Application Notes - ECM pmCAN Module Instruction Manual

Safety Note: To avoid getting shocked by the 1000V applied to the sensor or possibly
damaging the pmCAN's electronics, always turn the 1000V off before removing or attaching
the sensor from the cable (or the cable from the module). This is done using the Task:
"Toggle High Voltage". When the indicator light on the front of the pmCAN is solid red, the
1000V is off. When the indicator light is solid green, the 1000V is on.
For the successful use of pmCAN, three issues must be understood: Seeding, Fouling,
and Sources of Error.
Seeding the Sensor: As described in "How the PM Sensor Works", for the sensor to work, it
has to be seeded with PM. If the sensor is not seeded, it will report no PM. If the sensor is
insufficiently seeded, it will report a lower than actual PM concentration. The art to using
pmCAN is in keeping the sensor seeded. Here are some rules of thumb:
1. For the P/N 06-10T sensor, when the engine is at a PM level of 1.5 mg/m3 (7.2 M/cc),
seeding takes about 4 minutes. Half the PM level doubles the time. Double the PM level
halves the time.
2. A sensor will slightly deseed itself when the engine stops running or pmCAN is powered
down.
3. If the sensor is sprayed with liquid water (common during the first 15 minutes following
engine start-up), fuel, oil, or DEF (diesel exhaust fluid), it will sometimes deseed and/or
foul the sensor.
4. If the sensor is blown out with compressed air or is cleaned, it will be deseeded.
Fouling the Sensor: Fouling is the direct shorting (via carbon or a liquid) between two or
more of: the high voltage electrode, the ground electrode, or the shield (see Figure 2). Most
of the time, fouling occurs between the high voltage electrode and the ground electrode.
Fouling often occurs as follows:
1. First there will be spikes in the PM and PN readings (ie. intermittent fouling/shorting).
2. Then a steady short between the electrodes will occur resulting in PM and PN values
"pinned" at the upper range of the pmCAN.
3. The VHV will drop below 900V.
4. pmCAN will report an error and output PM and PN values of -1.
Liquid water fouling can occur during the first 15 minutes or so of engine operation (until the
exhaust temperature reaches approximately 80 ⁰C) and will often occur after a large
acceleration (when liquid water is sloshed onto the sensor). Soot fouling can occur at high
PM levels.
Fouling can be minimized by mounting the sensor vertical (i.e. wires going up, holes in the
sensor pointing down).

Application Notes

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