| PARAMETER |
TYPE |
UNITS |
RANGE @ WARM IDLE |
EXPLANATION |
| ROM ID |
|
- |
- |
the revision number of the ROM chip inside the ECU
|
|
the ID of the internal firmware version in the ECU's ROM varies
between years, models, and market where the car was delivered
the locations in the ECU's memory of the monitored values are
different for each different ROM; read why this matters
here
|
| System voltage |
|
V |
13-14 |
the voltage as measured at the ECU
|
|
this can be different than the voltage measured at the
battery, depending
upon the state of the grounding straps, connections, and wires between
the battery and the ECU
the ECU makes corrections to its calculations for those that
involve voltage-sensitive sensors
the ECU adjusts the fuel injector duration for an inherent
time lag that is also voltage sensitive
|
| Vehicle speed |
INPUT |
kph |
- |
speed of the vehicle as measured by the VSS
|
|
this is the speed measured by the vehicle speed sensor (VSS),
not the speed shown on the speedometer which
uses a mechanical device to measure speed
the ECU uses the vehicle speed for controlling the canister purge
and radiator fan, and holding the idle higher than normal to prevent
stalling at speed; some say it affects fuel trim also
the engine is able to run very well without the VSS
|
| Engine speed |
INPUT |
rev/min |
- |
RPM as measured by the cam and crank angle sensors
|
|
this is one of the primary values used as input parameters in the
internal lookup tables kept in the ECU's ROM
this is measured differently from the RPM shown on the tachometer
more on the cam and crank angle sensors
here
|
| Coolant temperature |
INPUT |
deg C |
80-95 |
temperature of coolant in the heads
|
|
the temperature indicated by the gauge on the dashboard is
measured from a completely different sensor
incomplete bleeding of the system can cause the two sensors to
read wildly different - one from coolant and the other from trapped air
coolant temp is used by the ECU to decide when to override 'normal'
operation in favor of a mode which works more effectively when the
engine is cold, and to make adjustments to calculations for temperature
sensitive sensors
|
| Ignition timing |
CONTROL |
deg BTDC |
12-28 (auto)
18-22 (manual)
9-21 (turbo)
[*1]
|
degrees BTDC that the spark is fired
|
this is one of the primary engine control parameters (outputs of the
ECU)
in addition to basic timing, timing is altered when knocking
is detected, and when angular velocity of the crankshaft fluctuates
(engine is jerking)
([*1]: warm idle, gear in neutral)
|
| Airflow signal |
INPUT |
V |
0.8-1.2 |
amount of air entering the engine
|
|
the EJ22 uses a hot-wire MAF which measures the mass
of the air entering the engine in a certain time
this varies with barometric pressure and ambient temperature
(changes in
pressure and temperature result in changes in air density, and thus a
greater or lesser mass of air, to enter each piston stroke)
more on the MAF here
|
| Load |
INPUT |
air mass/rev |
15-20 (non-turbo)
30-50 (turbo)
|
how hard the engine is working - mass of air consumed per
engine revolution
|
this is one of the primary values used as input parameters in the
internal lookup tables kept in the ECU's ROM
the load is calculated by the ECU rather than read from a sensor
this is calculated from the MAF sensor (mass/time) and the RPM
cam/crank sensor (rev/time):
mass/time / rev/time = mass/rev
if load value is out of range, the MAF is usually at fault; can also
potentially be the RPM sensors (cam/crank)
more on the load calculation here
|
| Throttle position signal |
INPUT |
V |
4.4-4.8 closed
(0.7-1.6 open)
|
how far the throttle is open
|
|
this is measured as the voltage drop across a potentiometer
(variable resistor) which changes resistance as the throttle body
opens
the ECU uses this partially to determine how hard the driver is
attempting to push the engine (regardless of the current load)
there is another separate binary throttle signal from a switch
on the throttle body which opens/closes just at
the very closed (throttle off) end of gas pedal travel (see "Idle
switch")
|
| Zeroed throttle position |
? |
? |
? |
? |
|
only on 90-91 manual and 91-94 turbo models
|
| Injector pulse width |
CONTROL |
ms |
3.0-3.7 (non-turbo)
2.0-3.5 (turbo)
|
time in msec that each fuel injector stays open
|
|
the amount of fuel injected into the cylinder
this is one of the primary engine control parameters (outputs of the
ECU)
note that there is only a very rough reading on 90-91 models;
later ECUs have much finer granularity
|
| IAC valve duty cycle |
CONTROL |
% duty cycle |
25-40 (non-turbo)
30-45 (turbo)
[*2]
|
how much air is allowed to bypass the throttle for idling purposes
|
the IAC valve is a solenoid valve that is continuously opened and
closed at a variable rate to effectively vary the amount of air that
is allowed through the valve
the duty cycle is measured as a percent of the time that the
solenoid is open; higher duty ratio means valve is open longer resulting
in higher idle speed
this is non-zero even when not idling; however the amount of air
the IAC allows into the engine becomes insignificant compared
to the air entering the engine via the open throttle
compensates for idle speed decreases due to: a/c operation &
electrical loads; prevents rich air/fuel during deceleration;
mechanically compensates for engine temperature
note that on some EJ22s, there is a air bypass screw on the
intake body which is used to adjust the idle air only enough so that
the IAC duty cycle remains in range
([*2]: warm idle, A/C off, radiator fan off,
battery>13V, sea level)
|
| Oxygen sensor signal |
INPUT |
V |
0-1 |
whether exhaust gasses indicate that the
fuel/air mixture is currently burning lean or rich
|
|
lower values (towards 0) indicate a lean mixture, higher (towards 1)
indicate rich
this oscillates rapidly during closed-loop operation;
as the fuel/air mixture is
changed to keep this centered, this varies rapidly between near 0 to
near 1
|
| Fuel trim |
CONTROL |
% |
-1.6 to 1.6 |
+/- incremental change added to the injector pulse
width to compensate for the lean/rich condition shown by
oxygen sensor
|
|
this is the incremental fuel added/subtracted to the main fuel/air
mixture to keep the ratio correct
if OXS indicates lean, the fuel trim correction is positive (+)
the fuel trim is changed rapidly to keep the OXS signal centered
more on air/fuel trim here
|
| Timing correction |
CONTROL |
deg |
-10 to 10 |
+/- the degrees of timing advance added to timing to correct for knock
|
|
this is changed to non-zero when pinging is detected by the knock
sensor
this is used to temporarily advance (often only for several seconds)
the timing to counteract pinging
|
| Boost control duty cycle |
? |
? |
? |
? |
|
turbo models only
|
| Barometric pressure |
INPUT |
mm Hg |
- |
atmospheric pressure as measured from a sensor inside the ECU
|
|
|
| Boost/vacuum |
? |
? |
? |
? |
|
turbo models only
|
| PARAMETER |
TYPE |
UNITS |
RANGE @ WARM IDLE |
EXPLANATION |
| PARAMETER |
TYPE |
EXPLANATION |
| Ignition switch |
|
ON if ignition key switch is on
|
| A/T mode |
? |
ON if ECU was shipped on an auto transmission model (and is intended
to be paired with sensors shipped with those models
|
|
some engine sensors vary between MT and AT models
|
| Test mode |
|
ON when the EJ22s green 'test mode' connectors are connected
|
|
in this mode, the ECU flashes the 'check engine' light to indicate
any fault codes that are currently being monitored
|
| Read memory mode |
|
ON when the EJ22s black fault code connectors are connected
|
|
in this mode, the ECU flashes the 'check engine' light to indicate
any fault codes that are stored in memory
|
| Neutral switch |
INPUT |
ON if transmission is in neutral
|
|
in most transplanted EJ22s, the original switch is missing and can
be mocked up to avoid the neutral switch trouble code
ECU needs to detect an occasional transition from OFF to ON to
avoid throwing the associated trouble code
|
| Park switch |
INPUT |
ON if automatic transmission is in park
|
|
in most transplanted EJ22s, the original switch is missing and can
be mocked up to avoid the park switch trouble code
ECU needs to detect an occasional transition from OFF to ON to
avoid throwing the associated trouble code
|
| California mode |
? |
ON if ECU delivered in a california emissions equipped auto
|
| Idle switch |
INPUT |
ON if throttle is at completely closed end of travel
|
|
note this binary (ON/OFF) input is different than the continuously
variable throttle position signal
indicates to the ECU that the gas pedal is fully released,
indicating full deceleration or idle
some generic auto idle references indicate that the ECU input
controls to the IAC may not become active unless this switch is triggered
|
| Air conditioning switch |
|
ON when air conditioning system is switched on (but not
necessarily active)
|
| Air conditioning relay active |
INPUT |
ON when the air conditioning compressor clutch
is currently engaged
|
|
the ECU adjusts for the increased load on the engine from the A/C
|
| Radiator fan relay active |
? |
ON when the radiator fan is active (?low or high speed?)
|
| Fuel pump relay active |
? |
ON when the fuel pump is activated
|
| Canister purge valve active |
? |
ON when the canister purge valve is activated
|
| Pinging detected |
INPUT |
ON when the knock sensor detects pinging in the engine
|
|
this detection is done by a piezoelectric sensor attached to the engine
block, which detects the higher frequencies of vibrations sent out
when the engine knocks
the ECU changes the Timing Correction in response to ping
detection
may stay ON for a short duration after pinging stops
|
| Pressure exchange |
? |
Atmospheric pressure is being measured (solenoid is ON) |
|
turbo models only
|
| O2 Monitor |
? |
Air/Fuel ratio is rich |
|
this value is not read by most aftermarket monitoring programs,
but appears in the SSM parameter list
|
| PARAMETER |
TYPE |
EXPLANATION |
