fuel pump relay energized
- idle speed control output signal functional
HLOS Disabled Outputs To Default State:
- exhaust gas recirculation (EGR) valve
no torque converter clutch lock-up
Power and Ground Signals
Gold and Silver Plated Pins
NOTE: When installing new terminals make sure new gold or silver plated terminals are used where they were originally used.
Some engine control hardware have gold or silver plated pins within .the connectors and mating harness connectors to improve electrical stability for low current draw circuits and to enhance corrosion resistance.
Keep Alive Power (KAPWR)
The KAPWR circuit supplies a constant battery voltage (B+) input to the PCM to maintain memory contents when the key is in the OFF position.
Power Ground (PWR GND)
The PWR GND circuit(s) is directly connected to the battery negative terminal. PWR GND provides a return path for the PCM vehicle power (VPWR) circuits.
Reference Voltage (VREF)
VREF is a consistent positive voltage (5.0 volts ± 0.5) provided by the PCM. VREF is typically used by 3-wire sensors and some digital input signals.
Signal Return (SIG RTN)
The SIG RTN circuit(s) is a dedicated return path for VREF applied components.
Vehicle Buffered Power (VBPWR)
VBPWR is a regulated voltage supplied by the PCM to vehicle sensors. These sensors require a constant 12 volts for operation and cannot withstand VPWR voltage variations. VBPWR is regulated to VPWR minus 1.5 volts and is also current limited to protect the sensors.
Vehicle Power (VPWR)
VPWR is the primary source of PCM power. VPWR is switched through the PCM power relay and is controlled by the PCM. With the key in the START or RUN position, voltage is supplied to the PCM through the ISP-R circuit. When the PCM senses that the key is in the START or RUN position, the PCM grounds the PCM power relay to energize it and close the internal contacts. With the relay contacts closed, VPWR is supplied to the PCM.