Abbreviation Legend

Abbrev.

Full Name

Description

Where positioned

ECM

Electronic Control Module

The ECM is a digital computer which takes inputs from sensors around the engine bay and computes the ideal fuel/air mixture at that point in time. It also maintains the Cruise Control.

Plastic cased, and approximately 2 x 6 x 8 inches, the ECM is behind the lower right instrument panel cover.

TACH

Distributor Tachometer Signal

Pulses from the distributor for RPM usage

Rear centre of the motor next to firewall

O2 Sensor

Oxygen Sensor

Senses Oxygen level of exhaust

Screwed into left hand exhaust manifold. If faulty, can cause mixture to be too rich or too lean.

CTS

Coolant Temperature Sensor

Measures Engine Coolant Temperature

Front left corner of Intake Manifold. When faulty, will usually cause the computer to sense you are in Alaska with appropriate fuel richness & black exhaust smoke

MAT

Manifold Air Temperature

Measures Intake Manifold Air Temperature

Intake Manifold in front of the Throttle Body. When faulty, will usually cause the computer to sense you are in Alaska with appropriate fuel richness & black exhaust smoke

MAP

Manifold Absolute Pressure

Intake Manifold Pressure, commonly known as Vacuum

Under the dash near the right hand A/C outlet. Connects to the throttle body via a vacuum hose.

BARO

Barometric Air Pressure

As measured with a normal house barometer, senses weather conditions & height above sea level.

Under the dash near the right hand A/C outlet. NOTE: swapping connections between MAP & BARO will cause the computer to sense you are on the top of Mount Everest & cause much too rich a mixture & black exhaust smoke.

TPS

Throttle Position Sensor

Senses Throttle Angle (0 to 90 degrees)

On the right side of the Throttle Body. A variable resistor is used for this sensor. When worn, will cause unstable idling.

EST

Electronic Spark Timing

Spark Angle

The ECM produces this signal using various parameters.

EGR

Exhaust Gas Recirculation

Recycles a percentage of exhaust gas to allow for cooler operating temperatures

Inlet manifold. When faulty, causes pinging/pinking.

PCV

Positive Crankcase Ventilation

Takes piston ring bypass gases from the oil sump to the inlet manifold for burning.

Rocker Arm Cover. When faulty to the extreme can suck oil into intake manifold causing white smoke from exhaust.

HEI

High Energy Ignition

HEI Distributor. Provides basic spark timing and final spark to plugs. Signals to and from ECM for modified spark angle

Centre Rear of motor. If faulty, weak spark or no spark.

ISC

Idle Speed Control

During idling, this motor will hunt to maintain a constant idle speed regardless of engine load

Left side of throttle body. Faulty or maladjusted will cause idle speed to be erratic. Needs to be adjusted concurrently with TPS.

TCC

Torque Convertor Clutch

Locks the torque convertor giving a mechanical drive between the engine and planetary gears within the automatic gear box. At 60mph, should lower the engine revs from about 1900 to about 1700. It is switched in by the ECM once a combination of conditions have been met.

Automatic gear box

None

Speed Sensor Circuit

Supplies pulses to the ECM according to the speed of the vehicle

Generated at the rear of the speedometer housing, by reflective surfaces on the two rotating field magnets using a light emitting diode and photo transistor. The two electronic components are at the end of a three-wire cable and screw onto the rear of the speedometer