What the CEL function does
When the Elite logs a fault, the Check Engine Light (CEL) function turns on a warning for the driver. If Knock Detection is enabled, it can also flash the light when the engine knocks, which is a very effective way to get a driver's attention on a dyno or a track day.
Wiring tab: where the light lives
You have three ways to show the warning, and you can combine them.
| Option | Use it when |
|---|---|
Light Output, Output Mode Digital Switch | You're wiring a lamp or LED directly to an Elite output |
Light Output, Output Mode CAN Output Switched | The car is a supported vehicle and you want the factory dash CEL to work over the vehicle CAN bus |
| Haltech CAN Supported Dash | You run a Haltech dash on the Haltech CAN bus (not the vehicle's own CAN bus) |
Connections
For a wired light, choose a free output for Check Engine Light Output. A DPO is the usual pick. Most lamps are wired with 12V on one side and the ECU output on the other, so the ECU switches the ground.
Active State decides which way round that works. The default, Low, grounds the output when the light should be on. High inverts it: the output is grounded when the light should be off and released when it should be on. Use High only if whatever you're driving expects that inverted signal.
Settings tab: when does it turn off?
The Activation Criteria setting controls how long the light stays on after a fault.
- Current and Past DTCs: the light stays on until someone clears the code in ESP, even if the fault has already gone away. Good for customer cars and race cars, because an intermittent fault can't hide.
- Current DTCs Only: the light is on only while the fault is present. Fix the problem and the light goes out by itself.
We usually use Current and Past DTCs. An intermittent sensor fault that clears itself is exactly the kind of thing you want someone to notice and look at.
Checking it works
With the ignition on, unplug a sensor you've set up with diagnostics, such as coolant temperature. The light should come on. Plug it back in, then clear the code in ESP. If the light never comes on, check the output assignment and Active State first. The DTC index explains each code, and engine protection covers how the Elite can react to faults, not just report them. For knock flashing, see knock control.
