SENSOR TESTING    and other related functions, including actuators      

Modern Engine control technology:

Basics on these SideKick and Tracker cars.
Sensors are inputs to the ECU,  (except fuel level ) (one sadly missed sensor is fuel pressure ,that came many years later.)
How many sensors are there; there are about 12. ( some are not used on early years)
ECT, IAT ,MAP/MAF, oxygen, TPS, Fuel level, Coolant Temperature , CMP(rpm and TDC), CKP crank TDC and timing) EGR MAP, Tank pressure,VSS (veh. speed), EGR thermoprobe.
Actuators are ECU outputs they are devices the ECU controls, (most are just magnetic coils, that move something )
The actuators are 13 total   (up to 4 VSV, vacuum solenoid valves )  and 1 to 4 injectors, a Dash pot,  Fuel pump regulator, the ISC and 2 or more relays.

The dash fuel gauge and sender (sensor)

The Dash engine temperature gauge and sender.

What is LimpHome mode?

What is the purpose of  the ECU and sensors , includes all Sensor names.
Thie page is the long version of the link below.

The long full list of Sensor testing procedures, including most Acutators  too (ISC ,EGR)
Shows the differences between 8v and 16v.

What is Command Authority ?, and how does this effect my AFR (air fuel ratio's)

How to find your sensors fast on your car? , See How to Find the Sensors!
(includes vacuum lines, actuators and coolant lines, too)

The below is my unified EFI drawing that works for both engines, TBI or MPI.
Let me explain CAS (cam or crank angle senders) it can be 1 sensor or 2.   (evolution)
In 89/90' the dizzy had one sender inside the dizzy and its own ignitor, and made spark all by itself. there is no X connection below , in those years.
Then in 1991 the old dizzy is abandoned and now has a CMP (CAS) sender and the ECU makes all spark  , the CAS in this case is a cam sender.
This lasted until 1996+ until the they added a CKP sender to the crank so that OBD2 can do,  MISFIRE detection (P030x).  CMP and CKP senders, 2 of them.
In 1999 they used 4 coils and 4 ignitors. 2.0L (and 96/98 Suzuki 1.8L motors.) these cars use on CAS mounted to the left rear cam shaft (DOHC)
In all cases the spark is listened to, that is, the ECU monitors spark , not shown below.

If any input is wrong the ECU may mess up, the spark or injection.   If the fuel pressure is wrong that too, is a bad input to the ECU.
The ECU listens to its sensors and then calculates spark timing and fuel injection rates. At all times hot or cold and at any reasonable altitude.
To start the engine, you need, power to the ECU, and a working CAS, and spark ,or it will not start.
If the CEL lamp is out key on, you have no power. (or the lamp is dead, new cars 96+ we can see the CEL lamp at the scan tool.)
These facts are just basics,  and the drawing below, shows most of what you need to understand this system.
Keep in mind, the ECU can not warn you of low or zero fuel pressure.
If you have a 96' or newer car , look here for the scan tool readings.(step by step) (if not?, its hard work)

v2:  11-21-2012  (expanded greatly for noobs the curious)  Happy Trails !