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Standards

These documents are the generic OBD layer. Manufacturer hybrid PIDs sit on top of them; they do not replace them.

Service modes

SAE J1979 defines ten standardised services (still often called modes). Mode 0x21 and 0x22 are manufacturer-enhanced and are not J1979. UDS 0x22 is a third thing.

Family Service Name
OBD 01

Show current powertrain data

Request live standard PIDs (engine speed, temperatures, fuel, and later hybrid/WWH items when the ECU implements them). This is the main PID catalog service.
OBD 02

Show freeze frame data

Snapshot of the same PID numbers as Mode 01, captured when the last emissions DTC was stored. If Mode 02 PID 02 returns zero, there is no snapshot.
OBD 03

Show stored Diagnostic Trouble Codes

Returns confirmed emissions-related DTCs. Encoding follows SAE J2012 / ISO 15031-6 (P/C/B/U plus four hex digits).
OBD 04

Clear Diagnostic Trouble Codes and stored values

Clears stored DTCs, freeze frame, and turns the MIL off when allowed. No PID payload.
OBD 05

Oxygen sensor test results (non-CAN)

Oxygen sensor monitor results on non-CAN protocols (ISO 9141-2, J1850, KWP). CAN vehicles report the equivalent information in Mode 06.
OBD 06

Test results, other component/system monitoring

On-board monitor results. On CAN this also covers oxygen sensor monitoring (replacing Mode 05).
OBD 07

Show pending Diagnostic Trouble Codes

DTCs detected during the current or last driving cycle that are not yet confirmed.
OBD 08

Control operation of on-board component/system

Bidirectional control of certain on-board devices. Manufacturer support varies widely.
OBD 09

Request vehicle information

VIN, calibration IDs, calibration verification numbers, ECU name, and in-use performance tracking.
OBD 0A

Permanent Diagnostic Trouble Codes

DTCs that survive a Mode 04 clear until the monitor runs and passes. Used for inspection programmes.
OBD 21

Manufacturer-specific (e.g. Toyota enhanced)

Not a J1979 service. Some Toyota and related ECUs use Mode 0x21 for enhanced live data (offsets rather than UDS DIDs).
OBD 22

Manufacturer-enhanced data (SAE J2190)

Enhanced OBD service used by some manufacturers (notably Ford/GM-style) for data beyond J1979. Often confused with UDS Service 0x22.
UDS 10

DiagnosticSessionControl

UDS: switch diagnostic session (default, extended, programming). Manufacturer DIDs often require an extended session.
UDS 19

ReadDTCInformation

UDS: read DTCs (a superset of J1979 Modes 03/07/0A on UDS ECUs).
UDS 22

ReadDataByIdentifier

UDS: read a Data Identifier (DID). This is the usual manufacturer-enhanced path for HV battery SOC, pack voltage, and similar hybrid signals.
UDS 27

SecurityAccess

UDS: unlock a secured session. Many manufacturer DIDs are unreadable until this succeeds. This catalog never publishes seeds or keys.
UDS 2E

WriteDataByIdentifier

UDS: write a DID. Out of scope for this read-oriented PID catalog except as a warning that it exists.
UDS 3E

TesterPresent

UDS: keep a diagnostic session alive.

European regulatory context

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