Code 12

Code 12 is the normal diagnostic-mode code displayed by the ECM when reading Diagnostic trouble codes on the Pontiac Fiero.

Code 12 does not normally indicate a fault. It indicates that the ECM is in diagnostic mode and that the check engine light is able to flash codes.

Overview

When the ECM is placed into diagnostic mode through the ALDL connector, the check engine light should flash Code 12 before any stored trouble codes are displayed.

Code 12 is usually flashed three times. If other trouble codes are stored, they are displayed after Code 12.

Flash pattern

Code 12 is displayed as:

• One flash
• Pause
• Two flashes

This represents code 12.

Animated flash pattern:

Meaning

Code 12 usually means:

• The ECM is in diagnostic mode.
• The check engine light is functioning.
• The ECM can display stored trouble codes.

It is expected when reading codes and is not normally a repair code by itself.

Reading codes

A typical code-reading sequence begins with Code 12.

For example, if Code 32 is stored, the sequence may appear as:

• Code 12
• Code 12
• Code 12
• Code 32
• Code 32
• Code 32

The exact sequence may repeat until diagnostic mode is exited.

Related topics:

• Diagnostic trouble codes
• ALDL diagnostics
• ALDL connector
• Check engine light

If Code 12 does not appear

If Code 12 does not appear when attempting to read codes, possible causes include:

• Incorrect ALDL terminals jumpered
• Ignition not in the correct position
• Check engine light bulb problem
• ECM power or ground problem
• Wiring problem
• Faulty ECM
• Incorrect diagnostic procedure

Related topics:

• ECM
• Check engine light
• Ground problems
• Fuses and relays
• Wiring diagrams

Notes

Code 12 should not be confused with a stored fault code. It is normally the confirmation that diagnostic mode is active.

If Code 12 appears and no other codes follow, the ECM may not have any stored trouble codes.

See also

• Diagnostic trouble codes
• ALDL diagnostics
• ECM
• Check engine light
• Electrical system