Monitor Light Indicator Values

The light or LED array on the upper left side of the Monitor displays the status of many key Powertrain Control Module (PCM) signals. By observing these lights, one can easily gain information about the condition of dynamic PCM signals

Preliminary: Light Test - Prior to operation of the Monitor it is a good practice to verify that all the lights are functional. Turn ON the Monitor. When the LIGHT TEST switch is set to TEST mode, all the lights (or LEDs) should light and beeper should sound. The red O2S or HO2S light will be dim. Return the switch back to NORM when the test is completed.

Power Indicators - The top group of indicators display power and STI signals. When the appropriate voltage is present the light will be lit. For example, at Key On, the KEYPWR (optional), VREF, and VPWR lights should all be visible. The STI light is ON when the signal is 0 volts (Key Off) and OFF when 5 volts are present at Key On.

Input Signal Indicators - The second group of indicators are selected input signals. They are lit when their voltage is above 2.5 volts, and OFF when their voltage is below 2.5 volts. There are two exceptions to this manner of operation:
The knock sensor and the Oxygen Sensor
The knock sensor lights when the signal is above 1.0 volt.
The OS2 (HO2S) has two lights; the green light for lean (below 0.45 volts) and the red light for rich (above 0.45 volts). During certain engine running conditions the OS2 (HO2S) can be seen switching back and forth between green (lean) and red (rich).

Output Signal Indicators - The bottom group of indicators are output signals such as solenoids, relays, and injectors. These signals are lit when their value is below 6.0 volts and OFF when above 6.0 volts. For example, this means that most solenoids will be lit when they are activated because they are controlled by ground. Injectors will be blinking ON and OFF in proportion to their on times.

Meter Function Indicators - The far right column of indicators display the type of units for the value on the remote display unit. During manual DCV or OHMS, the MANUAL TEST indicator will blink and the appropriate DCV or OHMS indicator will light. In AUTO mode the correct unit indicator will light automatically. Listed are examples of the types of AUTO units that apply for the various PCM signals.

Auto Mode Units
Signal Units
IDM, TACH RPM
IAC Duty Cycle %
Injectors MSEC
All Others DCV