How do you know if you need to use the software switchable 120ohm Termination Resistor
Every KrispyGauge ships with a software enabled 120Ω resistor. Whether you need it depends entirely on where your gauge sits in the CAN bus — so here's how to work that out.
Try without it first. Most installations don't need it. Only add it if you have communication problems.
A CAN bus is a single pair of wires with a resistor at each end. Those two resistors stop signals reflecting back down the wire and corrupting the data. The bus needs exactly two — one at each end. No more, no fewer.
Most Haltech ECUs already provide one of them, and many have it enabled in software by default. So the question is really just: is something else already terminating the other end?
Gauge spliced into the middle of an existing bus — no resistor. The two ends are already terminated by the ECU and whatever is at the far end.
Gauge is the last device on the bus — the ECU terminates one end, your gauge is the other. It probably needs the resistor.
Gauge is the only device on the bus, wired straight to the ECU — try without first. If the data is unreliable, add it.
Two or more gauges daisy-chained — only the last gauge in the chain gets a resistor. The ones in the middle don't.
Getting this wrong usually looks like:
NO CAN SIGNAL on the gauge despite correct wiringThat said, check your wiring first. Swapped CAN H and CAN L is a far more common cause of these symptoms than termination. Yellow to CAN High, green to CAN Low — confirm that before you start adding resistors.
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