L200 L4-2.2L VIN F (2002)
NOTE: Never probe secondary ignition wires, for any reason. Small pin holes in secondary ignition wires allow high voltage from the coil to arc from
the wire to a metal part, external to the secondary ignition circuit. This arcing can cause the engine to miss-fire, causing a driveability complaint.
Digital multimeters approved for use on Saturn vehicles must have an input impedance of ten megohms (10,000,000 Ohms). Input impedance is listed
in the multimeter's owner guide.
IMPORTANT: The input impedance of a multimeter stands for the resistance between the red and black leads, only when you are measuring voltage.
When measuring resistance, the only resistance other than in the circuit being measured is in the actual leads being used.
Circuits
Automotive circuits are divided into three categories: power, signal (control or data), and ground circuits.
Power Circuits
Power circuits are classified as those cables that provide battery or mechanically switched battery voltages to electrical loads. Some examples of these
circuits are:
^
Ignition circuit - 300
^
Battery circuit - 1
^
Headlamp circuit - 40
^
Defog circuits - 193, 1240, 292, 293
Signal (Control Or Data) Circuits
Signal circuits are classified as those cables that provide signal voltages from one electrical device to another device. Examples of these signals and
devices are:
^
Evaporative Emission Canister Purge Solenoid to PCM - 428
^
Fuel Level Sensor to PCM - 30
Signal wires are usually current limited by one of the devices that is attached to the wire. In the above examples the PCM and fuel gage limit the
current in these circuits through the use of electronics (pull up or pull down resistors, transistors, etc.). Signal wire current levels for short circuit
conditions normally do not exceed operating levels by an appreciable amount.
Ground Circuits
Ground circuits are classified as those circuits that provide a ground (zero voltage level with reference to the battery) to the electrical system.
Examples of these circuits are:
^
I/P Chassis ground - 350, 250
^
PCM ground - 551
Since ground circuits are already shorted to ground, the current level is based on the electrical load resistance. Like signal circuits, ground circuit
cable selection is a function of operating current.
Fuse Blocks
Fuse blocks provide a home for mini and maxi fuses, relays, and electronic modules, eliminating the need for separate connections and mounting
attachments. They are also a central connection point for major harnesses (Engine, Forward Lamp, I/P and Body). Inside the fuse block are layered buss
plates that help reduce the number of splices in the harnesses.
With the advances in automotive electronics over the past few years, the size and complexity of wiring harnesses have increased. The fuse blocks help
remove complexity from the wiring assemblies and provide a central location for circuit protection devices and relays. Fuse blocks help reduce the
complexity while also reducing cost and mass. This is accomplished by reducing the number of cut leads, eliminating the need for in-line connectors and
splice packs. This also helps reduce the bundle size of a wiring harness.
General Information
Circuit protection devices such as a maxifuse, minifuse, circuit breaker, or fusible link are utilized to protect the wiring system in case of an electrical
short.
Circuit protection is defined as the application of various electrical devices in an automotive electrical system, such that the components in the system
function properly during normal operating conditions, and during overload conditions. The result is the wiring assembly experiences minimum
degradation.
Examples of system components include electronic modules, relays, solenoids, motors, switches, connectors, wiring, terminals, etc.
The purpose of circuit protection is to protect the wiring assembly during normal and overload conditions. An overload is defined as a short circuit to
ground of a current carrying cable. The short circuit could be caused by a pinched or cut wire or an internal device short circuit, such as an electronic
module failure.
The primary intent of circuit protection devices is to protect the wiring assembly, and not the electrical load at the end of the assembly. In some eases,
