MaxxECU online help

The scope is used to:

•Check the input voltages of both digital and VR-sensors.

•Set the arming voltages for VR-sensors.

•Check the polarity of VR-sensors.

•Check for zero-crossing problems on VR-sensor.

•Check the relationship between the Crank and Cam sensors in some special cases (multitooth+home like the 2JZ and similar triggers).

The scope is NOT the tool to tell anything about the actual pattern on the trigger wheels. It can be used to tell basic stuff like if the inputs are swapped, but to analyze the patterns we use the Trigger Logger.

The trigger logger can be used to:

•Tell what pattern the trigger wheel on the crank and cam has

•See trigger problems caused by compression, bad trigger wheels, interference etc.

See, Trigger Logger for more information about the important trigger logger.

How to use the trigger oscilloscope

Examples of what settings might be used to set by using the built-in trigger oscilloscope.

1. Use the Trigger Oscilloscope to set the Trigger Input and Home Input sections. (Digital/VR, polarity and arming voltages).

Note: When cranking, start at 200ms, that's about 1 revolution at normal cranking speed (if the data is to compressed try lowering the time (necessary for wheels with lots of teeth)).

In the above we can see that the Trigger (crank) is a VR-signal and the HOME/CAM is a digital signal.

From the VR-signal we can tell:

•It has lots of voltage, we can set the ARM voltage high to make it less sensitive to interference.

•The polarity is FALLING, because that's it that's the fastest "edge" during the missing gap (rises slowly, falls fast)

From the digital signal we can tell:

•The voltage from the sensor is OK (it needs to be above the dotted red line, and then fall to about 0V).

•The polarity if digital signals can't often be determined from the scope.

Digital signal polarity:

• There are cases where it should be the edge farthest away from a crank wheel edge.

• In some cases, it's dependent on the selected Trigger system.

• In most cases, it doesn't matter for digital signals.

Common problems that can be seen in the scope:

Sampling time to long for the signal, looks compressed and uneven.

Sampling time to long, trigger-dots but no matching waveforms.

Incorrect polarity, it triggers on the falling edge, but it should be on the rising edge.

To long sampling time, many trigger dots that doesn't match the waveform. There's also more signals on the CAM input than on the CRANK, indicating that the CAM and CRANK inputs most likley are swaped.

The trigger logger can be used to:

•Tell what pattern the trigger wheel on the crank and cam has.

•See trigger problems caused by compression, bad trigger wheels, interference etc.

The trigger logger graphs the times (in microseconds) between each trigger signal received by the ECU. For this to show reliable results the trigger inputs need to be set up properly for the ECU to correctly trigger on the inputs.

The Trigger Logger doesn't care at all about the trigger system or its settings, just the trigger inputs (the Trigger input and Home input sections).

Note: Green and Blue mean the ECU doesn't have any trigger problems (but there could still be problems it's not seeing). Orange indicates some problem.

Example of a good trigger pattern.

In the above image we can see that it has a pattern of 3 short and 1 long pulse. Remember that these are the times between the trigger signals. What would this wheel actually look like? From the "lots of short and one long", we can conclude that it's a missing tooth wheel.

The missing gap is about 3 times as long as the regular teeth. That means that there are TWO missing teeth (if were ONE missing tooth the time would be about 40000µs).

The total number of teeth including the missing would be 3(the short ones)+1(the long one)+2(the missing ones), so 6 teeth.

This pattern is 6-2.

Example of a trigger loggers with problems

The small wave in the signal is the engine compression, the engine slows down a little during compression (which is totally fine for the ECU). BUT, there's a lot of triggers that are too long and it doesn't look like a pattern.

What's happening here is that the arming voltage is set to high and the ECU "misses" some of the triggers, so it registers several short signals as one long. This is not going to work.

The tooth after the missing is a little longer than expected. This is probably caused by incorrect polarity.

A good looking 60-2 trigger logger (57 short, 1 long, about three times longer than the other teeth)

This is when running, when cranking there's usually more variation in the pattern.

If the trigger pattern here looks irregular or has spikes and gaps in it, there's no way for the ECU to "sync" to the pattern and register RPM. Before continuing and trying to set up the trigger system (60-2 etc), we would need to figure out what the problem with the input signal is.