Fuel trim malfunction code may be set by
- Low fuel.
- Fuel pressure regulator malfunction.
- Fuel injector malfunction.
- Fuel pump malfunction.
- ECT sensor malfunction.
- MAF sensor malfunction.
- HO2S malfunction.
- Purge solenoid malfunction.
- Inlet air leak.
- PCM malfunction.
- Open or short circuit between fuel injector and PCM connector C249 terminals No. 11 and No. 12.
- IAT sensor malfunction.
- EGR pressure sensor malfunction.
- PCV malfunction.
- Ensure no air leaks in engine inlet system.
- Check fuel pressure. Refer to FUEL SYSTEM in the «BASIC TESTING»(ref-25093) article. If fuel pressure is okay, go to step 5). If fuel pressure is not within specifications, go to next step.
- Check maximum pressure. See FUEL SYSTEM in «BASIC TESTING»(ref-25093) article.
- Check fuel pressure regulator. See FUEL SYSTEM in the «BASIC TESTING»(ref-25093) article.
- Check fuel injectors. See «SYSTEM/COMPONENT TESTS»(ref-25100) article. If injectors are okay, go to next step. If injector(s) is bad, replace injector(s).
- Check ECT sensor. See «SYSTEM/COMPONENT TESTS»(ref-25100) article. If ECT sensor is okay, go to next step. If ECT sensor is bad, replace ECT sensor.
- Check MAF sensor. See «SYSTEM/COMPONENT TESTS»(ref-25100) article. If MAF sensor is okay, go to next step. If MAF sensor is bad, replace MAF sensor.
- Check TPS. See «ADJUSTMENTS»(ref-25084) article. If TPS is okay, go to next step. If TPS is bad, replace TPS.
- 1.6L only, 1.8L go to next step. Check closed throttle position switch. See «ADJUSTMENTS»(ref-25084) article. Adjust as needed. If switch is okay, go to next step. If switch is bad, replace TPS.
- Check IAT sensor. See SENSORS in «SYSTEM/COMPONENT TESTS»(ref-25100) article. If IAT sensor is okay, go to next step. If IAT sensor is bad, replace IAT sensor.
- Check EGR pressure sensor (1.6L) or EGR boost sensor(1.8L). See SENSORS in «SYSTEM/COMPONENT TESTS»(ref-25100) article. If EGR pressure or boost sensor is okay, go to next step. If EGR pressure or boost sensor is bad, replace sensor.
- Check purge solenoid. See EMISSIONS SYSTEMS & SUB-SYSTEMS in «SYSTEM/COMPONENT TESTS»(ref-25100) article. If purge solenoid is okay, go to next step. If purge solenoid is bad, replace purge solenoid.
- Check PCV valve. replace as needed.
- Clear code. Recheck codes. If code returns, replace PCM. If code does not return, problem is intermittent.