
Euro Stage III OBD MONITOR INFORMATION
Comprehensive Major Monitors Major Monitors
Components Non Fuel Control Fuel Control
Monitor & Non Misfire & Misfire
Run constantly Run Once Per Trip Run Constantly
Includes All Engine Hardware Monitors Entire Emission Monitors Entire System
- Sensors, Switches, System
Solenoids, etc.
One Trip Faults - Turns On Two Trip Faults - Turns On Two Trip Faults - Turns On
The MIL and Sets DTC After The MIL and Sets DTC After The MIL and Sets DTC After
One Failure Two Consecutive Failures Two Consecutive Failures
Priority 3 Priority 1 or 3 Priority 2 or 4
All Checked For Continuity Done Stop Testing = Yes
Fuel Control Monitor
Open Monitors Fuel Control
Short To Ground Oxygen Sensor Heater System For:
Short To Voltage Oxygen Sensor Response
Fuel System Lean
Fuel System Rich
Inputs Checked For
Requires 3 Consecutive Rationality
Catalytic Converter
Fuel System Good TripsTo Efficiency Except EWMA
Extinguish The MIL Outputs Checked For - up to 6 tests per trip
Functionality and a one trip fault
EGR System
Misfire Monitor
Evaporative Emission Monitors For Engine Misfire
System at:
(Purge and Leak) 1000 RPM Counter
Non-LDP (Type B)
or **200 RPM Counter
LDP (Type A)
Requires 3 Consecutive Requires 3 Consecutive Requires 3 Consecutive
Global/Alternate Good Trips Global Good Trips Misfire Good Trips
to Extinguish the MIL* to Extinguish the MIL* To Extinguish the MIL
*40 Warm Up Cyclesare required to erase **Type A misfire is a two
DTC's
afterthe MIL has been extinguished. trip failure. The MIL will
illuminate and blink at
the first failure.
3
GENERAL INFORMATION

3.2.3 OTHER CONTROLS
CHARGING SYSTEM
The charging system is turned on when the
engine is started and ASD relay energized. When
the ASD relay is on, ASD output voltage is supplied
to the ASD sense circuit at the PCM. This voltage is
connected in some cases, through the PCM and
supplied to one of the generator field terminals
(Gen Source +). All others, the Gen field is con-
nected directly to the ASD output voltage. The
amount of current produced by the generator is
controlled by the Electronic Voltage Regulator
(EVR) circuitry, in the PCM. Battery temperature is
determined from IAT. This temperature along with
sensed line voltage, is used by the PCM to vary the
battery charging rate. This is done by cycling the
ground path to the other generator field terminal
(Gen field driver).
SPEED CONTROL SYSTEM
The PCM controls vehicle speed by operation of
the speed control servo vacuum and vent solenoids.
Energizing the vacuum solenoid applies vacuum to
the servo to increase throttle position. Operation of
the vent solenoid slowly releases the vacuum allow-
ing throttle position to decrease. A special dump
solenoid allows immediate release of throttle posi-
tion caused by braking, cruise control switch turned
off, shifting into neutral, excessive RPM (tires spin-
ning) or ignition off.
LEAK DETECTION PUMP SYSTEM (IF EQUIPPED)
The leak detection pump is a device that pressur-
izes the evaporative system to determine if there
are any leaks. When certain conditions are met, the
PCM will activate the pump and start counting
pump strokes. If the pump stops within a calibrated
number of strokes, the system is determined to be
normal. If the pump does not stop or stops too soon,
a DTC will be set.
3.2.4 PCM OPERATING MODES
As input signals to the PCM change, the PCM
adjusts its response to output devices. For example,
the PCM must calculate a different injector pulse
width and ignition timing for idle than it does for
wide open throttle. There are several different
modes of operation that determine how the PCM
responds to the various input signals.
There are two types of engine control operation:
open loopandclosed loop.
Inopen loopoperation, the PCM receives input
signals and responds according to preset program-
ming. Inputs from the heated oxygen sensors are
not monitored.Inclosed loopoperation, the PCM monitors the
inputs from the heated oxygen sensors. This input
indicates to the PCM whether or not the calculated
injector pulse width results in the ideal air-fuel
ratio of 14.7 parts air to 1 part fuel. By monitoring
the exhaust oxygen content through the oxygen
sensor, the PCM can fine tune injector pulse width.
Fine tuning injector pulse width allows the PCM to
achieve the lowest emission levels while maintain-
ing optimum fuel economy.
The engine start-up (crank), engine warm-up,
and wide open throttle modes are open loop modes.
Under most operating conditions, closed loop modes
occur with the engine at operating temperature.
IGNITION SWITCH ON (ENGINE OFF) MODE
When the ignition switch activates the fuel injec-
tion system, the following actions occur:
1. The PCM determines atmospheric air pressure
from the MAP sensor input to determine basic
fuel strategy.
2. The PCM monitors the engine coolant tempera-
ture sensor and throttle position sensor input.
The PCM modifies fuel strategy based on this
input.
When the key is in the on position and the engine
is not running (zero rpm), the auto shutdown relay
and fuel pump relay are not energized. Therefore,
voltage is not supplied to the fuel pump, ignition
coil, and fuel injectors.
Engine Start-up ModeÐ This is an open loop
mode. The following actions occur when the starter
motor is engaged:
1. The auto shutdown and fuel pump relays are
energized. If the PCM does not receive the cam-
shaft and crankshaft signal within approxi-
mately one second, these relays are de-
energized.
2. The PCM energizes all fuel injectors until it
determines crankshaft position from the cam-
shaft and crankshaft signals. The PCM deter-
mines crankshaft position within one engine
revolution. After the camshaft position has been
determined, the PCM energizes the fuel injectors
in sequence. The PCM adjusts the injector pulse
width and synchronizes the fuel injectors by
controlling the fuel injectors' ground paths.
3. Once the engine idles within 64 rpm of its target
engine speed, the PCM compares the current
MAP sensor value with the value received dur-
ing the ignition switch on (zero rpm) mode. A
diagnostic trouble code is written to PCM mem-
ory if a minimum difference between the two
values is not found.
4
GENERAL INFORMATION

POWERTRAIN VERIFICATION TEST VER - 6 APPLICABILITY
1. NOTE: If the PCM has been replaced and the correct VIN and mileage have not
been programmed, a DTC will be set in the ABS Module, Airbag Module and the
SKIM.
2. NOTE: If the vehicle is equipped with a Sentry Key Immobilizer System, Secret
Key data must be updated. Refer to the Service Information for the PCM, SKIM and
the Transponder (ignition key) for programming information.
3. Inspect the vehicle to ensure that all engine components are properly installed and
connected. Reassemble and reconnect components as necessary.
4. The LDP Monitor Test Mode has been added to the DRBIII to verify repairs to the LDP
System. A DRB software program was written which causes the PCM to run the LDP Monitor
as part of this test. Test failures will be indicated through a stored DTC.
5. LDP Monitor Test Mode is a useful way to run a total system performance test. Use this test
to verify any type of LDP system repair.
6. Software program makes temporary changes to operating mode of PCM. For this reason, it
is critical that test not be interrupted. PCM's left in this mode as result of interrupted test will
illuminate the MIL for 8-10 mi of driving with no DTC's stored.
7. Erasing DTC's will not change this condition.
8. If a vehicle is found to be stuck in the mode described above, the LDP Dealer Test should be
re-run in its entirety so that the software program in the DRBIII can restore the PCM
operating mode.
9. Note similarity to LDP Monitor screen found under OBDII Monitors. Failure modes are
fewer in this System Test than OBDII LDP Monitor. System Test only stores Small Leak DTC
to indicate problem with system. No other type of failure mode indication given.
10. System Test failure may have been, for example, due to a large leak, but the PCM will set
the Small Leak DTC to indicate failures that occurred as part of the system test.
11. Connect the DRB to the data link connector. Engine running, turn off all accessories.
12. Note: While test is being performed, PCM must see RPM, minimum MAP, No Vehicle speed
and minimum Throttle Position sensor (At idle, in park.) With DRBIII in System Tests, perform
the LDP Monitor Test and follow the instructions on the screen.
13. If the LDP Monitor Test failed and a Small Leak DTC has set, the repair is not complete.
Check for any related Technical Service Bulletins and return to Symptom List.
14. If any other trouble code has set, return to Symptom List and follow the path specified for
that trouble code. If the LDP Monitor Test passed, the repair was successful and testing is now
complete.
Are any DTCs present?All
Ye s®Repair is complete.
No®Repair is not complete, refer to appropriate symptom.
280
VERIFICATION TESTS
VERIFICATION TESTS ÐContinued