dtc

This field contains some high level information about the Malfunction Indicator Lamp (MIL) of a vehicle.

High-Level Explanation

This field does not contain information about the reason for the malfunction indicator lamp (generally known as a "check engine light"), but these codes can now be scanned with DIMO. (Dylan Moreland - is there any documentation on how users do this? )

The three fields contained in this signal are:

1. distanceSinceClear: distance in kilometers the vehicle was driven since the malfunction. Note that this is an integer value.

2. distanceWithMil: distance in kilometers the vehicle was driven that the malfunction indicator lamp was illuminated without being reset. Note that this is an integer value.

3. warmupsSinceClear: Number of times that the following two conditions are met during a key cycle.

   1. Coolant temperature rises a minimum of (about) 20°C / 40°F after the engine is started

   2. Coolant temperature reaches a minimum of (about) 70°C / 160°F (60°C / 140°F for diesels)

   That is, turning the ignition on and off (i.e. a key cycle) is necessary for a warmup event to occur but not sufficient, as the engine coolant must increase in temperature according to the above as well as having a key cycle.

Enables

This field enables discovery of:

1. how long and far a vehicle is driven with a "check engine light" on.

2. locations where the DTCs are cleared (this has a high likelihood of being at a mechanic's shop)

3. how long ago and how far the "check engine light" was most recently on

Enabled By

Known Quirks

These three signals are not always populated.

• warmupsSinceClear is null for about 84% of records for an example vehicle

• distanceSinceClear is null for about 70% of records for an example vehicle

• distanceWithMil is null for about 70% of records for an example vehicle

To be explicit, not every record of dtc contains all three fields, some records contain only some of these three. For an example vehicle, when all three values are not present, warmupsSinceClear generally appears on its own while distanceWithMil and distanceSinceClear typically appear together.

When the values are missing, the most recent valid value can generally be filled forward, for example:

gdf['warmupsSinceClear'] = gdf['warmupsSinceClear'].ffill()

Visualizations with Explanations

A vehicle driving with the check engine light on

A vehicle driving after the dtc causing the check engine light is cleared

A vehicle achieving 31 warmups before the check engine light turns back on