Operation Section Table 2. Diagnostic Fault Codes (Flash Codes) cont’d. (*) Fault actions shown are default values specified by the OEM. 70 DFC PROBABLE FAULT FAULT ACTION * CORRECTIVE ACTION FIRST CHECK 424 EST4 Open _ EST4 output open, possibly open EST4 signal or defective spark module TurnOnMil Check coil driver wiring and connector for open circuit SECM Pin A6 (EST4) to OEM ignition system. See application manual. Verify GND on ignition module Pin A (of both connectors) Verify +12 Vdc on ignition module Pin B (of both connectors) Refer to application manual for specific engine details.
425 EST5 Open _ EST5 output open, possibly open EST5 signal or defective spark module None N/A 426 EST6 Open _ EST6 output open, possibly open EST6 signal or defective spark module None N/A 427 EST7 Open _ EST7 output open, possibly open EST7 signal or defective spark module None N/A 428 EST8 Open _ EST8 output open, possibly open EST8 signal or defective spark module None N/A 431 EST1 Short _ EST1 output shorted high or low, EST1 signal shorted to ground or power or defective spark module TurnOnMil Check coil driver wiring and connector for shorts SECM Pin A9 (EST1) to ignition module Pin D (4-pin connector) Verify GND on ignition module Pin A (of both connectors) Verify +12 Vdc on ignition module Pin B (of both connectors) Refer to application manual for specific engine details.