WORKSHOP DIAGNOSTICS

DTC lookup & ECU / TCU checks.

Find the code meaning, then work through the evidence.

Reference reviewed
1 October 2026

Loading code reference…Stored, pending or permanent?

Read the evidence before clearing codes.

EOBD is the European emissions diagnostic interface. Use an enhanced manufacturer scan for complete ECU / TCU faults, subcodes, adaptations and tests. This reference does not connect to the vehicle.

$03

Stored / confirmed

The monitor has met its storage criteria. A stored code can remain after an intermittent fault has stopped.

$07

Pending

A fault has been detected but may not yet have matured into a confirmed code. Retest under the recorded conditions.

$0A

Permanent

Where supported, the controller retains the code until its repair verification criteria pass. Scanner clearing does not erase it.

ENHANCED SCAN

Current / history

These labels depend on the manufacturer and scanner. Keep the original status and full code rather than treating history as an active fault.

Useful EOBD services

Service	What it shows	Workshop use
$01 · Live data	Supported parameters, MIL and readiness.	Compare readings with operating conditions.
$02 · Freeze frame	A snapshot associated with an emissions fault.	Save the conditions that triggered it.
$03 / $07 / $0A	Stored, pending and permanent code lists.	Record each list separately.
$04 · Clear data	Clears emissions diagnostic information.	Save evidence first; readiness may reset.
$05 / $06 · Monitor results	Oxygen-sensor / onboard monitor test results.	Interpret identifiers and limits using OEM data; availability varies.
$08 · System control	Supported emissions component commands.	Follow the vehicle’s test prerequisites.
$09 · Identification	Supported VIN and calibration information.	Compare with the vehicle and unit identity.

Supported services and data vary by vehicle. “Not ready” means the monitor has not completed, not that a component has failed. There is no single drive cycle that fits every car.

Snap-on · OBD-II service reference

A practical scan sequence

Confirm the vehicle and controller identity. Perform a complete module scan as well as EOBD.
Save all codes, suffixes, statuses, freeze frames and relevant live data before clearing or disconnecting the battery.
Check power, earths, wiring and related components using the exact service procedure. Repair the cause, then retest.
Record what returns, in which module and under what conditions. Confirm monitor completion where relevant.

Record the checks No communication guide