Flash Code Diagnostics

WARNING: This page is about a different car, the 1991 Geo Storm, 1991 Geo Metro, 1990 Geo Storm, and 1990 Geo Metro. However, it is still accessible from the selected car via links, so may be relevant.

Flash code diagnostics can only be used to read current codes and to determine if history codes are present. Flash code diagnostics cannot be used to clear codes or read history codes. Flash code diagnosis is enabled by grounding terminal "K" of ALDL connector with ignition switch in ON position. See Figure or Figure and Fig 1 . Grounding terminal "K" signals DERM to enter flash code diagnostic display mode.

Fig 1: Locating ALDL Connector (Storm)

Courtesy of GENERAL MOTORS CORP.

DERM identifies 2-digit trouble codes by activating INFLATABLE RESTRAINT indicator light via a lamp driver at SIR indicator low output. Each code is flashed once before moving on to next code. After all codes have been displayed, entire code sequence will continuously repeat until ground is removed from terminal "K" of ALDL connector.

Two special codes (Codes 12 and 13) exist when reading flash code mode. Code 12 will always be first code displayed when flash code mode is entered. Code 12 does not indicate a fault; it indicates flash code mode has been enabled. If there are no current or history codes present, DERM will display Code 12 until ground is removed from ALDL connector at terminal "K". Code 13 is displayed if history codes are present. To read history codes, a Scan tester must be used.