ECM pmCAN Module Instruction Manual page 14

Sometimes, the fouling will clean itself. It doesn't clear in 15 minutes, the sensor will have
to be taken out of the exhaust and blown out with compressed air for about 10 seconds. In
extreme cases, the sensor will need to be disassembled and cleaned. Appendix G describes
how to clean the sensor which should take less than 5 minutes.
Sources of Error:
1. Effect of flow: Unfortunately, the sensor has a sensitivity to flow velocity. At a fixed
particulate concentration, the reported PM (and PN) will scale with flow velocity. For that
reason, the PM sensors have been calibrated at a mid-exhaust flow velocity.
2. Effect of flow changes: When quickly transitioning from a high (or low) exhaust flowrate
to a low (or high) flowrate condition, an overshoot (or undershoot) in the reported PM may
be experienced.
3. Effect of deseeding: At a long period of operation at zero or low PM levels, the sensor will
sometimes deseed itself.
4. Effect of wiggling sensor cable: Tie the sensor cable down. Don't let it wiggle. If it
does, noise will appear in the PM and PN signals due to the triboelectric effect.
Usage: pmCAN can be used in engine-out and tailpipe-out installations with diesel and
spark-ignition engines. However in tailpipe-out installations, due to liquid water being in the
exhaust, getting data during start-up can be problematic. Keep in mind that not every start-up
will be affected by liquid water since during some start-ups, water droplets will not hit the
sensor.
Installation: The PM sensor should be mounted perpendicular to the flow of exhaust gases
using the supplied 18mm (thread diameter) x 1.5mm (thread pitch) x 6mm (tall) boss.
Finger-tighten the sensor. Do not use a wrench on the sensor or you may overtighten it and
crack the sensor body. Maximum tightening torque of 1.5 lbf-ft (2 N-m). Exhaust flow has
to pass by the sensor for it to work. Therefore, do not mount the sensor in a non-straight
piece of pipe where the flow past the sensor may be ambiguous. It is preferential to mount
the sensor vertical with the holes in the bottom pointing straight down. This will help
clear the sensor of water especially with tailpipe-out installations. To avoid the effects of
triboelectric changing (ex. noise in the PM signal), tie down the cabling to the sensor so that
it does not "wave in the wind".
Exhaust Stratification: PM is not necessarily evenly distributed over the cross-section of
the exhaust. In bends in the exhaust, PM will go straight rather than turn the corner.
Therefore the distribution of PM will be dependent of what is upstream of where the sensor is
located.
Power: The pmCAN kit requires 6 to 32 VDC and consumes 140 mA at 12 VDC.
Grounding is critical. The negative terminal of the power supply should be electrically
connected to the metal that the sensor is mounted in otherwise the system will be
susceptible to seemingly random electrical noise. With tailpipe-out installations, the PM
sensor may be mounted in an extension that is connected to the exhaust system using a small
length of silicon hose. In this case, a braided wire should be run from the extension to the
ground of the vehicle (which for most vehicles is connected to the negative terminal of the
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