Possible Causes
| Possible Causes |
|---|
| O2 SENSOR 1/1 SIGNAL CIRCUIT |
| O2 SENSOR CURRENT PUMP CIRCUIT |
| O2 SENSOR RETURN CIRCUIT |
| EXHAUST SYSTEM LEAK OR RESTRICTION |
| INTAKE SYSTEM LEAK OR RESTRICTION OR RESTRICTION |
| FUEL PRESSURE TOO LOW OR TOO HIGH |
| FOULED OR LEAKING FUEL INJECTOR |
| O2 SENSOR |
Always perform the PRE-DIAGNOSTIC TROUBLESHOOTING PROCEDURE before proceeding. Refer to PRE-DIAGNOSTIC TROUBLESHOOTING PROCEDURE .