1. Connect the WDS or equivalent to the DLC-2.
2. Measure the PID value.
Note
PID/DATA MONITOR AND RECORD function table

Dtc p0841
TroubleshootingMazda 6 Service Manual: Immobilizer System
The immobilizer system allows the engine to start only with a key the system
recognizes.
If someone attempts to start the engine with an unrecognized key, the engine
will not start, thereby helping to prevent vehicle theft.
If you have a problem with the immobilizer system or the key, consult ...
Mazda 6 Service Manual: Operation
NOTE
The engine may not start and security indicator light may illuminate
or flash if the key is placed in an area where it is difficult for the system
to detect the signal, such as on the dashboard or in the glove compartment.
Move the key to a location within the signal range, switch ...